AXIS Attributes (A-D)

Attribute

Axis Type

Data Type

Access

Description

Absolute Feedback Enable

AXIS_SERVO

SINT

GSV

Important:

Use this attribute only for an axis of a

This attribute controls whether or not the servo module uses the absolute position capability of the feedback device. If Absolute Feedback Enable is set to True, the servo module adds the Absolute Feedback Offset to the current position of the feedback device to establish the absolute machine reference position. Because absolute feedback devices retain their position reference even through a power-cycle, the machine reference system can be restored at power-up.

To establish a suitable value for the Absolute Feedback Offset attribute the MAH instruction may be executed with the Home Mode configured for Absolute (the only valid option when Absolute Feedback Enable is True). When executed, the servo module will compute the Absolute Feedback Offset as the difference between the configured value for Home Position and the current absolute feedback position of the axis. The computed Absolute Feedback Offset is immediately applied to the axis upon completion of the MAH instruction. Because the actual position of the axis is re-referenced during execution of the MAH instruction, the servo loop must not be active. If the servo loop is active the MAH instruction errors.

If Absolute Feedback Enable is set to False, the servo module ignores the Absolute Feedback Offset and treats the feedback device as an incremental position transducer. In this case, a homing or redefine position operation is therefore needed to establish the absolute machine reference position. The Absolute Home Mode in this case is considered invalid.

This attribute is configurable if the Transducer Type is set to SSI. For an LDT transducer the Absolute Feedback Enable is forced to True. For an AQB transducer the Absolute Feedback Enable is forced to False.

Absolute Feedback Offset

AXIS_SERVO

REAL

GSV

SSV

Position Units

Important:

Use this attribute only for an axis of a 1756-HYD02 or 1756-M02AS module.

Set the Absolute Feedback Enable attribute to True.

This attribute is used to determine the relative distance between the absolute position of the feedback device and the absolute position of the machine. At power-up this attribute is sent to the servo module and added to the current position of the feedback device to restore the absolute machine position reference.

If the axis is configured for Linear operation, absolute position may be recovered after power cycle as long as the feedback device has not exceeded its range limit. If the feedback device rolls over its count range, the absolute position of the axis is no longer valid.

If the axis is configured for Rotary operation, the servo module is responsible for adjusting the Absolute Feedback Offset dynamically based on the configured Unwind value and the rollover of the absolute feedback device. If necessary, absolute position may be recovered after power cycle by periodically updating the controller’s Absolute Feedback Offset value. This can be done by selecting the Absolute Feedback Offset enumeration for one of the Axis Info Select attributes.

Absolute Reference Status

AXIS_SERVO_DRIVE

BOOL

Tag

If the bit is

:

        

ON

OFF

Accel Limit Status

AXIS_SERVO Drive

BOOL

Tag

Set when the magnitude of the commanded acceleration to the velocity servo loop input is greater than the configured Velocity Limit.

Accel Status

AXIS_CONSUMED

BOOL

Tag

Set if the axis is currently being commanded to accelerate.

Use the Accel Status bit and the Decel Status bit to see if the axis is accelerating or decelerating. If both bits are off, then the axis is moving at a steady speed or is at rest.

Acceleration Command

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.

Acceleration Command in Position Units / Sec2

Acceleration Command is the current acceleration reference to the output summing junction, in the configured axis Position Units per Second

2

, for the specified axis. The Acceleration Command value, hence, represents the output of the inner velocity control loop. Acceleration Command is not to be confused with Command Velocity, which represents the rate of change of Command Position input to the position servo loop.

Acceleration Data Scaling

AXIS_SERVO_DRIVE

INT

GSV

This attribute is derived from the Drive Units attribute. See IDN 160 in IEC 1491.

Acceleration Data Scaling Exp

AXIS_SERVO_DRIVE

INT

GSV

This attribute is derived from the Drive Units attribute. See IDN 162 in IEC 1491.

Acceleration Data Scaling Factor

AXIS_SERVO_DRIVE

INT

GSV

This attribute is derived from the Drive Units attribute. See IDN 161 in IEC 1491.

Acceleration Feedback

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.

Acceleration Feedback in Position Units / Sec2

Acceleration Feedback is the actual velocity of the axis as estimated by the servo module, in the configured axis Position Units per Second

2

. The Estimated Acceleration is calculated by taking the difference in the Estimated Velocity over the servo update interval. Acceleration Feedback is a signed value—the sign (+ or -) depends on which direction the axis is currently moving.

Acceleration Feedforward Gain

AXIS_SERVO

REAL

GSV

%

When you connect to a torque servo drive, use the Acceleration Feedforward Gain to give the Torque Command output necessary to generate the commanded acceleration. It does this by scaling the current Command Acceleration by the Acceleration Feedforward Gain and adding it as an offset to the Servo Output generated by the servo loop. With this done, the servo loops do not need to generate much of a contribution to the Servo Output, hence the Position and/or Velocity Error values are significantly reduced. Hence, when used in conjunction with the Velocity Feedforward Gain, the Acceleration Feedforward Gain lets the following error of the servo system during the acceleration and deceleration phases of motion be reduced to nearly zero. This is important in applications such as electronic gearing and synchronization where the actual axis position must not significantly lag behind the commanded position at any time.

When you connect to a velocity servo drive, use Acceleration Feedforward to add a term to the Velocity Command that is proportional to the commanded acceleration. This can be effective in cases where the external drive shows a steady-state velocity error during acceleration and deceleration.

The best value for Acceleration Feedforward depends on the drive configuration. Excessive Acceleration Feedforward values tend to produce axis overshoot. For torque servo drive applications the best value for Acceleration Feedforward is theoretically 100%. However, the value may need to be increased slightly to accommodate servo loops with non-infinite loop gain and other application considerations. For velocity servo drive applications the best value for Acceleration Feedforward is highly dependent on the drive’s speed scaling and servo loop configuration. A value of 100%, in this case, means only that 100% of the commanded acceleration value is applied to the velocity command summing junction and may not be even close to the optimal value.

To find the best Acceleration Feedforward Gain, run a simple project that jogs the axis in the positive direction and monitors the Position Error of the axis during the jog. Usually Acceleration Feedforward is used in tandem with Velocity Feedforward to achieve near zero following error during the entire motion profile. To fine tune the Acceleration Feedforward Gain, the Velocity Feedforward Gain must first be optimized using the procedure described above. While capturing the peak Position Error during the acceleration phase of the jog profile, increase the Acceleration Feedforward Gain until the peak Position Error is as small as possible, but still positive. If the peak Position Error during the acceleration ramp is negative, the actual position of the axis is ahead of the command position during the acceleration ramp. If this occurs, decrease the Acceleration Feedforward Gain such that the Position Error is again positive. To be thorough the same procedure should be done for the deceleration ramp to verify that the peak Position Error during deceleration is acceptable. Note that reasonable maximum velocity, acceleration, and deceleration values must be entered to jog the axis.

The Acceleration Feedforward Gain attribute is used to provide the Torque Command output necessary to generate the commanded acceleration. It does this by scaling the current Command Acceleration by the Acceleration Feedforward Gain and adding it as an offset to the Servo Output generated by the servo loop. With this done, the servo loops do not need to generate much control effort, hence the Position and/or Velocity Error values are significantly reduced. When used in conjunction with the Velocity Feedforward Gain, the Acceleration Feedforward Gain allows the following error of the servo system during the acceleration and deceleration phases of motion to be reduced to nearly zero. This is important in applications such as electronic gearing and synchronization applications where it is necessary that the actual axis position not significantly lag behind the commanded position at any time.

