Design of bilateral drive circuit on electro hydraulic proportional amplifier and comparison of dither signal

LIU Ning, YOU You-peng
(College of Mechanical and Electrical Engineering, Nanjing University of
Aeronautics and Astronautics, Nanjing 210016, China)

Abstract: In order to improve the precision and rapidity of proportional valve controled by digital proportional amplifier, the current interruption phenomenon of commonly used inverse discharging drive circuit was analyzed. A bilateral drive circuit with flexible working mode and its control logic were proposed. At the same time, the dither superposition and its effects of digital proportional amplifier were studied. A method which contains the dither information in the duty cycle of PWM control signal was presented. The effects of several common dither on the motion sensitivity and hysteresis of the spool were compared by modeling simulation and experiment. The results indicate that the bilateral drive circuit and its control logic can avoid the current interruption, improve the positioning accuracy of the proportional spool, and realize the rapid commutation of the proportional directional valve. The square wave dither is superior to the triangular wave dither and the sine wave dither in improving the movement sensitivity of the spool and reducing hysteresis. The hysteresis of the valve spool with 20% square wave dither is reduced by nearly 40% of that without dither, which can significantly improve the positioning accuracy of the proportional valve.
Key words: digital proportional amplifier; drive circuit; dither superposition; modeling and simulation