Energy-Efficient Electro-Hydraulic Power Source Driven by Variable-Speed Motor

Abstract

Hydraulic systems are widely used in industry due to their small size-to-power ratios and their ability to produce very large linear force and torque. In traditional hydraulic systems, a variable pump driven by an electric motor is often used as power source. In these systems, the electro-hydraulic power source always operates at its rated speed, causing lots of noise and low energy consumption, especially in no-load and light-load conditions. These problems can be solved by changing the speed of the electric motor according to the load state of the electro-hydraulic power source. In order to improve the energy efficiency of the electro-hydraulic power source and realize pressure and flow control on the basis of low cost, this paper presents the power-source structure of a variable-displacement pressure-compensated pump driven by a variable-speed electric motor; this controls the flow by adjusting the electric motor speed and controls the pressure with the variable-displacement pressure-compensated pump. However, for the variable-speed system, the starting of the electric motor with a load is relatively slow; this makes it difficult to meet the demand of flow control, and will also have a great impact on the power grid. To address these problems, a hydraulic accumulator is introduced to the inlet port of the hydraulic pump to assist in starting the pump. This method can realize the combined control of pressure, flow and power, and has high energy efficiency. This research uses experiments to verify the feasibility of the scheme, and the results show that the starting periods of the power source can be shortened from 2.8 s to 0.7 s when the load pressure is about 18 MPa. Furthermore, regarding maintaining pressure without flow outputs, the energy consumption of the designed power source can be reduced by almost 30% compared with a pure variable-displacement power source.

Action research of lean 4.0 application to the maintenance of hydraulic systems in steel industry

“…However, these assets are susceptible to many kinds of failures, which became crucial to detect them prematurely to prevent dangerous conditions in an industrial environment. Fault diagnosis in hydraulic systems is a big challenge for industrial maintenance, so with artificial intelligence advances, it becomes possible to provide a diagnosis based on field signals such as temperature, pressure and vibrations (Yan et al. , 2022).…”

Static Characteristics and Energy Consumption of the Pressure-Compensated Pump

“…During the control process, the pump parameters change, whether it is the pump displacement or the pump speed. These changes affect the pump efficiency, which varies depending on the current boundary conditions [1][2][3]. In order to compare the different types of control, it is necessary to determine the pump characteristics and efficiencies for the different operating conditions that may occur during and after pump control [4].…”

“…In their results, it is summarized that after the displacement control from the maximum value to the minimum value and the subsequent speed control from 1800 min −1 to 300 min −1 , it is possible to save 83% of the original input power. Displacement control and speed control are also addressed in the study in [2]. Their results show that by reducing the speed from 1500 min −1 to 300 min −1 , they saved 3 kW of input power in their case.…”

An Energy-Efficient Adaptive Speed-Regulating Method for Pump-Controlled Motor Hydrostatic Drive Powertrains

“…Its core principle is to adopt the existing or added control freedom of a system to allow the prime mover (engine or electric motor) to work in its high-efficiency region, thus improving the overall efficiency of the transmission system. For example, Ge et pump speed through an electrohydraulic power source with variable speed and variable displacement and proposed a strategy of segmented speed and continuous displacement adjustment based on redundant freedom to meet the energy-saving regulation on output flow [13,14]. Wang et al designed a power split hydraulic torque converter to replace the traditional torque converter on a wheel loader and decoupled the engine and vehicle speeds by controlling the output pressure of the hydraulic torque.…”