Research On Flexible Robot Pressure Sensing Skin System Based On Textile Structure

The paper research the breaking strength and conductive properties of several new flexible materials,including substrate,electrode,nylon ply yarn and piezoelectric principle and properties of flexible PVDF piezoelectric film sensor,and the theory of mathematical model of composite structure and knitting structure.Afterwards,the flexible laminated composite structure and structure of the double layer of bag-like weft plain fabric of these two pressure sensing systems samples through integrating the perfect pressure sensing circuit.Finally,we can evaluate the comprehensive performance of tensile fatigue,bending and compressive mechanical and pressure sensing properties.In addition,in order to improve the surface friction effect of flexible textile pressure sensing fabric as robot’s manual skin and to attempt to improve its stability and high-efficiency in grasping objects.The study of this paper also deeply research the relationship between its surface texture microstructure and friction effect from the perspective of different organizational structure surface effect.Then,1+1 rib and 3 pin 2 set two categories density of four knitted samples are developed.Then,their friction property were compared and optimized with the skin fabric surface material(polyurethane elastic sponge fabric)of the flexible laminated composite structure system prepared earlier in this paper,which provides a good theoretical basis for the better development and application of the pressure sensing skin of robot’s manual.Through the testing and research of experiments in this paper,the following conclusion can be drawn:(1)The two of flexible layered composite structure and double bag structure flat knitting pressure-sensitive systems’ sensing circuit design are easy to integrate with large area,high resolution.And their flexibility and plasticity deformation resistance is wonderful.Moreover,it also can effectively protect and shield the external signal interference and increase the signal-to-noise ratio of the sensing system.(2)It can be discovered by 20 times cyclic tensile strain fatigue load,bending and compression properties such as mechanical performance that they doesn’t take place creep relaxation phenomenon obviously.The elastic deformation of pressure sensitive fabric with laminated composite structure recovered rapidly,while the pressure sensitive sample of the double bag-like knitting structure began to recover slowly in the 12th tensile load and its size remained stably at 94%.These two textile structure pressure sensitive fabrics both show the ideal flexibility,high elasticity and compression ratio and compression recover rate,good deformation degree and small rigidity index under the large curvature and bending moment.However,the elastic hysteresis of pressure sensitive fabric in double bag-like knitting system may appear after many bending loads or so-many times of bending loads.(3)From the pressure sensor integrated performance,flexible layered composite structure system of pressure-sensitive fabric in a static pressure load calibration experimental tests show the ideal pressure-voltage and strain-voltage linear fitting relationship,pressure and voltage linear fitting coefficient is 0.9865,the sensitivity of nonlinear error is 0.2%;The sensitivity coefficients of 0.5hz and 2.5hz under low frequency dynamic pressure loads were 30.37%higher than those under static pressure loads and 82.45%higher,respectively.Moreover,the voltage signal output waveform is complete and the cycle repeatability is good.With the increase of dynamic load frequency,its response speed and sensitivity are improved.The pressure sensitivity test of the flat needle knitting system with flexible double bag-like structure was mainly used to test its pressure induction capability under 1.25Hz dynamic pressure load.From sensitive degree,repeatability and stability of this kind of bag double layer structure of flat knitting pressure-sensitive system under the dynamic pressure load of integrated pressure sensor performance is good,pressure and voltage linear relationship is better,although because of its large jersey itself out,the nature of the edge,and poisson effect,combined with the raw materials of high elastic yarn without yarn steaming process,make it flexible layered composite structure system compared with pressure-sensitive fabric has a certain deviation sensitivity,but the sensitive coefficient nonlinearity control within 1.67%;Under 1.25hz low-frequency dynamic pressure load,the voltage signal waveform collected by oscilloscope is relatively complete,with obvious periodic regularity,good stability and repeatability,which meets the application requirements of the robot hand.Under the continuous 1.25hz dynamic load,its response speed has obvious hysteresis effect.(4)Based on surface microstructure and fabric texture of the skin friction effect after the study on the relationship between the theory and friction performance test to the following conclusion:the surface of the fabric texture and microstructure of geometry contour height,number,formed between adjacent contours of groove depth and the friction coefficient and ability were positively correlated.1 + 1 rib sample B,3 needle 2 set sample B,3 needle 2 set sampleA,1 + 1 rib sample A,flexible layered composite maximum static friction and the friction coefficient of pressure-sensitive sample decreases,and surface friction effect weakened.Article 1 + 1 rib fabric surface straight convex circle fabric texture structure and 3 pin 2 column set projections of cube texture structure to enhance the friction effect,while the elastic polyurethane sponge uniform fabrics surface level,there is no obvious geometry is concave and convex point texture structure and makes its friction coefficient is small,but it itself has a large sliding adhesion damping coefficient,in the actual process of sliding friction instead of friction effect is stronger.And on the mechanical properties of the tensile,compression and bending fatigue,with 1 + 1 rib sample Bs 1 + 1 rib sample A,3 needle 2 column set A and 3 needle 2 column set B around the four kinds of fabric for skin material preparation of laminar composite structure fabric better endurance strain fatigue effect,flexible,elastic and durable ability.However,in comparison,1 + 1 rib has the best texture,and there is a certain lag in the large strain elastic recovery behavior of 3 needle 2 row circular fabric and double bag-like flat needle fabric.