Which products are affected?
L_MCProfileGenerator profile generator of the LenzeMotionControlV0401.lib function library. This profile generator is used in the template as of version 4.1.
What happens?
A short-term speed setpoint step-change can be observed in the deceleration phase of a positioning profile with jerk limitation.
When does the problem occur?
The behaviour only occurs in case of profiles with jerk limitation (S-ramp time > 0) in the 'run-time-optimised' mode (wSProfileMode=0; in the Positioner template C3037 = 0) of the S-profile generation. The profile must be parameterised in such a way that there is no phase with constant deceleration. Thus the set speed value can sporadically, for one call-up cycle of the profile generator, increase to the parameterised maximum traversing speed. In the next cycle the setpoint again corresponds to an expected value according to the profile.
Possible diagnostics?
This setpoint step-change causes a torque setpoint step-change in the motor control. In this connection, a cracking noise at the drive can usually be heard. The behaviour no longer occurs when the S-ramp time has been reduced slightly.
Short-term measures/recommendations?
The behaviour can reliably be avoided if the profile parameters for the deceleration are selected in such a way that it is possible to reach the parameterised deceleration in the deceleration phase. The profile S-ramp time should therefore be smaller than ½ x profile speed / deceleration and the distance covered must be large enough to ensure that the profile speed can be reached.
Evaluation
The behaviour causes a very short torque-setpoint pulse at the drive. A worth-mentioning it movement is usually not executed. A resulting activation of the following error monitoring may interrupt the machine process. When the same profile parameters are used the behaviour can always be observed.
