Pulse-Width-Modulation-Based Time-Delay Compensation Control for High-Speed On/Off Valves

Abstract

The dynamic characteristics of high-speed on/off valves (HSVs) are a key factor in measuring their performance, and determining the control accuracy of valve-controlled systems. Furthermore, the hysteresis characteristics of HSVs can seriously affect their dynamic characteristics. This study evaluated the hysteresis characteristics of HSVs in a valve-controlled hydraulic control system, and considered the pressure changes in front of the valve during the opening and closing process of the valve core. A time-delay compensation control (TDCC) based on pulse-width modulation (PWM) was proposed. The reference PWM signal was used to control the opening and closing time of the HSV, while the loading signal was composed of an opening compensation PWM, an excitation PWM, an opening holding PWM, and a closing compensation PWM. Using an opening compensation PWM to start the initial current, combined with current feedback and pressure changes in front of the valve, the amplitude and duty cycle of different PWM signals were determined in real time. This reduced the time delay and working current of the HSV during opening and closing. A simulation comparison analysis was conducted, with a single PWM control and a pre-excitation control algorithm (PECA). The results showed that, compared to a single PWM control, the TDCC can reduce the overall opening and closing time delay by 78.1%, and the energy consumption by 64.7%. Compared with PECA, the overall opening and closing time delay was reduced by 10.9%, and the energy consumption was reduced by 28%. At the same time, the frequency response of the valve core displacement increased by 70%, compared to the single PWM control.