A cogging torque compensating disturbance estimator for DC motor speed regulation: Design and experimentation

Abstract

A disturbance estimator was designed and integrated into an existing proportional and integral controller DC motor speed control system to improve the speed regulation. The DC motor in the existing control system possessed a large amount of cogging torque, causing a periodic speed error. This cogging torque was treated as an equivalent input disturbance which then was estimated using a disturbance estimator. The estimated disturbance was utilized to reject the cogging torque. The speed response was largely improved by augmenting this disturbance estimator. The robust stability and performance of this scheme were investigated. Experiment results demonstrated the effectiveness of this scheme.

Observer-Based Rejection of Cogging Torque Disturbance for Permanent Magnet Motors

“…Then, we show that the gain of the proposed state observer is independent of the feedback motor speed. Simulation and experimental results for an actual brushless DC motor verify the effectiveness of the proposed method more than the previous study of [10].…”

“…Although the motor speed randomly oscillates around the reference trajectory due to the measurement noises, we can see effective tracking performance. Finally, we perform a simulation to compare the proposed observer with the conventional observer in [10] as depicted in Figure 6. While the motor speed tends to the reference trajectory all target speed 20, 40, and 10 rad/s, it is shown that with the conventional observer, the output speed effectively tracks the target speeds 20 and 10 rad/s, but not for 40 rad/s.…”

“…This may not be acceptable in some applications-in particular for low speed regulation. Thus it is not surprising that there have been a tremendous amount of studies for eliminating the cogging disturbance over the course of several decades [7][8][9][10][11][12].…”

“…More recently, under an assumption that the cogging torque can be expressed by a state-space harmonic representation, an observer using feedback motor velocity has been proposed to obtain more accurate speed regulation [7,8,10]. In the research, from the point of view of disturbance rejection, there exists a plant input disturbance equivalent to the cogging torque.…”

“…In this paper, unlike the observer in [10], we propose a control method with a state observer independent of the motor velocity. For this, several coordinate transformations for observable canonical form are used in order to make the motor speed an observer input.…”