The optimal value for Acceleration Feedforward is 100% theoretically. In reality, however, the value may need to be tweaked to accommodate torque loops with non-infinite loop gain and other application considerations. One thing that may force a smaller Acceleration Feedforward value is that increasing amounts of feedforward tends to exacerbate axis overshoot.

When necessary, the Acceleration Feedforward Gain may be "tweaked" from the 100% value by running a simple user program that jogs the axis in the positive direction and monitors the Position Error of the axis during the jog. Usually Acceleration Feedforward is used in tandem with Velocity Feedforward to achieve near zero following error during the entire motion profile. To fine-tune the Acceleration Feedforward Gain, the Velocity Feedforward Gain must first be optimized using the procedure described above. While capturing the peak Position Error during the acceleration phase of the jog profile, increase the Acceleration Feedforward Gain until the peak Position Error is as small as possible, but still positive. If the peak Position Error during the acceleration ramp is negative, the actual position of the axis is ahead of the command position during the acceleration ramp. If this occurs, decrease the Acceleration Feedforward Gain such that the Position Error is again positive. To be thorough the same procedure should be done for the deceleration ramp to verify that the peak Position Error during deceleration is acceptable. Note that reasonable maximum velocity, acceleration, and deceleration values must be entered to jog the axis.

Acceleration Limit Bipolar

AXIS_SERVO_DRIVE

REAL

GSV

Position Units / sec

2

This attribute maps directly to a SERCOS IDN. See the SERCOS Interface standard for a description. This attribute is automatically set. You usually do not have to change it.

Acceleration Limit Negative

AXIS_SERVO_DRIVE

REAL

GSV

Position Units / sec

2

This attribute maps directly to a SERCOS IDN. See the SERCOS Interface standard for a description. This attribute is automatically set. You usually do not have to change it.

Acceleration Limit Positive

AXIS_SERVO_DRIVE

REAL

GSV

Position Units / sec

2

This attribute maps directly to a SERCOS IDN. See the SERCOS Interface standard for a description. This attribute is automatically set. You usually do not have to change it.

Actual Acceleration

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.

Actual Acceleration in Position Units / Sec2

Actual Acceleration is the current instantaneously measured acceleration of an axis, in the configured axis Position Units per second per second. It is calculated as the current increment to the actual velocity per coarse update interval. Actual Acceleration is a signed value — the sign (+ or -) depends on which direction the axis is currently accelerating.

Actual Acceleration is a signed floating-point value. Its resolution does not depend on the Averaged Velocity Timebase, but rather on the conversion constant of the axis and the fact that the internal resolution limit on actual velocity is 1 feedback counts per coarse update period per coarse update period.

Actual Position

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.

Actual Position in Position Units

Actual Position is the current absolute position of an axis, in the configured Position Units of that axis, as read from the feedback transducer. Note, however, that this value is based on data reported to the controller as part of an ongoing synchronous data transfer process which results in a delay of one coarse update period. Thus, the Actual Position value that is obtained is the actual position of the axis one coarse update period ago.

Actual Velocity

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.

Actual Velocity in Position Units / Sec

Actual Velocity is the current instantaneously measured speed of an axis, in the configured axis Position Units per second. It is calculated as the current increment to the actual position per coarse update interval. Actual Velocity is a signed value—the sign (+ or -) depends on which direction the axis is currently moving.

Actual Velocity is a signed floating-point value. Its resolution does not depend on the Averaged Velocity Timebase, but rather on the conversion constant of the axis and the fact that the internal resolution limit on actual velocity is 1 feedback counts per coarse update.

Analog Input 1

AXIS_SERVO

REAL

GSV

This attribute applies only to an axis associated Analog Input 2, a Kinetix7000 Drive. This attribute with an integer range of +/-16384, represents the analog value of an analog device connected to the Kinetix7000 drive's analog input(s). These inputs are useful for web/converting applications with load cell (measuring web force on a roller) or dancer (measuring web force/position directly), which can be directly connected to the drive controlling the web.

Attribute Error Code

AXIS_SERVO

INT

GSV*

CIP Error code returned by erred set attribute list service to the module.

When an Axis Configuration Fault occurs, one or more axis parameters associated with a motion module or device has not been successfully updated to match the value of the corresponding parameter of the local controller. The fact that the configuration of the axis no longer matches the configuration of the local controller is a serious fault and results in the shutdown of the faulted axis. The Attribute Error Code is reset to zero by reconfiguration of the motion module.

Axis Configuration Fault information is passed from the motion module or device to the controller via a 16-bit CIP status word contained in the Set Attribute List service response received by the controller. A Set Attribute List service to the motion module can be initiated by a software Set Attribute List service to the controller, or by an SSV instruction within the controller’s program, referencing a servo attribute. Various routines that process responses to motion services are responsible for updating these attributes.

The Set and Get service responses provide a status response with each attribute that was processed. That status value is defined by CIP as follows: UINT16, Values 0-255 (0x00-0xFF) are reserved to mirror common service status codes. Values 256 – 65535 are available for object/class attribute specific errors.

Attribute Error ID

AXIS_SERVO

INT

GSV*

Attribute ID associated with non-zero Attribute Error Code.

The Attribute Error ID is used to retain the ID of the servo attribute that returned a non-zero attribute error code resulting in an Axis Configuration Fault. The Attribute Error ID defaults to zero and, after a fault has occurred may be reset to zero by reconfiguration of the motion module.

To quickly see the Attribute Error in the

Logix Designer

application, do the following.

Aux 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

If the bits are:

0

0       

1

0       

0

1       

1

1       

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.

Aux Feedback Fault

AXIS_SERVO

BOOL

Tag

Set for an auxiliary feedback source 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.

Aux Feedback Interpolation Factor

AXIS_SERVO_DRIVE

DINT

GSV

Feedback Counts per Cycle

The Feedback Interpolation attributes establish how many Feedback Counts there are in one Feedback Cycle. The Feedback Interpolation Factor depends on both the feedback device and the drive feedback circuitry. Quadrature encoder feedback devices and the associated drive feedback interface typically support 4x interpolation, so the Interpolation Factor for these devices would be set to 4 Feedback Counts per Cycle (Cycles are sometimes called Lines). High Resolution Sin/Cosine feedback device types can have interpolation factors as high as 2048 Counts per Cycle. The product of the Feedback Resolution and the corresponding Feedback Interpolation Factor is the overall resolution of the feedback channel in Feedback Counts per Feedback Unit. In our example, a Quadrature encoder with a 2000 line/rev resolution and 4x interpolation factor would have an overall resolution of 8000 counts/rev.

Aux 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 the following.

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.

Aux Feedback Ratio

AXIS_SERVO_DRIVE

FLOAT

GSV

Aux Feedback Units per Motor Feedback Unit

The Aux Feedback Ratio attribute represents the quantitative relationship between auxiliary feedback device and the motor. For a rotary auxiliary feedback device, this attribute’s value should be the turns ratio between the auxiliary feedback device and the motor shaft. For linear auxiliary feedback devices, this attribute value would typically represent the feed constant between the motor shaft and the linear actuator.

The Aux Feedback Ratio attribute is used in calculating range limits and default value calculations during configuration based on the selected motor’s specifications. The value is also used by the drive when running the dual feedback servo loop configuration.

Aux Feedback Resolution

AXIS_SERVO_DRIVE

DINT

GSV

Cycles per Aux 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.

Aux Feedback Type

AXIS_SERVO_DRIVE

INT

GSV

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

Aux 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

Aux Position Feedback

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.

Auxiliary Position Feedback in Position Units

Aux Position Feedback is the current value of the position feedback coming from the auxiliary feedback input.

Average Velocity

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.

