AXIS Attributes (E-R)

Attribute

Axis Type

Data Type

Access

Description

Enable Input Status

AXIS_SERVO_DRIVE

BOOL

Tag

If this bit is the following:

ON — The Enable input is active.

OFF — The Enable input is inactive.

External Drive Type

AXIS_SERVO_DRIVE

DINT

GSV

0 = torque servo

1 = velocity servo

2 = hydraulic servo

When the application requires the servo module axis to interface with an external velocity servo drive, the External Drive Type should be configured for velocity servo. This disables the servo module’s internal digital velocity loop.

If the External Drive Type attribute is set to torque servo, the servo module’s internal digital velocity loop is active. This configuration is the required configuration for interfacing to a torque loop servo drive.

If the External Drive Type attribute is set to hydraulic servo, the object will enable certain features specific to hydraulic servo applications.

In general, selecting the hydraulic External Drive Type configures the servo loop the same as selecting the velocity servo External Drive Type.

Fault Configuration Bits

AXIS_SERVO

DINT

GSV

Axis Type

AXIS_SERVO

AXIS_SERVO_DRIVE

Change to rotary or Overtravel Checking requires Home range checks.

Soft overtravel checking is only available for a linear axis.

Do you want a Positive Soft Overtravel Fault or Negative Soft Overtravel Fault to happen if the axis goes outside the configured travel limits?

YES — Set this bit.

NO — Clear this bit.

The Maximum Positive Travel and Maximum Negative Travel attributes set the travel limits. This check supplements but doesn’t replace hardware overtravel fault protection that uses hardware limit switches to directly stop axis motion at the drive and deactivate power to the system.

Hard overtravel checking is only available for a linear axis.

Do you want a Positive Hard Overtravel Fault or Negative Hard Overtravel Fault to happen if the axis activates the positive or negative overtravel limit switch inputs?

YES — Set this bit.

NO — Clear this bit.

The motion module provides a dedicated drive fault input for each axis. These inputs may be connected to fault outputs on the external drive (if provided) to notify the servo module of a fault in the drive itself.

Set the Drive Fault Checking bit if you are using the servo module’s drive fault input, and then specify the drive fault contact configuration of the amplifier’s drive fault output as described below.

The Drive Fault Normally Closed bit attribute controls the sense of the Drive Fault input to the servo module.

If this bit is set (true) then during normal (fault-free) operation of the drive, the Drive Fault input should be active, that is, 24 Volts.

If a drive fault occurs, the drive will open its drive fault output contacts and remove 24 Volts from the servo module’s Drive Fault input generating an axis Drive Fault condition. This is the default "fail-safe" configuration.

In some cases it may be necessary to clear the Drive Fault Normally Closed bit to interface with a drive system that closes its contacts when faulted. This is generally not recommended for "fail-safe" operation.

When the Drive Enable Input Fault Handling bit is set, it lets the drive post a fault based on the condition of the Drive Enable Input.

If an attempt is made to enable the drive axis without an active Drive Enable Input, the drive sets a Drive Enable Input Fault. If the Drive Enable Input ever goes from active to inactive while the drive axis is enabled, the drive also sets a Drive Enable Input Fault.

If the Drive Enable Input Fault Handling bit is clear (default), then the drive does not generate a Drive Enable Input Fault.

When the Drive Enable Input Checking bit is set (the default) the drive regularly checks the current state of the Drive Enable Input. This dedicated input serves as a permissive to enable the drive’s power structure and servo loop.

Once the drive is enabled, a transition of the Drive Enable Input from active to inactive results in a drive initiated axis stop where the axis is decelerated to a stop using the configured Stopping Torque and then disabled.

If the drive enable Input Checking bit is clear, then no Drive Enable Input checking is done, hence the state of the input is irrelevant to drive operation. The state of the switch is still reported as part of the Drive Status bits attribute.

Feedback Fault

AXIS_SERVO

BOOL

Tag

Set for a specific feedback source when one of the following conditions occurs:

The differential electrical signals for one or more of the feedback channels (for example, A+ and A-, B+ and B-, or Z+ and Z-) are at the same level (both high or both low). Under normal operation, the differential signals are always at opposite levels.

The most common cause of this situation is a broken wire between the feedback transducer and the servo module or drive.

Loss of feedback "power" or feedback "common" electrical connection between the servo module or drive and the feedback device. The controller latches this fault. Use a Motion Axis Fault Reset (MAFR) or Motion Axis Shutdown Reset (MASR) instruction to clear the fault.

Set when one of the feedback sources associated with the drive axis has a problem that prevents the drive from receiving accurate or reliable position information from the feedback device.

Set when one of the feedback sources for the axis can’t send accurate or reliable position information because there is a problem.

For AXIS_SERVO axis, possible problems are:

The differential electrical signals for one or more of the feedback channels (for example, A+ and A-, B+ and B-, or Z+ and Z-) are at the same level (both high or both low). Under normal operation, the differential signals are always at opposite levels. The most common cause of this situation is a broken wire between the feedback transducer and the servo module or drive;

Loss of feedback power or common electrical connection between the servo module or drive and the feedback device.

The controller latches this fault. Use a Motion Axis Fault Reset (MAFR) or Motion Axis Shutdown Reset (MASR) instruction to clear the fault.

Feedback Fault Action

AXIS_SERVO

SINT

GSV

Shutdown   

Disable Drive   

Stop Motion

Status Only

Feedback Noise Fault

AXIS_SERVO

BOOL

Tag

Set when there is noise on the feedback device’s signal lines.

For example, simultaneous transitions of the feedback A and B channels of an A Quad B is referred to generally as feedback noise.

Feedback noise (shown below) is most often caused by loss of quadrature in the feedback device itself or radiated common-mode noise signals being picked up by the feedback device wiring. You can see both of these on an oscilloscope.

To troubleshoot the loss of channel quadrature, look for:

Proper grounding and shielding usually cures radiated noise problems.

The controller latches this fault. Use a Motion Axis Fault Reset (MAFR) or Motion Axis Shutdown Reset (MASR) instruction to clear the fault.

Feedback Noise Fault Action

AXIS_SERVO

SINT

GSV

Shutdown

Disable Drive

Stop Motion

Status Only

Friction Compensation

AXIS_SERVO

REAL

GSV

0…100%

It is not unusual for an axis to have enough static friction (sticktion) that even with a significant position error it won’t move. Integral gain can be used to generate enough output to the drive to correct the error, but this approach may not be responsive enough for the application.

An alternative is to use Friction Compensation to break sticktion in the presence of a non-zero position error. This is done by adding, or subtracting, a fixed output level, called Friction Compensation, to the Servo Output value based on its current sign.

The Friction Compensation value should be just under the value that would break the sticktion. A larger value causes the axis to dither. Dither is when the axis moves rapidly back and forth centered on the commanded position.

Friction Compensation Window

AXIS_SERVO

REAL

GSV

To address the issue of dither when applying Friction Compensation and hunting from the integral gain, a Friction Compensation Window is applied around the current command position when the axis is not being commanded to move.

If the actual position is within the Friction Compensation Window the Friction Compensation value is applied to the Servo Output but scaled by the ratio of the position error to the Friction Compensation Window. Within the window, the servo integrators are also disabled.

Thus, once the position error reaches or exceeds the value of the Friction Compensation Window attribute, the full Friction Compensation value is applied. Of course, should the Friction Compensation Window be set to zero, this feature is effectively disabled.

A non-zero Friction Compensation Window has the effect of softening the Friction Compensation as its applied to the Servo Output and reducing the dithering effect that it can create. This generally allows higher values of Friction Compensation to be applied. Hunting is also eliminated at the cost of a small steady-state error.

Gearing Lock Status

AXIS_CONSUMED

BOOL

Tag

Set whenever the slave axis is locked to the master axis in a gearing relationship according to the specified gear ratio. The clutch function of the gearing planner is used to ramp an axis up, or down, to speed in a gearing process (MAG with Clutch selected).

This bit is cleared during the intervals where the axis is clutching.

Gearing Status

AXIS_CONSUMED

BOOL

Tag

Set if the axis is a slave that is currently gearing to another axis. Cleared when the gearing operation is stopped or is superseded by some other motion operation.

Ground Short Fault

AXIS_SERVO_DRIVE

BOOL

Tag

When the drive detects an imbalance in the DC bus supply current, the Ground Short Fault bit is set, indicating that current is flowing through an improper ground connection

Group Instance

AXIS_CONSUMED

DINT

GSV

Instance Number of Group assigned to Axis

The Group Instance attribute is used to determine what motion group object instance this axis is assigned to.

Hard Overtravel Fault Action

AXIS_SERVO_DRIVE

SINT

GSV

Shutdown   

Disable Drive   

Stop Motion

Status Only

Home Configuration Bits

AXIS_GENERIC

DINT

GSV

0 = (Reserved)

1 = Home Switch Normally Closed

2 = Marker Edge Negative

The Home Switch Normally Closed bit attribute determines the normal state of the home limit switch used by the homing sequence. The normal state of the switch is its state prior to being engaged by the axis during the homing sequence.

