Response of the new version:
Now the transmission times of the actual position are correctly taken into account when the system deviation (following error) is calculated.
What happens?
Position control in the PLC:
The transmission times of the actual position are not correctly taken into account when the system deviation (following error) is calculated.
The calculated following error, as input variable of the position controller, deviates accordingly from the actual value.
This has an effect on the behaviour of the position control.
The deviation of the following error depends on the type of position feedback:
- Actual position is read in via the backplane bus: The deviation corresponds to the path covered in 1 PLC cycle.
- Actual position via EtherCAT fieldbus: The deviation corresponds to the path covered in 3 PLC cycles.
When does this behaviour occur?
The behaviour occurs with position control in the PLC (PosControl PLC, external position control) and following error calculation in the PLC.
Which products are affected?
Library: L_MC1P_MotionControlBasic (FAST Motion)
Short-term measures:
If necessary, delay the setpoint position by a corresponding number of PLC cycles in the application to ensure that setpoint and actual position will match.
Evaluation/recommendations:
In most applications, position control is effected in the controller so that the EtherCAT transmission times will have no effect on position control.
