Overview

Task

When an axis is interpolated, the real actual position of the axes at the interpolated set position takes place with a certain time delay due to the properties of the position control algorithms used and bus delays. The difference between command and actual position is referred to as position lag.

Path errors occur on curved paths due to position lag. The is the case in particular for a path compound with axes of different dynamics.

Position lag and therefore the path error can be minimised by using feedforward control.

Feedforward control by the controller compensates for position lag based on the current speed and acceleration. Feedforward control can be adapted to the machine dynamics and the required path accuracy by entering the appropriate parameters in the axis parameter lists [AXIS] and also in the NC program.

Effectiveness

Feedforward control is available for all axis and drive types [AXIS].

Programming

The feedforward control mode is selected in the NC program. Programming takes place using the modal commands G135, G136 and G137 [PROG].

Parameterisation

The parameter P-AXIS-00223 enables feedforward control for each axis or spindle. The required parameters are entered in the constant V_SATZ_ANZ. For other parameters see Chapter “Parameters”.