For example, if the Home Switch Normally Closed bit is set (true) then the condition of the switch prior to homing is closed. When the switch is engaged by the axis during the homing sequence, the switch is opened, which constitutes a homing event.

Home Direction

AXIS_GENERIC

SINT

GSV

0 = unidirectional forward

1 = bidirectional forward

2 = unidirectional reverse

3 = bidirectional reverse

Home Event Armed Status

AXIS_CONSUMED

BOOL

Tag

Set when a home event has been armed through execution of the MAH (Motion Axis Home) instruction. Cleared when a home event occurs.

Home Event Status

AXIS_CONSUMED

BOOL

Tag

Set when a home event has occurred. Cleared when another MAH (Motion Axis Home) instruction is executed.

Home Event Task

AXIS_CONSUMED

DINT

MSG

User Event Task that is triggered to execute when a Home event occurs. An instance value of 0 indicates that no event task has been configured to be triggered by the Home Event.

This attribute indicates which user Task is triggered when a home event occurs.

The user Task is triggered at the same time that the Process Complete bit is set for the instruction that armed the home event.

This attribute is set through internal communication from the user Task object to the Axis object when the Task trigger attribute is set to select the Home Event Task Instance attribute of the Axis.

This attribute should not be set directly by an external device. This attribute is available to be read externally (Get attributes List) for diagnostic information.

Home Input Status

AXIS_SERVO

BOOL

Tag

If this bit is the following:

ON — The home input is active.

OFF — The home input is inactive.

Home Mode

AXIS_GENERIC

SINT

GSV

0 = passive

1 = active (default)

2 = absolute

Home Offset

AXIS_GENERIC

REAL

GSV

Position Units

When applied to an active or passive Homing Mode, using a non-immediate Home Sequence, the Home Offset is the desired position offset of the axis Home Position from the position at which the home event occurred. The Home Offset is applied at the end of the specified homing sequence before the axis moves to the Home Position. In most cases, Home Offset is set to zero.

After an active bidirectional homing sequence has completed, the axis is left at the specified Home Position. If the Home Offset is non-zero, the axis will then be offset from the marker or home switch event point by the Home Offset value. If the Home Offset is zero, the axis will sit right "on top of" the marker or home switch point.

Home Position

AXIS_GENERIC

REAL

GSV

Position Units

The Home Position is the desired absolute position for the axis after the specified homing sequence has been completed. After an active homing sequence has completed, the axis is left at the specified Home Position.

In most cases, Home Position is set to zero, although any value, within the Maximum Positive and Negative Travel limits of the axis (if enabled), may also be used. (A description of the Maximum Positive and Negative Travel configuration attributes may be found in the Servo and Drive Axis Object specifications). For a rotary axis, the Home Position is constrained to be a positive number less than the Position Unwind value divided by the Conversion Constant.

When configured for absolute Homing Mode, the Home Position value is applied directly to the absolute feedback device to establish an absolute position reference for the system.

Home Return Speed

AXIS_GENERIC

REAL

GSV

Position Units / Sec

The Home Return Speed attribute controls the speed of the jog profile used after the first leg of an active bidirectional homing sequence.

Home Sequence

AXIS_GENERIC

SINT

GSV

0 = immediate (default)

1 = switch

2 = marker

3 = switch then marker

4 = torque limit

5 = torque limit then marker

Home Speed

AXIS_GENERIC

REAL

GSV

Position Units / Sec

The Home Speed attribute controls the speed of the jog profile used in the first leg of an active homing sequence as described in the above discussion of the Home Sequence Type attribute.

Axis Homed Status

AXIS_CONSUMED

BOOL

Tag

Cleared at power-up or reconnection. Set by the MAH instruction upon successful completion of the configured homing sequence, and later cleared when the axis enters the shutdown state.

Homing Status

AXIS_CONSUMED

BOOL

Tag

Set if a Home motion profile is currently in progress. Cleared when the homing operation is stopped or is superseded by some other motion operation.

Inhibit Status

AXIS_SERVO

BOOL

Tag

Use the InhibitStatus bit of an axis to see if the axis is inhibited or uninhibited. If the bit is:

ON — The axis is inhibited.

OFF — The axis is uninhibited.

The controller changes the InhibitStatus bit only after all of these have happened:

The axis has changed to inhibited or uninhibited.

All uninhibited axes are ready.

The connections to the motion module are running again.

Inhibit Axis

AXIS_SERVO

INT

GSV

Block the controller from using the axis. This inhibits the axis.

Let the controller use the axis. This uninhibits the axis.

Integrator Hold Enable

AXIS_SERVO

SINT

GSV

When the Integrator Hold Enable attribute value is configured TRUE, the servo loop temporarily disables any enabled integrators while the command position is changing. This feature is used by point-to-point moves to minimize the integrator wind-up during motion. When the Integrator Hold Enable attribute value is FALSE, all active integrators are always enabled.

0 = disabled

1 = enabled

Inter Module Sync Fault

AXIS_SERVO

BOOL

Tag

If this bit is on, the analog servo cards of a SoftLogix5800 controller aren’t synchronized. The hardware or vbfirmware of the card causes this fault. For example, the cable between 2 cards isn’t connected.

Interpolated Actual Position

AXIS_CONSUMED

REAL

GSV

Interpolated Actual Position in Position Units

Interpolated Actual Position is the interpolation of the actual position, based on past axis trajectory history, at the time specified by the "Interpolated Time" attribute.

Interpolated Command Position

AXIS_CONSUMED

REAL

GSV

Interpolated Command Position in Position Units

Interpolated Command Position is the interpolation of the commanded position, based on past axis trajectory history, at the time specified by the "Interpolated Time" attribute.

Interpolated Time

AXIS_CONSUMED

DINT

GSV

CST time to interpolate to

Interpolated Time is the 32-bit CST time used to calculate the interpolated positions. When this attribute is updated with a valid CST value, the Interpolated Actual Position and Interpolated Command Position values are automatically calculated.

Jog Status

AXIS_CONSUMED

BOOL

Tag

Set if a Jog motion profile is currently in progress. Cleared when the Jog is complete or is superseded by some other motion operation.

LDT Calibration Constant

AXIS_SERVO

REAL

GSV

This attribute provides for setting a calibration constant for LDT devices. This attribute is only active if the Transducer Type is set to LDT.

LDT Calibration Constant Units

AXIS_SERVO

SINT

GSV

0 = m/sec

1 = Usec/in

This attribute provides a selection for the units of the LDT calibration constant attribute. This attribute is only active if the Transducer Type is set to LDT.

LDT Length

AXIS_SERVO

REAL

GSV

This attribute provides for setting the length of an LDT device. This attribute is only active if the Transducer Type is set to LDT.

LDT Length Unit

AXIS_SERVO

SINT

GSV

0 = m

1 = in

This attribute provides a selection for the units of the LDT length attribute. This attribute is only active if the Transducer Type is set to LDT.

LDT Recirculations

AXIS_SERVO

SINT

GSV

This attribute provides the number of recirculations. This attribute is only active if the Transducer Type is set to LDT and LDT Type is set to PWM.

LDT Scaling

AXIS_SERVO

REAL

GSV

This attribute provides for setting the scaling factor for LDT devices. This attribute is only active if the Transducer Type is set to LDT.

LDT Scaling Units

AXIS_SERVO

SINT

GSV

0 = Position Units/m

1 = Position Units/in

This attribute provides a selection for the units of the LDT scaling attribute. This attribute is only active if the Transducer Type is set to LDT.

LDT Type

AXIS_SERVO

SINT

GSV

0 = PWM

1 = Start/Stop Rising

2 = Start/Stop Falling

This attribute provides a selection for the LDT Type. It provides the following enumerated values: PWM, Start/Stop Rising, and Start/Stop Falling. This attribute is only active if the Transducer Type is set to LDT.

Load Inertia Ratio

AXIS_SERVO_DRIVE

REAL

GSV

%Rated / Pos Units per Sec2

The Motor Inertia value represents the inertia of the motor without any load attached to the motor shaft in Torque Scaling units of %Rated / Pos Units per Sec2. The Load Inertia Ratio attribute’s value represents the ratio of the load inertia to the motor inertia. Auto-tuning uses the Motor Inertia value to calculate the Load Inertia Ratio based on the following equation.

Load Inertia Ratio = (Total Inertia - Motor Inertia) / Motor Inertia.

Total Inertia is directly measured by the auto-tuning algorithm and applied to the Torque Scaling attribute in units of %Rated / Pos Units per Sec2.

If the Load Inertia Ratio value is known, the Motor Inertia value can also be used to calculate a suitable Torque Scaling value for the fully loaded motor without performing an auto-tune. The equation used by the

Logix Designer

application to calculate the Torque Scaling value is as follows:

Torque Scaling = (1 + Load Inertia Ratio) * Motor Inertia.

The value for Load Inertia may be automatically calculated using Rockwell Automation's MotionBook program while the value for Motor Inertia is derived from the Motion database file based on the motor selection.

