Self-tuning adaptive speed control of a pumplinverter-controlled hydraulic motor system

I n a hydrostatic transmission system the speed of the fixed displacement hydraulic motor can be controlled by varying either the pump displacement or the pump speed. The change of pump speed can be achieved via an inverter which governs the speed of an induction motor. In this paper, both the pump-controlled hydraulic motor system and the inverter-controlled hydraulic motor system are studied. A microcomputer-based self-tuning adaptive controller was designed and applied to both systems. A series of simulations and experi-ments was pe&rmed. The results show that both the pumpcontrolled system and the inverter-controlled system can be regulated to maintain a desired response under different speed commands, load inertias, oil temperatures and an external disturbance. Key words: pump/invertercontrolled hydraulic motor system, self-tuning adaptive speed controller NOTATION effective working area of the relief valve denominator of plant desired closed-loop characteristic polynomial viscous damping coefficient of hydraulic motor and load numerator of plant external and internal leakage coef-ficients of motor and pump discharge coefficient total leakage coefficients motor and pump displacement identity matrix total inertia of the hydraulic motor and load conversion gain of the displace-ment controller conversion gain of inverter spring constant precompensator transfer function speed of the induction motor upper line and lower line pressure relief valve cracking pressure setting pressure of charge pump estimation gain matrix feedback path compensator poly-nomial oil flow into the hydraulic motor real discharge of the pump replenish oil flowrate output flowrate for the relief valve forward path compensator poly-nomial reference command external torque disturbance column friction control signal total volume of oil under compres-sio