Research On Flexible Three-dimensional Force Tactile Seneor Based On The Piezoresistive Effect

The tactile perception is an important approach for intelligent robots to get information from the external environment, as the rapid development and application of intelligent robot technology, the research on tactile sensing becomes more and more important. Tactile sensors not only need to have the flexibility of human skin, which ensure them cover the complex shape of the surface of the carrier, but also need to be able to detect three-dimensional force of space at the same time, which makes the intelligent robots can complete a variety of complex and sophisticated tasks. In this paper, as it is difficult to give consideration to the current situation of flexibility and three-dimensional force measurement ability in the researches of tactile sensor, we designed and fabricated a kind of flexible three-dimensional force tactile sensor, based on the piezoresistive effect of PDMS/GNS composite, to meet the needs of the flexibility and measurement of three-dimensional force for tactile sensors at the same time.In this paper, a design of flexible three-dimensional force tactile sensor was presented, based on the piezoresistive effect of conducting polymer composite. The structure of the surface bump layer, piezoresistive layer and circuit board layer was designed, and the three-dimensional force measurement was analyzed, with the simulation of the surface bump layer and the by the Multiphysics COMSOL software.Based on the percolation theory and quantum tunneling effect theory, the conductive mechanism of conductive polymer composite is explained, and the piezoresistive law was theoretically deduced.GNS were prepared from natural graphite by microwave method, SEM was applied to observe the microstructure of GNS, Using PDMS as matrix and GNS as conductive filler, PMDS/GNS composites were prepared by solution blending method,and the SEM and Raman spectra of the composites were analyzed. The percolation curve of the PDMS/GNS composites was measured, and the percolation threshold was about 3.5wt%. The piezoresistive curves were measured for the composites, and the piezoresistive effect could be explained by percolation theory. When the GNS is 5wt%,it shows a good negative pressure resistance effect.Based on the photo etching and wet etching process, the PDMS surface layer and the 5wt% PDMS/GNS was prepared by casting the of the substrate, and the microstructure and the Raman spectra of the two layer structures were observed by SEM and Raman. The circuit board layer was prepared by the technology of silicon wafer lithography and evaporation electrode. As the three layer structures of the sensor were aligned with the displacement platform and the optical microscope, the flexiblethree-dimensional force tactile sensor was assembled.The static performance of one unit of the flexible three-dimensional force tactile sensor was tested. The test results showed that this sensor unit showing a nonlinear negative resistance characteristics, When the loading force is in the symmetrical plane of the sensor, while inclination angle is greater than 60, the range of the sensor is 2N,the resolution is 0.1N, the maximum sensitivity is 163.6%/N and the minimum sensitivity is 7.6%/N. Finally, the coupling error of the three-dimensional force tactile sensor was analyzed, and based on the BP neural network algorithm, the threedimensional force sensor was calculated with nonlinear decoupling, the maximum measurement error is 0.08 N.