Map Instance

AXIS_GENERIC

DINT

GSV

I/O Map Instance Number. This is 0 for virtual and consumed Data Types.

The axis is associated to a specific motion compatible module by specifying the instance of the map entry representing the module.

Marker Distance

AXIS_SERVO

REAL

GSV

Important:

To use this attribute, choose it as one of the attributes for Real Time Axis Information for the axis. Otherwise, you won’t see the right value as the axis runs. See Axis Info Select 1.

Marker Distance in Position Units

Marker Distance is the distance between the axis position at which a home switch input was detected and the axis position at which the marker event was detected. This value is useful in aligning a home limit switch relative to a feedback marker pulse to provide repeatable homing operation.

Master Input Configuration Bits

AXIS_GENERIC

DINT

GSV

0 = Master Delay Compensation

1 = Master Position Filter

By default, both the Position Camming and Gearing functions, when applied to a slave axis, perform Master Delay Compensation to compensate for the delay time between reading the master axis command position and applying the associated slave command position to the input of the slave’s servo loop.

When the master axis is running at a fixed speed, this compensation technique insures that the slave axis command position accurately tracks the actual position of the master axis; in other words, Master Delay Compensation allows for zero tracking error when gearing or camming to the actual position of a master axis.

The Master Delay Compensation algorithm extrapolates the position of the master axis at the predicted time when the command position is applied to the slave’s servo loop.

Since master axis position is measured in discrete feedback counts and is inherently noisy, the extrapolation process amplifies that noise according to the total position update delay. The total position update delay is proportional to the Coarse Update Period of the motion group, and, if the master or the slave involves an AXIS_SERVO_DRIVE data type, it also includes the delay term that is proportional to the SERCOS Update Period. The greater the delay, the greater the noise introduced by the extrapolator.

The Master Delay Compensation feature also has an extrapolation filter to filter the noise introduced by the extrapolation process. The time constant of the filter is fixed at 4x the total position update delay (independent of the Master Position Filter Bandwidth), which again is a function of the Coarse Update Period (and the SERCOS Update Period, if a AXIS_SERVO_DRIVE data type).

The controller uses a 1st order extrapolation algorithm that results in zero tracking error while the master axis is moving at constant velocity. If the master axis accelerates or decelerates the tracking error is non-zero and proportional to the acceleration or deceleration rate and also proportional to the square of the total position update delay time. From both a noise and acceleration error perspective, minimizing the coarse update period is vital.

Some applications don't need zero tracking error between the master and the slave axis. In these cases, it may be beneficial to disable the Master Delay Compensation feature to eliminate the disturbances the extrapolation algorithm introduces to the slave axis. When the Master Delay Compensation feature is disabled (bit cleared), the slave axis will appear to be more responsive to movements of the master and run generally smoother than when Master Delay Compensation feature is enabled (bit set). However, when the master axis is running at a constant velocity, the slave will lag the master by a tracking error that is proportional to the speed of the master.

Note that Master Delay Compensation, even if explicitly enabled, is not applied in cases where a slave axis is gearing or camming to the master axis’ command position. Since the controller generates the command position directly, there is no intrinsic master position delay to compensate for.

The Master Position Filter bit controls the activity of an independent single-pole low-pass filter that effectively filters the specified master axis position input to the slave’s gearing or position camming operation.

When enabled (bit set), this filter has the effect of smoothing out the actual position signal from the master axis, and thus smoothing out the corresponding motion of the slave axis.

The trade-off for smoothness is an increase in lag time between the response of the slave axis to changes in motion of the master.

Note that the Master Position Filter also provides filtering to the extrapolation noise introduced by the Master Delay Compensation algorithm, if enabled.

When the Master Position Filter bit is set, the bandwidth of the Master Position Filter is controlled by the Master Position Filter Bandwidth attribute, see below. This can be done by setting the Master Position Filter bit and controlling the Master Position Filter Bandwidth directly.

Setting the Master Position Filter Bandwidth to zero can be used to effectively disable the filter.

Master Offset

AXIS_CONSUMED

REAL

GSV

Important:

To use this attribute, make sure Auto Tag Update is Enabled for the motion group (default setting). Otherwise, you won’t see the right value as the axis runs.

Master Offset in Master Position Units

The Master Offset is the position offset that is currently applied to the master side of the position cam. The Master Offset is returned in master position units. The Master Offset will show the same unwind characteristic as the position of a linear axis.

Master Offset Move Status

AXIS_CONSUMED

BOOL

Tag

Set if a Master Offset Move motion profile is currently in progress. This bit is cleared when the Master Offset Move is complete or is superseded by some other motion operation.

Master Position Filter Bandwidth

AXIS_GENERIC

REAL

GSV

Hertz

The Master Position Filter Bandwidth attribute controls the activity of the single-pole low-pass filter that filters the specified master axis position input to the slave’s gearing or position camming operation.

When enabled, this filter has the effect of smoothing out the actual position signal from the master axis, and thus smoothing out the corresponding motion of the slave axis. The trade-off for smoothness is an increase in lag time between the response of the slave axis to changes in motion of the master.

If the Master Position Filter is disabled, the Master Position Filter Bandwidth has no effect.

Maximum Acceleration

AXIS_GENERIC

REAL

GSV

Position Units / Sec2

The Maximum Acceleration and Deceleration attribute values are frequently used by motion instructions such as MAJ, MAM, MCD, and so on, to determine the acceleration and deceleration rates to apply to the axis.

These instructions all have the option of specifying acceleration and deceleration as a percent of the Maximum Acceleration and Maximum Deceleration attributes for the axis.

The Maximum Acceleration and Maximum Deceleration values for the axis are automatically set to ~ 85% of the measured Tune Acceleration and Tune Deceleration by the MAAT (Motion Apply Axis Tune) instruction.

If set manually, these values should typically be set to ~85% of the maximum acceleration and maximum deceleration rate of the axis. This provides sufficient "head-room" for the axis to operate at all times within the acceleration and deceleration limits of the drive and motor.

Maximum Deceleration

AXIS_GENERIC

REAL

GSV

Position Units / Sec2

The Maximum Acceleration and Deceleration attribute values are frequently used by motion instructions such as MAJ, MAM, MCD, and so on, to determine the acceleration and deceleration rates to apply to the axis.

These instructions all have the option of specifying acceleration and deceleration as a percent of the Maximum Acceleration and Maximum Deceleration attributes for the axis.

The Maximum Acceleration and Maximum Deceleration values for the axis are automatically set to ~ 85% of the measured Tune Acceleration and Tune Deceleration by the MAAT (Motion Apply Axis Tune) instruction.

If set manually, these values should typically be set to ~85% of the maximum acceleration and maximum deceleration rate of the axis. This provides sufficient "head-room" for the axis to operate at all times within the acceleration and deceleration limits of the drive and motor.

Maximum Negative Travel

AXIS_SERVO

REAL

GSV

Position Units

The Axis Object provides configurable software travel limits via the Maximum Positive and Negative Travel attributes.

If the axis is configured for software overtravel limit checking by setting the Soft Overtravel Bit and the axis passes outside these maximum travel limits, a Software Overtravel Fault is issued.

When software overtravel checking is enabled, appropriate values for the maximum travel in both the Maximum Positive and Maximum Negative Travel attributes need to be established with Maximum Positive Travel always greater than Maximum Negative Travel.

Both of these values are specified in the configured Position Units of the axis.

Tip:

The software travel limits are not enabled until the selected homing sequence is completed.

Maximum Positive Travel

AXIS_SERVO

REAL

GSV

Position Units

The Axis Object provides configurable software travel limits via the Maximum Positive and Negative Travel attributes. If the axis is configured for software overtravel limit checking by setting the Soft Overtravel Bit and the axis passes outside these maximum travel limits, a Software Overtravel Fault is issued.

When software overtravel checking is enabled, appropriate values for the maximum travel in both the Maximum Positive and Maximum Negative Travel attributes need to be established with Maximum Positive Travel always greater than Maximum Negative Travel. Both of these values are specified in the configured Position Units of the axis.

Tip

: The software travel limits are not enabled until the selected homing sequence is completed.

Maximum Speed

AXIS_GENERIC

REAL

GSV

Position Units / Sec

The value of the Maximum Speed attribute is used by various motion instructions (for example, MAJ, MAM, MCD, and so on) to determine the steady-state speed of the axis. These instructions all have the option of specifying speed as a percent of the Maximum Speed attribute value for the axis.

The Maximum Speed value for the axis is automatically set to the Tuning Speed by the MAAT (Motion Apply Axis Tune) instruction.

This value is typically set to ~90% of the maximum speed rating of the motor. This provides sufficient "head-room" for the axis to operate at all times within the speed limitations of the motor.

Memory Usage

AXIS_CONSUMED

DINT

MSG

Amount of memory consumed for this instance (in bytes)

Memory Use

AXIS_CONSUMED

INT

GSV

Controller memory space where instance exists.

