Abstract: In order to solve the flow asymmetry of the differential cylinder caused by two-chamber area difference, the structure characteristics of asymmetrical pump is applied to compensate automatically flow during motion. However, because the difference of two-cavity area is not a strict proportion relation and there are nonlinear effects such as cavitations and leaks, the speed is inconsistent when differential cylinder stretched and retracted, the performance of dynamic and static is poor, and the energy consumption is big. In Light of this，the four-quadrant operation features of the asymmetrical pump controlled differential cylinder system are analyzed, the energy transfer model is established, the relationship between energy consumption and speed is theoretically explained, and the experiment of open-loop characteristics is verified. Further the characteristic curve of the differential cylinder velocity and motor speed is used as the feed-forward function of the closed-loop control. The control strategy of nonlinear dynamic feed-forward compensation is proposed. According to conditions the function is real-time called. The calculated value is used as the given value of motor speed to dynamically compensate the cylinder velocity. Simulation and experimental results show that the control strategy improves effectively the static and dynamic performance of speed when the differential cylinder stretched and retracted, raises the energy efficiency of the system.

Key words: Asymmetrical pump, Differential cylinder, Energy efficiency, Nonlinear dynamic feed-forward