Average Velocity in Position Units / Sec

Average Velocity is the current speed of an axis in the configured Position Units per second of the axis. Unlike the Actual Velocity attribute value, it is calculated by averaging the actual velocity of the axis over the configured Average Velocity Timebase for that axis.

Average velocity is a signed value. The sign doesn't necessarily show the direction that the axis is currently moving. It shows the direction the average move is going. The axis may be currently moving in the opposite direction.

The resolution of the Average Velocity variable is determined by the current value of the Averaged Velocity Timebase parameter and the configured Conversion Constant (feedback counts per Position Unit) for the axis.

The greater the Average Velocity Timebase value, the better the speed resolution but the slower the response to changes in speed.

The minimum Average Velocity Timebase value is the Coarse Update period of the motion group.

The Average Velocity resolution in Position Units per second may be calculated using the equation below.

For example, on an axis with position units of inches and a conversion constant (K) of 20000, an averaged velocity time-base of 0.25 seconds results in an average velocity resolution of the following.

Average Velocity Timebase

AXIS_CONSUMED

REAL

GSV

Sec

The Average Velocity Timebase attribute is used to specify the desired time in seconds to be used for calculating the Average Velocity of the axis. When the Average Velocity Value is requested, the value is computed by taking the total distance traveled by the axis in the amount of time given by the Average Velocity Timebase and dividing this value by the timebase.

The Average Velocity Timebase value should be large enough to filter out the small changes in velocity which would otherwise result in a "noisy" velocity value, but small enough to track significant changes in axis velocity. Typically, a value between 0.25 and 0.5 seconds works well for most applications.

Axis Address

AXIS_CONSUMED

GSV

Used for debugging.

Axis Configuration State

AXIS_CONSUMED

SINT

GSV

State of the axis configuration state machine

The Axis Configuration State attribute is used for debugging to indicate where in the axis configuration state-machine this axis presently is. Even consumed and virtual axes will utilize this attribute.

If the attribute is as follows:

128 — the axis is configured and ready for use.

Not 128 — the axis isn't configured.

Axis Control Bits

AXIS_SERVO

DINT

GSV

Bits

0 = Abort Process Request

Abort Process

If this bit is set, any active tuning or test process on the axis is aborted.

Shutdown Request

If this bit is set, the axis is forced into the shutdown state. For an AXIS_SERVO data type, the OK contact opens and the DAC output goes to 0.

Zero DAC Request — Only for AXIS_SERVO Data Type

If this bit is set, the servo module forces the DAC output for the axis to zero volts. This bit only has an affect if the axis is in the

Direct Drive

State with the drive enabled but no servo action.

Abort Home Request

If this bit is set, any active homing procedures are cancelled.

Abort Event Request

If this bit is set, any active registration or watch event procedures are cancelled.

Change Cmd Reference

If this bit is set, the controller switches to a new position coordinate system for command position. The servo module or drive uses this bit when processing new command position data from the controller to account for the offset implied by the shift in the reference point. The bit is cleared when the axis acknowledges completion of the reference position change by clearing its Change Position Reference bit.

Axis Data Type

AXIS_CONSUMED

SINT

MSG

Associated motion axis tag data type:

0 = Feedback

1 = Consumed

2 = Virtual

3 = Generic

4 = Servo

5 = Servo Drive

6 = Generic Drive

The Axis Data Type attribute is used to determine which data template, memory format, and set of attributes are created and applicable for this axis instance. This attribute can only be set as part of an axis create service.

Feedback

A feedback-only axis associated with feedback-only modules like PLS II and CFE, supporting, for example, quadrature encoder, resolver, and HiperFace.

Consumed

A consumed axis that consumes axis motion data produced by a motion axis on another controller.

Virtual

A virtual axis having full motion planner operation, but not associated with any physical device.

Generic

An axis with full motion planner functionality, but no integrated configuration support. Generic axes are associated with devices such as the 1756-DM.

Servo

An axis with full motion planner functionality and integrated configuration support. Servo axes are associated with modules closing a servo loop and sending an analog command to an external drive, that is, 1756-M02AE, 1756-HYD02, and 1756-M02AS modules.

Servo Drive

An axis with full motion planner functionality and integrated configuration support. Servo Drive axes are associated with digital drive interface modules sending a digital command to the external drive, that is, 1756-M03SE, 1756-M08SE, and 17556-M16SE (SERCOS interface).

Generic Drive

An axis of a SERCOS interface drive that is Extended Pack Profile compliant and on the ring of a 1756-M08SEG module.

Axis Event

AXIS_CONSUMED

DINT

Tag

Lets you access all the event status bits in one 32-bit word. This tag is the same as the Axis Event Bits attribute.

Event Status	Bit
Watch Event Armed Status	0
Watch Event Status	1
Reg Event 1 Armed Status	2
Reg Event 1 Status	3
Reg Event 2 Armed Status	4
Reg Event 2 Status	5
Home Event Armed Status	6
Home Event Status	7

Axis Event Bits

AXIS_CONSUMED

DINT

GSV

Lets you access all the event status bits in one 32-bit word. This attribute is the same as the Axis Event tag.

Event Status	Bit
Watch Event Armed Status	0
Watch Event Status	1
Reg Event 1 Armed Status	2
Reg Event 1 Status	3
Reg Event 2 Armed Status	4
Reg Event 2 Status	5
Home Event Armed Status	6
Home Event Status	7

Axis Fault

AXIS_CONSUMED

DINT

Tag

The axis faults for your axis is as follows:

Type of Fault	Bit
Physical Axis Fault	0
Module Fault	1
Config Fault	2

This attribute is the same as the Axis Fault Bits attribute.

Axis Fault Bits

AXIS_CONSUMED

DINT

GSV*

The axis faults for your axis is as follows:

Type of Fault	Bit
Physical Axis Fault	0
Module Fault	1
Config Fault	2
Group Fault	3

This attribute is the same as the Axis Fault tag.

Axis Info Select 1

Axis Info Select 2

AXIS_SERVO

AXIS_SERVO_DRIVE

DINT

GSV

GSV

An axis has a group of attributes that don’t get updated by default.

To use one of them, you must choose it for Real Time Axis Information for the axis. Otherwise, its value won’t change and you won’t see the right value as the axis runs.

You can choose up to 2 of these attributes.

To use a GSV instruction to choose an attribute for Real Time Axis Information, set the Axis Info Select 1 or Axis Info Select 2 attribute to the following.

AXIS_SERVO	AXIS_SERVO_DRIVE	Value
None (default)	None (default)	1
Position Command	Position Command	2
Position Feedback	Position Feedback	3
Aux Position Feedback	Aux Position Feedback	4
Position Error	Position Error	5
Position Integrated Error	Position Integrated Error	6
Velocity Command	Velocity Command	7
Velocity Error	Velocity Error	8
Velocity Integrated Error	Velocity Integrated Error	9
Acceleration Command	Acceleration Command	10
Acceleration Feedback	Acceleration Feedback	11
Servo Output Level		12
Marker Distance	Marker Distance	13
	Torque Command	14
	Torque Feedback	15
	Positive Dynamic Torque Limit	16
	Negative Dynamic Torque Limit	17
	Motor Capacity	18
	Drive Capacity	19
	Power Capacity	20
	Bus Regulator Capacity	21
	Motor Electrical Angle	22
	Torque Limit Source	23
	DC Bus Voltage	24
Absolute Offset		25

Axis Instance

AXIS_CONSUMED

INT

GSV

Instance Number assigned to Axis

The Axis Instance attribute is used to return the instance number of an axis. Major fault records generated for an axis major fault contains only the instance of the offending axis. This attribute would then typically be used by a user to determine if this was the offending axis; that is, if the instance number matches.

