Motion Planning and Differential Flatness of Mechanical Systems on Principal Bundles

Abstract

Mechanical systems often exhibit physical symmetries in their configuration variables, allowing for significant reduction of their mathematical complexity arising from characteristics such as underactuation and nonlinearity. In this paper, we exploit the geometric structure of such systems to explore the following motion planning problem: given a desired trajectory in the workspace, can we explicitly solve for the appropriate inputs to follow it? We appeal to results on differential flatness from the nonlinear control literature to develop a general motion planning formulation for systems with symmetries and constraints, which also applies to both fully constrained and unconstrained kinematic systems. We conclude by demonstrating the utility of our results on several canonical mechanical systems found in the locomotion literature.