Citation: Wu, J.; Liu, Y.; Zhao, J.;
Zang, X.; Guan, Y. Research on
Theory and a Performance Analysis
of an Innovative Rehabilitation Robot.
Sensors 2022, 22, 3929. https://
doi.org/10.3390/s22103929
Academic Editors: Yuansong Qiao
and Seamus Gordon
Received: 22 March 2022
Accepted: 17 May 2022
Published: 22 May 2022
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Article
Research on Theory and a Performance Analysis of an
Innovative Rehabilitation Robot
Junyu Wu , Yubin Liu *, Jie Zhao, Xizhe Zang and Yingzi Guan
Mechanical and Electrical Engineering, Harbin Institute of Technology, Harbin 150001, China;
21b908013@stu.hit.edu.cn (J.W.); jzhao@hit.edu.cn (J.Z.); zangxizhe@hit.edu.cn (X.Z.); guanyz@hit.edu.cn (Y.G.)
* Correspondence: liuyubin@hit.edu.cn
Abstract:
This paper presents an innovative application of a 6-DOF robot in the field of rehabilitation
training. This robot operates in a parallel fashion for lower limb movement, which adopts a new
structure that can help patients to carry out a variety of rehabilitation exercises. Traditional parallel
robots, such as the Stewart robot, have the characteristics of strong bearing capacity. However, it is
difficult to achieve high-speed, high-acceleration and long journey movement. This paper presents a
new robot configuration that can address these problems. This paper also conducts an all-around
characteristic analysis of this new parallel robot, including kinematics, dynamics and structure, to
better study the robot and improve its performance. This paper optimizes an algorithm to make
it more suitable for rehabilitation training. Finally, the performance improvements brought by
optimization are verified by simulations.
Keywords: parallel robot; washout algorithm; performance analysis; rehabilitation training
1. Introduction
Due to an aging population and increases in the number of stroke patients, physical
disabilities and other problems, the number of physically unstable people is growing.
Human balance disorders are not only a focus of current research in the medical field
but also an urgent problem to be solved. A large portion of instability problems can be
attributed to abnormalities in the human motion sensing system, especially the degradation
or loss of the vestibular sensing system [
1
]. The main function of a robot is to help patients
train through motion simulation. By compelling patients to carry out various rehabilitation
exercises, they are constantly stimulated to produce vestibular sensation to guide the brain
to actively integrate and improve the ability of various motion sensing organs [
2
]. Another
function occurs under the auxiliary protection of a suspension device; the robot can be
used to create an unstable simulation environment. We can then obtain a patient’s fall
information for a subsequent evaluation of the type or degree of balance disorder.
This paper introduces the structure and advantages of this new robot. The character-
istics of the new robot are analyzed. To realize a variety of motions in a limited range of
motion, this paper uses a washout control algorithm. To overcome the limitations of the
classic washout algorithm, the MOGA (Multi-Objective Genetic Algorithm) algorithm is
used to optimize the filter parameters, find the most suitable parameters, and improve the
fidelity of motion simulation.
2. Mechanisms of Lower Limb Rehabilitation Robots
2.1. Research Status
At present, the research on rehabilitation training robots is mainly divided into two
categories: wearable exoskeleton robots and end robots. Lokomat [
3
] and Bleex [
4
] are
notable exoskeleton robots. The Lokomat lower limb rehabilitation robot, developed by
the Hocoma Company in Zurich, Switzerland, is based on a traditional weight reduction
Sensors 2022, 22, 3929. https://doi.org/10.3390/s22103929 https://www.mdpi.com/journal/sensors
