基于STM32的机械手夹持力控制系统设计

为保证被夹持物品的完好以及机械手夹持的稳定性，提出了基于STM32的机械手夹持力闭环控制系统，该系统主要解决了在机械手夹持过程中夹持力控制问题。采用PID为控制策略，CAN总线为通讯方式，创新地提出无外置传感器的方式，实现机械手夹持力闭环控制。     

水下机器人手爪力感知系统研究

提出了一种水下机器人手爪力感知系统的组成结构,该力感知系统由一个六维力/力矩传感器和三指夹持器指端的三个指力传感器组成,本文介绍了上述两种传感器的设计和标定,并对利用该手爪系统抓取物体进行了实际测试和分析,实验结果表明;所设计的力感知系统能够实时地感知腕力和夹持力信息,可以满足机械手力控制的需要.     

骨骼服虚拟力控制方法研究

针对骨骼服运动中控制指令信息难以获取这一问题,提出了一种利用安装在操作者和骨骼服之间的多 维力／力矩传感器来估计骨骼服参考轨迹的方法．为了控制骨骼服跟随操作者的运动,并保持人机之间的作用力最 小,以达到辅助承重的目的,提出了一种虚拟力控制策略．该方法首先利用力／力矩传感器的测量信息构建骨骼服在 关节空间的关节控制力矩,然后产生控制骨骼服在操作空间运动的虚拟力,从而控制骨骼服在操作空间的轨迹跟随 操作者的运动．证明了其稳定性,并给出了仿真结果．仿真结果表明,所设计的控制器能实现骨骼服对人体运动的 跟踪,并有效降低人机之间的作用力．     

基于系统阻力变化的手术微器械夹持力检测

针对手术机器人微器械的力检测问题,搭建了3自由度微器械的等效实验平台.基于柔索驱动微器械关节完整的动力学模型设计了驱动关节综合阻力模型,并根据实验结果进行了BP （反向传播）神经网络模型的数据拟合,给出综合阻力神经网络模型.最后根据驱动单元综合阻力的变化提出了一种夹持力估计策略,并通过连续加载和阶梯加载实验验证了夹持力检测方法的性能.实验结果显示,夹持力检测的最大绝对误差可以达到0.24 N,在稳定阶段夹持力检测的精度可以达到90%左右.该方法可以成为实现手术机器人微器械力反馈的基础.     

基于行星齿轮机构的牵引式欠驱动机械手设计

为实现夹持力调节和目标物体抓取功能,设计了一种基于行星齿轮机构的牵引式欠驱动机械手。该机械手采用不固定输出轴和内齿圈的行星齿轮机构来分配2种互斥的运动,一种用于手指的转动,实现机械手的夹持功能;另一种用于皮带轮的无限转动,通过皮带实现目标物体的拉入功能。相对于腱绳式和连杆式欠驱动机械手,这种单输入双输出形式不仅能够保持机械手的自适应性,同时还能降低机械手的耦合程度。根据行星齿轮机构的这种传动特点,设计了阻力矩调节机构,实现了机械手的夹持力调节功能。夹持力测试实验表明,在阻力矩调节机构的作用下,机械手能有效调节夹持力。抓取实验结果表明,机械手能够实现对刚性和柔性目标物体的抓取操作,验证了机械手设计的有效性。     

机器人操作器力控制稳定性分析

当机械手同刚性环境接触时，机械手力控制难于保持系统的稳定性，这就是机械手力控制动态不稳定性，本文分析了机械手力控制未建模特性：１）机械手驱动电机动态特性；２）力传感器动态特性；３）接触环境的动态特性；４）机械手力控制采样控制延迟等对机械手力控制稳定性的影响，最后给出了仿真及实验研究结果。     

受动态约束的谐波传动式可重构模块机器人分散积分滑模控制

针对受外界动态约束的谐波传动式可重构模块机器人轨迹跟踪问题, 提出一种基于关节力矩反馈的分散积分滑模控制方法. 在无力/力矩传感器且存在耦合模型不确定性的条件下即能获得良好的控制品质. 基于谐波传动模型, 仅采用位置测量数据估计关节力矩, 并建立机器人子系统动力学模型. 基于可变增益超螺旋算法(VGSTA) 设 计分散积分滑模控制器, 补偿模型不确定性并削弱控制器抖振. 采用Lyapunov 理论对系统的渐近稳定性进行了证明. 值仿真结果验证了所设计的控制器的优越性.

