Design and optimization of a one-degree-of-freedom eight-bar leg mechanism for a walking machine

The purpose of this study is to contribute to the area of mechanism design and optimization of a single-degree-of-freedom leg mechanism. The leg mechanism is considered to be very energy efficient especially when walking on rough terrains. Furthermore, the mechanism requires very simple controls since a single actuator is required to drive the leg. Previous work in this area had common focuses. First, the optimization was set up to change the length of each link directly. This can be time consuming since there is no structure other then changing the lengths and seeing how it affects the outcome. Second, a static analysis was used to determine the forces acting on the links and joints as well as the torque applied to the crank. This study focuses on the use of mechanism design theory to synthesize each solution, which is then used to determine the configurations of the links. The use of mechanism design theory is seen as beneficial since returned solutions will satisfy a defined motion and avoid analysing solutions that are far from being acceptable. As a result, with mechanism design there is more control over the outcome of each solution. Furthermore, a dynamic analysis is performed to evaluate the joint forces and crank torques of each solution, thus taking into account inertia forces in the design. The combination of the mechanism design theory and the dynamic analysis formulates the necessary tools to perform the optimization. The optimization results will show that a large decrease in the energy of the system, as well as decreasing the maximum driving torque is obtained when compared to an initial design. A physical prototype is also constructed to demonstrate the design as a working machine and to verify the computer generated motion of the mechanism.