Abstract: In order to reveal dominant mechanism of the flow-dead-zone of a hydraulic pump in pump control system, a mathematical model of the hydraulic pump, including the flow-dead-zone, is established in this paper. The model takes into account the leakage in the hydraulic pump caused by differential pressure flow and shear flow as well as the compressibility of oil. Through analyses of the mathematical model, it is concluded that the width of the flow-dead-zone of the hydraulic pump increases with increase of the outlet cavity, load pressure, oil temperature and start-up acceleration of the hydraulic pump, and decreases with increase of displacement of the hydraulic pump. For this reason, taking a gear pump as an example, a Simulink-Amesim joint simulation model is established to study further effects of different load pressure, oil temperature and start-up acceleration on the dead zone width, and verify the results from theoretical analyses. The results show that the dead zone width of hydraulic pump flow has a linear relationship with load pressure and start-up acceleration, and is close to an exponential relationship with oil temperature.

Key words: pump control system, flow-dead-zone, leakage, gear pump, Simulink-Amesim