Optimal design and analysis of knee orthosis

• Main Authors: Li, Wei-Min, 李偉民
• Other Authors: Cheng, Pi-Ying
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/27616864168415718311

碩士 === 國立交通大學 === 機械工程學系 === 100 === The purpose of this research is to design an orthosis mounted at knee which is between thigh and shank. The proposed knee orthosis is aimed to help people whose legs muscle power are not sufficiently to raise them to stand from sit posture. This research has two parts. In the first part, the study focuses on the linkage-spring optimal design aspect applying the multiple variables optimization algorithm. Two kinds of MATLAB’s commands such as "fmincon" and "patternsearch" were adopted to search the optimal parameters of the object funtion. The variables are specified as link length and spring constant. The object was to find the most feasible combination of the link length and spring combination. The requested torques of knee joint at each moment were derived using Lagrange dynamic method and the simulated data of knee torque were also generated as an analytical function of time. Several optional model of the springs are considered, such as general tensional/compression spring, zero length spring, torsion spring, tensional-torsion composed spring system, and so on. The study presents a model of human body and knee orthosis using the kinematic model of linkages and springs. Human body are simplified and modeled as three links, such as shank, thigh and hat. For approaching the realistic model of human body with the simple uniform links, the study proposes a two masses synthesis method. Two additional counter-weight mass blocks were stuck on each link with synthesized mass distribution to form a proper mass distribution and moment inertia same as each simulated original limb segment. Then the synthesized models can thus be simulated in dynamic analysis simulation system like ADAMS. Stick-spring orthosis design is the second part of the research. The study proposes a new knee orthosis mechanism composes with stick, pallet and spring components etc. to solve the problem of S-T-S (Sit to Stand). Except the standard S-T-S processes suggested from ergonomic engineering, the study proposes new concept of keeping the two centers of weight of the limb segment of hat and thigh in a vertical straight line. The spring constant and the location position of the spring were derived by using gravity balance method. The proposed concept in the model was verified as the best choice of the design from the proposed design process. In the first part, the design group which adopts the "fmincon" optimization command and tensional-torsion composed spring system is the best. Average saving force index is 81.161%. In the second part, find that Average saving force index is approaching 100% when applying the Stick-spring orthosis model and the proposed S-T-S function . This result of the research demonstrated itself as a reference of related S-T-S knee orthosis design and study.