# Oscillation Suppression Method of Digital Proportional Valve Based on Fuzzy Intelligent PID Control
## 1 Introduction  
Traditional proportional valves utilize proportional electromagnets as electromechanical conversion elements to control the movement of valve spools, which gives rise to issues such as high cost, sensitivity to oil pollution, and low reliability. By contrast, digital proportional valves (DPV) with high-speed on/off valves (HSV) serving as the pilot part possess merits such as strong anti-pollution capability, high reliability, convenient manufacture, and flexible control. Moreover, as the core control element in the intelligent development of hydraulic systems, HSV has excellent application prospects. Several studies have employed proportional valves and systems with HSV as control components. In the mid-1990s, Eaton [1, 2] developed the Hydraulic Feedback Valvistor, a two-way cartridge proportional flow valve that uses a pulse width modulation (PWM) signal to control the two-position four-way proportional valve as the pilot section. Parker [3] developed the VPL series proportional valves, which use two two-position three-way HSV as the pilot section to control the movement of the main spool. Danfoss [4] developed PVG series proportional multi-way valves, comprising four HSV as the pilot section to control the pressure of the two control chambers of the main spool. SIL/PL, developedby Atos company, is a new DPV based on the bus [5]. [PERSON] et al. [6] designed a water-hydraulic DPV, in which eight HSV with pulse width modulation are used as the pilot section to control the movement of the main spool. Prof. [PERSON]'s research group studied the proportional valve controlled by the high-speed on/off valve bridge (HSVB) based on ARM and proposed the PWM complementary control method between the two half-bridges of the HSV [7]. [PERSON] et al. [8] studied the hydraulic cylinder position system controlled by two two-position three-way HSV and proposed a sliding mode control algorithm to suppress the un-certain factors in the model. [PERSON] et al. [9; 10] designed an adaptive robust control method for a hydraulic cylinder controlled by HSV and directional valve. [PERSON] et al. [11] used four pneumatic HSV to control the cylinder and adopted an adaptive robust controller considering the influence of viscosity and Coulomb friction, and the experimental error was less than 2.4%. [PERSON] et al. [12] studied the intelligent control method of the wheatstone valve bridge composed of four poppet valves. Tampere University of Technology used four groups of twenty threaded cartridge on/off valves to control the actuators and achieve more energy-saving flow control [13]. [PERSON] et al. [14] used a hybrid control method to regulate the pressure system controlled by the HSVB in real time. Purdue University in the United States used a combination of five poppet valves to study a robust adaptive control strategy and realize trajectory tracking control and energy-saving control [15]. Hunan Intelligent Digital Hydraulic Valve Company (Liling, China) has developed IDP series load-sensing proportional multi-way valves with the on/off type [16]. Evidently, considerable research has been conducted on the structure of the proportional valve with HSV as the pilot section and the hydraulic cylinder position system with HSV as the control element. However, the control method of the proportional valve controlled by four HSV as the pilot bridge, as well as the method of suppressing oscillation of DPV, have not been adequately investigated. [PERSON] et al. [17; 18; 19; 20; 21; 22] developed a series optimal intelligent control approach for seismic control of buildings equipped with active hybrid energy storage management in a wind-dominated standalone system, which combined classic PID control with intelligent control technology and represents more efficient control performance and robustness. In addition, we have noticed that the fuzzy intelligent PID control method has also been utilized in other fields. [PERSON], NM et al.