Testbed development for the measurement of slip ratio, sinkage, and resistive torque in small rover wheel-granular terrain interaction

The mobility of small wheeled vehicles, including Unmanned Ground Vehicles (UGVs) and planetary rovers, is critically dependent on wheel–soil interaction, particularly on sandy and granular terrains. To facilitate the design and testing of wheels optimized for these environments, dedicated test benches are essential to measure key performance parameters such as slip ratio, sinkage, and resistive torque. This paper presents a novel, low-complexity test bench specifically designed for small rover wheels. The system utilizes a torque meter and a vision-based fiducial marker tracking system for precise position and wheel rotation measurement, offering a low-complexity alternative to laser distance sensor-based and motion capture approaches. Performance evaluation was conducted on a 16 cm diameter sigma-type wheel at forward speeds up to 0.14 m/s under axial loads of up to 50 N. In addition to slip, resistive torque, and sinkage, derived parameters such as wheel sinkage speed and adherence recovery were evaluated. Measurements of adherence recovery time (time required to reach a stabilized value of slip) revealed a range from 0.03 s to 0.72 s, with observed variations attributed to imposed speed and load.