Trajectory Generation and Control of a Lower Limb Exoskeleton for Gait Assistance

The application of lower limb exoskeletons for gait assistance has attracted extensive attention in recent decades. Reference trajectory and assistive control are the important aspects determining the performance of the exoskeleton. During overground walking, there are certain variations in touchdow...

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Bibliographic Details
Published in:Journal of intelligent & robotic systems 2022-11, Vol.106 (3), Article 64
Main Authors: Luo, Lincong, Foo, Ming Jeat, Ramanathan, Manoj, Er, Jie Kai, Chiam, Chye Hsia, Li, Lei, Yau, Wei Yun, Ang, Wei Tech
Format: Article
Language:English
Subjects:
Angular position
Artificial Intelligence
Control
Electrical Engineering
Engineering
Exoskeletons
Fitness equipment
Gait
Legs
Mechanical Engineering
Mechatronics
Muscle strength
Regular Paper
Robotics
Spinal cord
Stroke
Trajectory control
Walking
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Summary:The application of lower limb exoskeletons for gait assistance has attracted extensive attention in recent decades. Reference trajectory and assistive control are the important aspects determining the performance of the exoskeleton. During overground walking, there are certain variations in touchdown position, step length and time as subjects have the requirement of adjusting gait pattern to maintain balance. In order to adapt to the different starting and ending foot location on the swing phase of gait, in this study, a dynamic movement primitives (DMPs)-based gait trajectory generation method is proposed to provide a flexible manner to online adjust the reference trajectory. Meanwhile, a time-independent path-based trajectory controller is developed to exert the assistance and guidance for the swing leg motion, where a lookahead distance is employed to search for the desired angular position in 4D hip-knee joint space. The combination of DMP-based reference generation and path-based trajectory control enables lower limb exoskeletons to reduce gait trajectory deviation while still allowing subjects’ own effort to change the gait pattern. Simulations and experiments involving five healthy subjects walking on level ground with a commercial lower limb exoskeleton, were conducted to validate the feasibility and effectiveness of the proposed approach. The results showed that the exoskeleton assistance improved subjects’ leg movement performance, and did not limit subjects’ active effort to adjust step length and time.
ISSN:0921-0296
1573-0409
DOI:10.1007/s10846-022-01763-5