A method for traction ability research of rover wheels on mixed planet terrain with movable stones

The Chang’e-6/7/8 exploration mission has been introduced formally by China lately, and the worldwide lunar and Mars analysis station plans shall be carried out inside the 2030s. It may be predicted that China’s future lunar and Mars floor exploration actions will last more, have a bigger exploration vary, and have a extra complicated terrain to traverse and discover, which is able to pose extreme challenges to the working efficiency of the planet rover and its adaptability to the planet floor surroundings.

One of many key issues shall be to check the connection between the mechanical properties of planet soil and the traction efficiency of the planet rover’s wheels. The blended terrains of terramechanics analysis are primarily composed of static stones and free soil.

Whereas, the motion habits of stones is commonly ignored whereas analyzing the affect of the wheel’s traction efficiency brought on by blended terrain. For the reason that current idea explaining the terramechanics drawback of the planetary automobile’s wheel transferring within the blended terrain of movable stones and free soil is imperfect and its calculation is comparatively complicated, the brand new answer of contact power of the wheel of a planetary rover underneath the blended terrain of a movable stone and free soil is worthy of analysis.

In a analysis paper lately revealed in Area: Science & Know-how, Jiangshan Du and Tieqiu Huang, from Beijing Jiaotong College, aiming at these issues, suggest a residual soil mannequin for fixing the interplay power between the remaining soil that’s not coated by stones and wheel and a plastic homogeneous soil mechanics mannequin to calculate the soil power provided to a movable stone.

First, the authors assessment two typical interplay mannequin between wheel and floor. Within the Wong–Reece mannequin and the Janosi mannequin, the contact between inflexible wheel and comfortable soil is proven. The Wong–Reece mannequin describes the relation between the angle of method Θ₁ and the sinkage z for given μ worth which is set by experiments.

The Janosi shear stress mannequin formulates τ(Θ) underneath μ =1. They two collectively consequence within the supporting power W and the drawbar pull DP by way of integrations. Within the contact mannequin of a inflexible wheel and stone, the nonlinear spring-damper mannequin based mostly on the Hertz contact idea is adopted to calculate the conventional power between a strong and a strong.

When a wheel runs throughout a stone, it additionally produces adhesion P calculated by the Coulomb friction mannequin and resistance second M_w.

Then, the authors elaborate two proposed fashions. The proposed fashions meet the next assumptions: 1) The fashions happen on the blended terrain with a movable stone and the loose soil; 2) there isn’t any contact between stones, irrespective of whether or not the stones transfer or not; 3) ignoring the lateral power, the fashions are solely used on the 2-dimensional aircraft.

In residual soil mannequin, the fundamental thought is to switch the mixing space for W and DP to unravel the interplay power between the wheel and remaining soil, when a transferring wheel is involved with a stone and soil on the similar time. Underneath this situation, a wheel passing via a stone is considered the method via which a stone successively passes via the angle of method Θ₁, the angle of most stress Θ_m, and the angle of departure Θ₂.

Finally, it leaves the world the place a wheel interacts with soil. Within the plastic homogeneous soil mechanics mannequin, Bekker’s pressure-sinkage mannequin, which displays the bearing properties of soil and could be roughly considered a typical nonlinear spring mannequin, could be additional prolonged to 2-dimensional space to analysis the relationships between stress and sinkage in 2 instructions.

Final, the authors perform the simulation and the experiment to confirm the proposed fashions. Wheel width is 14 cm. The wheel’s diameter is 30 cm. The ahead pace of the wheel is 0.03 m/s. The slip ratio is 0.3. The wheel is a uniform rectilinear movement alongside the optimistic X axis. In experiment, the touring motor 4 outputs second to the wheel by way of a belt conveyor to push the wheel ahead whereas one other driving motor 4 positioned beneath depends on a coupling to make the wheel rotate round its axis.

The touring and rotating speeds are measured by the encoders 3 related to the drive shafts. This examine takes the Martian soil because the analysis object; thus, dry sand is chosen because the soil and the topography is flat. The validity of the plastic homogeneous soil mechanics mannequin and the residual soil mannequin is verified by evaluating the traction efficiency error of the inflexible wheel involved with totally different rocks in simulation and experiment.

The outcomes present the next: 1) For the movable stones, the simulation outcomes of sinkage, drawbar pull, and resistance second are in good settlement with the experimental outcomes, which verifies the effectiveness of the above-proposed fashions; 2) In contrast with the mounted stone, it’s distinct that the motion states of stones have an necessary affect on the wheel’s traction efficiency. In some instances, ignoring the affect of the stone motion on the wheel traction capability, due to this fact, might result in giant errors.