Axis Response Bits

AXIS_SERVO

DINT

GSV

Bits

0 = Abort Process Acknowledge

1 = Shutdown Acknowledge

2 = Zero DAC Acknowledge

3 = Abort Home Acknowledge

4 = Abort Event Acknowledge

5-14 = Reserved

15 = Change Pos Reference

Abort Process Acknowledge

If this bit is set, the tuning or test process has been aborted.

Shutdown Acknowledge

If this bit is set, the axis has been forced into the shutdown state.

Zero DAC Acknowledge — Only for AXIS_SERVO Data Type

If this bit is set, the DAC output for the axis has been set to zero volts.

Abort Home Acknowledge

If this bit is set, the active home procedure has been aborted.

Abort Event Acknowledge

If this bit is set, the active registration or watch position event procedure has been aborted.

Change Pos Reference

If this bit is set, the Servo loop has switched to a new position coordinate system. The controller uses this bit when processing new position data from the servo module or drive to account for the offset implied by the shift in the reference point. The bit is cleared when the controller acknowledges completion of the reference position change by clearing its Change Cmd Reference bit.

Axis State

AXIS_CONSUMED

SINT

GSV

Operating state of the axis.

0 = Axis Ready

Axis Status

AXIS_CONSUMED

DINT

Tag

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

Axis Status	Bit
Servo Action Status	0
Drive Enable Status	1
Shutdown Status	2
Config Update In Process	3
Inhibit Status	4

Axis Status Bits

AXIS_CONSUMED

DINT

GSV*

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

Axis Status	Bit
Servo Action Status	0
Drive Enable Status	1
Shutdown Status	2
Config Update In Process	3
Inhibit Status	4

Axis Type

AXIS_GENERIC

INT

GSV

The Axis Type attribute is used to establish the intended use of the axis.

If:	Then set the attribute to:
the axis is unused in the application, which is a common occurrence when there are an odd number of axes in the system	0
you only want the position information from the feedback interface	1
the axis is intended for full servo operation	2

Axis Type is not only used to qualify many operations associated with the axis servo loop, it also controls the behavior of the servo module’s Axis Status LEDs. An Axis Type of "1" (Feedback Only) results in the DRIVE LED being blanked, while a value of "0" (Unused) blanks both the FDBK and DRIVE LEDs.

The

Logix Designer

application also uses the current configured value for Axis Type to control the look of many of the dialogs associated with configuring an axis.

Backlash Reversal Offset

AXIS_SERVO

REAL

GSV

Backlash Reversal Offset provides the user the capability to compensate for positional inaccuracy introduced by mechanical backlash. For example, power-train type applications require a high level of accuracy and repeatability during machining operations. Axis motion is often generated by a number of mechanical components such as a motor, a gearbox, and a ball-screw, which can introduce inaccuracies and which are subject to wear over their lifetime. Hence, when an axis is commanded to reverse direction, mechanical play in the machine (through the gearing, ball-screw, and so on.) may result in a small amount of motor motion without axis motion. As a result, the feedback device may indicate movement even though the axis has not physically moved.

Compensation for mechanical backlash can be achieved by adding a directional offset, specified by the Backlash Reversal Offset attribute, to the motion planner’s command position as it is applied to the associated servo loop. Whenever the commanded velocity changes sign (a reversal), the Logix controller adds, or subtracts, the Backlash Distance value from the current commanded position. This causes the servo to immediately move the motor to the other side of the backlash window and engage the load. It is important to note that the application of this directional offset is completely transparent to the user; the offset does not have any affect on the value of the Command Position attribute.

If a value of zero is applied to the Backlash Reversal Offset, the feature is effectively disabled. Once enabled by a non-zero value, and the load is engaged by a reversal of the commanded motion, changing the Backlash Reversal Offset can cause the axis to shift as the offset correction is applied to the command position.

Backlash Stabilization Window

AXIS_SERVO

REAL

GSV

The Backlash Stabilization Window attribute is used to control the Backlash Stabilization feature in the servo control loop. What follows is a description of this feature and the general backlash instability phenomenon..

Mechanical backlash is a common problem in applications that utilize mechanical gearboxes. The problem stems from the fact that until the input gear is turned to the point where its proximal tooth contacts an adjacent tooth of the output gear, the reflected inertia of the output is not felt at the motor. In other words, when the gear teeth are not engaged, the system inertia is reduced to the motor inertia.

If the servo loop is tuned for peak performance with the load applied, the axis is at best under-damped and at worst unstable in the condition where the gear teeth are not engaged. In the worst case scenario, the motor axis and the input gear oscillates wildly between the limits imposed by the output gear teeth. The net effect is a loud buzzing sound when the axis is at rest. If this situation persists the gearbox wears out prematurely. To prevent this condition, the conventional approach is to de-tune the servo so that the axis is stable without the gearbox load applied. Unfortunately, system performance suffers.

Due to its non-linear, discontinuous nature, adaptive tuning algorithms generally fall short of addressing the backlash problem. However, a very effective backlash compensation algorithm can be demonstrated using the Torque Scaling gain. The key to this algorithm is the tapered Torque Scaling profile as a function of the position error of the servo loop. The reason for the tapered profile, as opposed to a step profile, is that when the position error exceeds the backlash distance a step profile would create a very large discontinuity in the torque output. This repulsing torque tends to slam the axis back against the opposite gear tooth and perpetuate the buzzing effect. The tapered Torque Scaling profile is only run when the acceleration command to the servo loop is zero, that is, when we are not commanding any acceleration or deceleration that would engage the teeth of the gearbox.

Properly configured with a suitable value for the Backlash Stabilization Window, this algorithm entirely eliminates the gearbox buzz without sacrificing any servo performance. The Backlash Stabilization parameter determines the width of the window over which backlash stabilization is applied. In general, this value should be set to the measured backlash distance. A Backlash Stabilization Window value of zero effectively disables the feature. (Patent Pending)

Brake Engage Delay Time

AXIS_SERVO_DRIVE

REAL

GSV

Sec

The Brake Engage Delay attribute controls the amount of time that the drive continues to apply torque to the motor after the motor brake output is changed to engage the brake. This gives time for the motor brake to engage.

The following is the sequence of events associated with engaging the motor brake:

Disable axis is initiated (via MSF or drive disable fault action)

Drive stops tracking command reference, (Servo Action Status bit clears.)

Decel to zero speed using configured Stopping Torque.

Zero speed or Stopping Time Limit is reached.

Turn motor brake output off to engage the motor brake.

Wait Brake Engage Delay Time.

Disable the drive power structure. (Drive Enable Status bit clears.)

If the axis is shutdown through either a fault action or motion instruction the drive power structure is disabled immediately and the motor brake is engaged immediately.

Drive stops tracking command reference. (Servo Action Status bit clears.)

Disable drive power structure, (Drive Enable Status bit clears.)

Turn off brake output to engage brake.

Brake Release Delay Time

AXIS_SERVO_DRIVE

REAL

GSV

Sec

The Brake Release Delay attribute controls the amount of time that the drive holds off tracking command reference changes after the brake output is changed to release the brake. This gives time for the brake to release.

The following is the sequence of events associated with engaging the brake:

Enable axis is initiated (via MSO or MAH)

Drive power structure enabled. (Drive Enable Status bit sets.)

Turn motor brake output on to release the brake.**

Wait Brake Release Delay Time.

Track command reference. (Servo_Action_Status bit sets)

**The drive does not release the brake unless there is holding torque.

Bus Ready Status

AXIS_SERVO_DRIVE

BOOL

Tag

If the bit is:

ON — The voltage of the drive’s dc bus is high enough for operation.

