UBC Theses and Dissertations

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UBC Theses and Dissertations

Application of force feedback to heavy duty hydraulic machine Parker, Niall R.


Issues concerning the design and implementation of a force-reflecting controller for conven tional heavy duty hydraulic machines are addressed in this thesis. A computer simulation of a typical hydraulic machine (a feller/buncher) has been developed. It implements a graphical dis play and a dynamic simulation of the endpoint load. A magnetically levitated joystick has been integrated into the simulator to act as the force-reflecting master. The system has been used to evaluate various control strategies for their effectiveness and subjective feel. These studies have shown that simple rate control wifi be unstable in contact with a surface when direct force feed back is applied, and a novel stiffness control scheme was developed to circumvent this problem. The force-reflecting master was also used with a CAT 215 log loader, and experiments using the system to control the endpoint force were performed. The system was capable of repeatedly applying a desired target force based on force feedback to the operator alone. Large errors in the applied forces were due mainly to the poor resolution of the endpoint force sensing. The cylinder pressures in the main actuators were measured and used to derive the endpoint forces, with resolution on the order of 10% of a typical working load.

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