具有弹性轮辐的可变直径轮力学特性及柔顺变径机构设计方法研究

The diameter-variable wheel which is able to travel on highway or soft terrain is a new non-pneumatic wheel with excellent trafficability. The elastic spoke without rigid hinge was used in the diameter-variable mechanism, which avoided the problems of wear, lubrication and sealing and made the mechanism more compact and portable, besides having damping effect. So the diameter-variable mechanism is a typical compliant mechanism. Application of the diameter-variable wheel needs to solve the theoretical and engineering problems which included the design method of compliant mechanism, manufacturing method of the elastic spoke and the characteristics of the tire when travelling on highway or soft terrain. The research on the design method of the compliant diameter-variable mechanism: the pseudo-rigid-body model for the fixed-guided flexible segment was built, and gets initial parameter of the spoke by kinematic synthesis. The problems arising from anisotropic mechanical behavior are solved by using special-shape spring, variable stiffness spring and cluster spring. The issues which are caused by material yield limit, compliance of mechanism and bearing ability are settled by overlapping pieces of special-shaped spring. The model of multi-objective optimization for the spoke was built. The research on the vertical, longitudinal or lateral dynamic characteristics of the diameter-variable wheel: the dynamic model of the diameter-variable wheel was set respectively for unfolded/folded diameter-variable wheel. Vibration characteristics, tractive characteristic, rolling resistance characteristic and cornering characteristics were researched. The fatigue property of the spoke was researched. The problems on material, formation and performance problem of the elastic spoke were researched. The research on the project has theoretical significance and engineering value for the study on the theory about the design of compliant mechanism, the study of the non-pneumatic wheel and application of the diameter-variable wheel with excellent trafficability.

可变直径轮是能够在公路和松软地面行走的新型高通过性非充气轮胎，变径机构采用无刚性铰链弹性轮辐，避开了磨损、润滑和密封问题，是一种结构紧凑，具有减振作用的柔顺机构。项目主要研究柔顺变径机构的设计方法、弹性轮辐制造和轮胎在公路和松软地面特性等理论和工程问题。研究柔顺变径机构的设计方法：建立固定-导向片段伪刚体模型，通过运动综合确定轮辐的初始几何参数；用异形弹簧、变刚度弹簧和多片组合弹簧等措施解决轮辐各向异性的需求；用叠合弹簧解决材料屈服极限、机构柔顺性及承载能力的问题；建立轮辐结构的多目标优化模型。研究变径轮垂向、纵向以及横向动力学特性：分别建立变径轮张开与合拢状态的动力学模型；研究变径轮不同状态的振动特性、牵引特性与滚动阻力特性以及侧偏特性。研究轮辐结构的疲劳特性。研究弹性轮辐的材料、结构成形和性能问题。本项目研究对柔顺机构设计、非充气轮胎研究及高通过性变径轮应用具有重要理论意义和工程价值。

可变直径轮可在张开状态和合拢状态之间转换，可实现全地域行走，是一种新型高通过性非充气轮胎。变径机构采用弹性轮辐作为柔顺铰链，避开了润滑和密封问题，是一种结构紧凑并具有减振作用的柔顺机构。项目主要研究柔顺变径机构的设计方法及变径轮在公路和松软地面行走的力学特性，对柔顺机构设计、非充气轮胎研究及高通过性变径轮应用具有重要理论意义和工程价值。 . 提出一种采用非线性优化综合的集中柔顺变径机构两位置运动生成设计方法，该方法可根据轮径变化范围来确定机构的尺寸参数。基于伪刚体模型，得到集中柔顺变径机构变径过程中力与变形的解析表达式，可为轮径变化的控制提供理论依据。阐释了具有分布柔顺变径机构的可变直径轮的变径机理和设计思想，提出具有分布柔顺特性的多片叠加波纹片弹簧与多股钢丝弹簧的组合作为变径机构，形成整体式弹性轮辐，解决了刚度与柔顺性的矛盾。提出了该变径轮的新型螺旋传动机构及其原理，解决了变径与车轮驱动的双重需要。揭示了从单片波纹弹簧到多层叠合波纹弹簧的刚度与波纹大小、数量以及厚度的规律、应力的分布规律，可为异形弹性轮辐设计提供指导。提出了分布柔顺变径机构的尺寸设计方法。整轮的变径试验验证了设计预期。 建立合拢状态可变直径轮的垂向承载模型，提出弹性轮辐的圆弧变形假设和弹性外圈的椭圆变形假设，基于能量法得到的垂直刚度解析式可用于变径轮设计。建立合拢状态变径轮的单质量-弹簧垂直振动模型，得到了频率响应函数。在不平路面输入激励下，获取了轮心的时域位移、速度及加速度响应与频域功率谱密度响应，为变径轮的结构优化提供了改进方向。 基于刷子模型，建立合拢状态可变直径轮的纯侧偏特性简化模型，得到了变径轮侧偏力、回正力矩的解析表达式。进一步考虑弹性外圈的扭转和弯曲变形，建立了变径轮侧偏特性的精细模型，可为变径轮的结构优化设计提供理论参考。 构建了张开状态可变直径轮轮脚外缘任一点的摆线运动方程，得到了剪切位移。在此基础上，建立了小沉陷量工况下变径轮单个轮脚与软土的相互作用模型，分析表明轮径增大可提高通过性。考虑大沉陷量工况下多个轮脚与软土的相互作用，能为变径轮牵引特性的精确预测和控制提供理论依据。对研制的分布柔顺可变直径轮原理样机的部件和整轮进行了性能测试及实验。试验结果与理论分析结果吻合较好，验证了所建立的理论模型的正确性和分析的有效性。