A practical solution to the saturation problem in feedforward control for measurable disturbances

This paper treats the problem of control signal saturation caused by feedforward control from measurable load disturbances. An efficient feedforward compensator will often give significant peaks in the control signal at fast changes in the load disturbance. These peaks may cause the control signal to reach a saturation limit. In the paper, it is shown that the anti-windup function may cause unnecessarily sluggish responses in these cases. To overcome this problem, it is suggested to reduce the gain of the feedforward compensator during periods of control signal saturation. A method to calculate this gain reduction is presented, and several simulation examples show that this idea will result in a great performance improvement in cases of saturation problems. The proposed algorithm is also tested on a lab-scale temperature control system to demonstrate the noticeable practical capabilities.