欠驱动三稳态柔顺夹持机构及其双向驱动器的原理研究

Underactuated tristable compliant grasping mechanisms are able to grab objects with constant force and can switch between three stable equilibrium positions. They are easy to modularize and have many advantages such as high repeatable positioning precision, reduced friction and wear, reduced assembly processes and maintenance, and simplified control system. Based on the underactuated compliant five-bar mechanism and five-bar slider-crank mechanism, the conditions under which the compliant five-bar mechanism and five-bar slider-crank mechanism may have three stable equilibrium positions are derived to guide the design of linear and rotary tristable positioning mechanisms. The condition under which the compliant five-bar slider-crank mechanism may produce a constant output force is also derived to guide the design of a compliant constant-force mechanism for grasping objects. The optimization methods for the parameters of the compliant tristable and constant-force five-bar mechanisms are studied. A bidirectional actuating method of using shape memory alloy is studied to actuate the linear compliant tristable mechanism and a bidirectional actuating method based on electromagnetic principle is studied to actuate the rotary compliant tristable mechanism. Two underactuated compliant grasping mechanisms are designed and manufactured to verify the theoretical study, one is composed of a linear compliant five-bar tristable mechanism and a spatial grasping mechanism with four compliant constant-force mechanisms, and the other is composed of a rotary tristable compliant five-bar mechanism and a spatial grasping mechanism with four compliant constant-force mechanism.

欠驱动三稳态柔顺夹持机构可以以恒力抓取物体并在三个稳定平衡位置间切换，具有重复定位精度高，可实现模块化，摩擦、润滑少，装配、维护工作量减小，控制简单等优点。本项目拟以欠驱动柔顺五杆铰链机构和滑块机构为基础构型，系统地研究欠驱动柔顺五杆铰链机构和滑块机构实现三稳态的条件，研究欠驱动柔顺五杆滑块机构实现恒力输出的条件，研究柔顺五杆三稳态机构和恒力机构的参数优化方法，研究利用形状记忆合金和电磁原理双向驱动直线型和旋转型三稳态柔顺机构的原理，设计旋转型和直线型三稳态定位模块机构、柔顺恒力夹持模块机构，设计双向驱动器，组装得到直线型和旋转型欠驱动三稳态柔顺夹持机构以验证理论研究结果。

欠驱动三稳态柔顺夹持机构可以以恒力抓取物体并在三个稳定平衡位置间切换，利用柔性构件的弹性变形回复力实现在三个位置的稳定平衡以及恒力输出抓取，具有重复定位精度高，易于模块化，摩擦、润滑少，装配、维护工作量减小，控制简单等优点。本项目首先研究了用椭圆积分法建立簧片式LITF柔性铰链的模型，可以精确计算LITF柔性铰链在水平力、垂直力和力矩作用下的变形，校核强度，分析屈曲临界力，计算运动范围和承载能力；其次研究了以柔顺双稳态机构为基础模块，串联连接柔性平行-导向机构设计直线型柔顺多稳态机构的方法；设计了一种平面外直线型柔性三稳态机构；以欠驱动柔顺五杆机构为基础构型，系统地研究了欠驱动柔顺五杆机构实现三稳态的条件，设计了柔顺三稳态定位装置；研究欠驱动柔顺五杆滑块机构实现恒力输出的条件，设计了柔顺五杆恒力机构；用粒子群优化算法实现了柔顺五杆三稳态机构和恒力机构的参数优化；利用形状记忆合金的特性用两段形状记忆合金弹簧构成一级驱动模块，两级驱动模块嵌套可到达三个位置，设计了直线型三稳态定位装置的双向驱动器，可驱动直线型柔顺三稳态定位装置；根据电磁原理设计了旋转型三稳态柔顺机构的双向驱动器，可驱动旋转型柔顺三稳态定位装置。.本项目研究成果柔性铰链的椭圆积分解可用于非线性大变形柔性铰链的精确建模；直线型柔顺多稳态机构设计方法理论上可得到任意数目稳态的全柔顺多稳态机构；旋转型欠驱动三稳态柔顺五杆机构可实现任意两个稳态之间的切换，无需回到初始位置。后续工作将综合柔顺三稳态定位装置与柔顺恒力机构，作为生产制造业中的机械手，具有工程应用前景。