Research On The Controllable Amplifier Of High Speed On-off Valve Bridge Based On ARM

Compared with the traditional continuous control of proportional spool valve port, high-speed on-off valve has the advantages of easy processing, reliable, anti-pollution, easy maintenance and easy to realize computer-controlled, etc, hydraulic valves bridge constructed with high-speed on-off valves, it is usually as a pilot part of proportional valve, this kind of proportional valve displace traditional proportional valve is one of the trends in high contamination applications such as mechanical engineering. As the pilot part of proportional valve, high-speed on-off valves bridge control pilot flow into the main valve control chamber precisely according to the reference signal and the feedback signal of the main valve spool position, and then control the spool position of main valve. The key question is to build the control rule of high-speed on-off valves bridge and to design the hardware and software of valve bridge amplifier which can realize the control rule.In this paper, hydraulic valve bridge constructed with four high-speed on-off valves(two valves normally open and two normally closed valves)as the study focus, the research as following:The working principle of proportional valve as a pilot valve is analyzed, and to analogy negative sides of the slide valve works, two half-bridge PWM(pulse width modulation) control and complementary method of high-speed on-off valves bridge is proposed:1)In course of high-speed on-off valve work, according to the position deviation of the main valve spool, by the PID control algorithm to obtain the variation rule of the PWM signal duty cycle of four high-speed on-off valve; 2)The valves bridge is constitute of left half-bridge and right half-bridge, the PWM control signal of two high-speed on-off valves(one normally open valve and one normally closed valve) in each half bridge has same empty ratio variation law; 3)PWM signal duty cycle variation control of the left and right half-bridge high-speed on-off valve is contrary, and the sum of PWM control signal duty cycle of two half-bridge is always 1, the two half-bridge complementary control is formed; 4)When the main valve spool has not reached the target position, the left and right half-bridge high-speed on-off valves’ PWM signal duty cycle is different, the main valve in response to the average of PWM signal, the direction of movement corresponding to the larger duty cycle. 5)When the main spool reaches the target position, the complementary PWM signal duty cycle of the left and right half-bridge is equal, the main valve high frequency slight flutter at the target position, it can improve the dynamic characteristics of the main valve effectively. This control method has been applied for a patent.The model of proportional valve which pilot part is hydraulic valves bridge constructed with high-speed on-off valves is established, the simulation use two complementary half-bridge PWM control law in AMESim out to verify the validity of the complementary control method.The high-speed on-off valves bridge controller in which ARM chip is core and power amplifier with four tubes CMOS H-bridge driver circuit was designed, the power supply circuit, LVDT(spool position feedback sensor) driving circuit, LVDT feedback measuring amplifier, sampling signal amplifying circuit and CAN bus communication interface and other major hardware circuit also was designed, programmed the PWM signal generator, A/D converter and PID control algorithm procedures. The control amplifier parameter setting and commissioning of the control system of the host computer is developed by LabVIEW. To demonstrate the effectiveness of high-speed on-off valves bridge control program, the high-speed on-off valves bridge control experimental system is designed based on ARM development board and take the PVG valve of Danfoss as control target.