Brushless DC motor double closed-loop control system based on variable coefficient PID

A variable coefficient proportion integration differentiation (PID) algorithm used in the position loop was proposed and analyzed in the control system of electrical dual-redundancy brushless DC torque motor used in the direct drive valve. The steady-state error of the system was eliminated quickly by enhancing the influence of proportion regulator and integrator gradually according to the position deviation. The integration of position error was limited to ensure the system's stability. Experimental results show that the variable coefficient PID algorithm used in the position loop can ensure the system's stability and the accuracy of the position response, whatever the inner loop uses current loop or velocity loop. For the same step response, the step rise time of the double closed loop structure of the position and current reduced more than 32% compared with that of the double closed loop structure of the position and velocity. However, the double closed-loop structure of position/velocity loop performs strong loading appliance and strong robustness.