Motion Coordinated Linear Move (MCLM)

Use the Motion Coordinated Linear Move (MCLM) instruction to start a single or multi-dimensional linear coordinated move for the specified axes within a Cartesian coordinate system. You can define the new position as absolute or incremental.

Available Languages

Ladder Diagram

Function Block

This instruction is not available in function block.

Structured Text

MCLM (CoordinateSystem, MotionControl, MoveType, Position, Speed, Speedunits, Accelrate, Accelunits, Decelrate, Decelunits, Profile, Acceljerk, Deceljerk, Jerkunits, TerminationType, Merge, Mergespeed, CommandTolerance,LockPosition, LockDirection, EventDistance, CalculatedData);

Operands

There are data conversion rules for mixed data types within an instruction. See Data Conversion.

Ladder Diagram and Structured Text

The Motion Coordinated Linear Move (MCLM) instruction performs a linear move using up to three (3) axes statically coupled as primary axes in a Cartesian coordinate system. You specify whether to use an absolute or incremental target position, the desired speed, maximum acceleration, maximum deceleration, acceleration jerk, deceleration jerk, and the units of each. The actual speed is a function of the programmed units of the speed (Units per sec, or % of Maximum, as configured for the coordinate system), and the combination of primary axes that are commanded to move. Each axis is commanded to move at a speed that allows all axes to reach the programmed endpoint (target position) at the same time.

When you enter enumerations for the operand value in structured text, multiple word enumerations must be entered without spaces. For example: when entering Decel Units the value should be entered as unitspersec

2

rather than Units per Sec

2

as displayed in the ladder logic.

See Structured Text Syntax for more information on the syntax of expressions within structured text.

Use the entries in this table as a guide when entering structured text operands.

Coordinate System

The Coordinate System operand specifies the set of motion axes that define the dimensions of a Cartesian coordinate system. For this release the coordinate system supports up to three (3) primary axes. Only those axes configured as primary axes are included in the coordinate velocity calculations.

Motion Control

The following control bits are affected by the MCLM instruction.

Move Type

The Move Type operand specifies the method used to indicate the coordinated move path. The Move Type can be either Absolute or Incremental.

When the axis is configured for rotary operation, an Absolute Move type behaves in the same manner as for a linear axis. When the axis position exceeds the Unwind parameter, it is unwound. In this way, axis position is never greater than the Unwind value nor less than zero.

The sign of the specified position is interpreted by the interpolator and can be either positive or negative. Negative position values instruct the interpolator to move the rotary axis in a negative direction to obtain the desired absolute position, while positive values indicate that positive motion is desired to reach the target position. When the position value is greater than the unwind value, an error is generated. The axis never moves through more than one unwind cycle before stopping at an absolute position.

The specified distance is interpreted by the interpolator and can be positive or negative. Negative position values instruct the interpolator to move the axis in a negative direction, while positive values indicate positive motion is desired to reach the target position. Motion greater than one unwind cycle is allowed in Incremental mode.

Position

A one dimensional array, whose dimension is defined to be at least the equivalent of the number of axes specified in the coordinate system. The Position array defines either the new absolute or incremental position.

Speed

The Speed operand defines the maximum vector speed along the path of the coordinated move.

Speed Units

The Speed Units operand defines the units applied to the Speed operand either directly in coordinate units of the specified coordinate system or as a percentage of the maximum values defined in the coordinate system.

Accel Rate

The Accel Rate operand defines the maximum acceleration along the path of the coordinated move.

Accel Units

The Accel Units operand defines the units applied to the Accel Rate operand either directly in coordinate units of the specified coordinate system or as a percentage of the maximum values defined in the coordinate system.

Decel Rate

The Decel Rate operand defines the maximum deceleration along the path of the coordinated move.

Decel Units

The Decel Units operand defines the units applied to the Decel Rate operand either directly in coordinate units of the specified coordinate system or as a percentage of the maximum values defined in the coordinate system.

Profile

The Profile operand determines whether the coordinated move uses a trapezoidal or S-curve velocity profile.

The

ControlLogix

motion controller provides trapezoidal (linear acceleration and deceleration), and S-curve (controlled jerk) velocity profiles. A guide to the effects of these motion profiles on various application requirements is shown.

Velocity Profile Effects

Trapezoidal

The trapezoidal velocity profile is the most commonly used profile since it provides the most flexibility in programming subsequent motion and the fastest acceleration and deceleration times. The maximum change in velocity is specified by acceleration and deceleration. Since jerk is not a factor for trapezoidal profiles, it is considered infinite and is shown as series of vertical lines in this graph.

S-curve

S-curve velocity profiles are most often used when the stress on the mechanical system and load needs to be minimized. The S-curve profile, however, sacrifices acceleration and deceleration time compared to the trapezoidal. The maximum rate at which velocity can accelerate or decelerate is further limited by jerk.