105 (0x69) = I/O space

106 (0x6a) = Data Table space

The

Logix Designer

application uses this attribute to create axis instances in I/O memory for axes that are either to be produced or consumed.

The Memory Use attribute can only be set as part of an axis create service and is used to control which controller memory the object instance is created in.

Module Channel

AXIS_GENERIC

SINT

GSV

Zero based channel number of the module. 0xff, indicates unassigned.

The axis is associated to a specific channel on a motion module by specifying the Module Channel attribute.

Module Class Code

AXIS_SERVO

DINT

GSV

CIP Object class code of the motion engine in the module; for example, 0xAF for the M02AE module.

The CIP class code of the object in the motion module which is supporting motion; for example, 0xAF is the CIP object ID of the "Servo Module Axis Object" residing in the 1756-M02AE module.

Module Fault

AXIS_CONSUMED

BOOL

Tag

Set when a serious fault has occurred with the motion module associated with the selected axis.

Usually a module fault affects all axes associated with the motion module. A module fault generally results in the shutdown of all associated axes. Reconfiguration of the motion module is required to recover from a module fault condition.

Do you want this fault to give the controller a major fault?

YES — Set the General Fault Type of the motion group = Major Fault.

NO — You must write code to handle these faults.

Module Fault Bits

AXIS_CONSUMED

DINT

GSV*

Lets you access the module fault bits in one 32-bit word. This attribute is the same as the Module Faults tag.

Control Sync Fault

Module Sync Fault

Timer Event Fault

Module Hardware Fault

SERCOS Ring Fault

Inter Module Sync Fault

These faults have module scope instead of axis scope.

These faults show up in all the axes that are connected to the motion module.

The motion planner updates these fault bits every coarse update period.

Do you want any of these faults to give the controller a major fault?

YES — Set the General Fault Type of the motion group = Major Fault.

NO — You must write code to handle these faults.

Module Faults

AXIS_SERVO

DINT

Tag

Lets you access the module fault bits in one 32-bit word. This tag is the same as the Module Fault Bits attribute.

Control Sync Fault

Module Sync Fault

Timer Event Fault

Module Hardware Fault

SERCOS Ring Fault

Inter Module Sync Fault

These faults have module scope instead of axis scope.

These faults show up in all the axes that are connected to the motion module.

The motion planner updates these fault bits every coarse update period.

Do you want any of these faults to give the controller a major fault?

YES — Set the General Fault Type of the motion group = Major Fault.

NO — You must write code to handle these faults.

Module Hardware Fault

AXIS_SERVO

BOOL

Tag

If this bit is set, the motion module has a hardware problem that, in general, is going to require replacement of the module.

Module Sync Fault

AXIS_SERVO

BOOL

Tag

If this bit is set, the motion module lost communication with the controller and missed several position updates in a row.

The motion module can miss up to 4 position updates. After that, the motion module shuts down.

This bit clears when communication is reestablished.

Mot Feedback Fault

AXIS_SERVO_DRIVE

BOOL

Tag

Set for the A Quad B feedback device when one of these happens:

The differential electrical signals for one or more of the feedback channels (for example, A+ and A-, B+ and B-, or Z+ and Z-) are at the same level (both high or both low).

Under normal operation, the differential signals are always at opposite levels. The most common cause of this situation is a broken wire between the feedback transducer and the servo module or drive.

Loss of feedback "power" or feedback "common" electrical connection between the servo module or drive and the feedback device.

The controller latches this fault. Use a Motion Axis Fault Reset (MAFR) or Motion Axis Shutdown Reset (MASR) instruction to clear the fault.

Mot Feedback Noise Fault

                        

AXIS_SERVO_DRIVE

BOOL

Tag

Set when there is noise on the feedback device’s signal lines.

For example, simultaneous transitions of the feedback A and B channels of an A Quad B is referred to generally as feedback noise.

Feedback noise (shown below) is most often caused by loss of quadrature in the feedback device itself or radiated common-mode noise signals being picked up by the feedback device wiring. You can see both of these on an oscilloscope.

To troubleshoot the loss of channel quadrature, look for:

Proper grounding and shielding usually cures radiated noise problems.

The controller latches this fault. Use a Motion Axis Fault Reset (MAFR) or Motion Axis Shutdown Reset (MASR) instruction to clear the fault.

Motion Status

AXIS_CONSUMED

DINT

Tag

Lets you access all the motion status bits in one 32-bit word. This tag is the same as the Motion Status Bits attribute.

Accel Status

Decel Status

Move Status

Jog Status

Gearing Status

Homing Status

Stopping Status

Homed Status

Position Cam Status

Time Cam Status

Positive Cam Pending Status

Time Cam Pending Status

Gearing Lock Status

Position Cam Lock Status

Reserved

Coordinated Motion Status

Transform State Status

Controlled by Transform Status

Motion Status Bits

AXIS_CONSUMED

DINT

GSV

Lets you access all the motion status bits in one 32-bit word. This attribute is the same as the Motion Status tag.

Accel Status

Decel Status

Move Status

Jog Status

Gearing Status

Homing Status

Stopping Status

Homed Status

Position Cam Status

Time Cam Status

Positive Cam Pending Status

Time Cam Pending Status

Gearing Lock Status

Position Cam Lock Status

Reserved

Coordinated Motion Status

Transform State Status

Controlled by Transform Status

Motor Capacity

AXIS_SERVO_DRIVE

REAL

GSV

Important

: To use this attribute, choose it as one of the attributes for Real Time Axis Information for the axis. Otherwise, you won’t see the right value as the axis runs. See Axis Info Select 1.

The present utilization of motor capacity as a percent of rated capacity.

Motor Data

AXIS_SERVO_DRIVE

Struct {INT;

MSG

Struct {length; data[ ]}

The Motor Data attribute is a structure with a length element and an array of bytes that contains important motor configuration information needed by an A-B SERCOS drive to operate the motor. The length element represents the number of valid data elements in the data array.

The meaning of data within the data array is understood only by the drive. The block of data stored in the Motor Data attribute is derive

Motor Electrical Angle

AXIS_SERVO_DRIVE

REAL

GSV

Important

: To use this attribute, choose it as one of the attributes for Real Time Axis Information for the axis. Otherwise, you won’t see the right value as the axis runs. See Axis Info Select 1.

Degrees

The present electrical angle of the motor shaft.

Motor Feedback Configuration

AXIS_SERVO_DRIVE

INT

GSV

The controller and drive use this for scaling the feedback device counts. These attributes are derived from the corresponding Motor and Auxiliary Feedback Unit attributes.

Bit

0 = Feedback type

3 = Feedback Polarity (Aux Only)

If the bits are:

2	1	0
0		0	Feedback Cycles per Feedback Rev
1		0	Feedback Cycles per Feedback Rev
0		1	Feedback Cycles per mm
1		1	Feedback Cycles per inch

Motor Feedback Interpolation Factor

AXIS_SERVO_DRIVE

DINT

GSV

Feedback Polarity

The Feedback Polarity bit attribute can be used to change the sense of direction of the feedback device. This bit is only valid for auxiliary feedback devices.

When performing motor/feedback hookup diagnostics on an auxiliary feedback device using the MRHD and MAHD instructions, the Feedback Polarity bit is configured for the auxiliary feedback device to insure negative feedback into the servo loop.

Motor feedback devices must be wired properly for negative feedback since the Feedback Polarity bit is forced to 0, or non-inverted.

Motor Feedback Resolution

AXIS_SERVO_DRIVE

DINT

GSV

Cycles per Motor Feedback Unit

The Motor and Aux Feedback Resolution attributes are used to provide the A-B drive with the resolution of the associated feedback device in cycles per feedback unit.

These parameters provide the SERCOS drive with critical information needed to compute scaling factors used to convert Drive Counts to Feedback counts.

Motor Feedback Type

AXIS_SERVO_DRIVE

INT

GSV

The Motor and Aux Feedback Type attributes are used to identify the motor mounted or auxiliary feedback device connected to the drive.

Feedback Type	Code	Rotary Only	Linear Only	Rotary or Linear
<None>	0x0000	-	-	-
SRS	0x0001	X
SRM	0x0002	X
SCS	0x0003	X
SCM	0x0004	X
SNS	0x0005	X
MGH	0x0006	X
Resolver	0x0007	X
Analog reference	0x0008	X
Sin/Cos	0x0009			X
TTL	0x000A			X
UVW	0x000B			X
Unknown Stegmann	0x000C			X
Endat	0x000D			X
RCM21S-4	0x000E	X
RCM21S-6	0x000F	X
RCM21S-8	0x0010	X
LINCODER	0x0011		X
Sin/Cos with Hall	0x0012			X

Motor Feedback Units

AXIS_SERVO_DRIVE

INT

GSV

The Motor Feedback Units attribute establishes the unit of measure that is applied to the Motor Feedback Resolution attribute value. The Aux Feedback Units attribute establishes the unit of measure that is applied to the Aux Feedback Resolution attribute value. Units appearing in the enumerated list cover linear or rotary, english or metric feedback devices.

