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

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Abstract

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.

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Acknowledgements

This work was supported by the Grant No. W1925d0046 from the National Robotics Programme (NRP), Singapore.

Funding

This work was supported by the Grant No. W1925d0046 from the National Robotics Programme (NRP), Singapore.

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Authors and Affiliations

  1. Rehabilitation Research Institute of Singapore, Singapore, Singapore

    Lincong Luo, Ming Jeat Foo, Manoj Ramanathan, Jie Kai Er, Chye Hsia Chiam, Lei Li, Wei Yun Yau & Wei Tech Ang

  2. Institute for Infocomm Research, A*STAR, Singapore, Singapore

    Wei Yun Yau

  3. School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore, Singapore

    Wei Tech Ang

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  1. Lincong Luo
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All authors whose names appear on the submission made substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data; or the creation of new software used in the work; or the draft and revision of the paper content.

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Correspondence to Lincong Luo.

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This study was performed in line with the principles of the Declaration of Helsinki. Approval was granted by the Ethics Committee of Nanyang Technological University Singapore (On 2 June 2021, with reference No. IRB-2021-03-038).

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Luo, L., Foo, M.J., Ramanathan, M. et al. Trajectory Generation and Control of a Lower Limb Exoskeleton for Gait Assistance. J Intell Robot Syst 106, 64 (2022). https://doi.org/10.1007/s10846-022-01763-5

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