Novel Design and Implementation of a Knee Exoskeleton for Gait Rehabilitation with Impedance Control Strategy


  • Nattapat Kieuvongngam Chulalongkorn University
  • Anan Sutapun Haxter Robotics
  • Viboon Sangeveraphunsiri Chulalongkorn University



gait exoskeleton robot, rehabilitation robot, cable-driven mechanism, impedance control, active assistive control strategy


This paper presents a novel cable-driven robotic joint for a gait exoskeleton robot. We discussed in detail a lightweight, low inertia, and highly back-drivable, 1-DOF tension amplification mechanism based on a pulley system and block-and-tackle technique. The exoskeleton is controlled using an impedance controller under the active-assistive and resistive approaches. Four experiments were conducted to evaluate the proposed exoskeleton’s safety and controller performance: mechanical transparency analysis, active-assistive trajectory tracking, resistance of trajectory tracking, and gait rehabilitation. The exoskeleton demonstrated high transparency with the root mean square (RMS) torque of 0.457 Nm under no-load condition, suggesting that the mechanism is highly back-drivable, has a low moment of inertia, and is mechanically safe to operate. The active-assistive trajectory tracking experiment indicated that the output torque was generated under assist-as-needed approach, as the average robotic-assistance torque was lowered by more than 73% when the user provided assistance force to complete the task on their own.  Additionally, the resistance experiment revealed the feasibility of employing the exoskeleton to strengthen muscles with adjustable resistive torque from 0.94 Nm and 2.25 Nm. Finally, the result of gait rehabilitation experiment demonstrated that the robot was able to provide adequate torque to assist users in completing their gait cycle without causing any negative effects during or after the experiment.


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Author Biographies

Nattapat Kieuvongngam

Department of Mechanical Engineering, Faculty of Engineering, Chulalongkorn University, 254 Phayathai Rd., Pathumwan, Bangkok 10330, Thailand

Anan Sutapun

Haxter Robotics, Bangkok 10330, Thailand

Viboon Sangeveraphunsiri

Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand


Published In
Vol 26 No 11, Nov 30, 2022
How to Cite
N. Kieuvongngam, A. Sutapun, and V. Sangeveraphunsiri, “Novel Design and Implementation of a Knee Exoskeleton for Gait Rehabilitation with Impedance Control Strategy”, Eng. J., vol. 26, no. 11, pp. 13-27, Nov. 2022.