Cross-coupled Motor Control

In the conventional operation of the motion controller, the drive operates in CSP (positioning) mode, and the entire servo control loop is executed in the drive by passing the position command through EtherCAT from the XMC motion controller.

For Cross-Coupled Control, each axis must have the LS_MasterPLoopControlOn executed so the XMC motion controller will control the position loop of that axis. This will make each drive operate in CSV (speed) mode, and the XMC generates a speed command by comparing the position command input through the motion controller with the current position feedback from the drive.

This speed command is transmitted to the drive operating in CSV mode to execute the control servo loop. The position control part of the entire servo control loop is performed by the XMC motion controller. Make sure the tuning parameters for LS_MasterPLoopControlOn are configured correctly for your application. This will have a large impact on the performance of the system being controlled.

• LS_CrossCoupledControlOn must be executed after the LS_MasterPLoopControlOn function blocks.

• LS_CrossCoupledControlOn will share the position error across the two axes so that the two motors don’t interfere with each others movement.

• Identical movement commands must be executed on each axis, so they move synchronously.

• LS_CrossCoupledControlOff can be executed to disable cross-coupled control of two axes. This must be done before disabling the XMC’s control of the position loop.

• LS_MasterPLoopControlOff can be executed to disable the XMC’s control of an axis position loop and must be executed after LS_CrossCoupledControlOff.

Position Loop Control Diagram

Cross-Coupled Control Diagram

Cross-Coupling Restrictions and Error Codes

In the following cases, an error occurs and master position loop control/cross-coupled control cannot be executed:

• When executing or releasing master position loop control while the axis is in operation (Error code: 0x1230)

• When the servo driver that the XMC is trying to control master control loop does not support CSV operation mode (Error code: 0x1160)

• If there is no Target Velocity (0x60FF) object in RxPDO of the axis to execute master position loop control (Error code: 0x1161)

• When the P gain input value of the master position loop control function block is negative (error code: 0x1231)

• When the I gain input value of the master position loop control function block is negative (error code: 0x1232)

• When the control output limit value of the master position loop control function block is negative (error code: 0x1233)

• When executing or releaseing Cross-coupled control while the axis is in operation (Error code: 0x1234)

• When the same axis is set in Axis and PairAxis of Cross-coupled control function block (Error code: 0x1235)

• In case master position loop control is not being executed for Axis and PairAxis set in Cross-coupled control function block (Error code: 0x1236)

• When the P gain input value of cross-coupled control function block is negative (error code: 0x1237)

• When a command is executed on an axis for which cross-coupled control is not being executed (Error code: 0x1238)

• When homing start is executed during master position loop control (Error code: 0x10B8)

• Target Velocity (0x60FF) object must be present in the RxPDO list of the selected axis.

• CSV mode must be supported by the controlled servo drive.

• Can only be executed on an axis that is not in operation.

• Tuning values and CtrlLimit must be positive values.

• Make sure to tune the parameters for your application and the servo’s speed controller gain may need to be tuned.

This function block is used to release control of the master position loop of an axis. Can only be executed on an axis that is not in operation.

Each Axis must have LS_MasterPLoopControlOn before executing LS_CrossCoupledControlOn. Axis and PairAxis must be unique axes. Using the same will lead to an error.

• Must be executed on the axes while they are not in operation.

• Make sure the P_Gain value is set correctly for your application.

This function block releases cross-coupled control on a pair of axes.

• Can only be executed on axes that are being cross-couple controlled.

• Only execute the function block if the two axes are not in operation.

//Function block Calls

INST_Connect(Execute:=Connect_ECAT, ErrorID=>INST_Connect.ErrorID);

INST_Disconnect(Execute:=Disconnect_ECAT, ErrorID=>INST_Disconnect.ErrorID);

INST_PowerAll(Enable:=Power_On_Axes, Status=>INST_PowerAll.Status, Valid=>INST_PowerAll.Valid, ErrorID=>INST_PowerAll.ErrorID);

INST_Axis1PloopOn(Execute:=Execute_MPloopOn, Axis:=Axis1, P_Gain:=1100.0, I_Gain:=600.0, VelFF_Gain:=10000.0, CtrlLimit:=100000000.0,

InControl=>INST_Axis1PloopOn.InControl, ErrorID=>INST_Axis1PloopOn.ErrorID);

INST_Axis2PloopOn(Execute:=Execute_MPloopOn, Axis:=Axis2, P_Gain:=1100.0, I_Gain:=600.0, VelFF_Gain:=10000.0, CtrlLimit:=100000000.0,

InControl=>INST_Axis2PloopOn.InControl, ErrorID=>INST_Axis2PloopOn.ErrorID);

INST_CoupleOn(Execute:=Execute_CrossCoupleOn, Axis:=Axis1, PairAxis:=Axis2, P_Gain:=1100.0, SlaveMode:=FALSE, InControl=>INST_CoupleOn.InControl,

ErrorID=>INST_CoupleOn.ErrorID);

INST_Axis1Relative(Execute:=Execute_Move, Axis:=Axis1, ContinuousUpdate:=FALSE, Distance:=50000.0, Velocity:=500000.0, Acceleration:=500000.0,

Deceleration:= 500000.0, Jerk:=10000.0, BufferMode:=0, ErrorID=>INST_Axis1Relative.ErrorID);

INST_Axis2Relative(Execute:=Execute_Move, Axis:=Axis2, ContinuousUpdate:=FALSE, Distance:=50000.0, Velocity:=500000.0, Acceleration:=500000.0,

Deceleration:= 500000.0, Jerk:=10000.0, BufferMode:=0, ErrorID=>INST_Axis2Relative.ErrorID);

INST_Axis1PloopOff(Execute:=Execute_MPloopOff, Axis:=Axis1, ErrorID=>INST_Axis1PloopOff.ErrorID);

INST_Axis2PloopOff(Execute:=Execute_MPloopOff, Axis:=Axis2, ErrorID=>INST_Axis2PloopOff.ErrorID);

INST_CoupleOff(Execute:=Execute_CrossCoupleOff, Axis:=Axis1, PairAxis:=Axis2, ErrorID=>INST_CoupleOff.ErrorID);