Repetitive control – Actively suppressing periodic disturbances
Repetitive control is an addition to standard controller cascading for the ACOPOS family from B&R. This technology function is beneficial in manufacturing processes with stationary disturbances and requirements for constant speed. The periodicity of disturbances is used to counteract future disturbances, substantially increasing the performance of the machine or system.
Because of mechanical characteristics, stationary disturbing torque fluctuations can occur in position-controlled drive applications with constant speed, often resulting in lag errors tied to a certain location. By optimizing the drive controller configuration, these lag errors can be minimized, but the disturbance cannot be complete avoided.
To further increase the performance of these applications and to further reduce lag errors, it must be possible to compensate for the disturbing torque in a predictive manner. This requires detailed knowledge of the disturbing torque as well as its predictability. Both can be achieved through the use of repetitive control, an adaptive method for actively suppressing periodic disturbances.
Self-correcting algorithm detects changes in the load profile
Embedded in the standard speed control loop for the ACOPOS drive family, repetitive control adapts the torque setpoint of the drive in such a way that the periodic portions are drastically minimized in the speed or lag error. The algorithm undergoes a constant learning process so that changes to the load profile (e.g. caused by wear) have no effect whatsoever on the drive.
Simple and intuitive use
Active disturbance suppression can be used as an add-on to the standard control procedure and is easy and intuitive to configure. Because of the adaptive nature of the algorithm, no additional information about the process in the form of a mathematical system model is necessary. A well-configured standard control cascade provides a solid foundation for using repetitive control.