Motion Control Algorithm for a Lower Limb Exoskeleton Based on Iterative LQR and ZMP Method for Trajectory Generation

At present, the motion control algorithms of lower limb exoskeleton robots have errors in tracking the desired trajectory of human hip and knee joints, which leads to poor follow-up performance of the human-machine system. Therefore, an iterative learning control algorithm is proposed to track the desired trajectory of human hip and knee joints. In this paper, the experimental platform of lower limb exoskeleton rehabilitation robot is built, and the control system software and hardware design and robot prototype function test are carried out. On this basis, a series of experiments are carried out to verify the rationality of the robot structure and the feasibility of the control method. Firstly, the dynamic model of the lower limb exoskeleton robot is established based on the structure analysis of the human lower limb; secondly, the servo control model of the lower limb exoskeleton robot is established based on the iterative learning control algorithm; finally, the exponential gain closed-loop system is designed by using MATLAB software. The relationship between convergence speed and spectral radius is analyzed, and the expected trajectory of hip joint and knee joint is obtained. The simulation results show that the algorithm can effectively improve the gait tracking accuracy of the lower limb exoskeleton robot and improve the follow-up performance of the human-machine system.

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The control algorithm of the lower limb exoskeleton synchronous gait

MATEC Web of Conferences ◽

10.1051/matecconf/201816103010 ◽

2018 ◽

Vol 161 ◽

pp. 03010

Author(s):

Vladimir Antipov ◽

Alexey Postolny ◽

Andrey Yatsun ◽

Sergey Jatsun

Keyword(s):

Lower Limb ◽

Power Distribution ◽

Control Algorithm ◽

Center Of Mass ◽

Human Movement ◽

Lower Limbs ◽

Centre Of Mass ◽

Lower Limb Exoskeleton ◽

Synchronous Motion

In this article a study of algorithms for human movement in the lower limbs exoskeleton is presented. Human-machine system is considered, the classification of the existing exoskeletons by type of power distribution, the features of stable motion of the mechanism are presented. The law of the necessary trajectory of the center of mass of the exoskeleton is shown in the sagittal and frontal planes to maintain stability. The synchronous motion scheme of the centre of mass and the foot is described.

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Upper Extremity Load Reduction for Lower Limb Exoskeleton Trajectory Generation Using Ankle Torque Minimization

2020 16th International Conference on Control, Automation, Robotics and Vision (ICARCV) ◽

10.1109/icarcv50220.2020.9305430 ◽

2020 ◽

Author(s):

Yik Ben Wong ◽

Yawen Chen ◽

Kam Fai Elvis Tsang ◽

Winnie Suk Wai Leung ◽

Ling Shi

Keyword(s):

Upper Extremity ◽

Lower Limb ◽

Trajectory Generation ◽

Load Reduction ◽

Lower Limb Exoskeleton ◽

Ankle Torque

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Study on the control algorithm for lower limb exoskeleton based on ADAMS/Simulink co-simulation

Journal of Vibroengineering ◽

10.21595/jve.2017.17303 ◽

2017 ◽

Vol 19 (4) ◽

pp. 2976-2986 ◽

Cited By ~ 1

Author(s):

Lei Yan ◽

Hongfang Wu ◽

Tianyu Jia ◽

Na Li ◽

Jian Wu

Keyword(s):

Lower Limb ◽

Control Algorithm ◽

Lower Limb Exoskeleton

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Motion Adaption and Trajectory Generation of Stair Ascent and Descent with a Lower Limb Exoskeleton for Paraplegics

2019 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM) ◽

10.1109/aim.2019.8868901 ◽

2019 ◽

Author(s):

Chun-Hao Zhong ◽

Xuan Zhao ◽

Feng-Yan Liang ◽

Hao Ma ◽

Wei-Hsin Liao

Keyword(s):

Lower Limb ◽

Trajectory Generation ◽

Lower Limb Exoskeleton ◽

Stair Ascent

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Geriatric Walk Assist Robot - Design, Analysis and Implementation of a Modular Lower Limb Exoskeleton Robot

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.852.770 ◽

2016 ◽

Vol 852 ◽

pp. 770-775 ◽

Cited By ~ 1

Author(s):

P. Karthikeyan ◽

Gopal Satheesh Kumar ◽

M. Ajin

Keyword(s):

