Research On Structural Optimization Of Tactile Sensor With Cross-Beam Structure

The human skin-like tactile sensor is a kind of device of complex functions,and its multi-functional sensing capability enables its wide application prospects.Related research has been carried out for a long time,but it is still difficult to achieve the improvement of its comprehensive tactile performance.Further optimization of its performance and improved design methods will help it realize its wide application as soon as possible.For this technical need,this subject innovatively combines the structural optimization method represented by topology optimization,which has been maturely utilized in the industry,into the design and optimization of the sensing performance of the tactile sensor.And take the cross-beam structure as an example to carry out research including its structural optimization simulation,device preparation and fabrication,and the three-dimensional force sensing test as well.This subject is centered on three-dimensional force and deformation perception.For the resolution limited by the unit size due to its process,the focus is on the balance of range and sensitivity to achieve sensor performance enhancement,hence the cross-beam structure sensor is selected for its high feasibility of structural optimization.With 2*2 sensor unit array structure adopted,each sensor unit can be divided into a flexible-deformation layer,a strain-sensing layer,and an overload-protection layer according to the function of the component.The cross-distributed strain gauges play the role as sensitive elements of the strain-sensing layer.The design targets at improving the sensitivity of the device;the load conditions are analyzed mimicing three-dimensional force,and boundary conditions are set.Design domain set as the flexible-deformation layer and the overload-protection layer,and design constraints set to be the volume fraction as the lower limit in the progress of the topology optimization and ensuring the structure does not fail as well.Weighted structural flexibility is determined to be the objective function.The quantitative structural optimization method applied for tactile sensors is thus finally established based on topology optimization.According to this method,by the tool software Hyperworks which has the combination of Hypermesh and Optistruct,multiple results of optimized geometries are obtained by controlling the value of the topology optimization constraint parameter V_frac and post-processing parameterρ_T.Research on the preparation and fabrication method of the optimized device of the cross-beam structure tactile sensor is carried out.By applying the process of the screen-printing on the flexible PCB substrate with the material including conductive carbon paste,the strain-sensing layers are prepared.Besides,the 3D-printing method is carried out for the fabrication of the prototype and structural optimization of the flexible-deformation layer and overload-protection layer in the sensing unit.Simplified geometric output is used according to the simulation results.The assembly and fabrication of the testing device composed by layers are completed by gluing after welding the leads on the strain-sensing layer.The characterization of the morphology and chemical structure of the strain-sensing layer initially verified the feasibility of its sensing and the theoretical resistance of the strain gauge are calculated,and then the quantitative characterization method for the sensitivity of the tactile sensing device is determined in this subject.Before the three-dimensional sensing test,this subject further verified the feasibility of strain sensing through the circuit connectivity test and uniaxial tensile-sensitivity test,through which some devices are picked out for the final 3D tactile sensing test;and then the design and construction of the three-dimensional sensing test platform is carried out independently in the project.The functional module analysis and the assembly design of the test platform have realized the integration of the load（testing）cell module,the three-dimensional movable loading platform,and the multi-channel acquisition module of the resistance signals of the tactile sensor.Afterwards,the device’s vertical and lateral force sensing tests are carried out,and the sensing performance of the optimized device and the prototype of different parameters are compared correspondingly,which further verifies the enhancement of its sensitivity performance under the premise of fully guaranteeing its sensing range.The research of this subject has opened up the application field of structural topology optimization methods,for the design and performance optimization of tactile sensors.It definitely has an enlightening effect on the development of the industrial application of tactile sensors in the future.