Trajectory Generation on Rough Terrain Considering Actuator Dynamics

Abstract

Trajectory generation has traditionally been formulated on the assumption that the environment is flat. On rough terrain, however, deviations of the angular velocity vector from the vertical lead to errors which accumulate in a manner similar to the accumulation of attitude errors in odometry. In practice, feedback control can compensate for these errors in modeling by adjusting the path in real time. In many realistic cases, however, the 3D shape of the terrain is known beforehand, so it is possible to incorporate terrain shape into the predictive model --- rather than treat it as an unknown disturbance. This paper presents an algorithm for trajectory generation which compensates for terrain shape in a predictive fashion. The numerical implementation makes it adaptable readily to a broad class of vehicles and even a broad class of predictable disturbances beyond terrain shape. In support of the latter, we demonstrate the ability to invert models of actuator dynamics and wheel slip concurrently with 3D terrain. An example application for the Rocky 7 Mars rover platform is presented.