Force Control of Gripper Driven by Piezoelectric Actuator

本项目由日本东北大学和韩国全北国立大学合作进行了三年，实现了压电驱动器驱动的夹持器力控制。项目的具体情况如下：压电陶瓷是铁电的，其响应基本上是非线性的，对外加电压信号表现出明显的滞后环。研究了非线性压电陶瓷作动器的线性驱动问题。提出了一种补偿陶瓷作动器滞回线的线性驱动方法。研制了一种简单的非线性前置放大器。结果表明，在直流放大器和输入电压发生器之间安装非线性前置放大器后，滞回回路消失。为了测量微小力，研制了具有人体数字纸浆感的软触觉传感器。该传感器由两个矩形橡胶块和插入在橡胶块界面之间的多个橡胶片组成。应变计中的应变与施加在传感器上的载荷的大小成正比。因此，表面载荷可以通过测量量规的输出来确定。对橡胶块内嵌应变片的几种配置进行了理论和实验研究。结果表明，所提出的软传感器可以有效地测量传感器上的分散和集中的微小力。研制了一种由压电双晶片驱动的两指微型夹持器，并对该系统的位置/力混合控制进行了研究。该系统由两个柔性悬臂和一个紧凑型力传感器组成，该传感器连接在一个手指的尖端。建立了机电系统的理论模型，并将其应用于控制问题的研究，该控制问题是命令夹持器在指定的指端位置以0.01N的时间常数力抓取物体。采用PID和i_ *控制算法对夹持器进行驱动。对系统的控制行为进行了理论和实验研究。结果表明，双指系统作为一个微型抓手工作良好。可控制指尖0.01N量级的抓握力。少

The present project has been pursed for the past three years under the collaboration of Tohoku University, Japan and Chonbuk National University, Korea to achieve Force Control of Gripper Driven by Piezoelectric Actuator. The details of the project are as follows.1. Piezoelectric ceramics are ferroelectric and are fundamentally nonlinear in their response, showing a significant hysteretic loopto the applied voltage signal. The problem of the linear drive of nonlinear piezoelectric ceramic actuators was studied. A linear drive method was proposed for the ceramic actuators that compensates for the hysteretic loop. A simple nonlinear preamplifier was developed. It was shown that the hysteretic loop disapeppears when the nonlinear pre-amplifier is installed between the d. c. amplifier and the input voltage generator.2. Soft tactile sensor with a sense of human digital pulp was developed in order to measure minute force. The sensor is composed of two rectangular rubber blocks and several st … More arin gauges that are inserted between the interface of the rubber blocks. The strains in the gauges are propotional to the magnitude of the applied load on the sensor. Thus, the surface load can be determined by measuring the output of the gauges. Characteristics of the sensor are investigated both theoretically and experimentally for several configurations of the rubber blocks with a single embedded strain gauge. Obtained Results showed that the proposed soft sensor measures the distributed as well as the concentrated minute force on the sensor effectively.3. A two-fingerd miniature gripper driven by piezoelectric bimorph cells and was developed and the hybrid position/force control of the system was studied. The system is composed of two flexible cantilevers and a compact force sensor attached to the tip of one finger. The theoretical model of the electro-mechanical system was developed and applied to the study of a control problem where the gripper is commanded to grasp its object with a time-constant force 0.01N at a prescribed comanded fingertip position. The PID and II_* control algorithms were introduced to drive the gripper. The system control behavior was examined both theoretically and experimentally. The results showed the two-fingerd system works well as a miniature gripper. It can control the grasping force of order 0.01N at the tip of the finger. Less