     

七自由度番茄收获机械手动力学研究

在番茄收获机械手动力特性优化控制的研究中,采用Lagrange法,建立了七自由度番茄收获机械手的动力学模型,获得了机械手力、质量和加速度以及力矩、转动惯量和角加速度之间的关系,并得到了机械手在完成指定运动时各关节驱动器所需要的驱动力(力矩).利用Pro/E和ADAMS建立了机械手的虚拟样机,分别在MATLAB和ADAMS中进行了动力学仿真.结果表明,利用动力学模型与虚拟样机得到的各关节作用力(矩)均呈规律性变化,除关节2和关节4外,各关节力(矩)值是相同的.两种方法得到的关节2和关节4力(矩)的最大相对误差为3.76％,验证了动力学模型的正确性和虚拟样机的可靠性,为番茄收获机械手轨迹跟踪控制提供了动力学模型和基于虚拟样机的被控对象,并为优化设计提供了依据.     

基于多感知的空间机械手爪控制研究

对融合了视觉、滑觉、角位移等多种传感器的欠驱动空间机械手爪,研究其对不同形状、质地的物体实现自适应抓取控制。通过传感器反馈控制机械手运动、抓取力,提高机械手的自主能力。在抓取模式选择中,采用基于专家系统的抓取规划,根据物体不同的形状、尺寸选择不同的抓取模式;在抓取力控制中,通过由PVDF制作的滑觉传感器反馈,采用基于滑觉信号的模糊控制方法,对不同质地的物体选择不同的控制参数。通过实验研究验证基于多感知的控制方法对各种物体可以进行可靠的抓取。     

基于力矩外环的软物体抓取控制

为减少机械手抓取软物体造成的损害,提出基于关节力矩预测的力矩外环在线抓取控制方案。该方案通过建立灰色预测模型直接预测关节力矩的变化代替预测软物体刚度的变化;并能同时控制机械手抓取过程中关节力矩偏差和角速度关系。在实际关节力矩和灰色预测力矩之间采用线性插值,按采样周期将预测力矩逐渐加到力矩回路中。仿真表明,当抓取具有刚度变化的软物体时,基于关节力矩预测的力矩外环软物体抓取控制系统对机械手和软物体之间的动态接触过程具有一定的自适应性,可以快速跟踪设定值,而且无大的超调和振荡出现,使控制性能和动态品质得到较大改善,具有较强的鲁棒性,是适合软物体抓取的一种控制方法。     

The integrated force method versus the standard force method

A novel formulation termed the Integrated Force Method (IFM) has been developed for the analysis of structures wherein all the internal forces are taken as the independent variables, instead of the conventional way of treating the redundants as the primary unknowns in the popular force method, henceforth referred to as the Standard Force Method (SFM). As part of a continued effort to develop the force method, a project was taken up to compare the IFM and the SFM numerically and analytically. The conclusions of this study are summarised in this article. The primary conclusions of this study include the following: The IFM is the true force method. The SFM can, at best, be considered as a solution technique of the IFM for static analysis, and the IFM bypasses the popular concepts of redundants and basis determinant structure of the SFM. The IFM can handle the gross response of structures such as vibration and stability analysis. IFM has been developed for the analysis of plates following continuum mechanics approach. No SFM exist for vibration and stability analysis. SFM is practically non-existant for the analysis of plates and shells. The stability of equations of the IFM is superior to those of SFM. IFM takes less computation time than SFM for the determination of forces and displacements.     

用于昆虫足力测试的三维微力传感器

介绍一种三维微力传感器的结构和工作原理,该传感器量程为-0.01~0.01N,分辨力为10μN,用于测量昆虫爬行时足底与接触面间的三维接触力。通过运用Ansys有限元分析软件,对这种结构的传感器进行结构静力分析和模态分析,验证这种结构传感器用于小量程三维接触力测量的可行性。昆虫爬行足力试验测试以及相关的试验数据表明:可以满足生物试验要求。     

Vision-based force measurement

This paper demonstrates a method to visually measure the force distribution applied to a linearly elastic object using the contour data in an image. The force measurement is accomplished by making use of the result from linear elasticity that the displacement field of the contour of a linearly elastic object is sufficient to completely recover the force distribution applied to the object. This result leads naturally to a deformable template matching approach where the template is deformed according to the governing equations of linear elasticity. An energy minimization method is used to match the template to the contour data in the image. This technique of visually measuring forces we refer to as vision-based force measurement (VBFM). VBFM has the potential to increase the robustness and reliability of micromanipulation and biomanipulation tasks where force sensing is essential for success. The effectiveness of VBFM is demonstrated for both a microcantilever beam and a microgripper. A sensor resolution of less than +/-3 nN for the microcantilever and +/-3 mN for the microgripper was achieved using VBFM. Performance optimizations for the energy minimization problem are also discussed that make this algorithm feasible for real-time applications.     