Coordinate motion acceleration and deceleration jerk rate calculations are performed when these instructions are started.

The calculated Jerk Rate produces triangular acceleration and deceleration profiles, as shown in this diagram.

S-curve Accel/Decel Time

For an S-curve move, the Jerk rate is determined based on the programmed velocity, acceleration, and deceleration values, not on the length of the move.

Logix Designer

software attempts to keep the Jerk rate constant when blending moves that have the same acceleration and deceleration values, even though the move may not be long enough to reach the programmed velocity (velocity-limited move).

For S-curve moves that are programmed with a zero speed, the Jerk Rate is determined by the rate of speed programmed for the previous instruction with a non-zero speed.

See the MCCD instruction for more details about the impact changes made by an MCCD instruction.

Accel Jerk

Accel Jerk defines the maximum acceleration jerk for the programmed move. For more information on calculating Accel Jerk, refer to the Jerk Units section below.

Decel Jerk

Decel Jerk defines the maximum deceleration jerk for the programmed move. For more information on calculating Decel Jerk, refer to the Jerk Units section below.

Jerk Units

The jerk units define the units that are applied to the values entered in the Accel Jerk and Decel Jerk operands. The values are entered directly in the position units of the specified coordinate system or as a percentage. When configured using % of Maximum, the jerk is applied as a percentage of the Maximum Acceleration Jerk and Maximum Deceleration Jerk operands specified in the coordinate system attributes. When configured using % of Time, the value is a percentage based on the Speed, Accel Rate, and Decel Rate specified in the instruction.

Termination Type

For Master Driven Speed Control (MDSC), when all sequential instructions run in the same mode (Master Driven Mode or Time Driven Mode), then all termination types are supported. If the termination type switches in the coordinated motion queue, errors may generate depending on the sequence of motion types.

The following is only applicable if a move on a slave Coordinate System uses a Blending Termination Type (Termination Types 2, 3, or 6) and is programmed in MDSC mode.

If you use the Calculated Data returned in the last MCLM instruction of a motion sequence to program the length that the master axis has to move for the motion sequence to go PC, then there is the possibility that you will have to add a small safety margin to the Calculated Data. If you do not add this margin, there is a chance that the motion of the master axes completes before the entire motion sequence programmed on the Slave Coordinate System finishes. If this occurs, the last motion instruction on the Slave Coordinate System remains active and does not go PC. The value of the small safety margin is dependent on the Command Tolerance used for the first and last move in the motion sequence as shown:

Refer to the See also section for more information.

Merge

The Merge operand determines whether or not to turn the motion of all specified axes into a pure coordinated move. The Merge options include: Merge Disabled, Coordinated Motion, or All Motion.

Merge Speed

The Merge Speed operand defines whether the current speed or the programmed speed is used as the maximum speed along the path of the coordinated move when Merge is enabled.

Currently, Coordinated Motion only supports the queueing of one coordinated motion instruction. Therefore the MovePendingStatus bit and the MovePendingQueueFullStatus bit are always the same.

Additional Information On Merging Instructions

A move from point A to point B is initiated as shown in the figure below. When the axis is at point C, a incremental merge to point D is initiated. As a result the current instruction is terminated at point C. The control computes the deceleration distance needed at point C along the vector AB from the current velocity to zero velocity. This distance is shown as vector CF. The imaginary point F is then calculated by adding the vector CF to point C. The resultant merged motion from C to D is shown in the illustration below. The motion follows the curved line starting from C then joins the straight line from F to D. Point D is calculated from the original point of the merge (point C) using the incremental data in the merge instruction. This path is identical as if the original programmed move was made from point A to F then from F to D with a termination type of No Decel.

This example applies to linear merges.

Attempting to merge a circular move can result in programming errors if the resultant path does not define a circle. The circle center in incremental mode is calculated from point C (the point of the merge). However, a circle must exist from point F (the calculated end of the deceleration) to the end of the merged move.

Merging in Incremental Mode

The Merge for coordinated motion operates differently from a merge on an MAM. For the MCLM, any uncompleted motion at the point of the merge is discarded. For example, assume that you have a single axis MCLM programmed in incremental mode from a starting absolute position = 0 and with the programmed incremental distance = 4 units. If a merge occurs at an absolute position of 1 and the merge is another incremental move of 4 units, the move completes at a position = 5.

If this example occurs on a MAM programmed in incremental mode, the final position = 8.

MCLM Target Position Entry Dialog

The Target Position Entry Dialog for the MCLM instruction provides an easy format for editing Position. To gain access to the Target Position Entry dialog box you must have inserted the name of the coordinated system into the instruction, you must have a valid tag name entered in the position field with sufficient elements to handle the number of axes, and you must have selected a valid Move Type.

