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What is the Velocity Error in CSMIO/IP-A?

This message means there is too significant a difference in speed between the set speed (via the +/-10V signal) and the actual axis speed read out from the encoder input.

This error occurs in two cases:

  1. When the encoder has been damaged.
  2. When a servo drive does not respond briskly enough to the +-/10V signal.


The CSMIO/IP-A controller was initially equipped with a security feature that does not allow the difference between the set position and the actual position read from an encoder input to be greater than the following position error set by a user. This protection was designed to stop a machine when an axle does not keep up with a set position due to the following:

  • Too soft tuning of the velocity or current PID regulator in a servo drive.
  • Too soft tuning of the position PID regulator in CSMIO/IP-A
  • servo drive overloads
  • collision.

Unfortunately, after some time, it turned out that this security does not consider certain situations. We are talking here mainly about the situation in which an encoder has been damaged. Damage to an encoder is a hazardous situation because the actual position seen by the CSMIO/IP-A controller does not change. If the set movement is long and fast, the permissible position error will be exceeded very quickly, and thus the machine will stop, but what if the set movement is short and slow? In this situation, the following position error will not be exceeded, and the PID regulator of the position in CSMIO/IP-A will set the maximum voltage at the analog output +/-10V. Such a situation will cause an axis to accelerate to the maximum speed and probably hit a limit switch or even the end of the axis.

To prevent such situations, protection has been added, not allowing the difference between the set speed and the actual speed to be too large (the following speed difference is calculated dynamically). In this case, the set speed is the analog signal voltage +/- 10V, and the actual speed is the speed read at the encoder input. When there is a significant voltage at the +/10V analog output (i.e., a significant axis speed has been set), and the encoder input speed is 0 (because the encoder has been damaged) or is too low (because a servo drive is tuned too softly), the machine will be stopped immediately.

[Source:] The text was created by CS-Lab’s Technical Support section for CSMIO/IP users.



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