MC_TableBasedPositionCompensation

The MC_TableBasedPositionCompensation function block is used to correct the axis position with a correction factor depending on the current axis position. The correction values must be stored in an equidistant, monotonically increasing table.

Inputs

VAR_INPUT
    Enable         : BOOL;
    pTable         : POINTER To ST_PositionCompensationTableElement;
    TableSize      : UDINT;
    TableParameter : ST_PositionCompensationTableParameter;
    Ramp           : LREAL;
    DisableMode    : E_DisableMode;
    Options        : ST_PositionCompensationOptions;
END_VAR

Name	Type	Description
Enable	BOOL	The command is executed as long as Enable is active.
pTable	POINTER To ST_PositionCompensationTableElement	Pointer to the compensation table, which is an array of the type St_PositionCompensationTableElement.
TableSize	UDINT	Size of the compensation table
TableParameter	ST_PositionCompensationTableParameter	Data structure with additional parameters for the compensation table.
Ramp	LREAL	Velocity limit for the entered compensation (constant velocity and linear position as subprofiles for table compensation [mm/s]).
DisableMode	E_DisableMode	Disable mode: DisableModeHold = last correction is retained DisableModeReset = last correction is set to 0
Options	ST_PositionCompensationOptions	Optional parameters (not implemented)

Inputs/outputs

VAR_IN_OUT
    Axis : AXIS_REF;
END_VAR

Name	Type	Description
Axis	AXIS_REF	Axis data structure that unambiguously addresses an axis in the system. Among other parameters it contains the current axis status, including position, velocity or error state.

Outputs

VAR_OUTPUT
    Enabled           : BOOL;
    Busy              : BOOL;
    Error             : BOOL;
    ErrorID           : UDINT;
    CurrentCorrection : LREAL;
    Limiting          : BOOL;
END_VAR

Name	Type	Description
Enabled	BOOL	This output becomes TRUE when the table compensation was enabled without errors.
Busy	BOOL	This output becomes TRUE when the command is started with Enable and remains so as long as the function block executes the command.
Error	BOOL	This output becomes TRUE if an error has occurred during command execution.
ErrorID	UDINT	Contains the command-specific error code of the last executed command. Details of the error code can be found in the ADS error documentation or in the NC error documentation (error codes 0x4nnn and 0x8nnn).
CurrentCorrection	LREAL	Current compensation value, in the unit of the axis.
Limiting	BOOL	This output is TRUE if the correction value associated with the position has not yet been fully applied.

Further information

The following is an example of a position table and the corresponding table parameters:

VAR_INPUT
    …
    stParameter : ST_PositionCompensationTableParameter 
                  := (MinPosition := -10.0, MaxPosition := 10.0, 
                      NoOfTableElements := 21, Direction := WorkDirectionBoth);
    stPosTable  : ARRAY[0..20] OF ST_PositionCompensationTableElement 
                  := [ ( Position := -10.0, Compensation := 1.0 ),
                       ( Position :=  -9.0, Compensation := 0.9 ),
                       ( Position :=  -8.0, Compensation := 0.8 ),
                       ( Position :=  -7.0, Compensation := 0.7 ),
                       ( Position :=  -6.0, Compensation := 0.6 ),
                       ( Position :=  -5.0, Compensation := 0.5 ),
                       ( Position :=  -4.0, Compensation := 0.4 ),
                       ( Position :=  -3.0, Compensation := 0.3 ),
                       ( Position :=  -2.0, Compensation := 0.2 ),
                       ( Position :=  -1.0, Compensation := 0.1 ),
                       ( Position :=   0.0, Compensation := 0.0 ),
                       ( Position :=   1.0, Compensation := 0.1 ),
                       ( Position :=   2.0, Compensation := 0.2 ),
                       ( Position :=   3.0, Compensation := 0.3 ),
                       ( Position :=   4.0, Compensation := 0.4 ),
                       ( Position :=   5.0, Compensation := 0.5 ),
                       ( Position :=   6.0, Compensation := 0.4 ),
                       ( Position :=   7.0, Compensation := 0.3 ),
                       ( Position :=   8.0, Compensation := 0.2 ),
                       ( Position :=   9.0, Compensation := 0.1 ),
                       ( Position :=  10.0, Compensation := 0.0 )
                      ];
    …
END_VAR

As shown graphically, the table results in the following correction behavior:

Requirements

Development environment	Target platform	PLC libraries to include
TwinCAT v3.1.4024	PC or CX (x86/x64)	Tc2_MC2