基于振动力和风力作用的服装动态仿真*

为了真实地模拟服装的动态效果,本文提出了一种四元数产生振动运动的方法。本文首先介绍了四元数产生振动运动的过程,然后给出基于随机噪声函数构建随机风场的过程,调节不同的仿真参数,仿真出裙子在重力、振动力、风力作用下的动态效果。实验结果表明,该方法获得了不错的动态服装仿真效果。     

基于正弦力激励的预紧压电式力传感器的研究

为了校准预紧的压电式力传感器动态灵敏度并研究其频响特性和预紧结构的设计,首先介绍了正弦力激励的方法并建立校准数学模型。分别在传感器正立和倒立安装方式下进行测试,通过对比试验研究传感器端部等效质量引入的惯性力对传感器动态灵敏度的影响。然后根据传感器固有频率的落球测试方法,将传感器和附加质量块安装于振动系统。通过白噪声激励得到系统安装谐振频率,进而研究传感器有效频率范围和测量精度与安装谐振频率的关系。最后通过理论分析,说明传感器非对称设计的原因。试验结果表明,当附加质量块质量约为传感器质量的121倍时,可忽略端部等效质量对灵敏度标定的影响;压电式力传感器固有频率高达46kHz,但其有效使用频率范围受安装谐振频率限制,当试验频率与安装谐振频率比 时,压电式传感器精度等级为1%;传感器两端等效质量不同,预紧结构是非对称的,用于动态测试时要将端部等效质量轻的一端连接到被测物体。本研究结果可为开展传感器的现场标定和预紧结构的设计提供理论依据。     

Grip force and force sharing in two different manipulation tasks with bottles

Abstract

Grip force and force sharing during two activities of daily living were analysed experimentally in 10 right-handed subjects. Four different bottles, filled to two different levels, were manipulated for two tasks: transporting and pouring. Each test subject’s hand was instrumented with eight thin wearable force sensors. The grip force and force sharing were significantly different for each bottle model. Increasing the filling level resulted in an increase in grip force, but the ratio of grip force to load force was higher for lighter loads. The task influenced the force sharing but not the mean grip force. The contributions of the thumb and ring finger were higher in the pouring task, whereas the contributions of the palm and the index finger were higher in the transport task. Mean force sharing among fingers was 30% for index, 29% for middle, 22% for ring and 19% for little finger.

Practitioner Summary: We analysed grip force and force sharing in two manipulation tasks with bottles: transporting and pouring. The objective was to understand the effects of the bottle features, filling level and task on the contribution of different areas of the hand to the grip force. Force sharing was different for each task and the bottles features affected to both grip force and force sharing.     

基于力同步控制的双缸力加载系统控制策略

针对液压加载系统中双缸力同步控制需求,设计了并联控制方案。分别采用减压阀和伺服阀作为主要控制元件,建立双缸力同步控制系统数学模型。通过调节相应的液压参数和控制参数,采用Simulink对两类控制元件下的模型进行仿真研究。仿真结果表明,并联控制可以有效实现双液压缸的力同步加载,理论上当使用减压阀作为控制元件宜采用纯积分控制策略,当使用伺服阀作为控制元件宜采用PD控制策略,均可得到较优控制效果,为实际工程项目双缸加载试验提供理论指导。     

Flexible polyimide-based force sensor

We have realized a flexible force sensor, composed of four redundant capacitors, the operation of which is based on the measurement of a load-induced capacitance change. We use polyimide both as flexible substrate and as elastic dielectric between two levels of finger-shaped aluminum electrodes. In particular we have developed a technology for realization of two-level polyimide microstructures with gentle slopes to facilitate subsequent metallization processes. Thereby, we could improve step coverage and electrical contacting between the two metallization levels, as well as the mechanical stability of the sensor. The smooth polyimide slopes were obtained by combining lithographic resist-reflow techniques with dry etching procedures. We have analytically modeled the sensor's capacitance and its force sensitivity. We have electrically characterized the capacitors using an impedance analyzer and obtained capacitances in the range of 130 pF and a typical force sensitivity of 0.5-1 fF/N, in excellent agreement with our model.