Research On Flexible Tactile Sensing Array For Tactile And Slip Detection In Prosthesis Hand Grasping

Supported by the National Basic Research Program (973) of China (Grant No. 2011CB013300), National Natural Science Foundation of China (Grant No.51575485, 51105333), and Zhejiang Province Natural Science Foundation of China (LY16E050002), a flexible tactile sensing array with the capacities of 3D force measurement and slip detection for prosthetic hand were studied in this thesis. Firstly, a flexible tactile sensing array based on INASTOMER conductive rubber was designed, and the basic working principles including three dimensional force testing and slip detection were described in detail. Then, the manufacturing process of the tactile sensing array was presented and optimized. Next, the data acquisition system was developed, which included scanning circuit hardware based on DSP TMS320F2812 and data acquisition program on host computer based on LabVIEW software. Finally, using the data acquisition system, the static mechanical performance tests were conducted and the basic performance indexes were obtained, including resolution, sensitivity, measurement range, nonlinearity, repeatability, hysteresis. Prosthetic hand grasping experiment using tactile sensing array was carried out. Moreover, slip detection tests in grasping were conducted based on discrete wavelet transform theory.In chapter 1, the backgrounds and significances of this dissertation were introduced. Then, the current research situations were expatiated in detail, including intelligent prosthesis hand, flexible tactile sensors and three dimensional force and slip characteristic information processing method. Then, the main research contents and framework of the dissertation were proposed.In chapter 2, the flexible tactile sensing array based on INASTOMER conductive rubber was designed. The 3×3 tactile sensing array consisted of flexible electrode layer, conductive rubber layer and surface bump layer, and was designed with the structure of Velcro straps, which made it easy to install tactile sensing array on the irregular surfaces. The working principles of tactile sensing array were discussed in details, including its three dimensional force testing and slip detection using discrete wavelet transform theory.In chapter 3, the parallel interconnect method for flexible electrode layer was designed in order to solve the problem that the array structure causes massive interconnects. Five electrode structures were manufactured on flexible electrode layer using the flexible printed circuit technology. Different aluminum moulds were designed to fabricate conductive rubber layer and surface bump layer. The adhesive process for three layer structures was optimized through natural encapsulation of PDMS, and the flexibility performance thus was improved.In chapter 4, the data acquisition system for the flexible tactile sensing array was developed, including the tactile sensing array scanning circuit using the DSP TMS320F2812 chip and data acquisition program based on Lab VIEW. Moreover, the schematic, printed circuit board and the control program for the DSP were accomplished.In chapter 5, the mechanical properties tests of tactile sensing array, three dimensional force measurments and slip detection experiments in grasping process were conducted with the developed data acquisition system. Firstly, the mechanical properties tests were conducted. The tactile sensing array with the resolution of 0.1 N had force measurement arrages of 0-30 N,-5-5 N,-5-5 N, respectively in z-, x- and y- directions, and sensitivities of 0.081 V/N,0.210 V/N, 0.247 V/N respectively and the force measurement accuracies of 3.15%,4.63%,7.56% respectively. The repeatability index for the tactile sensing array was 5.22%, the hysteresis index was 4.97%, and the nonlinear error was 3.10%. Then, the grasping experiments for tactile sensing array installed on prosthetic hand were contacted to detect three dimensional forces and slip. Experiment results were shown that the developed flexible tactile sensing array was provided with the functions of distributed flexible three-dimensional force measurement and slip detection, and the method based on the discrete wavelet transform theory can effectively identify characteristic slip information in the grasping process.In chapter 6, the chief work of this dissertation was summarized, and future work was proposed.