滑转条件下星球车坡面通过性评估试验

Experiment of slope trafficability assessment of planetary rover under slip condition

星球车是执行深空探测任务的主要移动平台,针对星球表面崎岖地形地貌,开展滑转条件下星球车坡面沉陷研究,确保其安全通过性能具有重要意义。基于传统地面力学研究方法,以速度和坡度为试验因素,车轮滑转率和沉陷为试验指标,开展滑转条件下的缩比星球车坡面沉陷试验;分析了试验因素对各车轮滑转率影响,以及不同滑转率和速度条件下沉陷变化规律,建立了滑转率关于坡度的一元二次模型。结果表明,模型车前轮和中间轮的滑转率随速度和坡度变化趋势总体趋于一致,与后轮滑转率变化趋势明显不同。坡度为25°时,前轮和中间轮滑转率最大值达到92.3%,后轮相应的最大滑转率为61.8%。试验条件下,各车轮沉陷最大值分别为33.1 mm（前轮）、33.9 mm（中间轮）和13.6 mm（后轮）;当滑转率的范围为25%～60%时,前轮和中间轮沉陷增加的较为平缓,平均增加率为22.5%,对于后轮滑转率超过35%后,沉陷变化较小,波动范围为-1.3～1.8 mm;速度对各车轮沉陷的影响明显较滑转率的小,沉陷的相对变化率范围为-12.5%～10.7%。该研究可为低重力环境下星球车研制、坡面通过性评估提供参考。

Planetary rover is the main mobile platform for deep space exploration mission, in view of the rugged landscape on planetary surface, it is significant to study the planetary rover＇s sinkage characteristic on slope terrain under slip condition, and ensure its reliable and secure trafficability. A scaling rover model was designed based on similarity principle theory and traditional terramechanics method; taking the velocity and slope as influence factor, the slip ratio and sinkage as experimental indices, the rover＇s slope-climbing tests were carried out under the slip condition. The influence of the test factors on the slip ratio was analyzed, and the quadratic equation between slip ratio and slope was established. The rule of the sinkage vary with slip ratios and velocity was also found. The results indicate that the variation tendency of the front and middle wheel＇ s slip ratio with the slope was consistent, and had the great different with that of the rear wheel. The influence of the velocity on slip ratio was not obvious, and the average error of the slip ratio was 9.0%（the front wheel）, 8.9%（the middle wheel） and 8.7%（the rear wheel）, respectively, when the slope remained constant. The influence of the slope on slip ratio was more significant than that of the velocity, and the corresponding average increase rate was 96.2%（the front wheel）, 105.6%（the middle wheel） and 79.6%（the rear wheel）, respectively. When the slope increased from 15° to 20°, the increase of the front and middle wheel＇s slip ratio became obvious, which was because of the rapid decrease of the wheel load in the vertical direction of the slope surface, and the increase of the component force of wheel load in the parallel direction of the slope surface. The rear wheel＇s slip ratio was smaller than that of the front and middle wheel, which may be due to the compaction effect on the soil. The maximum slip ratio of the front and middle wheel reached 92.3% when the terrain slope was 25°, while the corresponding value was 61.8% for the rear wheel. In this paper, the front and middle wheel＇s sinkage increased with the increase of the slip ratio. For the rear wheel, the sinkage increased firstly with the increase of the slip ratio, and then decreased since the slip ratio reached 23.4%; the rover＇s wheel sinkage was 33.1 mm（the front wheel）, 33.9 mm（the middle wheel） and 13.6 mm（the rear wheel）, respectively. When the slip ratio range was from 25% to 60%, the increase of the sinkage was gently for the front and middle wheel, and the average increasing rate was 22.5%. For the rear wheel, the sinkage changed less when the slip ratio was up to 35%, the sinkage average value was 11.6 mm, and the sinkage fluctuation range was from-1.3 to 1.8 mm. The influence of the velocity on the wheel sinkage was obviously smaller than that of the slip ratio, and the relative change rate range of the sinkage was from-12.5% to 10.7%. This study is hoped to provide the technical reference and basic data for the planetary rover＇s development and slope trafficability assessment under low gravity environment.