0 = revs

1 = inches

2 = mm

Motor ID

AXIS_SERVO_DRIVE

INT

GSV

The Motor ID attribute contains the enumeration of the specific A-B motor catalog number associated with the axis. If the Motor ID does not match that of the actual motor, an error is generated during the drive configuration process.

Motor Inertia

AXIS_SERVO_DRIVE

REAL

GSV

%Rated / Pos Units per Sec

2

The Motor Inertia value represents the inertia of the motor without any load attached to the motor shaft in Torque Scaling units of %Rated / Pos Units per Sec

2

. The Load Inertia Ratio attribute’s value represents the ratio of the load inertia to the motor inertia. Auto-tuning uses the Motor Inertia value to calculate the Load Inertia Ratio based on the following equation.

Load Inertia Ratio = (Total Inertia - Motor Inertia) / Motor Inertia.

Total Inertia is directly measured by the auto-tuning algorithm and applied to the Torque Scaling attribute in units of %Rated / Pos Units per Sec

2

.

If the Load Inertia Ratio value is known, the Motor Inertia value can also be used to calculate a suitable Torque Scaling value for the fully loaded motor without performing an auto-tune. The equation used by the

Logix Designer

application to calculate the Torque Scaling value is as follows:

Torque Scaling = (1 + Load Inertia Ratio) * Motor Inertia.

The value for Load Inertia may be automatically calculated using Rockwell Automation's MotionBook program while the value for Motor Inertia is derived from the Motion database file based on the motor selection.

Motor Overtemp Fault

AXIS_SERVO_DRIVE

BOOL

Tag

Set when the motor’s temperature exceeds the motor shutdown temperature.

Motor Thermal Fault Action

AXIS_SERVO_DRIVE

SINT

GSV

Shutdown

Disable Drive

Stop Motion

Status Only

Move Status

AXIS_CONSUMED

BOOL

Tag

Set if a Move motion profile is currently in progress. Cleared when the Move is complete or is superseded by some other motion operation.

Net Dynamic Torque Limit

AXIS_SERVO_DRIVE

REAL

Tag

The currently operative negative positive torque/current limit magnitude. It should be the lowest value of all torque/current limits in the drive at a given time, including: amplifier peak limit, motor peak limit, user current limit, amplifier thermal limit, and motor thermal limit.

Neg Hard Overtravel Fault

AXIS_SERVO_DRIVE

BOOL

Tag

Set if the axis moves beyond the negative direction position limits as established by hardware overtravel limit switches mounted on the equipment. This fault can only occur when the drive is in the enabled state and the Hard Overtravel Checking bit is set in the Fault Configuration Bits attribute.

If the Hard Overtravel Fault Action is set for Stop Command, the faulted axis can be moved or jogged back inside the soft overtravel limits. Any attempt, however, to move the axis further beyond the hard overtravel limit switch using a motion instruction results in an instruction error.

To recover from this fault, the axis must be moved back within normal operation limits of the equipment and the limit switch closed. This fault condition is latched and requires execution of an Motion Axis Fault Reset (MAFR) or Motion Axis Shutdown Reset (MASR ) instruction to clear.

Any attempt to clear the fault while the overtravel limit switch is still open and the drive is enabled is unsuccessful.

Neg Overtravel Input Status

AXIS_SERVO_DRIVE

BOOL

Tag

If this bit is the following:

ON — The Negative Overtravel input is active.

OFF — The Negative Overtravel input is inactive.

Neg Soft Overtravel Fault

AXIS_SERVO

BOOL

Tag

If this bit is the following:

ON — The axis moved or tried to move past the Maximum Negative travel limit.

OFF — The axis moved back within the Maximum Negative travel limit

This fault can only happen when the drive is enabled and you configure the axis for Soft Travel Limits.

If the Soft Overtravel Fault Action is set for Stop Command, the faulted axis can be moved or jogged back inside the soft overtravel limits. Any attempt, however, to move the axis further beyond the soft overtravel limit using a motion instruction results in an instruction error.

As soon as the axis is moved back within the specified soft overtravel limits, the corresponding soft overtravel fault bit is automatically cleared. However the soft overtravel fault stays through any attempt to clear it while the axis position is still beyond the specified travel limits while the axis is enabled.

Negative Dynamic Torque Limit

AXIS_SERVO_DRIVE

REAL

GSV

Important

: To use this attribute, choose it as one of the attributes for Real Time Axis Information for the axis. Otherwise, you won’t see the right value as the axis runs. See Axis Info Select 1.

%Rated

The currently operative maximum negative torque/current limit magnitude. The value should be the lowest value of all torque/current limits in the drive at a given time. This limit includes the amplifier peak limit, motor peak limit, user current limit, amplifier thermal limit, and the motor thermal limit.

Output Cam Execution Targets

AXIS_CONSUMED

DINT

GSV

Represents the number of Output Cam nodes attached to this axis. Valid range = 0-8 with default of 0.

The Output Cam Execution Targets attribute is used to specify the number of Output Cam nodes attached to the axis. This attribute can only be set as part of an axis create service and dictates how many Output Cam Nodes are created and associated to that axis.

Each Output Cam Execution Target requires approximately 5.4k bytes of data table memory to store persistent data. With four Output Cam Execution Targets per axis, an additional 21.6k bytes of memory is required for each axis.

The ability to configure the number of Output Cam Execution Targets for a specific axis reduces the memory required per axis for users who do not need Output Cam functionality, or only need 1 or 2 Output Cam Execution Targets for a specific axis. Each axis can be configured differently.

Output Cam Lock Status

AXIS_CONSUMED

DINT

GSV

Set of Output Cam Lock Status bits

The Output Cam Lock Status bit is set when an Output Cam has been armed. This would be initiated by executing an MAOC instruction with Immediate execution selected, when a pending output cam changes to armed, or when the axis approaches or passes through the specified axis arm position.

As soon as this output cam current position moves beyond the cam start or cam stop position, the Output Cam Lock bit is cleared. This bit is also cleared if the Output Cam is terminated by a MDOC instruction.

Output Cam Lock Status

AXIS_CONSUMED

DINT

Tag

A set of bits that are set when an Output Cam is locked to the Master Axis. The bit number corresponds with the execution target number. One bit per execution target.

Output Cam Pending Status

AXIS_CONSUMED

DINT

GSV

A set of bits that are set when an Output Cam is waiting for an armed Output Cam to move beyond its cam start/cam end position.

The bit number corresponds with the execution target number. One bit per execution target.

The Output Cam Pending Status bit is set if an Output Cam is currently pending the completion of another Output Cam. This would be initiated by executing an MAOC instruction with Pending execution selected. As soon as this output cam is armed, being triggered when the currently executing Output Cam has completed, the Output Cam Pending bit is cleared.

This bit is also cleared if the Output Cam is terminated by a MDOC instruction.

Output Cam Status

AXIS_CONSUMED

DINT

GSV

A set of bits that are set when the Output Cam has been initiated. The bit number corresponds with the execution target number. One bit per execution target.

The Output Cam Status bit is set when an Output Cam has been initiated. The Output Cam Status bit is reset when the cam position moves beyond the cam start or cam end position in "Once" execution mode with no Output Cam pending or when the Output Cam is terminated by a MDOC instruction.

Output Cam Transition Status

AXIS_CONSUMED

DINT

GSV

0.0…10.0V

The Output Limit attribute provides a method of limiting the maximum servo output voltage of a physical axis to a specified level. The servo output for the axis as a function of position servo error, both with and without servo output limiting, is shown below.

The servo output limit may be used as a software current or torque limit if you are using a servo drive in torque (current) loop mode. The percentage of the drive’s maximum current that the servo controller commands is equal to the specified servo output limit. For example, if the drive is capable of 30 Amps of current for a 10 Volt input, setting the servo output limit to 5V limits the maximum drive current to 15 Amps.

The servo output limit may also be used if the drive cannot accept the full ±10 Volt range of the servo output. In this case, the servo output limit value effectively limits the maximum command sent to the amplifier. For example, if the drive can only accept command signals up to ±7.5 Volts, set the servo output limit value to 7.5 volts.

Output Limit

AXIS_SERVO

REAL

GSV

If this bit is the following:

ON — The servo output is at or past the Output Limit value.

OFF — The servo output is within the Output Limit value.

Output LP Filter Bandwidth

AXIS_SERVO

REAL

GSV

Hertz

The Output LP (Low Pass) Filter Bandwidth controls the bandwidth of the drive’s low-pass digital output filter. The programmable low-pass output filter is bypassed if the configured Output LP Filter Bandwidth for this filter is set to zero (the default).

This output filter can be used to filter out, or reduce, high frequency variation of the drive output to the motor. The lower the Output LP Filter Bandwidth, the greater the attenuation of these high frequency components of the output signal.

Unfortunately, since the low-pass filter adds lag to the servo loop which pushes the system towards instability, decreasing the Output LP Filter Bandwidth usually requires lowering the Position or Velocity Proportional Gain of the system to maintain stability.