OFF — The voltage of the drive’s dc bus is too low.

Bus Regulator 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 bus regulator as a percent of rated capacity.

Bus Regulator ID

AXIS_SERVO_DRIVE

INT

GSV

The Bus Regulator ID attribute contains the enumeration of the specific A-B Bus Regulator or System Shunt catalog numbers associated with the axis. If the Bus Regulator ID does not match that of the actual bus regulator or shunt hardware, an error is generated during the drive configuration process.

C2C Connection Instance

AXIS_CONSUMED

SINT

GSV

Producer/Consumed axis’s associated C2C connection instance in reference to the C2C map instance

When Axis Data Type is specified to be ’r;Consumed’ then this axis is associated to the consumed data by specifying both the C2C Map Instance and the C2C Connection Instance. This attribute is the connection instance under the C2C map instance, which provides the axis data being sent to it from another axis via a C2C connection.

For all other Axis Data Types if this axis is to be produced then this attribute is set to the connection instance under the local controller’s map instance (1) that is used to send the remote axis data via the C2C connection.

C2C Map Instance

AXIS_CONSUMED

SINT

GSV

Producer/Consumed axis’s associated C2C map instance

When the Axis Data Type attribute is specified to be ’r;Consumed’ then this axis is associated to the consumed data by specifying both the C2C Map Instance and the C2C Connection Instance. For all other Axis Data Types if this axis is to be produced then this attribute is set to 1 (one) to indicate that the connection is off of the local controller’s map instance.

Command Acceleration

AXIS_CONSUMED

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.

Command Acceleration in Position Units / Sec2

Command Acceleration is the commanded speed of an axis, in the configured axis Position Units per second per second, as generated by any previous motion instructions. It is calculated as the current increment to the command velocity per coarse update interval. Command Acceleration is a signed value—the sign (+ or -) depends on which direction the axis is being commanded to move.

Command Acceleration is a signed floating-point value. Its resolution does not depend on the Averaged Velocity Timebase, but rather on the conversion constant of the axis and the fact that the internal resolution limit on command velocity is 0.00001 feedback counts per coarse update period per coarse update period.

Command Position

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.

Command Position in Position Units

Command Position is the desired or commanded position of a physical axis, in the configured Position Units of that axis, as generated by the controller in response to any previous motion Position Control instruction. Command Position data is transferred by the controller to a physical axis as part of an ongoing synchronous data transfer process which results in a delay of one coarse update period. Thus, the Command Position value that is obtained is the command position that is acted upon by the physical servo axis one coarse update period from now.

The figure below shows the relationship between Actual Position, Command Position, and Position Error for an axis with an active servo loop. Actual Position is the current position of the axis as measured by the feedback device (for example, encoder). Position error is the difference between the Command and Actual Positions of the servo loop, and is used to drive the motor to make the actual position equal to the command position.

Command position is useful when performing motion calculations and incremental moves based on the current position of the axis while the axis is moving. Using command position rather than actual position avoids the introduction of cumulative errors due to the position error of the axis at the time the calculation is performed.

Command Velocity

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.

Command position is useful when performing motion calculations and incremental moves based on the current position of the axis while the axis is moving. Using command position rather than actual position avoids the introduction of cumulative errors due to the position error of the axis at the time the calculation is performed.

Command Bus Fault

AXIS_SERVO_DRIVE

BOOL

Tag

The drive shuts down if you give it 3-phase power while it’s configured for Common Bus Follower mode. If that happens, this bit turns on.

Communication Fault

AXIS_SERVO_DRIVE

DINT

BOOL

Set when the commutation feedback source associated with the drive axis has a problem that prevents the drive from receiving accurate or reliable motor shaft information to perform commutation.

Config Fault

AXIS_CONSUMED

BOOL

Tag

Set when an update operation targeting an axis configuration attribute of an associated motion module has failed. Specific information concerning the Configuration Fault may be found in the Attribute Error Code and Attribute Error ID attributes associated with the motion module.

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.

Config Update In Process

AXIS_CONSUMED

BOOL

Tag

When you use an SSV instruction to change an attribute, the controller sends the change to the motion module. If you want to wait until the change is done, monitor the ConfigUpdateInProcess bit of the axis.

If the bit is:

ON — The controller is changing the attribute.

OFF — The change is done.

Continuous Torque Limit

AXIS_SERVO_DRIVE

REAL

GSV

%Rated

The Torque limit attribute provides a method for controlling the continuous torque limit imposed by the drive’s thermal model of the motor. Increasing the Continuous Torque Limit increases the amount of continuous motor torque allowed before the drive either folds back the motor current or the drive declares a motor thermal fault. Motors equipped with special cooling options can be configured with a Continuous Torque Limit of greater than 100% rated to attain higher continuous torque output from the motor. Motors operating in high ambient temperature conditions can be configured with a Continuous Torque Limit of less than 100% rated torque to protect the motor from overheating.

The Continuous Torque Limit specifies the maximum percentage of the motor's rated current that the drive can command on a continuous or RMS basis. For example, a Continuous Torque Limit of 150% limits the continuous current delivered to the motor to 1.5 times the continuous current rating of the motor.

Control Sync Fault

AXIS_CONSUMED

BOOL

Tag

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

The controller can miss up to 4 position updates. After that, the Control Sync Fault bit is set. The motion module may fault later or may already be faulted.

For a consumed axis, this bit means that communication is lost with the producing controller.

This bit clears when communication is reestablished.

Controlled By Transform Status

AXIS_CONSUMED

BOOL

Tag

If the bit is:

ON — A transform is moving the axis.

OFF — A transform is not moving the axis.

Conversion Constant

AXIS_CONSUMED

REAL

GSV

Counts / Position Unit

Range = 0.1 - 1e

12

Default = 8000.0

To allow axis position to be displayed and motion to be programmed in the position units specified by the Position Unit string attribute, a Conversion Constant must be established for each axis. The Conversion Constant, sometimes known as the K constant, allows the Axis Object to convert the axis position units into feedback counts and vice versa. Specifically, K is the number of feedback counts per Position Unit.

Note that the 1756M02AE encoder based servo module uses 4X encoder feedback decoding (both edges of channel A and B are counted). The count direction is determined from both the direction of the edge and the state of the opposite channel. Channel A leads channel B for increasing count. This is the most commonly used decode mode with incremental encoders, since it provides the highest resolution.

For example, suppose this servo axis utilizes a 1000 line encoder in a motor coupled directly to a 5 pitch lead screw (5 turns per inch). With a user defined Position Unit of Inches, the conversion constant is calculated as shown below:

K = 1000 Lines/Rev * 4 Counts/Line * 5 Revs/Inch = 20,000 Counts/Inch.

Important:

If 'Conversion Constant' is changed it invalidates all of the configurable attributes with "Position Unit" conversions in "Description" column. To be valid the ’r;Conversion Constant’ must be set to the desired value prior to setting (including defaulting) any of the affected attributes.

Coordinated Motion Status

AXIS_CONSUMED

BOOL

Tag

Set if any coordinated motion profile is currently active upon the axis. It is cleared as soon as Coordinated Motion is complete or stopped.

Damping Factor

AXIS_SERVO

REAL

GSV

The Damping Factor attribute value is used in calculating the maximum Position Servo Bandwidth (see below) during execution of the MRAT (Motion Run Axis Tune) instruction. In general the Damping Factor attribute controls the dynamic response of the servo axis. When gains are tuned using a small damping factor (like 0.7), a step response test performed on the axis would demonstrate under-damped behavior with velocity overshoot. A gain set generated using a larger damping factor, like 1.0, would produce a system step response that has no overshoot but has a significantly lower servo bandwidth. The default value for the Damping Factor of 0.8 should work fine for most applications.

