一种新型的可变刚度柔性关节设计与控制研究

发布时间：2018-05-18 19:09

本文选题：可变刚度 + 非线性　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：可变刚度的柔性关节,因其刚度可调的特性,相比传统的刚性关节和单纯柔性关节有更强的环境适应性,特别在人机交互较多的场合拥有极高的应用价值。但是刚度可变也带来了结构复杂,刚度稳定性差等问题,而且,当前已有的变刚度机构中,刚度同多个参数间皆为非线性关系,使得关节刚度辨识困难,控制器难以准确实现刚度动态调节。本文针对上述问题,设计了一种利用机构间几何关系实现刚度变化的新型变刚度机构,并在此基础上完成了刚度动态可调的给定值控制系统的研究与设计。首先,针对变刚度原理中存在的非线性问题,本文提出了一种类曲柄滑块机构,利用支点运动时机构间的几何关系预压缩弹簧,实现了刚度关于支点偏移量的近似线性变化。该原理中引入的支点-滑块-滑动轴承的压缩形式解决了现有的支点-滑槽结构中的摩擦间隙,运行不够稳定等问题,同时,支点依靠行星轮机构驱动,也使得关节整体结构更为紧凑。在此基础上,课题对各功能模块进行分割,设计了包括刚度调节,刚调传动,主传动以及关节附属测量等功能模块的结构。其次,针对关节系统刚度模型中仍存在的非线性特性,利用刚度同支点偏移量之间的线性关系,对刚度模型进行了参数解耦合和泰勒展开处理,完成了刚度曲线的拟合。在此基础上,考虑到关节运行中输出刚度动态调整的需求,设计了基于轨迹发生器的给定值控制模式,实现了需求刚度、位置同电机轨迹之间的映射。之后,对控制算法的软硬件实现进行了研究,针对系统通讯、供电、电路集成化等要求,设计了具有命令处理、CAN通讯、RS485通讯、电压转换、状态指示等功能的硬件电路,并依据算法对其软件实现进行了编写和优化,完成了控制命令从上位机到下位机再到运动调节模块的传输与反馈,实现了控制系统的总体设计。最后,基于上述结构和控制系统,搭建了单关节实验平台,设计了静态刚度辨识、动态刚度跟随实验以及多种负载、刚度、需求信号下的位置跟随实验,对关节刚度特性和位置特性进行了实验验证,证实了课题设计的控制器在一定范围内实现刚度和位置连续调整的可行性。
[Abstract]:Because of its adjustable stiffness, flexible joints with variable stiffness have stronger environmental adaptability than traditional rigid joints and simple flexible joints, especially in the case of more man-machine interaction. However, the variable stiffness also brings about the problems of complex structure and poor stiffness stability. Moreover, in the existing variable stiffness mechanisms, the stiffness and several parameters are nonlinear, which makes it difficult to identify the stiffness of joints. It is difficult for the controller to realize the dynamic adjustment of stiffness accurately. In order to solve the above problems, a new type of variable stiffness mechanism is designed, which utilizes the geometric relationship between the mechanisms to realize the stiffness change. On the basis of this, the research and design of the dynamic and adjustable stiffness control system with given values are completed. Firstly, aiming at the nonlinear problem in the principle of variable stiffness, a kind of crank slider mechanism is proposed in this paper. By using the geometrical relation between the mechanisms when the fulcrum is moving, the precompressed spring is used to realize the approximate linear variation of stiffness with respect to the offset of the fulcrum. The compression form of fulcrum-slider-sliding bearing introduced in this principle solves the problems of friction clearance in the existing fulcrum-chute structure and its operation is not stable. At the same time, the fulcrum is driven by the planetary wheel mechanism. It also makes the whole structure of the joint more compact. On the basis of this, the thesis divides the functional modules and designs the structure of the modules including stiffness adjustment, rigid transmission, main transmission and joint accessory measurement. Secondly, according to the nonlinear characteristics of the stiffness model of the joint system, using the linear relationship between the stiffness and the offset of the fulcrum, the parametric decoupling and Taylor expansion of the stiffness model are carried out, and the fitting of the stiffness curve is completed. On this basis, considering the need of dynamic adjustment of output stiffness in joint operation, a given value control mode based on trajectory generator is designed, and the mapping between required stiffness, position and motor trajectory is realized. After that, the hardware and software realization of the control algorithm is studied. According to the requirements of system communication, power supply and circuit integration, the hardware circuit with command processing can communication and RS485 communication, voltage conversion, state indication and other functions is designed. According to the algorithm, the software implementation is programmed and optimized, and the control command is transmitted and feedback from the upper computer to the lower computer to the motion adjustment module, and the overall design of the control system is realized. Finally, based on the above structure and control system, a single joint experiment platform is built, and static stiffness identification, dynamic stiffness following experiment and position following experiment under various loads, stiffness and demand signals are designed. The stiffness and position characteristics of joints are verified by experiments, and the feasibility of continuous adjustment of stiffness and position is verified by the controller designed in this paper.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP242

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