• Title/Summary/Keyword: Electro hydrostatic actuator

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Robust Internal-loop Compensation of Pump Velocity Controller for Precise Force Control of an Electro-hydrostatic Actuator (EHA의 정밀 힘제어를 위한 펌프 속도 제어기의 강인 내부루프 보상)

  • Kim, Jong-Hyeok;Hong, Yeh-Sun
    • Journal of Drive and Control
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    • v.15 no.4
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    • pp.55-60
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    • 2018
  • Force-controlled electro-hydrostatic actuators have to exhibit high backdrivability, to quickly compensate for force control errors caused by externally disturbed rod movement. To obtain high backdrivability, the servomotor for driving the hydraulic pump, should rotate exactly to such a revolution to compensate for force control errors, compressing or decompressing cylinder chambers. In this study, we proposed a modified velocity control structure, including a robust internal-loop compensator (RIC)-based velocity controller, for the servomotor to improve backdrivability of a force-controlled EHA. Performance improvement was confirmed experimentally, wherein sinusoidal velocity disturbance was applied to the force-controlled EHA, with constant reference input. Its dynamic force control errors reduced effectively, with the proposed control scheme, compared to test results with a conventional motordriver, for motor velocity control.

Comparison of Force Control Characteristics between Double-Rod and Single-Rod Type Electro-Hydrostatic Actuators (II): Back-Drivability (양로드형과 편로드형 EHA의 힘 제어 특성 비교(II): 역구동성)

  • Kim, Jong Hyeok;Hong, Yeh Sun
    • Journal of Drive and Control
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    • v.14 no.4
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    • pp.17-22
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    • 2017
  • In this study, the back-drivability of the single-rod and double-rod type EHAs (Electro-Hydrostatic Actuators) was compared by computer simulation and experiments. The back-drivability of EHAs exhibit non-linear behavior like their force tracking performance. In case of the double-rod type EHA, the back-drivability was mostly influenced by the bulk modulus of oil that changes with the working pressure due to entrapped air. The back-drivability of the single-rod type EHA was directly affected by the operation states of its pilot-operated check valves, while the asymmetrical piston geometry and the non-linear bulk modulus of oil also made the dynamic response in building up the cylinder pressure dependent on the operating conditions.

Force Fighting Suppressive Technique of Dual Redundant Asymmetric Tandem Electro-Hydrostatic Actuator for Aircraft (항공기용 이중화 비대칭형 직렬 전기-정유압 구동기의 Force Fighting 억제 기법)

  • Song, Woo Keun;Kim, Sang Seok;Choi, Jeong Seok;Lee, JungUn;Lee, Jong Cheol;Lee, Jun won;Choi, Jong Yoon
    • Journal of Aerospace System Engineering
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    • v.16 no.5
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    • pp.62-69
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    • 2022
  • EHA (Electro-Hydrostatic Actuator) is more energy efficiency than a centralized hydraulic system. In particular, the EHA used for aircraft has a redundant design in preparation for failure scenario. Also, due to the aircraft's internal space limitation, the actuator's length must be optimized. Therefore, a series configuration of double rod and single rod cylinder is advantageous. However, due to the asymmetry of the cross-sectional area of the piston, the force fighting phenomenon between the two cylinder areas occurs during redundant operation with a general control system. In this paper, the force fighting phenomenon of redundant EHA was simulated. A controller with load compensation and a force control-based position controller as a method to suppress its stimulation

A Position Control of EHA Systems using Adaptive PID Sliding Mode Control Scheme (적응PID 슬라이딩 모드 제어기법을 적용한 EHA 시스템의 위치제어)

  • Lee, Ji-Min;Park, Sung-Hwan;Park, Min-Gyu;Kim, Jong-Shik
    • Journal of Power System Engineering
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    • v.17 no.4
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    • pp.120-130
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    • 2013
  • An adaptive PID sliding mode controller is proposed for the position control of electro-hydrostatic actuator(EHA) systems with system uncertainties and saturation in the motor. An EHA prototype is developed and system modeling and parameter identification are executed. Then, adaptive PID sliding mode controller and optimal anti-windup PID controller are designed and the performance and robustness of the two control systems are compared by experiment. It was found that the adaptive PID sliding mode control system has better performance and is more robust to system uncertainties than the optimal anti-windup PID control system.

Synchronous Control of an Asymmetrical Dual Redundant EHA (비대칭 이중화 EHA의 동기 제어)

  • Lee, Seong Ryeol;Hong, Yeh Sun
    • Journal of Drive and Control
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    • v.13 no.2
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    • pp.1-9
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    • 2016
  • In this paper, an elementary force fighting problem was investigated. The problem is encountered when a double-rod type EHA(electro-hydrostatic actuator) is combined with a single-rod type EHA to build a redundant actuator system with synchronized motion. When the rod-side chambers of the two different types of EHAs have the same effective piston areas and are simultaneously pressurized by an external load, the two EHAs behave identically, sharing the external load equally. However, when the piston head-side chamber of the single rod type EHA, having a larger effective area than the rod-side chamber, is pressurized by the external load, an abnormal force fighting between the two EHAs occurs, unless their pump speeds are properly decoupled. In this study, the output drive forces of each EHA were obtained from the cylinder pressure signals and applied to the position control for each EHA to maintain the balance between their pump speeds. Adding minor force difference feedback loops to the position control, the force fighting phenomena could be eliminated and steady state synchronization errors were reduced. The power consumption of the pumps also could be remarkably reduced, avoiding unnecessarily high load pressures to the pumps.

Comparison of Force Control Characteristics Between Double-Rod and Single-Rod Type Electro-Hydrostatic Actuators (I): Tracking Performance (양로드형과 편로드형 EHA의 힘 제어 특성 비교(I): 추종 성능)

  • Kim, Jong Hyeok;Hong, Yeh Sun
    • Journal of Drive and Control
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    • v.14 no.4
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    • pp.9-16
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    • 2017
  • In this study, the force tracking performance of the single-rod and double-rod type EHAs (Electro-Hydrostatic Actuators) was compared by computer simulation and experiments. The force-controlled EHAs exhibit non-linear behavior that are significantly dependent on operation conditions. The investigation focused on localizing the parameters that provide significant rise to the non-linearity. For this, the single-rod and double-rod type EHAs were mathematically expressed to derive their linear models. In parallel, they were modeled by a commercial simulation program including non-linear properties based on experimental results. It was shown that the dependency of the bulk modulus of oil with entrapped air on working pressure dominated the non-linearity in force control performance in case of the double-rod type EHA. The force control of the single-rod type EHA was influenced by much more elements. Besides the asymmetrical piston geometry and the non-linear bulk modulus of oil, its pilot-operated check valves made it dependent not only on the magnitude of reference input but also on its direction.