Application of force feedback to heavy duty hydraulic machines

The design and implementation of a force-reflecting controller for conventional heavy duty hydraulic machines are described. The unsuitability of direct force feedback with rate control has been shown analytically and confirmed on a simulator of a typical hydraulic machine. A stiffness control scheme to circumvent this problem was developed and 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, and the endpoint forces were obtained from hydraulic cylinder pressures.<>