Digital Hydraulic System Using Pumps and On/Off Valves Controlling the Actuator

Abstract

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.

Application of Hydraulic Energy-Saving Technology in the Teaching, Research, and Practice of Mechanical Engineering

“…Cristiano et al used on-off valves in the control process of digital hydraulic system actuators, where large-flow-rate quantitative pumps or variable displacement pumps were decomposed into multiple small flow rate quantitative pumps, and the actuator speed, inlet and outlet pressure, flow rate of the quantitative pump, and system flow rate were analyzed. The results showed that the proposed hydraulic control system exhibited stable speed changes, good dynamic characteristics, low power consumption, and high energy storage capacity [30]. Based on this research, Li et al proposed a digital control method for different actuators to share a hydraulic drive system.…”

A Review on Energy Consumption, Energy Efficiency and Energy Saving of Metal Forming Processes from Different Hierarchies

“…Another control strategy with particular potential to solve the mismatch problem is the application of digital hydraulics, which has recently achieved significant development. In a digital hydraulic system, a piston pump can be turned on or off by the valves to control the distribution of flow of the intervals between several outlets and to match the demanded flow of the cylinder [55]. Compared with traditional systems, digital hydraulics can reduce considerable energy loss, especially during partial load [56][57][58].…”

Classification and Review of Variable Displacement Fluid Power Pumps and Motors

“…This allowed each pump element to work in either pump, motor, or idling mode. Furthermore, digital pump solutions have also been proposed for aircraft actuators [49,59].…”