Multiple Hybrid Control of Pump Displacement

The paper reports upon numerical simulation tests carried out on a variable displacement axial piston pump equipped with multiple automatic controls. The swashplate control circuit includes two classical hydraulic stages with two tandem 3-way valves (the pressure compensator and the flow limiter), and a digitally driven valve which acts as a hybrid torque or/and speed limiter. The dynamic response of the system is evaluated for both separate and combined control functions. The effect of changes in the design parameters of the digital control circuit is discussed with reference to the system response to various load demands.