A Study of the Mechanism and Characteristics of a Pwm-based Valve Control System with No Throttle Loss

For the problem of low efficiency of conventional valve control systems, an economical PWM-based valve control system with no throttle loss is put forward and examined in this paper. There are four no-throttling-loss units used to control a single rod cylinder in this fixed displacement pump system, which breaks the mechanical linkage of meter-in and meter-out flow in the traditional four way directional valve. The no-throttle-loss valve control unit includes a normal opened 3/2 high speed ON/OFF valve as a pilot valve and a two-way cartridge valve as a main valve. Due to the special designs, the maximum pump flow could run through the unit with no throttle loss. The high response frequency of the unit allows to control the average flow of the main valve, as well as the position and speed of the load by regulating the duty cycle of PWM signal. Parallel to the main oil circuit, an energy recovery device is used to absorb the high pressure pump oil when the main valve is closed during a control period, which would ensure the relief valve works as a safety valve and avoid the overflow loss. First, the paper proposes a concept of no-throttling-loss valve control unit. And then, the principle of achieving the dual objectives of energy saving and fast dynamic response is illustrated. Finally, the system model is established based on AMESim, and the feasibility of the system program is verified by the simulation in this paper. Besides, the influence of the control frequency of PWM signal and the pilot valve frequency is discussed. The simulation results ensures the system’s merits of high dynamic response and energy saving.