Observer-Based Single-Loop Feedback Systems for Speed Servo Applications via Critical Damping Injection Approach

This article presents an output-feedback solution involving the observer to the speed control problem in servo systems by eliminating the true system model and reducing the number of sensors. The novel active injection technique derives the observation mechanism for speed, acceleration, and speed control law. The resulting benefits are stated as follows. First, a model-free observer outputs information that emulates the speed and acceleration from the output measurement based on the desired estimation error dynamics obtained by the order reduction property. Second, the observed speed and acceleration enable the constitution of the proposed pole-zero cancellation (PZC) control law leading to the critical damping performance. It is experimentally verified that the resultant critically damped system performs similarly to a conventional PZC controller while reducing the peak current level in the transient periods using a 420 W brushless dc motor dynamo system.