Architectural design and development of an upper-limb rehabilitation device: a modular synthesis approach

Purpose Enormous assistance is required during rehabilitation activities, which might result in a variety of complications if performed manually. To solve this issue, several solutions in the form of assistive devices have been presented recently. Another issue highlighted is the lack of kinematic compatibility in low degrees-of-freedom (dof) systems. The proposed approach of developing a human-motion-oriented rehabilitation device deals with the problem through hybrid architectures. A novel modular synthesis approach is used for the purpose to induce generality in the design process. Materials and methods Using a modular strategy, three planar hybrid configurations are generated for two-dof mechanisms for supporting flexion/extension motion. Three such architectures are optimally synthesised and kinematically analysed over the entire workspace. A Genetic Algorithm (GA) is used to synthesise the architecture parameters optimally. Moreover, the outcomes are evaluated against a set of seven poses and posture locations of the wrist to choose the most suitable configuration among the others. Subsequently, kinematic compatibility is analysed for the coupled system - formed by the selected architecture and the human arm - while wearing the proposed mechanism. Results According to the findings of optimal synthesis, workspace and singularity analysis, configuration-III is capable of achieving the optimal postures for all task space locations (TSLs). Further, the work modifies the design by attaching additional three revolute passive joints for correcting misalignment concerns using coupled mobility analysis. Conclusion The modular strategy for hybrid architectures and the subsequent mobility analysis provides an algorithmic framework for synthesising a task-based rehabilitation device.IMPLICATIONS OF REHABILITATION Manual physiotherapy is reported as repeated task, expensive and time-consuming, and considered stressful for the therapist or assistants to provide one-on-one physiotherapy to each patient in the traditional method. Robotic rehabilitation is, therefore, a viable option. In the several reported works on robotic rehabilitation exoskeletons, misalignment of the exoskeleton and the human motion is considered an open challenge. Normally, it is being managed through large number of degrees of freedom, which is certainly expensive and complex in control. The proposed approach of developing a human-motion-oriented rehabilitation device deals with the problem through hybrid architectures and modular strategy to develop them. While focusing upon the emulation of natural human motion trajectory, the compatibility of orthotic joint and human joint motion needs attention. As biological joint possesses complex kinematic characteristics, closed-loops are used in the design. Overall, a complete framework of a cost effective low-dof rehabilitation device is proposed and detailed through coupled analysis.