Hybrid feedforward-feedback LQR controller based on model prediction for open channel water level control

ABSTRACT Linear quadratic regulator (LQR), as one of the most popular optimal feedback controllers, has been used in open-channel automatic control. However, existing hybrid feedforward-feedback controllers are simple combinations lacking consistency and neglect the potential of model prediction in the feedforward part. This paper presents a novel hybrid linear quadratic regulator (HLQR) controller with a feedforward-feedback structure. Rather than achieving feedforward control by compensation of discharge or volume, HLQR incorporates a water level prediction of the canal model into the conventional LQR, allowing consistent optimal control and flexible adjustment of weight coefficients in both feedforward and feedback parts. The designed hybrid controller can provide a simple effective way for canal control. It has been numerically tested in a test canal compared with the discharge compensation linear quadratic regulator (DCLQR). Results show that the proposed HLQR can reduce the water level fluctuations and shorten the transition time. The maximum absolute error of the water level can be reduced by 56.65%, the gate movement is decreased by 69.69%, and the transition time is cut down from 21.5 to 7.5 h. With outstanding control performance, the proposed HLQR controller can promote water distribution practically and flexibly, showing great potential in hydraulic control.