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机器人单足系统沙土跳跃刚−散耦合动力学分析

RIGID-DISCRETE COUPLING DYNAMIC ANALYSIS OF ROBOT MONO-PEDAL SYSTEM JUMPING IN SAND

  • 摘要: 在行星探索过程中涉及探测器在星壤上着陆、运动以及收集、存储某些样本材料等问题, 因此需要建立探测机器人在沙土上运动的动力学模型, 从而优化其系统构型. 近年来, 对跳跃型探测机器人研究得到了越多越多的关注. 本文采用离散元法对颗粒场进行建模, 以及采用多体动力学方法对机械系统进行建模, 对机器人单足系统在沙土上的跳跃问题进行耦合动力学仿真分析. 基于经典土力学Prandtl-Reissne理论, 从颗粒场受压分层的形式和动量传递出发, 对描述颗粒侵入阻力的惯性力动阻力项进行了修正, 提出了一种修正的Poncelet公式. 通过与离散元仿真结果对比, 说明所提出修正公式比原始的Poncelet公式更准确地计算了机械足受到的沙土侵入阻力, 尤其在达到一定侵入深度表现出更好的收敛性. 最后分析了机械腿足部的不同尺寸和形状对沙土中跳跃效果的影响, 给出了锥形足部和柱形足部的体积对跳跃效果影响的近似计算公式. 本研究将拓展刚−散耦合动力学理论, 并且为新型探测器在行星土壤上运动的系统设计提供技术支撑.

     

    Abstract: In the process of planetary exploration, it involves the landing and movement of the probe on the earth, as well as the collection, storage and return of some sample materials. Therefore, it is necessary to establish a dynamic model of the motion of the probe robot on the sand, so as to optimize the system configuration. In recent years, the studies on jumping detection machinery have received considerable attentions. In this paper, the discrete element method is used to simulate the particle field deformation. The multibody dynamics method is used to model the mechanical system. Then the coupling dynamics simulation and analysis are carried out for the jumping problem of the robot single foot system on the sand. Based on Prandtl-Reissne theory of classical soil mechanics, starting from the form of pressure stratification and momentum transfer of particle field, a modified Poncelet formula is proposed while the inertia force dynamic resistance term describing particle intrusion resistance is modified. The modified formula adds supplementary items related to rigid body acceleration and intrusion depth, and no new fitting coefficient is added compared with the original formula. By comparing with the results of discrete element simulation, it is shown that the proposed modified Poncelet formula can more accurately calculate the sand and soil invasion resistance of the mechanical foot than the original Poncelet formula. Especially, it shows better convergence when reaching a certain invasion depth. Finally, the influence of different size and shape of the mechanical leg's foot on the jumping effect in sand is analyzed, and the approximate calculation formula of the volume of the conical foot and the cylindrical foot on the jumping effect is presented. The simulation results show that the conical sole will replace the volume of the consolidation zone of the particle field. Furthermore, the influence of particles in the consolidation zone of robot foot on the invasion resistance is discussed. This study will expand the rigid-discrete coupling dynamics theory, and provide technical support for the system design of the new type probe moving on the planetary soil.

     

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