  Understanding the wheel-terrain interaction is of great importance to improve
the maneuverability and traversability of the rovers. A well-developed sensing
device carried by the rover would greatly facilitate the complex risk-reducing
operations on sandy terrains. In this paper, an instrumented wheel-on-limb
(WOL) system of planetary rovers for wheel-terrain interaction characterization
is presented. Assuming the function of a passive suspension of the wheel, the
WOL system allows itself to follow the terrain contour, and keep the wheel
remain lowered onto the ground during rover motion including climbing and
descending, as well as deploy and place the wheel on the ground before a drive
commanding. The system concept, functional requirements, and pre-design work,
as well as the system integration are presented.
