72.1 Saturday, Jan. 5 Locomotion Analysis of Dynamic in-Plane Hexapod ZARROUK, D.; PULLIN, A.*; FEARING, R.; UC Berkeley; UC Berkeley; UC Berkeley firstname.lastname@example.org
This research focuses on the velocity of in-plane dynamic hexapedal robots. The velocity of the robot and the thrust forces are calculated as a function of robot geometry, leg compliance, static and dynamic friction coefficients, stride rate. In our model, the body of the robot is rigid and each of the legs has two compliant degrees of freedom, one along its length and the other, rotational, at the hip. We first formulate the velocity of the robot for the rigid legs case and then compare the influence of the leg compliance on the locomotion using a dynamic multi-body numeric simulation and analyze the influence of the kinetic coefficient of friction on the locomotion speed. During a stride, the robot experiences a varying thrust which results in decelerating at the beginning and the end of each step while accelerating through the middle. The velocity decreases with surface incline and the advance ratio on inclined surfaces is a function of the step angle only. For experimental validation, a purpose built robot with high, nearly flat, sprawl angle, was developed to examine the in-plane mechanics model and simulation. The experimental robot was run on two different surfaces using rigid and flexible legs while changing the slope. For rigid legs, the running stall angle was ultimately limited by the minimum of the range of the kinetic COF values. For flexible legs, the advance ratio of the locomotion was reduced due to bending, but in certain cases such as running over acrylic, the stall angle was the maximum of the kinetic COF. The static COF was practically irrelevant to the locomotion for both rigid and compliant legs because the locomotion is dominated by slip. The results of the simulation, analysis and experiments were compared and found to be in excellent agreement.