Robot Leg Design: A Constructive Framework

Abstract

Most robot leg designs are either based on biomimetics of humans' or animals' leg morphologies or on being mechanically optimized for specific task(s). In the first approach, differences between the actuation of the mechanical leg and the original biological structure usually result in inefficiencies and control malfunction, and legs in the second group are often limited to good performance for a single task and would fail when used for others. In this paper, we present a constructive framework for robot leg design, which tries to take advantage of the positive factors of both aforementioned approaches. For this purpose, we first, through selection of a template whose biological relevance for a wide range of tasks has been proven, establish a foundation on which mechanical design can be built. Then, we present a general theorem for designing a mechanism based on a template in order to maximize efficiency. In the final step and once the mechanism is designed, we address the problem of selecting the actuators and formulate it as a constrained optimization problem. In a case study with experimental walking data, we show how the mechanism design theorem and the formulated optimization problem can be used together to improve the walking energy efficiency by more than 50%. The proposed three-step approach is not limited to any template and should provide a more structured procedure for leg design, result in optimal energy economy, and maintain important bioinspired factors vital for control and versatility of legged robots.

Keywords

• Legged locomotion
• legged robots
• mechanism design
• design optimization
• reduced order systems