DC Bus Voltage

AXIS_SERVO_DRIVE

DINT

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.

Volts

This parameter is the present voltage on the DC Bus of the drive.

Decal Status

AXIS_CONSUMED

BOOL

Tag

Set if the axis is currently being commanded to decelerate.

Use the Accel Status bit and the Decel Status bit to see if the axis is accelerating or decelerating. If both bits are off, then the axis is moving at a steady speed or is at rest.

Direct Drive

Ramp Rate

AXIS_SERVO

REAL

GSV

Volts/Second

The

Direct Drive

Ramp Rate attribute contains a slew rate for changing the output voltage when the

Direct Drive

On (MDO) instruction is executed. A

Direct Drive

Ramp Rate of 0, disables the output ramp rate limiter, allowing the

Direct Drive

On voltage to be applied directly.

Directional Scaling Ratio

AXIS_SERVO

REAL

GSV

In some cases, the speed or velocity scaling of the external drive actuator may be directionally dependent. This non-linearity can be substantial in hydraulic applications. To compensate for this behavior, the Directional Scaling Ratio attribute can be applied to the Velocity Scaling based on the sign of the Servo Output. Specifically, the Velocity Scaling value is scaled by the Directional Scaling Ratio when the sign of the Servo Output is positive. Thus, the Directional Scaling Ratio is the ratio of the Velocity Scaling in the positive direction (positive servo output) to the Velocity Scaling in the negative direction (negative servo output). The value for the Directional Scaling ratio can be empirically determined by running the auto-tune procedure in the positive direction and then in the negative direction and calculating the ratio of the resulting Velocity/Torque Scaling values.

Drive Axis ID

AXIS_SERVO_DRIVE

INT

GSV

Product Code of Drive Amplifier

The Drive ID attribute contains the CIP Product Code of the drive amplifier associated with the axis. If the Product Code does not match that of the actual drive amplifier, an error is generated during the configuration process.

Drive 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 drive capacity as a percent of rated capacity.

Drive Control Voltage Fault

AXIS_SERVO_DRIVE

BOOL

Tag

Set when the power supply voltages associated with the drive circuitry fall outside of acceptable limits.

Drive Cooling Fault

AXIS_SERVO_DRIVE

BOOL

Tag

Set when the ambient temperature surrounding the drive’s control circuitry temperature exceeds the drive ambient shut-down temperature.

Drive Enable Input Fault

AXIS_SERVO_DRIVE

BOOL

Tag

This fault would be declared if either one of two possible conditions occur: 1) If an attempt is made to enable the axis (typically via MSO or MAH instruction) while the Drive Enable Input is inactive. 2) If the Drive Enable Input transitions from active to inactive while the axis is enabled.

This fault can only occur when the Drive Enable Input Fault Handling bit is set in the Fault Configuration Bits attribute.

If the Drive Enable Input Fault Action is set for Stop Command and the axis is stopped as a result of a Drive Enable Input Fault, the faulted axis cannot be moved until the fault is cleared. Any attempt to move the axis in the faulted state using a motion instruction results in an instruction error.

Tip:

If the Drive Enable Fault Action setting is Status Only or Stop Command and an attempt is made to enable the axis (typically via MSO or MAH instruction) while the Drive Enable Input is active, the axis enables in the faulted state indicating a Drive Enable Input Fault. When the Drive Enable Fault Action setting is Stop Command, instructions that both enable the axis and initiate motion (MAH, MRAT, MAHD) abort the motion process leaving the instruction with both the IP and PC bits clear.

This fault condition is latched and requires execution of an explicit MAFR (Motion Axis Fault Reset) or MASR (Motion Axis Shutdown Reset) instruction to clear. Any attempt to clear the fault while the drive enable input is still inactive and the drive is enabled is unsuccessful. However, the drive enable input fault may be cleared with the drive enable input inactive if the drive is disabled.

If the Drive Enable Input Checking bit is clear, then the state of the Drive Enable Input is irrelevant so no fault would be declared in any of the above conditions.

Drive Enable Input-Fault Action

AXIS_SERVO_DRIVE

SINT

GSV

Shutdown

Disable Drive

Stop Motion

Status Only

Drive Enable Status

AXIS_CONSUMED

BOOL

Tag

If this bit is:

ON — The Drive Enable output of the axis is on.

OFF — Drive Enable output of the axis is off.

If this bit is:

ON — The drive’s power structure is active.

OFF — The drive’s power structure is not active.

Drive Fault

AXIS_SERVO

BOOL

Tag

If this bit is set, then the external servo drive has detected a fault and has communicated the existence of this fault to the servo module via the Drive Fault input. This fault condition is latched and requires execution of an explicit MAFR (Motion Axis Fault Reset) or MASR (Motion Axis Shutdown Reset) instruction to clear.

Drive Fault

AXIS_SERVO_DRIVE

DINT

Tag

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

Tag	Bit
Pos Soft Overtravel Fault	0
Neg Soft Overtravel Fault	1
Pos Hard Overtravel Fault	2
Neg Hard Overtravel Fault	3
Mot Feedback Fault	4
Mot Feedback Noise Fault	5
Aux Feedback Fault	6
Aux Feedback Noise Fault	7
Reserved	8
Drive Enable Input Fault	9
Common Bus Fault	10
Precharge Overload Fault	11
Reserved	12
Ground Short Fault	13
Drive Hard Fault	14
Overspeed Fault	15
Overload Fault	16
Drive Overtemp Fault	17
Motor Overtemp Fault	18
Drive Cooling Fault	19
Drive Cooling Voltage Fault	20
Feedback Fault	21
Communication Fault	22
Drive Overcurrent Fault	23
Drive Overvoltage Fault	24
Drive Undervoltage Fault	25
Power Phase Loss Fault	26
Position Error Fault	27
SERCOS Fault	28
Overtravel Fault	29
Reserved	30
Manufacturer Specific Fault	31

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.

Drive Fault Action

AXIS_SERVO

SINT

GSV

Shutdown

Disable Drive

Stop Motion

S

tatus Only

Drive Fault Bits

AXIS_SERVO_DRIVE

DINT

GSV

Lets you access all the drive fault bits in one 32-bit word. This attribute is the same as the Drive Fault tag.

Tag	Bit
Pos Soft Overtravel Fault	0
Neg Soft Overtravel Fault	1
Pos Hard Overtravel Fault	2
Neg Hard Overtravel Fault	3
Mot Feedback Fault	4
Mot Feedback Noise Fault	5
Aux Feedback Fault	6
Aux Feedback Noise Fault	7
Reserved	8
Drive Enable Input Fault	9
Common Bus Fault	10
Precharge Overload Fault	11
Reserved	12
Ground Short Fault	13
Drive Hard Fault	14
Overspeed Fault	15
Overload Fault	16
Drive Overtemp Fault	17
Motor Overtemp Fault	18
Drive Cooling Fault	19
Drive Cooling Voltage Fault	20
Feedback Fault	21
Communication Fault	22
Drive Overcurrent Fault	23
Drive Overvoltage Fault	24
Drive Undervoltage Fault	25
Power Phase Loss Fault	26
Position Error Fault	27
SERCOS Fault	28
Overtravel Fault	29
Reserved	30
Manufacturer Specific Fault	31

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.

Drive Fault Input Status

AXIS_SERVO

BOOL

Tag

Digital output from the drive that shows if there is a fault.

If this bit is:

ON — The drive has a fault.

