A Switched Controller Design for Supply Pressure Tracking of Variable Displacement Axial Piston Pumps

In this paper, the supply pressure control problem is studied for a self-supplied variable displacement axial piston pump subjected to unknown time varying load flow disturbance. Due to the self supply mechanism of the pump, the mathematical model demonstrates a switching characteristic, in addition, one of the two subsystems is non-minimum phase, which complicates the controller design. A control strategy which uses the method of output redefinition combined with a switching control scheme is proposed. By defining a new output, the new system is minimum phase with respect to the revised output, which facilitates feedback controller design. Based on the proposed load flow disturbance observer, a new desired output is proposed to reduce tracking errors in the presence of time varying load flow disturbance. Two feedforward controllers along with a switching scheme are also proposed, furthermore, a common feedback controller is used to stabilize the system. The stability of the whole system is proved using common Lyapunov method and bounded tracking error can be guaranteed. Experimental results are provided to illustrate the effectiveness of the proposed controller.