• Title/Summary/Keyword: Backdrivability

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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.

Design of Clutch Mechanism for Increased Actuator Energy Efficiency of Electrically Actuated Lower Extremity Exoskeleton (전기식 하지 외골격 로봇의 구동기 에너지 효율 향상을 위한 클러치 메커니즘 설계)

  • Kim, Ho Jun;Kim, Wan Soo;Lim, Dong Hwan;Han, Chang Soo
    • Journal of the Korean Society for Precision Engineering
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    • v.33 no.3
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    • pp.173-181
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    • 2016
  • This paper reports on the development of a roller-cam clutch mechanism. This mechanism can transfer bidirectional torque with high backdrivability, as well as increase actuation energy efficiency, in electrical exoskeleton robots. The developed mechanism was installed at the robot knee joint and unclutched during the swing phase which uses less metabolic energy, thereby functioning as a passive joint. The roller-cam clutch aimed to increase actuation energy efficiency while also producing high backdrivability by generating zero impedance for users during the swing phase. To develop the mechanism, mathematical modeling of the roller-cam clutch was conducted, with the design having more than three safety factors following optimization. Titanium (Ti-6AL-4V) material was used. Finally, modeling verification was done using ANSYS software.

A Study of Hydraulic Actuator Based On Electro Servo Valve For A Walking Robot (보행 로봇을 위한 서보밸브 구동 유압 액추에이터의 특성 분석)

  • Cho, Jung San
    • Journal of Drive and Control
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    • v.13 no.2
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    • pp.26-33
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    • 2016
  • This paper describes of a mathematical and real experimental analysis for a walking robot which uses servo valve driven hydraulic actuator. Recently, many researchers are developing a walking robot based on hydraulic systems for the difficult and dangerous missions such as walking in the rough terrain and carrying a heavy load. In order to design and control a walking robot, the characteristics of the hydraulic actuators in the joint through the view point of walking such as controllability and backdrivability must be analyzed. A general mathematical model was used for analysis and proceeds to position and pressure changes characteristic of the input and backdrivability experiment. The result shows the actuator is a velocity source, had a high impedance, the output stiffness is high in contact with the rigid external force. So stand above the controller and instruments that complement the design characteristics can be seen the need to apply a hydraulic actuator in walking robot.

Development of a 4-DOF Continuum Robot Using a Spring Backbone (스프링 구조를 이용한 4자유도 연속체 로봇의 개발)

  • Yoon, Hyun-Soo;Yi, Byung-Ju
    • The Journal of Korea Robotics Society
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    • v.3 no.4
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    • pp.323-330
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    • 2008
  • This work deals with a 4-DOF flexible continuum robot that employs a spring as its backbone. The mechanism consists of two modules and each module has 2 DOF. The special features of the proposed mechanism are the flexibility and the backdrivability of the whole body by using a spring backbone. Thus, even in the case of collision with human body, this device can ensure safety. The design and the kinematics for this continuum mechanism are introduced. The performance of this continuum mechanism was shown through simulation and experiment.

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Design of a novel haptic mouse system

  • Choi, Hee-Jin;Kwon, Dong-Soo;Kim, Mun-Sang
    • 제어로봇시스템학회:학술대회논문집
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    • 2002.10a
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    • pp.51.4-51
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    • 2002
  • $\textbullet$ A noval haptic mouse system is developed for human computer interface. $\textbullet$ Five bar mechanism is adapted for 2 dof force feedback with virtual environment. $\textbullet$ Double prismatic joint type mechanism is adapted to reflect 1 dof grabbing force feedback. $\textbullet$ Cable driven mechansim is used for actuation to reduce backlash and endow backdrivability. $\textbullet$ Virtual wall perception experiment is conducted to obtain force specification for haptic mouse. $\textbullet$ Average mouse workspace is measured using magnetic position tracker.

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Impedance Control of Backdrivable Hydraulic Actuation Systems with Explicit Disturbance Estimation (직접 외란 추정을 통한 역구동성 유압 구동 시스템의 임피던스 제어)

  • Yoo, Sunkyum;Chung, Wan Kyun
    • The Journal of Korea Robotics Society
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    • v.14 no.4
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    • pp.348-356
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    • 2019
  • The backdrivable servovalve is a desirable component for force and interaction control of hydraulic actuation systems because it provides direct force generation mechanical impedance reduction by its own inherent backdrivability. However, high parametric uncertainty and friction effects inside the hydraulic actuation system significantly degrade its advantage. To solve this problem, this letter presents a disturbance-adaptive robust internal-loop compensator (DA-RIC) to generate ideal interactive control performance from the backdrivable-servovalve-based system. The proposed control combines a robust internal-loop compensator structure (RIC) with an explicit disturbance estimator designed for asymptotic disturbance tracking, such that the controlled system provide stable and ideal dynamic behavior for impedance control, while completely compensating the disturbance effects. With the aid of a backdrivable servovalve, we show that the proposed control structure can be implemented based on a simplified nominal model, and the controller enables implementation without accurate knowledge of the target system parameters and disturbances. The performance and properties of the proposed controller are verified by simulation and experiments.

Joint Position Control using ZMP-Based Gain Switching Algorithm for a Hydraulic Biped Humanoid Robot (유압식 이족 휴머노이드 로봇의 ZMP 기반 게인 스위칭 알고리즘을 이용한 관절 위치 제어)

  • Kim, Jung-Yup;Hodgins, Jessica K.
    • Journal of Institute of Control, Robotics and Systems
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    • v.15 no.10
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    • pp.1029-1038
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    • 2009
  • This paper proposes a gain switching algorithm for joint position control of a hydraulic humanoid robot. Accurate position control of the lower body is one of the basic requirements for robust balance and walking control. Joint position control is more difficult for hydraulic robots than it is for electric robots because of an absence of reduction gear and better back-drivability of hydraulic joints. Backdrivability causes external forces and torques to have a large effect on the position of the joints. External ground reaction forces therefore prevent a simple proportional-derivative (PD) controller from realizing accurate and fast joint position control. We propose a state feedback controller for joint position control of the lower body, define three modes of state feedback gains, and switch the gains according to the Zero Moment Point (ZMP) and linear interpolation. Dynamic equations of hydraulic actuators were experimentally derived and applied to a robot simulator. Finally, the performance of the algorithm is evaluated with dynamic simulations.