Task space motion control of autonomous planetary vehicles

Autonomous planetary vehicles require local autonomy based on on-board measurements combined with Cartesian position measurements. The wheeled planetary vehicle is assumed to operate under ideal rolling conditions, i.e. non-holonomic constraints. Numerous proposed open-loop solutions to motion control problems of autonomous vehicles have been based on control schemes in which a trajectory is planned subject to non-holonomic constraints. Closed-loop control and inclusion of the dynamics of the system are difficult in this case. In this paper a new control scheme, combining a smooth feedback with a discontinuous controller is proposed. An outer loop generates a path which is obtained from the solution of a differential equation subject to the given current and final positions and orientations conditions. The solution can be updated regularly as Cartesian measurements from an orbiter permit to verify the estimated position obtained continuously from calculation. For the planned path a linearization feedback loop generates commands to the vehicle with regard to steering and driving torques. Simulation results illustrate the performance of the proposed controller. The features of the proposed scheme recommend it as an interesting candidate for the control of autonomous planetary vehicles.