Design and Development of 3-DoF Mechanism for the Exoskeleton Hip Joint

Exoskeletons find a wide range of applications in medical fields especially for rehabilitation purpose. Exoskeletons also serve as a human-assistive device to perform hard tasks in various non-medical fields as well. Among different types of exoskeletons, lower-extremity exoskeleton’s design is more complex. One of the major reasons for the complexity of the design of lower-extremity exoskeleton is due to the presence of hip joint in it. As human hip joint has three degrees of freedom and its load carrying capacity is high, these similar characteristics have to be inherited into the hip joint of the lower-extremity exoskeleton. However, three degrees of freedom and high load-carrying capacity characteristics of the hip joint make its design complex. In this work, an exoskeleton is designed and fabricated which can function similar to healthy human hip joints. The gait pattern of the developed three degrees of exoskeleton is recorded using video analysis method and it is compared with a healthy human gait pattern and found in agreement. To find the critical points in the model, a static analysis was done and on those critical points the dynamic analysis was conducted after giving the motions to each link as per the standard gait cycle values. The CAD model of the proposed exoskeleton mechanism was finalized based on the analysis done and a 3D printed prototype of the same was made. The motion analysis of the prototype and the required corrections to the model based on the prototype need to be done before moving on to the final model design. The power sources each for the joints were selected as electric and pneumatic systems, and necessary modifications in the model were done in order to accompany them. The exoskeleton model was tested to find whether the exoskeleton joint trajectories are in agreement with the normal human joint gait trajectories.