Energy saving control of a hydraulic manipulator using five cartridge valves and one accumulator

In this paper, a novel energy-saving control strategy is proposed for the accurate motion tracking of a hydraulic manipulator. To achieve independent pressure regulation for each chamber of the cylinder as well as energy recovery during the back-and-forth movement of the cylinder, a hardware configuration with five low-cost programmable cartridge valves and an accumulator is developed to control the motion of the cylinder. Based on the hardware configuration, a novel control algorithm consisting of three levels is proposed. In level I, an adaptive robust controller is synthesized to generate the desired flow rates for the two chambers of the cylinders Q_1m and Q_2m so that the joint angle of the manipulator tracks the desired trajectory as accurately as possible, and the offside pressure of the cylinder also follows the desired pressure profile to be generated in level III accurately. In level II, an energy-optimum flow distribution law is designed and implemented to generate the desired flow rates passing through the five programmable valves. In level III, the desired offside pressure of the cylinder is generated so that the total energy consumption during the whole movement cycle is minimized. Experimental study validates that the proposed strategy can indeed achieve both accurate motion tracking and minimum energy consumption simultaneously. Compared to the previous 4-valve scheme and 5-valve flow regeneration scheme without the use of accumulator in Liu and Yao (2008), the proposed strategy has much less total energy consumption and equally good tracking performance.