الفهرس 
DECLARATION AND CERTIFICATE OF ORIGINALITY IOnly 14 pages are availabe for public view
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Abstract
This thesis describes a novel multi-function mobility assistive device. The proposed device aims to help patients who don’t have enough physical strength on their lower limbs due to aging or diseases. Rather than one function device, the proposed device is designed to interactively assist in different lower limbs activities; namely, sit to stand (STS), transfer paralyzed patients from bed to wheelchair and help them stand in the upright position to improve blood circulation. In addition, the device is equipped with an active walker for walking activity. The device is based on a non-conventional structure of 3-RPR planer parallel manipulator which offers besides the high rigidity of the parallel structure other interesting kinematic advantages. It provides kinematic decoupling between the position and orientation that required to position shoulder and orient trunk of the user. Also, it provides a suitable free of singularity workspace that required to perform the abovementioned activities. Direct, inverse and differential kinematics, as well as the workspace and singularity analyses, are developed. The first type of Lagrange equations is used to model the dynamics of the device. Dimensional synthesis is used to obtain the geometric parameter that optimizes the performance of the device. The performance of the device is presented by a weighted sum cost function of workspace index and global force transmission and stiffness indices. The optimization is conducted using the genetic algorithm which is a well-known global optimization technique. The optimal geometric dimensions are used for the fabrication of a prototype for the device. The prototype shows a good ability to assist subjects with different heights. Furthermore, the minimum jerk criterion is used to model the natural STS motion. This model is used generate shoulder and hip trajectories in the real-time. In order to verify the efficacy of the minimum jerk criterion in replicating the natural STS motion, a dual-arms assistive system is developed to achieve the same assisting modes provided by the developed multi-function assistive device. Anthropometry and characteristics of the natural STS motion are used to increase the simplicity and applicability of the STS motion model. This enables providing assistance either at the upper trunk or at the upper trunk and the hip simultaneously without inducing abnormal motion kinematics. A set of experiments are conducted to verify the performance of the minimum jerk trajectory. These experiments include capturing natural and commercial device-assisted trajectories and using different trajectories while assisting subjects with different heights. The results show that the proposed motion model can accurately replicate the natural STS motion and results in a lower interaction force. Moreover, the subjects are more satisfied when they assisted using the proposed method as indicated by the results of the post-experiment questionnaire.