MC_TorqueControl

The MC_TorqueControl function block switches an axis under NC control to the "Cyclic Synchronous Torque Mode" (CST) and sets a torque setpoint for it. In this operation mode, the NC also provides the parameterized "VelocityLimitHigh" & "VelocityLimitLow" as linkable objects to the drive controller (Axis->Drive->Outputs->nDataOut5/nDataOut6) in the cyclic interface.

To change the operation mode without jerking, the dead time compensation must be activated in the NC axis.

DANGER

Danger to life or risk of serious injury or damage to property due to unintentional movements of the axis

When using the function block, the axis is switched to CST mode. After using the function block (especially after error situations), the axis may still be in CST mode. This can lead to sudden and unplanned movements (especially with lifting axes) when the axis is released.

Ensure that there is no hazard as defined by the risk assessment.
Check the current operation mode via the function block MC_ReadDriveOperationMode.
If the axis is not in a position-related operation mode (CSV/CSP), transfer it before an enable:
– directly with MC_WriteDriveOperationMode into the desired position-related operation mode (CSV/CSP) or
– indirectly with MC_Halt / MC_Stop into the desired position-related operation mode (CSV/CSP) (from TwinCAT 3.1.4024.40)
Other function blocks that switch the axis indirectly into a position-related operation mode can only do this to a limited extent and are therefore not to be used for a deliberate operation mode change.

Subsequently, it is necessary to check again whether the axis is really in a position-related operation mode (CSV/CSP), if not, an abort with error handling is required.

In order for this module to be used sensibly, the drive controller must support switching of the operating modes on the fly, as well as speed limitation in torque mode.

The relevant parameters are available for scaling the actual and setpoint torque in the Drive area in the NC axis parameters.

Inputs

VAR_INPUT
    Execute            : BOOL; 
    ContinuousUpdate   : BOOL; 
    Relative           : BOOL; 
    Torque             : LREAL; 
    TorqueRamp         : LREAL;
    VelocityLimitHigh  : LREAL;
    VelocityLimitLow   : LREAL;
    BufferMode         : MC_BufferMode;
    Options            : ST_TorqueControlOptions; 
END_VAR

Name	Type	Description
Execute	BOOL	The command is executed with a rising edge.
ContinuousUpdate	BOOL	If this input is TRUE on the rising edge at the "Execute" input, the "Torque", "TorqueRamp", "VelocityLimitHigh" and "VelocityLimitLow" inputs can be changed during the execution of the command and made effective as quickly as possible.
Relative	BOOL	If this input is TRUE, the torque value is changed relatively by the specified value "Torque".
Torque	LREAL	Torque setpoint with which the drive is operated ("Relative" = FALSE) or by which the torque is to be changed ("Relative" = TRUE). (e.g. %) Here, a positive torque setting means torque in a logically positive direction of movement.
TorqueRamp	LREAL	Rate of change of the torque setpoint ( e.g. %/s)
VelocityLimitHigh	LREAL	Upper velocity limit for limitation in CST mode (e.g. mm/s). This limitation must be configured accordingly in the process image.
VelocityLimitLow	LREAL	Lower velocity limit for limitation in CST mode (e.g. mm/s). This limitation must be configured accordingly in the process image.
BufferMode	MC_BufferMode	Currently only "Aborting" is supported.
Options	ST_TorqueControlOptions	Data structure containing additional, rarely used parameters. The input can normally remain open.

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
    InTorque           : BOOL;
    Busy               : BOOL;
    Active             : BOOL;
    CommandAborted     : BOOL;
    Error              : BOOL;
    ErrorID            : UDINT;
END_VAR

Name	Type	Description
InTorque	BOOL	TRUE, if the axis has built up the set torque and no velocity limitation is active.
Busy	BOOL	TRUE as soon as the command is started with Execute and as long as the command is processed. If "Busy" is FALSE, the function block is ready for a new order.
Active	BOOL	Indicates that the function block controls the axis.
CommandAborted	BOOL	TRUE if the command could not be executed completely.
Error	BOOL	TRUE, if an error occurs.
ErrorID	UDINT	If the error output is set, this parameter supplies the error number.

Sample MC_TorqueControl with AX8xxx

VAR
    Axis_Main              : AXIS_REF;
    bExecute_TorqueControl : BOOL;
    fTorque                : LREAL;
END_VAR

fTorque := 35;

fbTorqueControl(
    Axis               := Axis_Main,
    Execute            := bExecute_TorqueControl,
    ContinuousUpdate   := TRUE,
    Relative           := FALSE,
    Torque             := fTorque,
    TorqueRamp         :=   10,
    VelocityLimitHigh  :=  400,
    VelocityLimitLow   := -500,
    BufferMode         := ,
    Options            := ,
    InTorque           => ,
    Busy               => ,
    Active             => ,
    CommandAborted     => ,
    Error              => ,
    ErrorId            => );

Requirements

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