Design and kinematic analysis of redundantly actuated parallel mechanisms for ankle rehabilitation

Abstract

Link to this article: http://journals.cambridge.org/abstract_S0263574714000241How to cite this article: Congzhe Wang, Yuefa Fang, Sheng Guo and Changchun Zhou (2015). Design and kinematic analysis of redundantly actuated parallel mechanisms for ankle rehabilitation. Robotica, 33, pp 366-384 SUMMARYIn this paper, we present the design of two serial spherical mechanisms to substitute for a single spherical joint that is usually used to connect the platform with the base in three degrees of freedom parallel mechanisms. According to the principle derived from the conceptual design, through using the two serial spherical mechanisms as the constraint limb, several redundantly actuated parallel mechanisms are proposed for ankle rehabilitation. The proposed parallel mechanisms all can perform the rotational movements of the ankle in three directions while at the same time the mechanism center of rotations can match the ankle axes of rotations compared with other multi-degree-of-freedom devices, due to the structural characteristics of the special constraint limb and platform. Two special parallel mechanisms are selected to analyze their kinematical performances, such as workspace, dexterity, singularity, and stiffness, based on the computed Jacobian. The results show that the proposed scheme of actuator redundancy can guarantee that the redundantly actuated parallel mechanisms have no singularity, better dexterity, and stiffness within the prescribed workspace in comparison with the corresponding non-redundant parallel mechanisms. In addition, the proposed mechanisms possess certain reconfigurable capacity based on control strategies or rehabilitation modes to obtain sound performance for completing ankle rehabilitation exercise.

Design and Workspace Analysis of a Parallel Ankle Rehabilitation Robot (PARR)

“…Several multiobjective optimization schemes [11–14] were also carried out to provide better design solutions. Two kinds of serial spherical mechanisms, also called equivalent spherical joints, with a symmetrical structure were designed by Wang et al [15] to actualize 3-DOFs rotational motion and ensure the mechanism center of rotation matches that of the ankle. Three types of 3-UPS/RRR redundantly actuated parallel mechanisms were selected to analyze and compare their kinematic performance, in which the redundant actuator was installed on the serial spherical mechanism to achieve the features of no singularity, better dexterity, and higher stiffness.…”

“…Three types of 3-UPS/RRR redundantly actuated parallel mechanisms were selected to analyze and compare their kinematic performance, in which the redundant actuator was installed on the serial spherical mechanism to achieve the features of no singularity, better dexterity, and higher stiffness. Analogous to study [15], a 3-RUS/RRR redundantly actuated parallel mechanism was designed and analyzed by Wang et al [16], the prototype of which was built according to geometrical parameters selected via multiobjective optimization [17]. Zhang et al [9] presented a redundantly actuated reconfiguration robotic design called CARR, which was driven by four Festo fluidic muscles; and the robot provided an adjustable workspace and actuator torque to meet the requirements of range of motion exercises and muscle strengthening exercises.…”

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

“…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. By selecting two types of identical active branches, i.e., 3-UPS structure and 3-RUS (revolute-universal-spherical), to produce obliquity of the platform and using serial equivalent spherical mechanisms to satisfy all 3-DOF rotational ankle rehabilitation, actuated parallel mechanisms introduced by Wang et al (2013Wang et al ( , 2015 are another typical instance.…”

Kinematic Calibration of a Parallel 2-UPS/RRR Ankle Rehabilitation Robot

“…To improve the effect of rehabilitation training, many active rehabilitation training methods including the active participation of patients have been developed such as the ARBOT [ 5 ], CARR [ 10 ], and Anklebot [ 11 ]. Among different kinds of ankle rehabilitation robots, the platform ones are better suited for ankle exercises [ 12 ], and parallel mechanism is the most common among them with the above-mentioned exercise modes [ 5 , 6 , 13 , 14 ].…”