# Fault Detection, Isolation and Reconfiguration of Four-Bar Mechanism-Based Knee Exoskeleton

## TL;DR

This paper presents a fault-tolerant control system for a knee exoskeleton that continues to operate safely even when an actuator fails.

## Contribution

A novel fault detection, isolation, and reconfiguration system using analytical redundancy relations for knee exoskeletons.

## Key findings

- The FDI system successfully detects and isolates faults in the rotary actuator.
- The exoskeleton reconfigures itself using another actuator to maintain functionality.
- Simulations show improved robustness during sit-to-stand motions with the proposed system.

## Abstract

Knee exoskeletons are sophisticated wearable devices engineered to aid or augment human movement, especially in rehabilitation and mobility assistance contexts. To address reliability concerns, the proposed knee exoskeleton incorporates a fault-tolerant control system using a fault detection, isolation and reconfiguration (FDI) technique. This system enables the exoskeleton to continue functioning even if one of the actuators experiences a fault, ensuring user safety and continuous operation. For actuator fault detection, analytical redundancy relations (ARRs) are derived from the bond graph model of the knee exoskeleton. ARRs are monitored for actuator fault detection and isolation. In this work, there is no fault initially; after some time, a fault is created in the rotary actuator; finally, the faulty actuator is reconfigured by another rotary actuator. Simulation findings illustrate the suggested FDI system’s effectiveness in improving the robustness of knee exoskeletons during the sit-to-stand motion. The proposed system successfully reconfigures itself in response to faults.