Numerical Methods for the Force Reflection of Contact

An important problem in the field of force-reflecting systems and telerobotics is poor rendering of contact, particularly of contact with stiff surfaces. There are numerous possible sources of poor performance, including poor contact models, sampling errors, and delays due to computation or data transmission. In this paper we examine effects due to sample-and-hold, which is a fundamental property of both the discrete domain and also of the sensors and power amplifiers used in a force-reflecting system. We propose sample-and-hold be generalized to sample-estimate-hold. We show why ordinary sample-and-hold generates an active contact interface, and provide ways of improving the feeling of the interface. We have developed a suite of numerical methods for improving the performance of rendering of surfaces by force reflection. We have conducted both simulations and experiments to demonstrate the efficacy of the proposed scheme. Our contributions are a new method of digitally processing force data, and a systematic method for coupling force-processing systems that run at different rates.