Study on the unidirectional force sensitive beam structure with the overload protection mechanism

各种力/扭矩传感器被用于工程应用领域。大多数力/扭矩传感器被设计为对弱信号敏感，因此，它们意外地失去了刚度。这种柔性传感器倾向于感测耦合的力，并且通常难以使它们解耦。本研究的目的是设计并发展一种单向力敏梁结构，以克服上述问题。在设计过程中，采用有限元分析和实验相结合的方法，对H型狭缝和平行梁结构的特点进行了分析。主要研究结果如下：1.通过对H缝梁和平行梁的实验和有限元分析，发现在相同灵敏度下，H缝梁比平行梁具有更高的刚性。这一结果表明，H型狭缝梁是一个合适的形状的单向力传感器，因为它可以是敏感的和刚性。2. H型狭缝梁结构可以模拟为一个4杆封闭的链接结构。因此，该结构本身可以是过载的机械止动器。施加的力使梁的狭缝宽度减小，当狭缝宽度为零时，梁不再变形。3.研究了H型狭缝梁的最佳参数和尺寸，以避免应力集中。研究结果表明，抛物线形切口（短轴与长轴之比为1：10）具有较好的应力分布。4.将H型狭缝力传感器应用于仿人机器人ZMP传感器。所开发的ZMP传感器具有6个传感点，配备有12个H狭缝。传感器安装在仿人机器人的脚底，用于控制机器人。

A variety of force/torque sensors are used in the engineering application fields. Most of the force/torque sensors are designed to be sensitive for a weak signal, and thus, they unexpectedly lose the stiffness. Such flexible sensors tend to sense the coupled forces, and it is generally difficult to decouple them. Furthermore, the flexible sensors cause the positioning error.The objective of this study is to design and develop a unidirectional force sensitive beam structure to overcome the problems described above. In the design process, the characteristics of the H-slit and parallel beam structure was analyzed by FEA (Finite Element Analysis) and experiments. The results of this research are summarized as follows.1.From the results of experiments and FEA for the H-slit beam and parallel beam, we found that the H-slit beam was more rigid than the parallel beam if they had same sensitivity. This result indicates that the H-slit beam is an appropriate shape for the unidirectional force sensor, since it can be sensitive and stiff.2.The H-slit beam structure can be modeled by a 4-bars closed-link structure. Therefore, the structure itself can be a mechanical stopper for the overloads. The applied force decreases the width of the slit of the beam, and when the width of the slit becomes zero, the beam does not deform anymore.3.The Optimal parameter and dimensions of the H-slit beam are investigated in order to avoid the stress concentration. As a result of this study, it is found that a parabola shaped notches (minor and major axis ratio is 1:10) exhibits a relatively, adequate stress distribution.4.The H-slit force sensor is applied to the ZMP sensor for a humanoid robot. The developed ZMP sensor has 6 sensing points equipped with 12 H-slits. The sensor is attached at the sole of a humanoid robot and used for the control of the robot.