【作者】 刘振；

【导师】 邓宗全；

【作者基本信息】 哈尔滨工业大学 ， 机械设计及理论， 2013， 博士

【摘要】 为模拟星球车在低重力环境中的运动性能，需要对星球车进行重力补偿。传统的重力补偿方法是使用吊索向构件质心施加补偿力。由于星球车是多自由度系统，传统补偿方法需使用多根吊索。这给重力补偿的实施带来很大难度。为此，本文前半部分进行单吊索重力补偿的模型和实验研究。按照探月二期需求，重力补偿系统的位置跟踪范围30m×30m，位置跟踪误差小于28mm，恒拉力控制误差小于5‰(1σ)。针对此系统的设计问题，本文后半部分进行大范围重力补偿系统的设计和实验研究。补偿力的约束方程组称为“重力补偿模型”，模型的每一组解都对应一种重力补偿方案。建立重力补偿模型的目的是获得补偿力解系，以获得单吊索的补偿力解。为建立重力补偿模型，首先给出在约束力学体系内建立星球车动力学方程的方法；然后通过对比低重力状态和重力补偿状态的星球车动力学方程，获得补偿力应服从的约束(适用所有悬架构型)。针对只含转动自由度和差速器自由度的星球车，建立了重力补偿模型的表达式。按照星球车的构型特点，分别求解单关节链、多关节链、分叉关节链和差速器耦合关节链的补偿力解系，明确多关节链和分叉关节链的解系独立原则。在此基础上，获得星球车补偿力的解系。在补偿力解系中，总存在一类特殊的解向量。此类解向量中只含一个正分量，其余分量均为负值；正分量对应吊索补偿力，负分量对应配重补偿力，此解即对应“单索重力补偿”。通过向“重力补偿模型”的解系中加入的单索约束条件，得到“单吊索重力补偿模型”的解系。给出六轮和八轮摇臂—转向架式星球车的单索补偿力解系的算例。建立了轮地力模型，在此基础上证明单吊索重力补偿能够准确地模拟星球车轮地力。通过软件仿真，验证了单吊索重力补偿模型的正确性。为避免拆解星球车进行质心测量，提出通过星球车轮地力计算、校正补偿力系的方法；给出轮地力测试台结构。为向星球车车厢内部施加吊索补偿力，利用平行全等体的性质设计了车厢平行吊架，通过平行吊架等效地向车厢内部施加补偿力。为进行星球车重力补偿，研究重力补偿系统的设计方法。针对拉力系统激发位置系统主梁谐振的问题，设计大小电机同轴驱动系统，利用双输入系统等效惯量可变的性质，实现按工作频带配置等效惯量的目的。针对拉力系统马达高频响应滞后的问题，设计主动、被动响应结合的拉力系统：使用恒力机构张紧吊索，大量降低吊索等效刚度，吸收高频拉力干扰。针对位置系统主梁惯性大、运动精度差的问题，设计粗控、精控结合的位置系统。使用天车系统搭载二维跟踪平台，实现大范围的精确位置跟踪。针对位置系统激发主梁横振的问题，为天车系统和二维跟踪平台的距离设置阈值，使天车系统在完全静止和匀速运动两个状态间缓慢、平稳地切换。为验证重力补偿系统的工作性能，进行重力补偿系统性能实验。针对拉力系统，进行星球车平地越硬障碍、下坡越硬障碍、平地过缓坑三组测试。针对位置系统，进行星球车斜穿场地的测试。通过综控系统记录的数据，验证重力补偿系统的工作性能，证明系统设计的正确性。本文建立了单吊索重力补偿模型，给出了单吊索重力补偿的实验方法，解决了大范围重力补偿系统的关键设计问题。本文研究结果成功地应用于探月二期的星球车运动性能测试实验中，实现了大范围、高精度的星球车重力补偿。更多还原

