MapleSim Used to Create Tire-Soil Interaction Models for Planetary Rovers - User Case Studies - Maplesoft

User Case Study: MapleSim Used to Create Tire-Soil Interaction Models for Planetary Rovers

The use of robotic equipment in space has become increasingly important as the limits of space exploration are pushed further. Current aerospace research by organizations such as NASA and the Canadian Space Agency (CSA) has been focused on planetary exploration through the development of unmanned mobile robots. Like NASA’s “Curiosity” rover, new rover designs are being developed, that will allow us to explore the surfaces of the moon, Mars and even asteroids.

At the University of Waterloo, Willem Petersen, a researcher in the Motion Research Group, is working with John McPhee, Professor of Systems Design Engineering, and the CSA, to develop a high-fidelity planetary rover wheel model to understand the interaction between rover locomotion and soft terrain. Because loss of traction during exploration could cause the rover to become stranded, jeopardizing the success of a mission, understanding the wheel-soil interaction is absolutely essential to design an efficient and effective planetary rover.

The team chose MapleSim, an advanced physical modeling tool from Maplesoft, as a key tool in their development process. They have found that the symbolic approach in MapleSim helps produce high-fidelity models while providing simulations above or near real-time performance. This approach provides the fastest simulation times when compared to similar models created in conventional modeling tools.

Juno Rover Model

Using MapleSim and the MapleSim Tire Library, Mr. Petersen and Prof. McPhee designed a symbolic multibody dynamics model of the CSA’s Juno rover, including a novel tire-soil interaction model. The Juno rover model maps directly to the structure of the physical system and consists of a main chassis, a dependent walking beam suspension, and four tires. The suspension mechanism, designed with three interconnected rockers, allows the two tires on either side of the rover to pivot relative to the chassis. This distributes the load evenly over the four wheels and keeps the chassis level while the rover navigates freely over rough terrain – including large obstacles.

The tire-soil interaction model was validated using two separate Juno rover experiments, which compared the results of the MapleSim simulation with actual results using a physical prototype. The first experiment was a drawbar pull test, used for the identification of the unknown soil parameters, while the second allowed for parameter verification during which a driving maneuver of the rover on 3-dimensional terrain was performed. The researchers compared the results of a forward dynamics simulation performed in MapleSim to the experimental data generated by a physical prototype of CSA’s Juno rover, and found that the MapleSim tire-soil model results matched well with the experimental data.

Future research will aim to gain more insights into the model parameters, their sensitivity and how they affect the dynamics of the rover. This will help to develop a more general tire model. Research will also examine the behavior of the model for hard surface contact. Implementation of the contact models on parallel computing systems to allow for faster simulations of more complex geometries is another recommendation for future research.

“With the outstanding modeling fidelity of MapleSim, physical prototyping will be far less necessary in future rover design. As a result, engineers will benefit greatly from substantial cost savings and improved production times – not to mention design flexibility,” concluded Prof. John McPhee.