Locomotion Design

The physical interface between a rover and the planetary surface is at the core of mission success. A stuck wheel can end a billion-euro mission. Our locomotion design research combines theoretical terramechanics, hardware engineering, and experimental validation to understand and improve how rovers interact with deformable, unconsolidated planetary regolith. We study wheel–soil interaction experimentally and through models, characterizing slip, sinkage, and traction forces as a function of wheel geometry, soil properties, and normal load. A key contribution is our work on reconfigurable locomotion modes: we showed formally and experimentally that selecting the right locomotion mode (standard driving, wheel-walking, crabbing, or point-turn) for each terrain segment can substantially reduce energy consumption and slip. We integrated this insight directly into our path planners. Our wheel-walking locomotion analysis and slip-ratio experiments on the ExoTeR rover are among the most detailed open evaluations of this locomotion mode in the literature. We are also contributors to the long-running ESA testbed evolution program, informing wheel and suspension design choices over multiple testbed generations.

KEY CAPABILITIES
Locomotion mode selection Formal framework and experimental evidence for choosing drive / wheel-walk / crab / point-turn modes based on terrain and energy cost.	Wheel–soil interaction modelling Slip, sinkage, and traction characterizxzation on planetary simulant soils; validated against ExoTeR field and lab experiments.
Slip-ratio analysis (wheel walking) Detailed experimental analysis of slip ratios during wheel-walking locomotion on sandy slopes; identifies optimal actuation strategies.	Testbed-informed hardware design Decades of collaboration with ESA on HDPR, ExoTeR, MaRTA testbeds have produced lessons learned that feed back into rover design.

 

IN THE LAB & IN THE FIELD

 

SELECTED PUBLICATIONS
01	Field Assessment of Force Torque Sensors for Planetary Rover Navigation Gerdes L., Pérez-del-Pulgar C., Castilla-Arquillo R., Azkarate M. Journal of Intelligent and Robotic Systems, 111(4) (2025)
02	Design, Testing, and Evolution of Mars Rover Testbeds: European Space Agency Planetary Exploration Azkarate M., Gerdes L., Wiese T., Zwick M., Pagnamenta M., Hidalgo-Carrió J., Poulakis P., Pérez-del-Pulgar C.J. IEEE Robotics & Automation Magazine, 29(3), 10–23 (2022)
03	Experimental Analysis of Slip Ratio Using the Wheel Walking Locomotion Mode in Reconfigurable Rovers Domínguez-Durante S., Pérez-del-Pulgar C., Paz-Delgado G., Azkarate M. 30th Mediterranean Conf. on Control and Automation (MED), 749–754 (2022)
04	Choosing the Best Locomotion Mode in Reconfigurable Rovers Pérez-del-Pulgar C.J., Romeo-Manrique P., Paz-Delgado G.J., Sánchez-Ibáñez J.R., Azkarate M. Electronics, 8(7), 818 (2019)
05	Multi-scale Path Planning for a Planetary Exploration Vehicle with Multiple Locomotion Modes Sánchez-Ibáñez J.R., Azkarate M., Pérez-del-Pulgar C.J. Int. Symposium on Artificial Intelligence, Robotics and Automation in Space (i-SAIRAS) (2018)
06	Path Planning for Reconfigurable Rovers in Planetary Exploration Pérez-del-Pulgar C.J., Sánchez J.R., Sánchez A.J., Azkarate M., Visentin G. IEEE Int. Conf. on Advanced Intelligent Mechatronics (AIM), 1453–1458 (2017)

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