A single-actuator control design for hydraulic variable displacement pumps

It has been shown that the conventional two-actuator configuration for the discharge pressure control of variable displacement axial piston pumps essentially is an open loop unstable system, which imposes inherent constraints on the stability and performance of the closed loop control design. In addition, a large force is required to balance the load generated by the two parallel actuators, which in turn requires large size bearings to hold the swash plate in place. To overcome these two drawbacks in the conventional pump configuration, a novel control configuration is proposed in this paper. By balancing the torque induced from the pressure carry-over angle, the presented control design uses only one actuator that is arranged in a manner such that the open loop dynamics are strictly stable. Efficient control algorithms are developed for the proposed new scheme. Experimental tests show some significant advantages of the proposed design over the conventional counterpart