Disturbance Modeling based on Fourier Series for Precise Reaction Force Estimation in Semicircular Linear Motor

Abstract

This paper presents a disturbance modeling method for a semicircular linear motor called circular shaft motor (CSM). The CSM is a direct-drive motor that moves along the circumference of a circle, and is expected to realize multiple-degree-of-freedom (MDOF) haptic applications. To control the contact force in a CSM system, an observer is implemented to estimate the reaction force instead of using a force sensor. However, the estimated reaction force includes an estimation error caused by forces other than the reaction force. Therefore, a disturbance modeling method for the CSM is proposed to exclude the estimation error. In the proposed method, the variation in characteristics that depend on the velocity is approximated by a Fourier series. To evaluate the adequacy of the model, Akaike's information criterion (AIC) is introduced. To validate the effectiveness of the proposed method, a force control test is performed with the proposed disturbance model on a CSM. In addition, a bilateral control test is conducted to demonstrate the usefulness of the proposed method for force transmission.