Reconfigurable workspace and torque capacity of a compliant ankle rehabilitation robot (CARR)

Abstract

This paper presents the analysis of the workspace and torque capacity of a compliant ankle rehabilitation robot (CARR). The robot has three rotational degrees of freedom (DOFs) redundantly actuated by four compliant actuators. However, it suffers from conflicting workspace and actuation torque due to the use of a parallel mechanism and compliant actuators. To address these issues, also considering physical constraints imposed by human users, the CARR was designed with reconfigurability to make a trade-off between robot workspace and torque capacity for meeting different training requirements. Theoretical analysis indicates that varying kinematic and dynamic performance of the robot can be achieved by reconfiguring the layout of the actuators. Experiments with/without load also demonstrate the validity of the reconfigurable robotic design for practical applications on robotassisted ankle rehabilitation. Future work will focus on the design aspects of the robot for easy adjustments, and the integration of force-distribution based actuator force control for optimal robot torque performance.

Hierarchical Compliance Control of a Soft Ankle Rehabilitation Robot Actuated by Pneumatic Muscles

“…To get the Jacobian matrix, inverse kinematics of the robot must be modeled. Geometric model of the developed robot is illustrated in Figure 2 (Zhang et al, 2017a ). The vector of each active link L i can be calculated given a desired end effector orientation θ = [θ x ; θ y ; θ z ].…”

“…RUPERT is another four actuated DOF upper extremity exoskeleton driven by compliant PMAs (Sugar et al, 2007 ). Recently, Zhang and colleagues from Auckland research group developed a compliant ankle rehabilitation robot (CARR) actuated by four Festo pneumatic muscles (Meng et al, 2017a ; Zhang et al, 2017a ). These systems usually applied impedance-based controllers to achieve the desired movements (Lerner et al, 2017 ), however, the potential of PMA in design of fully compliant robot and how to realized complete compliance control have not been deeply explored.…”

Compliance adaptation of an intrinsically soft ankle rehabilitation robot driven by pneumatic muscles

“…Kinematic model maps the relation between robot endeffector movement with the joint link displacements [21]. Define vector of each active link is and it can be calculated by a given end effector orientation .…”

Design and Performance Evaluation of a Novel Wearable Parallel Mechanism for Ankle Rehabilitation

“…Thanks to the inherent muscle-like behavior, compliant motions can be achieved during different treatment modes with the help of a fuzzy logic controller. Analogous to Jamwal et al (2014), in Zhang et al (2017), The University of Auckland developed the other compliant robot powered by four PMAs that arranged in a tilted manner. A three-linkage serial mechanism was set as the kinematic constraint of this robot, and the connection points (i.e., spherical joints) can be adjusted along certain directions to achieve reconfigurable workspace and torque capacity.…”