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.
Highlights
Upper extremity paralysis occurs as a conse‐ quence of lesions such as injuries to the central or peripheral nervous system
The robot appears weightless to the user and helps to support their arms if they stop in the middle of an exercise. These schemes may encourage the patient to actively participate in the exercise by attempting to follow the target trajectory and motivating them to improve their level of accomplishment
To obtain the inverse dynamics, it is necessary to calculate the forces required for the links and the torques required by the joints
Summary
Upper extremity paralysis (the inability of a muscle or group of muscles to move voluntarily) occurs as a conse‐ quence of lesions such as injuries to the central or peripheral nervous system. The ETS - Motion Assistive Robotic-exoskeleton for Superior Extremity (ETS-MARSE) was developed in our laboratory [10,11,12,13] in order to provide rehabilitation assistance for the upper limbs It comprises a seven-degree-of-freedom (DOF) exoskeleton, designed to cope with the full motion capabilities of the human arm; that is, at the shoulder, elbow and wrist levels, combined or individually. The robot appears weightless to the user and helps to support their arms if they stop in the middle of an exercise These schemes may encourage the patient to actively participate in the exercise by attempting to follow the target trajectory and motivating them to improve their level of accomplishment.
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