[ARTICLE] Multimodal robotic system for upper-limb rehabilitation in physical environment – Full Text HTML

Abstract

This article researches the feasibility of use of a multimodal robotic system for upper-limb neurorehabilitation therapies in physical environments, interacting with real objects. This system consists of an end-effector upper-limb rehabilitation robot, a hand exoskeleton, a gaze tracking system, an object tracking system, and electromyographic measuring units. For this purpose, the system architecture is stated, explaining the detailed functions of each subsystem as well as the interaction among them. Finally, an experimental scenario is designed to test the system with healthy subjects in order to check whether the system is suitable for future experiments with patients.

Introduction

The use of robotic systems in neurorehabilitation therapies may be justified because of its potential impact on better treatment and motor learning.¹ For this reason, in the recent years, a wide variety of robotic devices for upper-limb neurorehabilitation have been developed by research groups around the world.^{2⇓⇓⇓⇓⇓⇓⇓⇓–11}

In conjunction with these robotic devices, a wide range of robot-oriented rehabilitation interfaces and environments have been stated. Many of the current devices use virtual reality systems to set up the rehabilitation context;^{12⇓⇓⇓⇓–17} and just few examples use physical environments.^18,19 It should be pointed out that all these examples, except Badesa et al.’s¹⁴ work, use robotic exoskeletons.

Virtual reality systems are specially suitable for early stages of the disease,²⁰ due to the flexibility that it offers when designing tasks and feedback stimuli, and the safety that it provides due to the absence of interaction with physical objects that can lead to injuries. However, in order to obtain a realistic interaction, it is necessary to use haptic devices,^{21⇓⇓–24} which result in expensive and complex systems. In contrast, physical environments may suppose a good and inexpensive alternative to perform more complex, and functional, rehabilitation tasks in later stages of the disease, when patients have recovered some motor control of their upper limb.

The objective of this article is to check whether an end-effector rehabilitation robot²⁵can be used to develop a fully functional multimodal rehabilitation system in physical environments. In contrast to Frisoli et al.’s¹⁹ work, the use of an end-effector robot instead of an exoskeleton is expected to result in a considerable reduction in the setup time as well as in an increase in user’s comfort. Additionally, the brain–computer interface (BCI) is replaced by electromyography, which does not require previous training, reducing user’s mental fatigue²⁶ and saving additional time.

In this regard, the experimentation will focus on testing whether the mechanical system can be controlled with precision and safety enough to interact with some objects and perform a simple occupational therapy activity successfully, so that further researches in this path can be done.

 

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Figure 1. System architecture and communications between components.

 

Figure 2. Difference between hand position and end-effector position with respect to the reference frame of the end-effector.