Analysis and application of pump controlled motor speed servos with/without a position loop

Mathematic models and a test system of pump controlled motor speed servos (PCMSS) with /without a position loop are established and their dynamic performances are studied by simulation and experiments. Results indicate that PCMSS with a position loop can achieve high stability and speed precision relying on the position closed loop in the pump and the motor speed closed loop, whereas PCMSS without a position loop is unstable only depending on the speed closed loop. Therefore, to achieve nice performances for PCMSS, the displacement of a variable delivery pump should be independently adjusted while motor's rotary speed is fed back and controlled in closed loop.