Performance Analysis on Wheels Lifting-off-Ground for Mars Rover with Active Suspension

Based on the analysis of wheel faults in operating planet rovers, a wheel lifting-off strategy based on the suspension freedom is proposed to guarantee that the mobile system still can work after some wheels sink or break down. A novel active suspension configuration is proposed based on the standard rocky-bogie suspension. A brake and an angle regulator are added at each side of suspension. The brake is used to consolidate the rear main rocker and the auxiliary rocker, and thus the rotary pair between main and auxiliary rockers is cancelled. The angle regulator is used to change the angle between the front and rear branches of main and auxiliary rockers. The kinematics and transient statics analyses of lifting-off-ground of a single wheel are carried out, and the load icalculation methods of the brake and the angle regulator are given. A prototype is designed and manufactured, on which wheel lifting-off-ground test and traveling test are carried out in soft soil terrain. Xinjiang sand with low granularity and low viscosity is selected as the test soil, and the soil depth in test tank is 400mm. The test results show that lifting-off-ground of a single wheel can be realized effectively and reliably by making use of center-of-mass change and wheel-ground interaction, and the wheels at corresponding position on both sides also can lift off ground at the same time. The tests prove that the load calculation methods of the brake and the angle regulator are correct when the rover works in Earth gravity field. With the proposed methods, the loads of the brake and the angle regulator in Mars gravity field can be deduced. In Earth gravity field, the maximum loads of the angle regulator and the brake are 650 N·m and 260 N·m respectively, and they are 220 N·m and 90 N·m respectively in Mars gravity field. The sensor requirements are proposed according to the demands in various conditions by combining analysis and test results.