The output filter is particularly useful in high inertia applications where resonance behavior can severely restrict the maximum bandwidth capability of the servo loop.

Output Notch Filter Frequency

AXIS_SERVO_DRIVE

REAL

GSV

Hertz

The Output Notch Filter Frequency attribute controls the center frequency of the drive’s digital notch filter. Currently implemented as a 2

nd

order digital filter with a fixed Q, the Notch Filter provides approximately 40DB of output attenuation at the Notch Filter Frequency. The programmable notch filter is bypassed if the configured Output Notch Filter Frequency for this filter is set to zero (the default). This output notch filter is particularly useful in attenuating mechanical resonance phenomena.

The output filter is particularly useful in high inertia applications where mechanical resonance behavior can severely restrict the maximum bandwidth capability of the servo loop.

Output Offset

AXIS_SERVO

REAL

GSV

+/-10V

Another common situation when interfacing an external Servo Drive, particularly for velocity servo drives, is the effect of drive offset. Cumulative offsets of the servo module’s DAC output and the Servo Drive Input result in a situation where a zero commanded Servo Output value causes the axis to "drift".

If the drift is excessive it can play havoc on the Hookup Diagnostic and Tuning procedures as well as result in a steady-state non-zero position error when the servo loop is closed.

Output offset compensation can be used to correct this problem by adding a fixed value, called Output Offset, to the Servo Output. This value is chosen to achieve near zero drive velocity when the uncompensated Servo Output value is zero.

Overload Fault

AXIS_SERVO_DRIVE

BOOL

Tag

When the load limit of the motor/drive is first exceeded, the Overload warning bit is set. If the condition persists, the Overload fault is set. Often this bit is tied into the IT limit of the drive.

Overspeed Fault

AXIS_SERVO_DRIVE

BOOL

Tag

Set when the speed of the axis as determined from the feedback has exceeded the overspeed limit which is typically set to 150% of configured velocity limit for the motor.

Physical Axis Fault

AXIS_GENERIC

BOOL

Tag

If this bit is set, the physical axis has one or more faults. The specific faults can then be determined through access to the fault attributes of the associated physical axis.

Do you want this fault to give the controller a major fault?

YES — Set the General Fault Type of the motion group = Major Fault.

NO — You must write code to handle these faults.

Planner Command Position - Integer

AXIS_GENERIC

AXIS_GENERICDRIVE

AXIS_CIP DRIVE

DINT

GSV

Integer component of Motion Planner generated command position in planner counts. The command position data type is represented internally as a 64-bit floating point value that Motion Task restricts to a signed 32-bit integer range. The resulting range restricted Double Float is then expressed as two 32-bit attributes to preserve precision. This is accomplished by representing the command position as a floating point number in the form of x. y, x is the integer component nd y is the fractional component.

Planner Command Position - Fractional

AXIS_GENERIC

AXIS_GENERICDRIVE

AXIS_CIP DRIVE

REAL

GSV

Fractional component of Motion Planner generated command position in planner counts. Representing the command position as a floating point number in the form of x.y, x is the integer component and y is the fractional component

Planner Actual Position

AXIS_GENERIC

AXIS_GENERICDRIVE

AXIS_CIP DRIVE

DINT

GSV

Motion Planner generated actual position in planner counts. The internal 64-bit signed integer representation of actual position is range limited by Motion Task to a signed 32-bit integer.

Pos Dynamic Torque Limit

AXIS_SERVO_DRIVE

REAL

Tag

The currently operative maximum positive torque/current limit magnitude. It should be the lowest value of all torque/current limits in the drive at a given time, including: amplifier peak limit, motor peak limit, user current limit, amplifier thermal limit, and motor thermal limit.

Pos Hard Overtravel Fault

AXIS_SERVO_DRIVE

BOOL

Tag

Set if the axis moves beyond the current position limits as established by hardware overtravel limit switches mounted on the equipment. This fault can only occur when the drive is in the enabled state and the Hard Overtravel Checking bit is set in the Fault Configuration Bits attribute.

If the Hard Overtravel Fault Action is set for Stop Command, the faulted axis can be moved or jogged back inside the soft overtravel limits. Any attempt, however, to move the axis further beyond the hard overtravel limit switch using a motion instruction results in an instruction error.

To recover from this fault, the axis must be moved back within normal operation limits of the equipment and the limit switch closed. This fault condition is latched and requires execution of an Motion Axis Fault Reset (MAFR) or Motion Axis Shutdown Reset (MASR ) instruction to clear.

Any attempt to clear the fault while the overtravel limit switch is still open and the drive is enabled is unsuccessful.

Pos Lock Status

AXIS_SERVO

DINT

Tag

Set when the magnitude of the axis position error has become less than or equal to the configured Position Lock Tolerance value for the associated physical axis.

Pos Overtravel Input Status

AXIS_SERVO

BOOL

Tag

If this bit is the following:

ON — The Positive Overtravel input is active.

OFF — The Positive Overtravel input is inactive.

Pos Soft Overtravel Fault

AXIS_SERVO

BOOL

Tag

If this bit is the following.

ON — The axis moved or tried to move past the Maximum Positive travel limit.

OFF — The axis moved back within the Maximum Positive travel limit

This fault can only happen when the drive is enabled and you configure the axis for Soft Travel Limits.

If the Soft Overtravel Fault Action is set for Stop Command, the faulted axis can be moved or jogged back inside the soft overtravel limits. Any attempt, however, to move the axis further beyond the soft overtravel limit using a motion instruction results in an instruction error.

As soon as the axis is moved back within the specified soft overtravel limits, the corresponding soft overtravel fault bit is automatically cleared. However the soft overtravel fault stays through any attempt to clear it while the axis position is still beyond the specified travel limits while the axis is enabled.

Position Cam Lock Status

AXIS_CONSUMED

BOOL

Tag

Set whenever the master axis satisfies the starting condition of a currently active Position Cam motion profile. The starting condition is established by the Start Control and Start Position parameters of the MAPC instruction. This bit is bit is cleared when the current position cam profile completes, or is superseded by some other motion operation.

In unidirectional master direction mode, the Position Cam Lock Status bit is cleared when moving in the "wrong" direction and sets when moving in the "correct" direction.

Position Cam Pending Status

AXIS_CONSUMED

BOOL

Tag

Set if a Position Cam motion profile is currently pending the completion of a currently executing cam profile. This would be initiated by executing an MAPC instruction with Pending execution selected. This bit is cleared when the current position cam profile completes, initiating the start of the pending cam profile. This bit is also cleared if the position cam profile completes, or is superseded by some other motion operation.

Position Cam Status

AXIS_CONSUMED

BOOL

Tag

Set if a Position Cam motion profile is currently in progress. Cleared when the Position Cam is complete or is superseded by some other motion operation.

Position Data Scaling

AXIS_SERVO_DRIVE

INT

GSV

This attribute is derived from the Drive Units attribute. See IDN 76 in IEC 1491.

Position Data Scaling Exp

AXIS_SERVO_DRIVE

INT

GSV

This attribute is derived from the Drive Units attribute. See IDN 78 in IEC 1491.

Position Data Scaling Factor

AXIS_SERVO_DRIVE

DINT

GSV

This attribute is derived from the Drive Units attribute. See IDN 77 in IEC 1491.

Position Differential Gain

AXIS_SERVO

REAL

GSV

In some External Velocity Servo Drive applications where the level of damping provided by the external drive is insufficient for good position servo loop performance, additional damping may be achieved via the Position Loop Differential Gain.

Assuming a non-zero Position Loop Differential Gain value, the difference between the current Position Error value and the last Position Error value is computed. This value is then multiplied by the Position Loop Differential Gain to produce a component to the Servo Output or Velocity Command that attempts to correct for the change in position error, creating a "damping" effect.

Increasing this gain value results in greater "damping" of the axis.

Position Error

AXIS_SERVO

REAL

GSV

Important

: To use this attribute, choose it as one of the attributes for Real Time Axis Information for the axis. Otherwise, you won’t see the right value as the axis runs. See Axis Info Select 1.

Position Error in Position Units

Position Error is the difference, in configured axis Position Units, between the command and actual positions of an axis. For an axis with an active servo loop, position error is used, along with other error terms, to drive the motor to the condition where the actual position is equal to the command position.

Position Error Fault

AXIS_SERVO

BOOL

Tag

Set when the axis position error exceeds the Position Error Tolerance. This fault can only occur when the drive is in the enabled state.

The controller latches this fault. Use a Motion Axis Fault Reset (MAFR ) or Motion Axis Shutdown Reset (MASR) instruction to clear the fault.

Position Error Fault Action

AXIS_SERVO

SINT

GSV

Shutdown

Disable Drive

Stop Motion

Status Only

Position Error Tolerance

AXIS_SERVO

REAL

GSV

Position Units

The Position Error Tolerance parameter specifies how much position error the servo or drive tolerates before issuing a Position Error Fault. Like the position lock tolerance, the position error tolerance is interpreted as a ± quantity.

