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Advances in Simulation of Planetary Wheeled Mobile Robots

Ever since the Sojourner rover of the United States landed on Mars in 1997 (Jet Propulsion Laboratory [JPL], a), there has been an upsurge in the exploration of planets using wheeled mobile robots (WMRs or rovers). The twin rovers that followed, Spirit and Opportunity, have endured many years of activity on Mars and have made many significant discoveries (JPL, b). Several other new missions are in progress to explore Mars (Volpe, 2005; Van et al., 2008) and the Moon (Neal, 2009) using planetary rovers that are expected to traverse more challenging terrain with scientific objectives such as searching for evidence of life and investigating the origin of the solar system. The present planet exploration rovers are advanced WMRs that show excellent performance and have integrated the cutting-edge technologies of many fields, and overcoming new frontier issues that are specific to planetary rovers has promoted the development of terrestrial WMRs. Simulation technology plays an important role in both the research and development (R&D) and exploration phases of planetary WMRs (Ding et al., 2008). During the R&D phase of a WMR, a simulation system can be used for mechanical design (e.g., performance analysis and optimization), control algorithm verification, and performance testing, and during the exploration phase, the simulation system can be used to support three-dimensional (3D) predictive displays for successive teleoperation (such as in the case of a lunar rover) or to validate command sequences for supervised teleoperation (such as in the case of a Mars rover). As compared to conventional simulation systems used for WMRs, the simulation system for planetary rovers is characterized by high fidelity, high speed, and comprehensiveness. The recent development and cutting-edge technologies of simulation systems for planetary rovers are summarized in this article to extend their application to conventional WMRs. The significance of simulation for planetary WMRs is discussed in Section 2. An overview of the simulation technology for planetary WMRs is presented in Section 3. Section 4 introduces key theories (models of terramechanics, dynamics, and terrain geometry) for developing a simulation system for planetary rovers. In Section 5, the research results for the simulation of planetary rovers at the State Key Laboratory of Robotics and System (SKLRS) of China, including simulation methods, systems, and verification results, are presented to provide examples of different simulation methods (based on the commercial dynamics simulation software, general simulation software, and real-time simulation software) in detail for different applications.