Admittance-Based Upper Limb Robotic Active and Active-Assistive Movements

Abstract

This paper presents two rehabilitation schemes for patients with upper limb impairments. The first is an active-assistive scheme based on the trajectory tracking of predefined paths in Cartesian space. In it, the system allows for an adjustable degree of variation with respect to ideal tracking. The amount of variation is determined through an admittance function that depends on the opposition forces exerted on the system by the user, due to possible impairments. The coefficients of the function allow the adjustment of the degree of assistance the robot will provide in order to complete the target trajectory. The second scheme corresponds to active movements in a constrained space. Here, the same admittance function is applied; however, in this case, it is unattached to a predefined trajectory and instead connected to one generated in real time, according to the user's intended movements. This allows the user to move freely with the robot in order to track a given path. The free movement is bounded through the use of virtual walls that do not allow users to exceed certain limits. A human-machine interface was developed to guide the robot's user.

Novel robust control of a 7-DOF exoskeleton robot

“…The proposed robot can perform active assistive motion (electromyography, respond to force, and/or be compliant with the subject to accompany and assist humans in the intended motion) and passive (completely support and perform the motion on the subjects upper limb). The characteristics of ETS-MARSE robot are completely summarized in [ 24 – 27 ].…”

Feasibility and preliminary efficacy of a combined virtual reality, robotics and electrical stimulation intervention in upper extremity stroke rehabilitation

“…Advances in rehabilitation technology, in particular robotics, virtual reality (VR) and neuromuscular electrical stimulation (NMES), have been shown to be individually effective for improving UE function of individuals with stroke, through the provision of such repetitive and task-oriented training. Robotic devices can be used to assist individuals who are unable to complete arm movements by themselves [ 6 ]. Robotic rehabilitation has demonstrated functional gains in individuals with mild and moderate stroke impairments [ 7 – 9 ].…”

Compliant control for wearable exoskeleton robot based on human inverse kinematics

“…After detecting the initiation of a motion, usually predetermined, the robot will guide the achievement of the activity, often using an impedance and/or admittance control. 11,12 Additionally, these strategies can be utilized for the evaluation or the study of subject movements. In these modes, theoretically, the patient should not feel the presence of the exoskeleton robot.…”

“…Admittance control is a typical choice for the rehabilitation application of compliance control. 12 –16 This control structure aims to create a dynamic relationship between a measured position (and its derivative) and the user’s force. The admittance scheme is implemented by two loops.…”