Position controller setup

NAVIGATION: Closed-loop control > Position control > Position controller setup

Position controller setup

The higher the dynamism of the speed controller, the more dynamically the position controller can be set and the tracking error minimized. The variables for the pre-control of the speed and position controller are additionally determined either from the change in reference values or alternatively are already calculated and outputted by the motion control. The time-related values for the position, speed and torque are transmitted to the drive control.
If the dynamic change in these values is within the limits which the drive is able to follow dynamically, the load on the controllers is significantly reduced. In order to improve the dynamism of the position controller, the following dialog box is provided to optimize the speed and acceleration pre-control.

Filters and scaling

Bild: Pre-control dialog box

No.	Function
	Delay time and scaling for torque pre-control
	Delay time and scaling for speed pre-control
	Delay time for position pre-control
	Scaling of friction torque

Tabelle: Legend to pre-control dialog box

NOTE:

When a standard motor data set is read-in, the position controller gain is also adopted. The setting equates to a controller with a medium rigidity. In the default setting no smoothing is selected!

Position controller pre-control

The pre-control of the acceleration torque relieves the strain on the speed controller and optimizes the control response of the drive. To pre-control the acceleration torque, the mass inertia reduced to the motor shaft must be known.
f the parameter for the overall mass inertia of the system P 1516 SCD_Jsum has a value ≠ 0, that value will be automatically used to pre-control the acceleration torque.
The pre-control of the speed reference is preset by default to 100% via parameter
P 0375 CON_IP_SFF_Scale. This value should not be changed.
The acceleration torque pre-control can be optimized with
P 0376 CON_IP_TFF_Scale. Reducing this reduces the pre-control value; conversely, increasing this value also increases the pre-control value. The position tracking error can be further reduced by predictive torque and speed pre-control – that is, in advance of the position reference setting. Owing to the time-discrete mode of operation of the control circuits and the limited dynamism of the current control circuit, this prediction is necessary to prevent the individual control circuits from oscillating against one another. Prediction in pre-control is achieved by retarding the references for speed and position controllers.

Parameters for setting the pre-control

P. no.	Parameter name	Function
P 0360	CON_PCON_KP	Position controller gain
P 0372	CON_IP_SFFTF	Prediction (delay time) for speed controller pre-control
P 0374	CON_IP_EpsDly	Prediction (delay time) for position controller pre-control
P 0375	CON_IP_SFFScale	Speed controller pre-control scaling factor
P 0376	CON_IP_TFFScale	Torque controller pre-control scaling factor
P 0378	CON_IP_ACC_FFTF	Prediction (delay time) for torque controller pre-control
P 0386	CON_SCON_TFric	Scaling factor for friction compensation Friction torque compensation.htm
P1516	SCD_Jsum	Reduced mass inertia

Tabelle: Parameters for setting the pre-control

ATTENTION:

When using linear interpolation torque pre-control is inactive.
The overall moment of inertia in P 1516 SCD_Jsum must not be changed to optimize the pre-control, because this would also have an effect on other controller settings!
In multi-axis applications requiring precise three-dimensional axis coordination, such as in the case of machine tools, the delay of the position signal must be equally set on all axes via parameter P 0374-IP_EpsDly. Otherwise the synchronization of the axes may suffer, leading to three-dimensional path errors.