Attempt at Two-Degree-of-Freedom Link Leg Mechanisms Design through a Genetic Algorithm

Legged robots can move more varied environments than wheeled robots. However, a disadvantage of legged robots is their energy inefficiency, which stems from the weight of actuators located within the leg joints. Although leg mechanisms using link mechanisms offer a potential solution to this problem, the analytical design of link mechanisms is challenging due to their nonlinearity. Therefore, we developed a design method for one-degree-of-freedom link leg mechanism in our preliminary research. While this method can design effective leg mechanisms, one-degree-of-freedom link leg mechanisms are unsuitable for real-world applications. In this study, we developed the design method for two-degree-of-freedom link leg mechanisms that can switch their motion for various purposes to suit real-world environments. The mechanisms designed by developed method demonstrate that they can switch the motion for three purposes: superior walking distance, superior foot lift height, and superior body rocking suppression. On the other hand, it was also found that challenges exist in designing the superior leg mechanisms stably.