OFF — The drive does not have a fault.

Drive Hard Fault

AXIS_SERVO_DRIVE

BOOL

Tag

Set when the drive detects a serious hardware fault.

Drive Model Time Constant

AXIS_SERVO

REAL

GSV SSV

Sec

The value for the Drive Model Time Constant represents the lumped model time constant for the drive’s current loop used by the MRAT instruction to calculate the Maximum Velocity and Position Servo Bandwidth values. The Drive Model Time Constant is the sum of the drive’s current loop time constant, the feedback sample period, and the time constant associated with the velocity feedback filter. This value is set to a default value when you configure the axis.

AXIS_SERVO

AXIS_SERVO_DRIVE

Drive Overcurrent Fault

AXIS_SERVO_DRIVE

BOOL

Tag

Set when drive output current exceeds the predefined operating limits for the drive.

Drive Overtemp Fault

AXIS_SERVO_DRIVE

BOOL

Tag

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

Drive Overvoltage Fault

AXIS_SERVO_DRIVE

BOOL

Tag

Set when drive DC bus voltage exceeds the predefined operating limits for the bus.

Drive Polarity

AXIS_SERVO_DRIVE

DINT

GSV

0 = Custom Polarity

1 = Positive Polarity

2 = Negative Polarity

Custom Polarity is used to enable custom polarity configurations using the various polarity parameters defined by the SERCOS Interface standard.

Positive and Negative Polarity bit attribute determines the overall polarity of the servo loop of the drive. All the advanced polarity parameters are automatically set based on whether the Drive Polarity is configured as Positive or Negative. Proper wiring guarantees that the servo loop is closed with negative feedback. However there is no such guarantee that the servo drive has the same sense of forward direction as the user for a given application. Negative Polarity inverts the polarity of both the command position and actual position data of the servo drive. Thus, selecting either Positive or Negative Drive Polarity makes it possible to configure the positive direction sense of the drive to agree with that of the user. This attribute is configured automatically using the MRHD and MAHD motion instructions.

Drive Resolution

AXIS_SERVO_DRIVE

DINT

GSV

Drive Counts / Drive Unit

The Drive Resolution attribute determines how many Drive Counts there are in a Drive Unit. Drive Units may be configured as Revs, Inches, or Millimeters depending on the specific drive application. Furthermore, the configured Drive Unit may apply to either a motor or auxiliary feedback device. All position, velocity, and acceleration data to the drive is scaled from the user’s Position Units to Drive Units based on the Drive Resolution and Conversion Constant. The ratio of the Conversion Constant to Drive Resolution determines the number of Position Units in a Drive Unit.

Conversion Constant / Drive Resolution = Drive Units (rev, inch, or mm) / Position Unit

Conversely, all position, velocity, and acceleration data from the drive is scaled from the user’s Position Units to Drive Units based on the Drive Resolution and Conversion Constant. The ratio of Drive Resolution and the Conversion Constant determines the number of Position Units in a Drive Unit.

Drive Resolution / Conversion Constant = Position Units / Drive Unit (rev, inch, or mm)

In general, the Drive Resolution value may be left at its default value of 200000 Drive Counts per Drive Unit, independent of the resolution of the feedback device(s) used by the drive. This is because the drive has its own set of scale factors that it uses to relate feedback counts to drive counts.

Because the drive’s position parameters are ultimately limited to signed 32-bit representation per the SERCOS standard, the Drive Resolution parameter impacts the drive’s travel range. The equation for determining the maximum travel range based on Drive Resolution is as follows:

Drive Travel Range Limit = +/- 2,147,483,647 / Drive Resolution.

Based on a default value of 200,000 Drive Counts per Drive Unit, the drive’s range limit is 10,737 Drive Units. While it is relatively rare for this travel range limitation to present a problem, it is a simple matter to lower the Drive Resolution to increase the travel range. The downside of doing so is that the position data is then passed with lower resolution that could affect the smoothness of motion.

In some cases, however, the user may also want to specifically configure Drive Resolution value to handle fractional unwind applications or multi-turn absolute applications requiring cyclic compensation. In these cases where the Unwind value for a rotary application does not work out to be an integer value, the Rotational Position Scaling attribute may be modified to a value that is integer divisible by the Unwind value.

The following examples demonstrate how the Drive Resolution value may be used together with the Conversion Constant to handle various applications.

Based on a rotary motor selection, Drive Resolution would be expressed as Drive Counts per Motor Rev and be applied to the Rotational Position Resolution IDN. The user would set the Conversion Constant to Drive Counts per user-defined Position Unit. If it is a 3:1 gearbox, and the user's Position Unit is, say, Revs of the gear output shaft, the Conversion Constant is 200,000/3, which is irrational! But, in this case, you could simply set the Drive Resolution to 300,000 Drive Counts/Motor Rev and the Conversion Constant could then be set to 100,000 Drive Counts/Output Shaft Rev. This system would work with this configuration without any loss of mechanical precision, that is, a move of 1 output shaft revolution would move the output shaft exactly 1 revolution.

Based on a rotary motor selection, Drive Resolution would be expressed as Drive Counts per Motor Rev and be applied to the Rotational Position Resolution IDN. The user would set the Conversion Constant to Drive Counts per user-defined Position Unit. If it is a 5mm pitch ball-screw, and the user's Position Unit is, say, mm, the user simply sets the Conversion Constant to 200,000/5 or 40,000 Drive Counts per mm based on the default Drive Resolution value of 200,000 Drive Counts/Motor Rev. If the pitch is irrational, the method for addressing this is the same as described in Rotary Gear-Head WITHOUT Aux Feedback Device.

Based on a rotary motor feedback selection, Drive Resolution would be expressed as Drive Counts per Aux Rev and be applied to the Rotational Position Resolution IDN. Now that position is based on the auxiliary feedback device according to the Servo Loop Configuration, the Data Reference bit of the various Scaling Types should be Load Referenced rather than Motor Referenced.

The motor feedback would be rotary and resolution expressed in cycles per motor rev. The aux feedback device is also rotary and its resolution expressed in cycles per aux rev. The Aux Feedback Ratio would be set to the number of aux feedback revs per motor rev and internally applied to IDNs 121 and 122 for the purpose of relating position servo loop counts to velocity servo loop counts in a dual servo loop configuration. The Aux Feedback Ratio attribute is also used in range limit and default value calculations during configuration based on the selected motor’s specifications.

If the application uses a 3:1 gearbox, and the user's Position Unit is, say, Revs of the gearbox output shaft, the Conversion Constant is still rational, since our scaling is Load Referenced! The user simply sets the Conversion Constant to 200,000 Drive Counts/Output Shaft Rev based on the default Drive Resolution value of 200,000 Drive Counts/Aux Rev. The system would work in this configuration without any loss of mechanical precision, that is, a move of 1 output shaft revolution would move the output shaft exactly 1 revolution.

Based on a linear aux feedback selection, Drive Resolution would be expressed as Drive Counts per Linear Unit, say Millimeters (Metric bit selection), and be applied to the Linear Position Data Scaling IDNs. Now that position is based on the auxiliary feedback device according to the Servo Loop Configuration, the Data Reference bit of the various Scaling Types should again be Load Referenced rather than Motor Referenced.

The motor feedback would be rotary and resolution expressed in cycles per motor rev. The aux feedback device is now linear and its resolution expressed in cycles per, say, mm. The Aux Feedback Ratio would be set to the number of aux feedback units (mm) per motor rev and internally applied to IDN 123 to relate position servo loop counts to velocity servo loop counts in a dual servo loop configuration. The Aux Feedback Ratio attribute is also used in range limit and default value calculations during configuration based on the selected motor’s specifications.

