Nonlinear controller design of brushed DC motor

In order to improve the transient and steady-state performance of brushed DC motor, a novel control system is developed on the basis of dual closed-loop control system. For the speed loop, considering the nonlinear characteristics of the friction torque and the un-measurable load torque, an Extended State Observer (ESO) based Triple-Step (TS) nonlinear control method is developed. First, the speed controller is designed using the TS method, which consists of the steady-state control, the feed-forward control related to the reference variation and the error feedback control. The structure of the designed nonlinear controller is concise. Then, an ESO based on model compensation is applied to estimate and compensate disturbances. The estimated errors are bounded and can converge to a prescribed range in a finite time. The estimated error is considered as disturbance input with the bounded amplitude. The method to analyze the robustness of this system is discussed in the framework of input state stability theory. For the current loop, current dynamics is neglected due to the fast electric response, the commonly used feedforward controller and PI feedback controller are designed to reduce torque ripple. The designed control system is evaluated by experiments. Results show that the proposed controller can improve the transient and steady-state performance of brushed DC motor significantly. The effectiveness and engineering implementation of this controller is also verified. © 2017, Editorial Board of Jilin University. All right reserved.