Implementing the Analytical Reachable Body Workspace for Calculating the Obstacle-Crossing Ability of a Hexapod Robot

Abstract

Calculating the maximum obstacle-crossing ability accurately at the mechanism design stage can better ensure that the manufactured robot prototype meets the predefined indices. The obstacle-crossing task of the legged robot is achieved by the collaborative movement of the leg and body. The reachable workspace constrains the spatial movement boundary of the foot tip and the robot body. The reachable workspace of the foot tip is invariant, while the shape and volume of the reachable body workspace vary with the supporting footholds. In this study, the body movement is modeled as a six-bar mechanism, and the reachable body workspace means the reachable region of the specified target point located on the moving platform of the six-bar mechanism. Unlike the previous work, the analytical method of calculating the reachable workspace for the target point outside the moving platform, named the external target point, is further studied. The influence of supporting footholds and shank-ground interference on the reachable body workspace is considered. The selection of supporting footholds, the collaborative motion sequences of the robot body and legs, and the determination of the maximum ability for crossing a ditch and climbing a step are demonstrated as cases of implementing the analytical reachable body workspace for the internal target point and the external target point, respectively. Finally, simulations verify the correctness of the theoretical analysis.