DIGITAL HYDRAULIC SYSTEM USING PUMPS AND ON/OFF VALVES CONTROLLING THE ACTUATOR

Hydraulic systems employed in several industrial and mobile applications present significant advantages, such as a high power-to-weight ratio and fast dynamic response. However, these systems have low efficiency due to high power dissipation. A recent concept called "digital hydraulics" comprises particularities that create opportunities for a reduction in load loss. This paper proposes a configuration and control method for actuator speed control based on the principles of digital hydraulics. In this context, several fixed displacement units and on/off valves are connected directly to the actuators without throttling valves. The system studied here presents three operation methods (pump mode, motor mode and idle mode), which allows discrete valves to replace continuous or flow control valves in order to control the actuator. Furthermore, a fixed or variable displacement pump with large displacement is replaced by several small, fixed displacement units. Simulations are performed with a co-simulation technique using AMESim and MATLAB. The actuator speed, inlet and outlet pressures on the fixed displacement units and flow rate in the circuit lines are analysed. Preliminary simulation results exhibit smooth transitions between speed levels, adequate dynamic performance, low power dissipation and high energy-storage capacity. A specific limitation of this technology is the obtained actuator discrete speed. The main contributions of this research are the development of a digital hydraulic system configuration and its control strategy, which allows speed control of hydraulic actuators and provides the capacity to store energy.