主动悬架式火星车车轮抬离地面性能分析

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

针对国内外火星车车轮相关故障进行分析,从悬架自由度角度提出车轮抬离地面策略,确保车轮沉陷或故障后移动系统仍具有行驶能力.在标准摇臂悬架式移动系统基础上提出一种新的主动悬架式移动系统构型,左、右悬架中各增加了1个制动器和1个张角调节器.制动器工作将主摇臂后段和副摇臂固结,消去主、副摇臂间的回转副;张角调节器工作调节主、副摇臂前段和后段间的夹角.对各轮单独抬升过程进行运动学和瞬时静力学分析,给出制动器负载和张角调节器负载的计算方法.完成地面原理样机的设计制造,并进行松软土壤中车轮抬离地面及行驶测试.测试用土槽内沙土深度为400 mm,土壤为低粒度和低黏度的新疆沙.结果表明,利用构件质心迁移和轮-地相互作用能够有效、可靠地实现各轮单独抬离地面,两侧对应位置车轮也具备同时抬离地面的能力,验证了制动器负载和张角调节器负载的计算方法在地球重力场中的正确性,并推得火星重力场中制动器负载和张角调节器负载.地球重力下张角调节器最大负载650 N·m,制动器最大负载260 N·m;火星重力下张角调节器最大负载220 N·m,制动器最大负载90 N·m.针对各工况要求,综合分析和测试结果,提出了传感器需求.

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 liftingoff-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 400 mm. 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. © 2017, Science Press. All right reserved.