Kinematics, Path Following Control,
and Visualization of Mars Rovers

The goal of this NASA-sponsored project was to significantly increase the capabilities of Mars rovers to enable long traversals in rugged Martian terrain. The project consists of the following tasks:

Development of Kinematics of Rocky 7 Mars Rover
Rocky 7 has a complex mobility mechanism to enable it climb over rocks. This high mobility, however, makes the kinematic modeling of the rover and its interaction with the terrain a challenging task. We have developed such a model by defining a number of coordinate frames for rover gravity center, differential, steering, wheel axle, terrain contact, etc.

Since some joint quantities are not measurable and some maybe contaminated by noise, a least square solution was applied to extract rover the quantities of interest. Three types of kinematics, namely navigation, actuation and slip kinematics were derived.

The slip kinematics is of particular interest since detection of rolling, side and turn slips provide information for proper actuation and control to reduce undesirable motions such as sliding, sliding and fishtailing. The actuation kinematics determines the commands to wheels and steering motors to achieve desired body motion.

Path Following Control
A method has been developed for path following which consists of taking a set of way points specified by a path planner, and determining the desired rover heading and velocity in order to follow the path closely. Both classical controllers and fuzzy logic controller have been used for this task, and simulation studies have been carried out.

Simulation and Visualization
A simulation package consisting of rover kinematics, path following controller and rover contact kinematics was developed in the Matlab/Simulink environment. The graphics show the animation of the rover when following a path over a rugged terrain.