6-REXOS: Upper Limb Exoskeleton Robot with Improved pHRI

Abstract

Close interaction can be observed between an exoskeleton robot and its wearer. Therefore, appropriate physical human-robot interaction (pHRI) should be considered when designing an exoskeleton robot to provide safe and comfortable motion assistance. Different features have been used in recent studies to enhance the pHRI in upper-limb exoskeleton robots. However, less attention has been given to integrating kinematic redundancy into upper-limb exoskeleton robots to improve the pHRI. In this context, this paper proposes a six-degrees-of-freedom (DoF) upper-limb exoskeleton robot (6-REXOS) for the motion assistance of physically weak individuals. The 6-REXOS uses a kinematically different structure to that of the human lower arm, where the exoskeleton robot is worn. The 6-REXOS has four active DoFs to generate the motion of the human lower arm. Furthermore, two flexible bellow couplings are attached to the wrist and elbow joints to generate two passive DoFs. These couplings not only allow translational motion in wrist and elbow joints but also a redundancy in the robot. Furthermore, the compliance of the flexible coupling contributes to avoiding misalignments between human and robot joint axes. The redundancy in the 6-REXOS is verified based on manipulability index, minimum singular value, condition number and manipulability ellipsoids. The 6-REXOS and a four-DoF exoskeleton robot are compared to verify the manipulation advantage due to the redundancy. The four-DoF exoskeleton robot is designed by excluding the two passive DoFs of the 6-REXOS. In addition, a kinematic model is proposed for the human lower arm to validate the performance of the 6-REXOS. Kinematic analysis and simulations are carried out to validate the 6-REXOS and human-lower-arm model.

A Review on Design of Upper Limb Exoskeletons

“…It has been noted that the introduction of the kinematic redundancy improves the maximum and minimum manipulability index by 21.13% and 22.25%, respectively [37]. Furthermore, it is concluded that adding kinematic redundancy to the 6-REXOS through a flexible coupling improves the manipulation, which guarantees a comfort motion assistance.…”

“…This category of exoskeletons is designed to assist the user in motion amplification or augmentation, where it can be used to assist the users for motion amplification [7,[30][31][32][33][34][35][36][37]; helps to reduce the burden while working in a harsh industrial environment [38,39]; or supplements the physically weak individuals in their activities of daily living. So far, many new systems have been developed and tested during past few years.…”

“…Gunasekara et al [37] proposed a 6-DOF upper-limb exoskeleton (called 6-REXOS) for supporting users with weak neuromuscular impairment. 6-REXOS is equipped with three motion generation units to supplement forearm and wrist movements with four active rotational DOFs and two passive translational movements.…”

Design of Shape Memory Alloy-Based Soft Wearable Robot for Assisting Wrist Motion

“…In the past decades, researchers have developed many robotic rehabilitation systems [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. A few investigations show that the improvement of recovery for acute and chronic patients facing stroke, cerebral palsy and injury to the spinal cord was observed from rehabilitation treatment by applying robotic systems [19][20][21][22][23].…”

Device to rehabilitate one’s Physical and Learning Abilities

“…Such exercises focus on grasping and squeezing, and enable the patient to move in 3D space while recording test results, modifying levels of difficulty and generating automated clinical reports. Some other examples of such solutions are the Amadeo or ReJoyce technologies [9][10][11][12][13][14][15][16][17].…”