【Abstract】 To simulate the low-gravity wheel pressure, the rover’s gravity shall becompensated. Traditionally, compensation forces are applied onto center of massesof each moving part. Since planetary rovers are multiple DOF systems, themethod always includes multiple cables, which difficulties to the implementationprocess. Therefore, the first half of the dissertation is contributed to research on theSingle-Cable Gravity Compensation model and its implementations. According tothe demand of lunar exploration program, the gravity compensation system shallcover an area of30m×30m, with a position servo error no more than28mm and atension servo error no more than5‰(1σ). The second half of the dissertation iscontributed to research on the design of the Large-Scale gravity compensationsystem and its experimental researches.The constraint on the gravity compensation forces is named “model of thegravity compensation”, each solution of which forms a gravity compensationscheme. The reason to model gravity compensation is to acquire its solution system,which contains the single-cable solution. To model gravity compensation, thedynamic modeling of planetary rovers is firstly presented, and then the constraintson compensation forces, by comparing the dynamic models in low gravity situationand in compensated situation, are acquired (applicable to all rovers). Specifically,an expression of the compensation model is built for rovers with only rotation DOFand differential DOF. The solution of the model, with respect to topology relation ofplanetary rovers， is acquired according the single joint-chain, the multiplejoint-chains, the bifurcation joint-chains, and the chains coupled by differentialmechanism. Also acquired are the independence of compensation forces solution inmultiple chains and bifurcation chains. The solution system of compensation forcesis then acquired.In the solution system, there are always such solution that includes only onpositive elements and that all other elements are negative. The positive elementcorresponds to a force applied by a cable, and the negative element corresponds to aforce applied by a counterweight, and this solution corresponds to single-cablegravity compensation. By imposing single-cable constraint onto the solution systemof gravity compensation model, the solution system of the single-cable gravitycompensation model is acquired. Two examples are presented according tosix-wheeled and eight-wheeled rocker-bogie rovers. The wheel pressure model isbuilt to prove that single-cable gravity compensation can correctly simulate thewheel pressures. Additionally, software simulations are also presented to prove the single-cable gravity compensation model. To avoid measuring the centers of massof rovers and avoid dissembling the rover, the method to calculate and adjustcompensation forces by the measure of contact forces is brought forward. Alsopresented are the method and platform to measure wheel pressures. To apply a forceto an inner point in the carriage of rovers, the property of parallel congruent bodiesis used to design the parallel suspension platform, which constantly transforms theforce on the similar suspension to the inner point.To implement gravity compensation over a large test field, the design ofLarge-Scale Gravity Compensation System is researched on. Because that theposition system could easily excite the resonance of the girder, a macro-microcoaxial dual-motor-driven system is designed. The system utilize the property thatthe inertia of a double-input system could be changed, and arranging its inertial withrespect to working frequency. Because that the motor are incapable to reducehigh-frequency disturbance, an active-passive tension system is designed. Thesystem tightens the cable with a constant-force mechanism, and therefore reducesthe equivalent stiffness of the cable greatly to absorb impacts. Because that thegirder possess a massive inertia and can hardly be precisely controlled, amacro-micro position system is designed. The girder-trolley system carries thetwo-dimensional servo platform, and the position system can precisely follow therover over a large area. Because that the horizontal resonance of the girder could beeasily excited, the threshold method is employed to control the girder-trolley system,so that the girder-trolley system is either moving or resting, switching slowly andstably between motion and motionless.To prove the property of the gravity compensation system, experimentalresearches are carried out to test the system. To test the tension system, the rover aremade to traverse over hard obstacle on flat terrain and on descending slop, as wellas traverse shallow holes on flat terrain. To test the position system, the rovers aremade to travel the diagonal line of the test field. By analyzing data from the system,the property of the system and the correctness of system design, is verified.This dissertation builds the single-cable gravity compensation model, presentsthe experimental methods of single-cable gravity compensation, and solved keyproblems in Large-Scale Gravity Compensation design. The dissertation finds itsuses in the mobility test on rovers in the lunar exploration program, which appliesgravity compensation on rovers over a large field with high precision.更多还原