Abstract: Wheels will slip or skid when planetary exploration rovers traversing on soft deformable terrain. Wheel’s real forward velocity is larger than its theoretical forward velocity when planetary rovers brake or move down a slope, and wheel will be in skid. Skid covers longitudinal skid and lateral skid. Recent literatures most focus on wheel-soil interaction in slip, but skid mechanics has rarely been carried out. The influences of many factors related to planetary exploration rovers on longitudinal skid experimental results were studied using experiments. Install wheels with different configuration to wheel performace test−bed to study the influences of wheel radius, lug number, forward velocity and vertical load. Experimental results show that：The increasing of forward velocity has small influence on wheel sinkage, forward resistance force and electromotor output torque; Absolute values of electromotor output torque increase with the increasing of wheel radius; Absolute values of forward resistance force increase with the increasing of vertical load; Resistance force coefficient increases with the increasing of skid ratio and larger downhill angle needs larger skid ratio; The change rate of electromotor output torque when skid ratio ranges from 0 to 0.2 is bigger than that when skid ratio ranges from 0.2 to 0.6.

Key words: downhill ability, longitudinal skid experiments, planetary exploration rover, wheel-soil interaction force/torque