VARIABLE LOAD SENSING AND ANTI-STALL ELECTRONIC CONTROL WITH SLIDING MODE AND ADAPTNE PID

Abstract

A variable displacement axial piston pump with Pressure compensator and Load Sensing control is coupled to a diesel engine. The pump is in an open circuit topology for load control in a typical excavator, skid-steer or front loader circuit. The active torque generated by the engine is subject to overloads, due to uncontrolled priority and sum of torque requests from hydrostatic transmission, implements and upper-structure control. In order to avoid engine overload a third 2 ways proportional valve is added to the control circuit. The valve controls the delivery pressure on the load sensing valve port, and the pressure is managed by an electronic system. This circuit architecture allow the designer to use the valve as a variable load sensing system, modifying the load sensing differential pressure depending on working conditions. The control must be in real time and a feed forward control based on the valve characteristic map is useful and helpful but a feedback control is needed to correct the steady state error; a PID and a Sliding mode are superimposed, in order to react to high dynamic transient. The controls runs properly on the bench and the advantages are: more engine efficiency and continuously working capacity, adapting load sensing pressure a more efficient use of power is possible.