To access the MCLM Instruction Target Position Entry Dialog box, press the ellipsis after the Position line on the instruction faceplate.

MCLM Ladder Valid Values for Accessing Target Position Entry Box

Pressing the ellipsis button at the Position line of the ladder instruction faceplate calls the Target Position tab for editing the position values

The dialog title indicates the Coordinate System and Tag Names for the instruction.

The selected Move type governs the appearance and the availability of the Set Targets = Actuals button.

When the Move Type is Absolute, the target column is entitled Target Position and when the Move Type is Incremental, the target column is entitled Target Increment and the Set Targets = Actuals button appears dimmed.

MCLM is a transitional instruction:

Structure

See

Input and Output Parameters Structure for Single Axis Motion Instructions

for the input and output parameters that are available for the MCLM instruction via the Master Driven Speed Control (MDSC) function. Before any of these parameters is active, you must execute an MDCC instruction and it must be active (IP bit is set).

Affects Math Status Flags

No

Major/Minor Faults

None specific to this instruction. A major fault can occur if an uninitialized reference or a reference of the incorrect type is passed to the Coordinate System operands. See Common Attributes for operand-related faults.

Execution

Ladder Diagram

Structured Text

Runtime Error Conditions

You cannot switch from Time Driven Mode to Master Driven Mode if the master speed is zero unless the slave speed is also zero.

Extended Error Codes

Extended Error codes help to further define the error message given for this particular instruction. Their behavior is dependent upon the Error Code with which they are associated.

The Extended Error Codes for Servo Off State (5), Shutdown State (7), Axis Type Not Servo (8), Axis Not Configured (11), Homing In Process Error (16), and Illegal Axis Data type (38) errors all function in the same fashion. A number between 0...n is displayed for the Extended Error Code. This number is the index to the Coordinate System indicating the axis that is in the error condition.

For Error Code Axis Not Configured (11) there is an additional value of -1 which indicates that Coordinate System was unable to setup the axis for coordinate motion. See Motion Error Codes (ERR) for Motion Instructions.

For the MCLM instruction, Error Code 13 - Parameter Out of Range, Extended Errors return a number that indicates the offending parameter as listed on the faceplate in numerical order from top to bottom beginning with zero. For example, 2 indicates the parameter value for Move Type is in error.

For the Error Code 54 – Maximum Deceleration Value is Zero, if the Extended Error returns a positive number (0-n) it’s referring to the offending axis in the coordinate system. Go to the Coordinate System Properties General Tab and look under the Brackets ([ ])column of the Axis Grid to determine which axis has a Maximum Deceleration value of 0. Click on the ellipsis button next to the offending axis to access the Axis Properties screen. Go to the Dynamics tab and make the appropriate change to the Maximum Deceleration Value. If the Extended Error number is -1, this means the Coordinate System has a Maximum Deceleration Value of 0. Go to the Coordinate System Properties Dynamics Tab to correct the Maximum Deceleration value.

MCLM Changes to Status Bits

Status bits provide a means for monitoring the progress of the motion instruction. There are three types of Status bits that provide pertinent information.

When the MCLM instruction initiates, the status bits undergo the following changes.

Motion Instruction Predefined Data Type Status Bits

See

Status Bits for Motion Instructions

(MCLM, MCCM) when MDCC Is Active

Axis Status Bits

Coordinate System Status Bits

Coordinated Motion Status Bits

Currently, Coordinated Motion only supports the queueing of one coordinated motion instruction. Therefore, the MovePendingStatus bit and the MovePendingQueueFullStatus bit are always the same.

Master Driven Speed Control (MDSC) and Motion Direct Command Support

The Motion Direct commands are not available in the instruction tree for the MCLM instruction. You must program an MCLM in one of the supported programming languages before you execute an MAM or MAJ in Time Driven Mode. A runtime error will occur if an MCLM is not previously executed in an MAM and MAJ in Master Driven Mode.

Examples

Ladder Diagram

Structured Text

MCLM(myMclmCoordinateSystem, myMclmMotionControl, myMclmMoveType, myMclmPosition[0], myMclmSpeed, Unitspersec, myMclmAccelRate, Unitspersec2, myMclmDecelRate, Unitspersec2, Trapezoidal, 100.0, 100.0, %ofTime, myMclmTermType, CoordinatedMotion, Programmed, 0, 0, None, 0, 0);

Relay Ladder

Structured Text

MCLM(myMclmCoordinateSystem,myMclmMotionControl,myMclmMoveType,myMclmPosition[0],myMclmSpeed,Unitspersec,myMclmAccelRate,Unitspersec2,myMclmDecelRate,Unitspersec2,Trapezoidal,100.00,100.0,%ofTime,myMclmTermType,CoordinatedMotion,Programmed,0,0,None,0,0);