For example, specifying a position error tolerance of 0.75 Position Units means that a Position Error Fault is generated whenever the position error of the axis is greater than 0.75 or less than -0.75 Position Units, as shown below.

The self tuning routine sets the position error tolerance to twice the following error at maximum speed based on the measured response of the axis. In most applications, this value provides reasonable protection in case of an axis fault or stall condition without nuisance faults during normal operation.

If you need to change the calculated position error tolerance value, the recommended setting is 150% to 200% of the position error while the axis is running at its maximum speed.

Position Integral Gain

AXIS_SERVO

REAL

GSV

1/mSec-Sec

Position Integral Gain (Pos I Gain) improves the steady-state positioning performance of the system.

By using Position Integral Gain, it is possible to achieve accurate axis positioning despite the presence of such disturbances as static friction or gravity. Increasing the integral gain generally increases the ultimate positioning accuracy of the system. Excessive integral gain, however, results in system instability.

Every servo update, the current Position Error is accumulated in a variable called the Position Integral Error. This value is multiplied by the Position Integral Gain to produce a component to the Velocity Command that attempts to correct for the position error.

The characteristic of Pos I Gain correction, however, is that any non-zero Position Error accumulates in time to generate enough force to make the correction.

This attribute of Pos I Gain makes it invaluable in applications where positioning accuracy or tracking accuracy is critical. The higher the Pos I Gain value the faster the axis is driven to the zero Position Error condition. Unfortunately, Pos I Gain control is intrinsically unstable. Too much Pos I Gain results in axis oscillation and servo instability.

If the axis is configured for an external velocity loop servo drive, the Pos I Gain should be zero–most analog velocity loop servo amplifiers have integral gain of their own and do not tolerate any amount of Pos I Gain in the position loop without producing severe oscillations. If Pos I Gain is necessary for the application, the velocity integrator in the drive must be disabled.

In certain cases, Pos I Gain control is disabled. One such case is when the servo output to the axis’ drive is saturated. Continuing integral control behavior in this case would only exacerbate the situation. Another common case is when performing certain motion. When the Integrator Hold Enable attribute is set, the servo loop automatically disables the integrator during commanded motion.

While the Pos I Gain, if employed, is typically established by the automatic servo tuning procedure, the Pos I Gain value may also be set manually.

You can compute the Pos I Gain based on the current or computed value for the Pos P Gain using the following formula:

Pos I Gain = 0.25 * 0.001 Sec/mSec * (Pos P Gain)

2

Assuming a Pos P Gain value of 100 Sec

-1

this results in a Pos I Gain value of 2.5 ~0.1 mSec

-1

-Sec

-1

Position Integrator Error

AXIS_SERVO

REAL

GSV

Important

: To use this attribute, choose it as one of the attributes for Real Time Axis Information for the axis. Otherwise, you won’t see the right value as the axis runs. See Axis Info Select 1.

Position Integrator Error in Position Units - mSec

Position Integrator Error is the running sum of the Position Error, in the configured axis Position Units, for the specified axis. For an axis with an active servo loop, the position integrator error is used, along with other error terms, to drive the motor to the condition where the actual position is equal to the command position.

Position Lock Status

AXIS_SERVO

BOOL

Tag

If this bit is the following:

ON — The axis position error is less than or equal to the Position Lock Tolerance value of the axis.

OFF — The axis position error is greater than the Position Lock Tolerance value of the axis.

Position Lock Tolerance

AXIS_SERVO

REAL

GSV

Position Units

The Position Lock Tolerance attribute value specifies how much position error the motion module tolerates when giving a true Position Locked Status indication. When used in conjunction with the Position Locked Status bit, it is a useful parameter to control positioning accuracy. The Position Lock Tolerance value should be set, in Position Units, to the desired positioning accuracy of the axis.

Note that the position lock tolerance value is interpreted as a ± quantity. For example, if your position units are Inches, specifying a position lock tolerance of 0.01 provides a minimum positioning accuracy of ±0.01 inches as shown below.

Position Polarity

AXIS_SERVO_DRIVE

INT

GSV

This attribute is derived from the Drive Polarity attribute. See IDN 55 in IEC 1491.

Position Proportional Gain

AXIS_SERVO

REAL

GSV

1/Sec

The Position Error is multiplied by the Position Proportional Gain (Pos P Gain) to produce a component to the Velocity Command that tries to correct for the position error.

Increasing this gain increases the bandwidth of the position servo loop and results in greater static stiffness of the axis, which is a measure of the corrective force that is applied to an axis for a given position error.

Too little Pos P Gain results in excessively compliant, or mushy, axis behavior. Too large a Pos P Gain results in axis oscillation due to servo instability.

A well-tuned system moves and stops quickly and shows little or no ringing during constant velocity or when the axis stops. If the response time is poor, or the motion sloppy or slow, you may need to increase the proportional gain. If excessive ringing or overshoot is observed when the motor stops, you may need to decrease the proportional gain.

While the tuning procedure sets the Pos P Gain, you can also set it manually. You can compute the Pos P Gain based on either the desired loop gain or the desired bandwidth of the position servo system.

If you know the desired loop gain in Inches per Minute per mil or millimeters per minute per mil, use the following formula to calculate the corresponding P gain.

Pos P Gain = 16.667 * Desired Loop Gain (IPM/mil)

A loop gain of 1 IPM/mil (Pos P gain = 16.7 Sec

-1

) gives stable positioning for most axes. However, position servo systems typically run much tighter than this. The typical value for the Position Proportional Gain is ~100 Sec

-1

.

If you know the desired unity gain bandwidth of the position servo in Hertz, use the following formula to calculate the corresponding P gain.

Pos P Gain = Bandwidth (Hertz) / 6.28

Position servo systems typically run with at least a unity gain bandwidth of ~16 Hertz. The typical value for the Position Proportional Gain is ~100 Sec

-1

.

There are limitations to the maximum bandwidth that can be achieved for the position loop based on the dynamics of the inner velocity and torque loops of the system and the desired damping of the system, Z. These limitations may be expressed as follows:

Bandwidth (Pos) = 0.25 * 1/Z

2

* Bandwidth (Vel) = 0.25 * 1/Z

2

* Bandwidth (Torque)

For example, if the bandwidth of the drive’s torque loop is 100 Hz and the damping factor, Z, is 0.8, the velocity bandwidth is approximately 40 Hz and the position bandwidth is 16 Hz. Based on these numbers the corresponding proportional gains for the loops can be computed. Note that the bandwidth of the torque loop includes feedback sampling delay and filter time constant.

Position Servo Bandwidth

AXIS_SERVO

REAL

GSV

Hertz

The value for the Position Servo Bandwidth represents the unity gain bandwidth that is to be used to calculate the gains for a subsequent MAAT (Motion Apply Axis Tune) instruction.

The unity gain bandwidth is the frequency beyond which the position servo is unable to provide any significant position disturbance correction. In general, within the constraints of a stable servo system, the higher the Position Servo Bandwidth is the better the dynamic performance of the system.

A maximum value for the Position Servo Bandwidth is generated by the MRAT (Motion Run Axis Tune) instruction. Computing gains based on this maximum value via the MAAT instruction results in dynamic response in keeping with the current value of the Damping Factor described above.

Alternatively, the responsiveness of the system can be "softened" by reducing the value of the Position Servo Bandwidth before executing the MAAT instruction..

There are limitations to the maximum bandwidth that can be achieved for the position loop based on the dynamics of the inner velocity and current loops of the servo system and the desired damping of the system, Z. Exceeding these limits could result in an unstable system. These bandwidth limitations may be expressed as follows:

Max Position Bandwidth (Hz) = 0.25 * 1/Z

2

* Velocity Bandwidth (Hz)

For example, if the maximum bandwidth of the velocity servo loop is 40 Hz and the damping factor, Z, is 0.8, the maximum the maximum position bandwidth is 16 Hz. Based on these numbers the corresponding proportional gains for the loops can be computed.

Position Units

AXIS_CONSUMED

STRING

MSG

Fixed length string of 32 characters

The Position Units attribute can support an ASCII text string of up to 32 characters. This string is used by the

Logix Designer

application in the axis configuration dialogs to request values for motion-related parameters in the specified Position Units.

Position Unwind

AXIS_CONSUMED

DINT

GSV

Counts per Revolution

If the axis is configured as a rotary axis by setting the corresponding Rotary Axis bit Servo Configuration Bit word, a value for the Position Unwind attribute is required. This is the value used to perform automatic electronic unwind of the rotary axis.

Electronic unwind allows infinite position range for rotary axes by subtracting the unwind value from both the actual and command position every time the axis makes a complete revolution.

To avoid accumulated error due to round-off with irrational conversion constants the unwind value is requested in units feedback counts per axis revolution and must be an integer.

For example, suppose that a given axis is configured as a Rotary Axis with Position Units of "Degrees" and 10 feedback counts per degree. It is desired to unwind the axis position after every revolution. In this case, the Position Unwind attribute should be set to 3600 since there are 3600 feedback counts (10 * 360) per revolution of the axis.

