This paper presents a summary of the design and implementation of a force-reflecting controller for conventional heavy duty hydraulic machines. The unsuitability of direct force feedback with rate control has been shown analytically and confirmed on a simulator of a typical hydraulic machine. A novel stiffness control scheme was developed to circumvent this problem and was used successfully in controlling the endpoint force on a CAT 215 log loader to better than 10% of a typical working load. A magnetically levitated wrist was used as a force-reflecting master, while the endpoint forces were obtained from hydraulic cylinder pressures.
N. Parker, S. E. Salcudean, P. D. Lawrence