Energy-saving design of variable-displacement bi-directional pump-controlled electrohydraulic system

Abstract

Losses in control valves drag down the average overall efficiency of electrohydraulic systems to only about 22% from nearly 75% for standard pump-motor sets. For achieving higher energy efficiency in slower systems, direct pump control replacing fast-response valve control is being put in place through variable-speed motors. Despite the promise of a quicker response, displacement control of pumps has seen slower progress for exhibiting undesired oscillation with respect to the demand in some situations. Hence, a mechatronic simulation-based design is taken up here for a variable-displacement pump–controlled system directly feeding a double-acting single-rod cylinder. The most significant innovation centers on designing an axial-piston pump with an electrohydraulic compensator for bi-directional swashing. An accumulator is conceived to handle the flow difference in the two sides across the load piston. A solenoid-driven sequence valve with P control is proposed for charging the accumulator along with setting its initial gas pressure by a feedforward design. Simple proportional–integral–derivative control of the compensator valve is considered in this exploratory study. Appropriate setting of the gains and critical sizing of the compensator has been obtained through a detailed parametric study aiming low integral absolute error. A notable finding of the simulation is the achievement of the concurrent minimum integral absolute error of 3.8 mm s and the maximum energy saving of 516 kJ with respect to a fixed-displacement pump. This is predicted for the combination of the circumferential port width of 2 mm for the compensator valve and the radial clearance of 40 µm between each compensator cylinder and the paired piston.

Load sensitive control characteristics of a novel two-dimensional pulse width modulated variable mechanism

“…At present, the relatively common load sensing system is the combination of load sensing plunger pump and load sensing control valve, 5,6 which enables the entire hydraulic system to be supplied with the appropriate pressure and flow rate for the load required. When the system is in operation, the pressure compensator of the variable piston pump can sense the flow demand of the system and provide adjustable flow according to the flow demand caused by the change of system conditions.…”

“…There are many factors that affect the efficiency of the hydraulic system, 1 so there should be many solutions to improve the efficiency of the hydraulic system, load sensitivity is one of ideal design schemes which is widely used in various fields such as engineering machinery, aerospace, weapons, and equipment. [2][3][4] At present, the relatively common load sensing system is the combination of load sensing plunger pump and load sensing control valve, 5,6 which enables the entire hydraulic system to be supplied with the appropriate pressure and flow rate for the load required. When the system is in operation, the pressure compensator of the variable piston pump can sense the flow demand of the system and provide adjustable flow according to the flow demand caused by the change of system conditions.…”

Modeling and control of a high-quality electro-hydraulic actuator driven via an induction motor under intelligent indirect vector control

“…Electro-hydraulic system (EHS) covers all combinations of electrical (electronic) signal processing with hydraulic drives. The EHS consists of high-power hydraulic devices such as pumps, valves, and actuating cylinders or motors with fast response electronically controlled drives [1]. In many engineering applications, electro-hydraulic components are often employed [2][3][4][5].…”

Modeling and Control of a High-Quality Electro-hydraulic Actuator Driven by an Induction Motor under Intelligent Indirect Vector Control

“…The intelligent speed controller for a three-phase IM which drives an electro-hydraulic system loaded by a hydraulic hoist is shown in the block diagram of Fig (1) and is based on PI fuzzy logic. Following subsections will go into more detail on the modeling of the major parts of the proposed electrohydraulic system that was completed in the MATLAB/Simulink environment.…”

“…The term Electro-hydraulic system (EHS) covers all combinations of electrical (electronic) signal processing with hydraulic drives. The EHS consists of high powerdensity hydraulic devices such as pumps, valves, and actuating cylinders or motors together with fast response electronically controlled drives [1]. In many engineering applications, electro-hydraulic components are often employed [2][3][4][5].…”