Shape space planner for shape-accelerated balancing mobile robots

Abstract

This paper introduces shape-accelerated balancing systems as a special class of underactuated systems wherein their shape configurations can be mapped to the accelerations in the position space. These systems are destabilized by gravitational forces and have non-integrable constraints on their dynamics. Balancing mobile robots, such as the ballbot, are examples of such systems. The ballbot is a human-sized dynamically stable mobile robot that balances on a single ball. This paper presents a shape trajectory planner that uses dynamic constraint equations to plan trajectories in the shape space, which when tracked will result in approximate tracking of desired position trajectories. The planner can handle systems with more shape variables than position variables, and can also handle cases where a subset of the shape variables is artificially constrained. Experimental results are shown on the ballbot with arms where different desired position space motions are achieved by tracking shape space motions of either body lean angles, or arm angles or combinations of the two; and also by tracking only the body lean motions while the arm angles are artificially constrained.