Dynamics Modeling and Traction Control for Mars Rovers

Paper number

IAC-07-A5.2.08

Author

Mr. David Cowan, McGill University, Canada

Coauthor

Prof. Inna Sharf, McGill University, Canada

Year

2007

Abstract

The continuing success of the Mars Exploration Rovers, as well as information about the likely presence of water on Mars, has rekindled interest in the Red Planet. Future rover missions to Mars are planned with the goal of increased exploration of the planet’s environment. Rover mobility in challenging terrain is paramount to the success of these missions. As such, it is necessary to be able to accurately predict the performance of potential rover designs beforehand and to develop control strategies to improve the mobility performance of the rover.

To this end, MacDonald, Dettwiler and Associates (MDA) have recently developed a simulator for the dynamics simulation of Mars rovers in support of their current and future developments towards missions to Mars. The simulator was created using SimMechanics Toolbox from MathWorks, within the Simulink environment. The rover simulator is currently used to predict the dynamics response, develop controllers, and plan missions for the ExoMars program. The research presented in the paper will be directly related to this simulator and has three main sections: the development of an independent rover simulator, the modeling of wheel-obstacle and wheel-soil interactions for the Mars rover, and the research and development of a traction control strategy for obstacle climbing.

The independent rover simulator has been developed using MSC ADAMS software. A detailed model of the rover has been developed, including inertia, geometry of the body and suspension, and using existing ADAMS modeling methods for wheel-ground and wheel-obstacle interactions. Despite the complicated geometry of the rigid wheels with grousers, the ADAMS simulator is able to accurately determine the wheel-obstacle contact instances. The obstacle is modeled as a rigid body with a step geometry, and forces are calculated using stiffness and damping coefficients and a Coulomb friction model. A soft-soil model will be implemented which uses Bekker Theory to calculate pressure-sinkage and shear-deformation relationships and takes into consideration soil compaction resistance and the effect of grousers on the wheels. An estimation of the soil parameters necessary for these calculations has been completed by MDA and is currently used in their simulator. The final objective of this project is to investigate, develop, and test traction control strategies for the Mars Rover. Specifically, traction control strategies for situations in which the entire rover must climb onto an obstacle with step-like geometry are, needed to fulfill one of the requirements put forth by the ESA for the ExoMars program. The chosen technique will be implemented on the ADAMS simulator, and possibly tested on MDA’s simulator and prototype.

In this paper we will present a comparison and analysis of the results obtained using MDA’s simulator and the simulator in ADAMS, as well as details of the development and implementation of the wheel-soil model and traction control strategy.

Abstract document

IAC-07-A5.2.08.pdf

Manuscript document

IAC-07-A5.2.08.pdf (🔒 authorized access only).

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