Lower Limb ◽

Control Algorithm ◽

Applied Pressure ◽

Pressure Sensors ◽

Gait Pattern ◽

The Body ◽

Sensors And Actuators ◽

Aged People ◽

Lower Limb Exoskeleton ◽

Exoskeleton Robot

Among the problems of major concern faced by the geriatric community the fore most is considered to be: “as we grow older it gets difficult to walk”. As they lose their strength to withstand their weight they become weak to walk on their own. Through this project a design is proposed for an assistive modular lower limb exoskeleton robot to enable aged people to walk on their own. The design is mainly based on the amplification of the pressure applied on the thighs and ankles of the legs and these pressures are used to move the legs of the robot which support the legs of the user. Since the user is capable of generating a minimum pressure on their own the working of the gait pattern is mainly based on the movement of knee and ankle, and so only the knee and the ankle are considered in this design. Another reason is that the major weight of the body acts on the knee and the foot while walking. The working of the robot is mainly based on the layered control algorithm embedded on the microcontroller acting through the sensors and actuators. Pressure sensors are used to measure the applied pressure and electrical actuators are used due to their lesser weight. Based on the experimental results obtained with the working robot the design would be fine-tuned for optimized performance.

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Simulating human–machine coupled model for gait trajectory optimization of the lower limb exoskeleton system based on genetic algorithm

International Journal of Advanced Robotic Systems ◽

10.1177/1729881419893493 ◽

2020 ◽

Vol 17 (1) ◽

pp. 172988141989349

Author(s):

Bin Ren ◽

Jianwei Liu ◽

Jiayu Chen

Keyword(s):

Genetic Algorithm ◽

Lower Limb ◽

Trajectory Optimization ◽

Physical Simulation ◽

Trajectory Generation ◽

Coupled Model ◽

Human Motion ◽

Machine Model ◽

Lower Limb Exoskeleton ◽

Simulation Engine

The lower limb exoskeleton robot is capable of providing assisted walking and enhancing exercise ability of humans. The coupling human–machine model has attracted a lot of research efforts to solve the complex dynamics and nonlinearity within the system. This study focuses on an approach of gait trajectory optimization of lower limb exoskeleton coupled with human through genetic algorithm. The human–machine coupling system is studied in this article through multibody virtual simulation environment. Planning of the motion trajectory is carried out by the genetic algorithm, which is iteratively generated under optimization of a set of specially designed fitness functions. Human motion captured data are used to guide the evolution of gait trajectory generation method based on genetic algorithm. Experiments are carried out using the MATLAB/Simulink Multibody physical simulation engine and genetic algorithm-toolbox to generate a more natural gait trajectory, the results show that the proposed gait trajectory generation method can provide an anthropomorphic gait for lower limb exoskeleton device.

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Trajectory Generation for a Lower Limb Exoskeleton for Sit-to-Stand Transition Using a Genetic Algorithm

Volume 1: Aerospace Applications; Advances in Control Design Methods; Bio Engineering Applications; Advances in Non-Linear Control; Adaptive and Intelligent Systems Control; Advances in Wind Energy Systems; Advances in Robotics; Assistive and Rehabilitation Robotics; Biomedical and Neural Systems Modeling, Diagnostics, and Control; Bio-Mechatronics and Physical Human Robot; Advanced Driver Assistance Systems and Autonomous Vehicles; Automotive Systems ◽

10.1115/dscc2017-5261 ◽

2017 ◽

Cited By ~ 1

Author(s):

Ameya S. Chamnikar ◽

Gaurav Patil ◽

Mohammadreza Radmanesh ◽

Manish Kumar

Keyword(s):

Genetic Algorithm ◽

Lower Limb ◽

Degrees Of Freedom ◽

Fitness Function ◽

Trajectory Generation ◽

The Body ◽

Assistive Device ◽

Reference Trajectory ◽

Lower Limb Exoskeleton ◽

Sit To Stand

Population of the world above the age of 65 years is increasing rapidly. Aging causes weakening of human joints which increases constraints on mobility of the body. Sit-to-Stand (STS), an important part of Activities of Daily Living (ADL) is one of the motions that is affected because of weakened joints. With the lack of personal care there is going to be a need for devices which can assist the aging population in STS. We propose the use of a lower-limb exoskeleton as an assistive device. One of the main challenges in this area is to generate a human like reference trajectory for exoskeleton to follow. This paper proposes the use of Genetic Algorithm (GA), to generate reference trajectories for the joint angles for lower limb exoskeleton for STS transition. The fitness function for the GA presented here is constructed based on the fact that for a successful STS center of mass (COM) needs to stay in the area of support. After the trajectory generation a simple controller is proposed to control a 3 degrees of freedom exoskeleton. The dynamics of the system being controlled are modelled as an inverse 3 degrees of freedom pendulum and the equations are derived using the Euler-Lagrange equation. The highly non-linear dynamics are linearized using an input-output feedback linearization technique. A PD controller is presented for this linearized dynamic system and the validation of the controller is done using simulations. Simulation results show that GA successfully generates a human like trajectory which eliminates the need to use motion tracking system for measuring human trajectories.

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