Development and analysis of a gravity-balanced exoskeleton for active rehabilitation training of upper limb

Abstract

Robot-assisted therapy has become an important technology applied in rehabilitation engineering, allowing patients with motion impairment problems to perform training programs without continuous supervision from physiotherapists. The goal of this paper is to develop a gravity balanced exoskeleton for active rehabilitation training of upper limb. The mechanical structure and kinematics of the exoskeleton are described and optimized to enable natural interaction with user and avoid singular configurations within the desired workspace. The gravity balancing of the human arm and mechanism is achieved through a hybrid strategy making use of auxiliary links and zero-free-length springs to balance the effect of gravity over the range of motion. The balance errors resulting from the variation of anthropometric parameters are analyzed and discussed. Further experiments involving trajectories tracking tasks with and without gravity balancing are conducted to evaluate the improvement of the control performance and energetic efficiency made by the developed balanced mechanism. The experimental results indicate that the proposed balance strategy can achieve a reduction of 34.56% in overall power consumption compared with the cost in unbalanced condition.

A Review on Design of Upper Limb Exoskeletons

“…Wu et al [70] proposed a gravity-balanced exoskeleton for active rehabilitation training of the upper limb. The kinematic structure of the exoskeleton is described and optimized to enable natural mode of interaction with the user and to avoid singular configurations inside the workspace.…”

“…The complex relative movements between the radial and ulna bones make it difficult to develop a mechanism which can precisely replicate the forearm supination/pronation. Few studies [6,22,33,34,50,58,70,72,167] have presented a design that can actively support the users in executing forearm supination/pronation by taking into account the effect of radial/ulnar deviation.…”

Kinematics and Dynamics Analysis of a 3-DOF Upper-Limb Exoskeleton with an Internally Rotated Elbow Joint

“…The shoulder joint can be modeled as a 3-DOF ball-and-socket joint: flexion/extension (Z 2 ), abduction/adduction (Z 3 ) and internal/external-rotation (Z 1 ); The wrist joint can be modeled as a 3-DOF ball-and-socket joint: palmar flexion/dorsiflexion (Z 6 ), ulnar deviation/radial deviation (Z 7 ) and medial rotation (Z 5 ); The elbow joint can be modeled as a 1-DOF hinge joint with (Z 4 ) [20][21][22]. The motion range of the joints is shown in Table 1 [23].…”

Design and control of a diagnosis and treatment aimed robotic platform for wrist and forearm rehabilitation: DIAGNOBOT

“…This leads to the instability of the system. For this reason, the (B d min ) is added to equation (17) and the following equation is obtained…”

“…The use of such exoskeleton robots in rehabilitation is becoming more and more commonplace, and there are a big number of studies cited in the literature. [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] As seen in the literature, many robots have been developed for the rehabilitation. These robots have some limitations.…”