Comparative study of leg mechanisms for fast and stable water-running

Bio-inspired water-running robots are widely researched for fast and energy-efficient locomotion on water surfaces. The leg mechanism is very important for achieving fast and stable cyclic motion locomotion of the footpads. In this paper, four-bar, Klann, and Watt-I leg mechanisms are compared for water-running robotic platforms. Each mechanism was compared using many groups of random variables to achieve the best performance for fast and stable water running. Many solutions for composing each mechanism were obtained based on random variables that satisfy constraint conditions. Kinematical analysis of the mechanisms was then conducted using the random variables. The four-bar and Klann mechanisms showed better performance for generating propulsion. The lifting forces were similar among the three mechanisms. The results can be a guideline for choosing mechanisms for water-running robots.