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Event-triggered critic learning impedance control of lower limb exoskeleton robots in interactive environments

Published: 01 February 2024 Publication History
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  • Abstract

    In this paper, we present an event-triggered critic learning impedance control algorithm for a lower limb rehabilitation exoskeleton robot in an interactive environment, where the control objective is specified by a desired impedance model. In comparison to many other traditional impedance controller design algorithms, in this paper, the impedance control problem is transformed into an optimal control problem. Firstly, the interactive environment accounts for the interaction between the exoskeleton, the human, and the environment, and is modeled by a linear time-invariant exogenous system. Secondly, in contrast to time-triggered control design mechanisms, the event-triggered controller is updated only when the system states deviate from prescribed threshold values. To obtain the event-triggered optimal controller, a critic neural network is developed through the framework of reinforcement learning. A modified gradient descent method is introduced to update the weights of the critic network with an additional stable term employed to eliminate the need for an initial admissible control. Meanwhile, with the simultaneous application of historical and transient state data to the critic neural network, the persistent excitation conditions are relaxed. The Lyapunov method is used to rigorously demonstrate the stability of the overall system. Finally, the effectiveness of the proposed algorithm is demonstrated via simulation.

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    Cited By

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    • (2024)Machine Learning-Based Multiagent Control for a Bunch of Flexible RobotsComplexity10.1155/2024/13304582024Online publication date: 1-Jan-2024
    • (2024)Enhancing Service Offloading for Dense Networks Based on Optimal Stopping Theory in Virtual Mobile Edge ComputingJournal of Grid Computing10.1007/s10723-024-09765-322:2Online publication date: 1-Jun-2024

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              Published In

              cover image Neurocomputing
              Neurocomputing  Volume 564, Issue C
              Jan 2024
              278 pages

              Publisher

              Elsevier Science Publishers B. V.

              Netherlands

              Publication History

              Published: 01 February 2024

              Author Tags

              1. Critic neural network
              2. Impedance control
              3. Lower limb rehabilitation exoskeleton robot
              4. Interactive environments
              5. Event-triggered mechanism

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              • (2024)Machine Learning-Based Multiagent Control for a Bunch of Flexible RobotsComplexity10.1155/2024/13304582024Online publication date: 1-Jan-2024
              • (2024)Enhancing Service Offloading for Dense Networks Based on Optimal Stopping Theory in Virtual Mobile Edge ComputingJournal of Grid Computing10.1007/s10723-024-09765-322:2Online publication date: 1-Jun-2024

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