Positive Dynamic Torque Limit

AXIS_SERVO_DRIVE

REAL

GSV

Important

: To use this attribute, choose it as one of the attributes for Real Time Axis Information for the axis. Otherwise, you won’t see the right value as the axis runs. See Axis Info Select 1.

%Rated

The currently operative maximum positive torque/current limit magnitude. The value should be the lowest value of all torque/current limits in the drive at a given time. This limit includes the amplifier peak limit, motor peak limit, user current limit, amplifier thermal limit, and the motor thermal limit.

Power Capacity

AXIS_SERVO_DRIVE

REAL

GSV

Important

: To use this attribute, choose it as one of the attributes for Real Time Axis Information for the axis. Otherwise, you won’t see the right value as the axis runs. See Axis Info Select 1.

The present utilization of the axis power supply as a percent of rated capacity.

Power Limit Status

AXIS_SERVO_DRIVE

BOOL

Tag

Set when the magnitude of the actual supplied power is greater than the configured Power Threshold.

Power Phase Loss Fault

AXIS_SERVO_DRIVE

BOOL

Tag

Set when the drive detects that one or more of the three power line phases is lost from the 3 phase power inputs.

Power Supply ID

AXIS_SERVO_DRIVE

INT

GSV

The Power Supply ID attribute contains the enumeration of the specific A-B Power Supply or System Module catalog numbers associated with the axis. If the Power Supply ID does not match that of the actual supply hardware, an error is generated during the drive configuration process.

Precharge Overload Fault

AXIS_SERVO_DRIVE

BOOL

Tag

The drive’s precharge resistor gets too hot if you cycle 3-phase power too many times. If that happens, this bit turns on.

Primary Operation Mode

AXIS_SERVO_DRIVE

INT

GSV

This attribute is derived from the Servo Loop Configuration attribute. See IDN 32 in IEC 1491.

Process Status

AXIS_SERVO

BOOL

Tag

Set when there is an axis tuning operation or an axis hookup diagnostic test operation in progress on the axis.

Programmed Stop Mode

AXIS_GENERIC

SINT

GSV

Determines how a specific axis will stop when the controller has a critical controller mode change or when an MGS (Motion Group Stop) instruction executes with it’s stop mode set to Programmed.

The modes of the controller are: Program Mode, Run Mode, Test Mode, and Faulted Mode. Any mode change into or out of program mode (prog->run, prog->test, run->prog & test->prog) will initiate a programmed stop for every axis owned by that controller.

Each individual axis can have its own Programmed Stop Mode configuration independent of other axes.

When the Programmed Stop Mode attribute is configured for Fast Stop, the axis is decelerated to a stop using the current configured value for Maximum Deceleration. Servo action is maintained after the axis motion has stopped.

When the Programmed Stop Mode attribute is configured for Fast Disable, the axis is decelerated to a stop using the current configured value for Maximum Deceleration. Servo action is maintained until the axis motion has stopped at which time the axis is disabled, that is, Drive Enable disabled, and Servo Action disabled

When configured for Hard Disable, the axis is immediately disabled, that is, Drive Enable disabled, Servo Action disabled, but the OK contact is left closed. Unless the drive is configured to provide some form of dynamic breaking, this results in the axis coasting to a stop.

When configured for Fast Shutdown, the axis is decelerated to a stop as with Fast Stop but, once the axis motion is stopped, the axis is placed in the Shutdown state, that is, Drive Enable disabled, servo action disabled, and the OK contact opened. To recover from the Shutdown state requires execution of one of the axis or group Shutdown Reset instructions (MASR or MGSR).

When configured for Hard Shutdown, the axis is immediately placed in the Shutdown state, that is, Drive Enable disabled, Servo Action disabled, and the OK contact opened. Unless the drive is configured to provide some form of dynamic breaking, this results in the axis coasting to a stop. To recover from the Shutdown state requires execution of one of the axis or group Shutdown Reset instructions (MASR or MGSR).

PWM Frequency Select

AXIS_SERVO_DRIVE

SINT

GSV

The PWM Frequency Select attribute controls the frequency of the pulse width modulated voltage applied to the motor by the drive’s power structure. Higher PWM Frequency values reduce torque ripple and motor noise based on the motor’s electrical time constant. Higher PWM frequencies, however, mean higher switching frequencies, which tends to produce more heat in the drive’s power structure. So, for applications that have high torque demands, a lower PWM frequency would be more appropriate.

0 = low frequency (default)

1 = high frequency

Reg 1 Input Status

AXIS_SERVO

BOOL

Tag

If this bit is the following:

ON — Registration 1 input is active.

OFF — Registration 1 input is inactive.

Reg 2 Input Status

AXIS_SERVO

BOOL

Tag

If this bit is the following:

ON — Registration 2 input is active.

OFF — Registration 2 input is inactive.

Reg Event 1 Armed Status

AXIS_CONSUMED

BOOL

Tag

Set when a registration checking has been armed for registration input 1 through execution of the MAR (Motion Arm Registration) instruction. Cleared when either a registration event occurs or a MDR (Motion Disarm Registration) instruction is executed for registration input 1.

Reg Event 1 Status

AXIS_CONSUMED

BOOL

Tag

Set when a registration event has occurred on registration input 1. Cleared when either another MAR (Motion Arm Registration) instruction or a MDR (Motion Disarm Registration) instruction is executed for registration input 1.

Reg Event 2 Armed Status

AXIS_CONSUMED

BOOL

Tag

Set when a registration checking has been armed for registration input 2 through execution of the MAR (Motion Arm Registration) instruction. Cleared when either a registration event occurs or a MDR (Motion Disarm Registration) instruction is executed for registration input 2.

Reg Event 2 Status

AXIS_CONSUMED

BOOL

Tag

Set when a registration event has occurred on registration input 2. Cleared when either another MAR (Motion Arm Registration) instruction or a MDR (Motion Disarm Registration) instruction is executed for registration input 2.

Registration 1 Position

AXIS_CONSUMED

REAL

Tag

Registration 1 Position in Position Units.

Registration 1 Event Task

AXIS_CONSUMED

DINT

MSG

These attributes show which task is triggered when the registration event happens.

An instance of 0 means that no event task is configured to be triggered by the registration event.

The task is triggered at the same time that the Process Complete bit is set for the instruction that armed the watch event.

The controller sets these attributes. Don’t set them by an external device.

Registration 1 Position

AXIS_CONSUMED

REAL

GSV

Position Units

Two registration position attributes are provided to independently store axis position associated with two different registration input events. The Registration Position value is the absolute position of a physical or virtual axis (in the position units of that axis) at the occurrence of the most recent registration event for that axis.

The figure below shows how the registration position is latched by the registration input when a registration event occurs. The latching mechanism can be implemented in the controller software (soft registration) or, for greater accuracy, in physical hardware (hard registration).

The Registration Latch mechanism is controlled by two Event Control instructions, MAR (Motion Arm Registration) and MDR (Motion Disarm Registration).

The accuracy of the registration position value, saved as a result of a registration event, is a function of the delay in recognizing the specified transition (typically 1 µsec for hardware registration) and the speed of the axis during this time. The uncertainty in the registration position is the distance traveled by the axis during this interval as shown by the equation below.

Use the formula given above to calculate the maximum registration position error for the expected axis speed. Alternatively, you can calculate the maximum axis speed for a specified registration accuracy by re-arranging this formula as shown below

       

Registration 1 Time

AXIS_CONSUMED

DINT

GSV

Lower 32 bits of CST time

The two Registration Time values contain the lower 32-bits of CST time at which their respective registration events occurred. Units for this attribute are in microseconds.

Resistive Brake Contact Delay

AXIS_SERVO_DRIVE

REAL

GSV

Sec

This attribute controls an optional external Resistive Brake Module (RBM). The RBM is between the drive and the motor and uses an internal contact to switch the motor between the drive and a resistive load. The drive’s RBM output controls this contact.

When the drive’s RBM output is energized, the RBM contact is switched from the load resistors to the UVW motor lines connecting the drive to the motor. This switching does not occur instantaneously and enabling the power structure too early can cause electrical arcing across the contact.

The resistive brake contact delay is the time that it takes to fully close the contact across the UVW motor lines. In order to prevent electrical arcing across the contact the enabling of the drive’s power structure is delayed.

The delay time is variable depending on the RBM model. When applying an RBM, you must set the Resistive Brake Contact Delay to the recommended value found in the RBM specification.

The following cases outline how the RBM output relates to the normal enable and disable sequences.

Rotary Axis

AXIS_CONSUMED

SINT

GSV

0 = Linear

1 = Rotary

When the Rotary Axis attribute is set true (1), it lets the axis unwind. This gives infinite position range by unwinding the axis position whenever the axis moves through a complete physical revolution. The number of encoder counts per physical revolution of the axis is specified by the Position Unwind attribute. For Linear operation, the counts don’t roll over. They are limited to +/- 2 billion.