Dynamic performance is an important index of high-speed on/off valve in the digital hydraulic field. Optimizing the control algorithm is an effective method to improve the dynamic performance of existing high-speed on/off valves. Usually, a high-voltage excitation method is used to realize fast switching of the high-speed on/off valve, but this also leads to a high temperature rise, large energy consumption, and long delay times when switching off. In this article, an intelligent pulse-width modulation control algorithm is proposed to improve dynamic performance while minimizing temperature rise and energy consumption of high-speed on/off valves. A high-frequency voltage source with full positive, low positive, full negative, and zero duty ratios is applied to drive the high-speed on/off valve in opening, maintaining opened, closing and maintaining closed states, respectively. The adaptive switching of these four duty ratios is realized by real-time current feedback which can estimate the operational state of the high-speed on/off valve, so that the current in the loop is always in the optimal state. A mathematical model of the high-speed on/off valve is built, and based on it, the theoretical formulas for the delay time, temperature rise, and energy consumption of the high-speed on/off valve are deduced. Simulation results indicate that the intelligent pulse-width modulation control algorithm has a better performance in dynamic characteristics than normal high-voltage excitation methods. Moreover, experimental results from a test system indicate that the intelligent pulse-width modulation control has the potential to shorten the opening time by 23.6% and closing time by 17.0%, which confirms the simulation results. Results also showed the ability to extend the controllable working duty ratio by 83.3%, to reduce temperature rise by 69.9%, and reduce energy consumption by 88.8% when compared to the matched controller of the tested high-speed on/off valve. This article presents an effective and practical method to improve the performance of high-speed on/off valves.

The limit working parameters and service life of axial piston pump are determined by the carrying ability and lubrication characteristic of its key friction pairs. Therefore, the design and optimization of the key friction pairs are always a key and difficult problem in the research on axial piston pump. In the traditional research on piston/cylinder pair, the assembly relationship of piston and cylinder bore is simplified into ideal cylindrical pair, which can not be used to analyze the influences of radial micro-motion of piston on the distribution characteristics of oil-film thickness and pressure in details. In this paper, based on the lubrication theory of the oil film, a numerical simulation model is built, taking the influences of roughness, elastic deformation of piston and pressure-viscosity effect into consideration. With the simulation model, the dynamic characteristics of the radial micro-motion and pressure distribution are analyzed, and the relationships between radial micro-motion and carrying ability, lubrication condition, and abrasion are discussed. Furthermore, a model pump for pressure distribution measurement of oil film between piston and cylinder bore is designed. The comparison of simulation and experimental results of pressure distribution shows that the simulation model has high accuracy. The experiment and simulation results demonstrate that the pressure distribution has peak values that are much higher than the boundary pressure in the piston chamber due to the radial micro-motion, and the abrasion of piston takes place mainly on the hand close to piston ball. In addition, improvement of manufacturing roundness and straightness of piston and cylinder bore is helpful to improve the carrying ability of piston/cylinder pair. The proposed research provides references for designing piston/cylinder pair, and helps to prolong the service life of axial piston pump.