If the application uses a 3:1 gearbox and a 5 mm pitch ball-screw, and the user's Position Unit is, say, cm, the Conversion Constant is again rational, since we are Load Referenced! The user sets the Conversion Constant to 20,000 Drive Counts/cm based on the default Drive Resolution value of 200000 Drive Counts/mm. This system would work in this configuration without any loss of mechanical precision, that is, a move of 10 cm would move the actuator exactly 10 cm.

Drive Scaling Bits

AXIS_SERVO_DRIVE

DINT

GSV

The Drive Scaling Bits attribute configuration is derived directly from the Drive Units attribute.

0 = Scaling type

The Scaling Type bit attribute is used to enable custom scaling using the position, velocity, acceleration, and torque scaling parameters defined by the SERCOS Interface standard. When the bit is clear (default), these scaling parameters are all set based on the preferred

Rockwell Automation

SERCOS drive scaling factors. Currently there is no Logix support for custom scaling.

The Scaling Unit attribute is used to determine whether the controller scales position, velocity, and acceleration attributes based on rotary or linear scaling parameters and their associated Drive Units that are defined by the SERCOS Interface standard. When the bit is clear (default), the corresponding bits in the SERCOS Position Data Scaling, Velocity Data Scaling, and Acceleration Data Scaling parameters are also cleared, which instructs the drive to use the rotary scaling parameters. When the bit is set, the corresponding bits in the SERCOS Position Data Scaling, Velocity Data Scaling, and Acceleration Data Scaling parameters are also set, which instructs the drive to use the linear scaling parameters.

When the Scaling Unit is set to linear, the Linear Scaling bit attribute is used to determine whether the controller scales position, velocity, and acceleration attributes based on Metric or English Drive Units as defined by the SERCOS Interface standard. When the bit is clear (default), the corresponding bits in the SERCOS Position Data Scaling, Velocity Data Scaling, and Acceleration Data Scaling parameters are also cleared, which instructs the drive to use the Metric scaling parameters. When the bit is set, the corresponding bits in the SERCOS Position Data Scaling, Velocity Data Scaling, and Acceleration Data Scaling parameters are also set, which instructs the drive to scale in English units.

If the Scaling Unit is set to rotary, the Linear Scaling Unit bit has no affect.

When interfacing to Rockwell SERCOS drive products, the Standard Drive Units based on the Scaling Unit and Linear Scaling Unit bit selections are shown in the following table.

Standard Drive Units
	Metric	English
Rotary	Rev	Rev
Linear	Millimeter	Inch

The Data Reference bit determines which side of the mechanical transmission to reference position, velocity, acceleration, and torque data. If motor is selected then position, velocity, acceleration, and torque data is referenced to the motor side of the transmission. If load is selected then position, velocity, acceleration, and torque data is referenced to the load-side of the transmission. This is only applicable when using an auxiliary feedback device.

Drive Status Bits

AXIS_SERVO_DRIVE

DINT

GSV

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

Tag	Bit
Servo Action Status	0
Drive Enable Status	1
Shutdown Status	2
Process Status	3
Bus Ready Status	4
Reserved	5
Home Input Status	6
Reg 1 Input Status	7
Reg 2 Input Status	8
Pos Overtravel Input Status	9
Neg Overtravel Input Status	10
Enable Input Status	11
Accel Limit Status	12
Absolute Reference Status	13
Safe-Off Mode Active Status (requires Drive firmware revision 1.85 or higher)	14
Reserved	14
Reserved	15
Velocity Lock Status	16
Velocity Standstill Status	17
Velocity Threshold Status	18
Torque Threshold Status	19
Torque Limit Status	20
Velocity Limit Status	21
Position Lock Status	22
Power Limit Status	23
Reserved	24
Low Velocity Threshold Status	25
High Velocity Threshold Status	26

Drive Status

AXIS_SERVO_DRIVE

DINT

Tag

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

Tag	Bit
Servo Action Status	0
Drive Enable Status	1
Shutdown Status	2
Process Status	3
Bus Ready Status	4
Reserved	5
Home Input Status	6
Reg 1 Input Status	7
Reg 2 Input Status	8
Pos Overtravel Input Status	9
Neg Overtravel Input Status	10
Enable Input Status	11
Accel Limit Status	12
Absolute Reference Status	13
Reserved	14
Reserved	15
Velocity Lock Status	16
Velocity Standstill Status	17
Velocity Threshold Status	18
Torque Threshold Status	19
Torque Limit Status	20
Velocity Limit Status	21
Position Lock Status	22
Power Limit Status	23
Reserved	24
Low Velocity Threshold Status	25
High Velocity Threshold Status	26

Drive Thermal Fault Action

AXIS_SERVO_DRIVE

SINT

GSV

Shutdown

Disable Drive

Stop Motion

Status Only

Drive Undervoltage Fault

AXIS_SERVO_DRIVE

BOOL

Tag

Set when drive DC bus voltage is below the predefined operating limits for the bus.

Drive Unit

AXIS_SERVO_DRIVE

INT

GSV

The Drive Unit attribute establishes the unit of measure that is applied to the Drive Resolution attribute value. Units appearing in the enumerated list may be linear or rotary, english or metric. Further discrimination is provided in the enumerated list to specify whether the Drive Unit is referenced directly to the motor or to the external, or auxiliary feedback.

0 = motor revs

Drive Warning Bits

AXIS_SERVO_DRIVE

DINT

GSV

Warning

Drive Overload

Drive Overtemperature Warning

Motor Overtemperature Warning

Cooling Error Warning

When the load limit of the motor is exceeded, the Overload Warning bit is set. If the condition persists, an Overload Fault occurs. This warning bit gives the control program an opportunity to reduce motor loading to avoid a future shutdown situation.

When the over-temperature limit of the drive is exceeded, the Drive Overtemperature Warning bit is set. If the condition persists, a Drive Overtemperature Fault occurs. This warning bit gives the control program an opportunity to reduce motor loading, or increasing drive cooling, to avoid a future shutdown situation.

When the over-temperature limit of the motor is exceeded, the Motor Overtemperature Warning bit is set. If the condition persists, a Motor Overtemperature Fault occurs. This warning bit gives the control program an opportunity to reduce motor loading, or increasing motor cooling, to avoid a future shutdown situation.

When the ambient temperature limit inside the drive enclosure is exceeded, the Cooling Error Warning bit sets. If the condition persists, a Cooling Error Fault occurs. This warning bit gives the control program an opportunity to increase drive cooling to avoid a future shutdown situation.

Dynamics Configuration Bits

AXIS_CONSUMED

DINT

GSV

Revision 16 improved how the controller handles changes to an S-curve profile.

Do you want to return to revision 15 or earlier behavior for S-curves?

NO — Leave these bits ON (default).

YES — Turn OFF one or more of these bits:

To turn off this change	Turn off this bit
Reduced S-curve Stop Delay This change applies to the Motion Axis Stop (MAS) instruction. It lets you use a higher deceleration jerk to stop an accelerating axis more quickly. The controller uses the deceleration jerk of the stopping instruction if it is more than the current acceleration jerk.	0
Reduced S-curve Velocity Reversals Before revision 16, you could cause an axis to momentarily reverse direction if you decreased the deceleration jerk while the axis was decelerating. This typically happened if you tried to restart a jog or move with a lower deceleration rate while the axis was stopping. This change prevents the axis from reversing in those situations.	1
Reduced S-curve Velocity Overshoots You can cause an axis to overshoot its programmed speed if you decrease the acceleration jerk while the axis is accelerating. This change keeps to overshoot to no more than 50% of the programmed speed.	2