Modeling and Experimental Analysis of the Single-Shaft Coaxial Motor-Pump Assembly in Electrohydrostatic Actuators

Summary

We built a simulation model to evaluate pump flow characteristics and performance of the single-shaft coaxial motor-pump assembly in electrohydrostatic actuators and investigate the overall efficiency in a wide set of working conditions of the motor-pump assembly experimentally.

Abstract

An electrohydrostatic actuator (EHA) can be the most promising alternative compared with the traditional hydraulic servo actuators for its high power density, ease of maintenance, and reliability. As the core power unit that determines the performance and service life of the EHA, the motor-pump assembly should simultaneously possess a wide speed/pressure range and a high dynamic response.

This paper presents a method to test the performance of the motor-pump assembly through simulation and experimentation. The flow output characteristics were defined through simulation and analysis of the assembly at the beginning of the experiment, leading to the conclusion of whether the pump could meet the requirements of the EHA. A series of performance tests were conducted on the motor-pump assembly via a pump test bench in the speed range of 1,450-9,000 rpm and the pressure range of 1-30 MPa.

We tested the overall efficiency of the motor-pump assembly under various working conditions after confirming the consistency between the test results of the flow output characteristics with the simulation results. The results showed that the assembly has higher overall efficiency when working at 4,500-7,000 rpm under the pressure of 10-25 MPa and at 2,000-2,500 rpm under 5-15 MPa. Overall, this method can be utilized for determining in advance whether the motor-pump assembly meets the requirements of EHA. Moreover, this paper proposes a rapid test method of the motor-pump assembly in various working conditions, which could assist in predicting EHA performance.

Introduction

Known as a typically integrated actuator with high power density, the EHA has broad prospects in areas such as aerospace, aviation, construction machinery, and robotics^1,2. The EHA mainly consists of a servo motor, pump, cylinder, pressurized reservoir, valve block, mode control valves, module control valves, and sensors, constituting a highly integrated, pump-controlled, closed hydraulic system. The schematic diagram and physical model are shown in Figure 1^3,4,5,

Protocol

1. Simulation of pump flow characteristics

1. Build the simulation model of the motor-pump assembly. Open the AMESim simulation platform and enter the SKETCH mode.
   1. Build the simulation model for a single piston according to the kinematic mathematic model and the distribution curve (Figure 3). Encapsulate the single-piston model as a super component (Figure 4).
      NOTE: The main kinemati.......

Discussion

When conducting these experimental steps, it is important to make sure that the pressure measuring points are close enough to the oil port of the pump, which would greatly influence the experimental results. In addition, pay attention to the pressure of the inlet port of the motor-pump assembly to ensure that no cavitation exists, especially at high-speed working conditions.

This method enables a dynamic adjustment of oil supply pressure, realizing an accurate simulation of different working c.......

Materials

Name	Company	Catalog Number	Comments
AmeSim simulation platform	Siemens	Amesim 16
DAQ card	Advantech	PCI1710
Flowmeter	KRACHT	VC0.04E1RS, 0.02-4 L/min
Flowmeter	KRACHT	VC0.4E1RS, 0.2-40 L/min
Industrial Computer	Advantech	610H
Oil supply motor	Siemens	1TL0001-1BB23-3JA5
Oil supply pump	Kangbaishi	P222RF01DT
OriginPro	OriginLab Corporation	OriginPro 2021 (64-bit) 9.8.0.200
Pressure sensor	Feejoy	PI131G(0-5 MPA)F4MCAH5C
Proportional relief valve	Huade hydraulic	DBE10-30B/50YV
Proportional relief valve	Huade hydraulic	DBE10-30B/315YV
Spindle motor	HAOZHI	DGZX-18020 / 22A2-KFHWVJLS	Max speed: 18,000 rpm;  Power: 22 kW
Temperature sensor	Feejoy	TI-A42M1A180/30+F1