Adaptive active disturbance rejection control for velocity tracking trajectory tasks

This work reports a Proportional plus Adaptive Desired Disturbance Observer (P+ADDOB) controller for a perturbed servo system aimed to track time-varying references. The controller is composed of three parts. The first part is an adaptive feedforward term, the second part corresponds to a proportional action, and a term aimed to compensate the disturbances affecting the closed-loop system corresponds to the third part. The structure of the ADDOB is inspired in the Ohnishi Disturbance Observer, however, instead resorting on measurements of the velocity and acceleration, the ADDOB employs their desired values thus reducing the impact of measurement noise in the closed loop system. The ADDOB is computed using the servo system parameter estimates obtained by means of a gradient algorithm endowed with a parameter projection mechanism. A stability analysis allows concluding boundedness of all the closed-loop signals. Real-time experiments assess the effectiveness of the proposed controller.