| Traditional crutches are simple and easy to manufacture. The drawbacks of traditional crutches are low energy efficiency and they cause pains under armpit for new users. These drawbacks are mainly caused by the arc motion of the supporting part during walking. In each step, the user needs to raise and lower his/her body for a couple of inches, which is similar to do a mini push-up.;The legged mechanism of a walking machine has a strong influence on the performance of the machine. In order to achieve good energy efficiency, a walking machine leg should be able to generate an exact or approximate straight line with only one drive actuator. The purpose of this study is to design an energy-efficient crutch based on legged mechanism.;In this thesis, two kinds of crutches, under-armpit crutch and under-knee crutch, are designed based on an inverse Robert's linkage, a type of four-bar linkage that generates an approximate straight line. By using SQP optimization method, the legged mechanism is optimized to generate an approximate straight line and meet the design constraints including size, weight and strength. The direct and inverse kinematics and velocities of the crutch are analyzed. The distributions of actuator force/moment during walking are also studied. A prototype of each type of crutch is built for experimental study. The results of experimental study and the recommendations for further study are presented. |
