A continuously variable hydraulic pressure converter based on high-speed on–off valves

A continuously variable hydraulic pressure converter utilizing high-speed on–off valves is studied in this paper. The hydraulic pressure converter is analogous to a switchmode buck converter in power electronics. Substituting the electronic components in the buck converter with their hydraulic counterparts, a hydraulic pressure converter is built. The steady state and fluctuation characteristics of the hydraulic pressure converter are studied in both the theoretical analysis and the simulation. The hydraulic pressure converter was built and tested. Experimental results show that the system output pressure can be continuously adjusted by changing the duty ratio of the PWM signal supplied to the high-speed on–off valve. Although there is fluctuation on the output pressure, the system output pressure has a quasi-linear relationship with the PWM signal duty ratio. Results also show that the output pressure fluctuation is greatly influenced by the PWM signal frequency and the flywheel inertia. The hydraulic pressure converter based on high-speed on–off valves brings a new way to transform system pressure continuously.