An External Force Estimator Using Elastoplastic Friction Model With Improved Static Friction Behavior

This paper proposes an external force estimator including an elastoplastic friction model with improved static friction behavior. Hayward and Armstrong's elastoplastic friction model is one of the simplest model representing friction phenomena with compliance. This model however produces non-zero output force in the static friction state, which results in steady-state error in external force estimation. This paper improves the estimation accuracy by applying a friction model with the output force being reduced in the static friction state. The proposed estimator was validated through experiments with an actuator system comprised of a ball screw and a timing belt. The experimental results shows that the estimation accuracy is improved by the proposed estimator.