Research On Soft Electrostatic Adsorption Unit Driven By SMA Wire

Because of its infinite freedom,continuous deformation and strong environmental adaptability,software execution unit has broad application prospects.In order to realize the functions of the software execution unit,such as fast crawling,flexible grasping,etc.,it is required that the software execution unit has the ability of continuous deformation such as bending,shrinking,stretching,etc.,and at the same time has a greater adhesion force with the target surface.In this paper,a soft electrostatic adsorption unit driven by shape memory alloy(SMA)wire is studied.The SMA wire is embedded in silica gel to make a soft unit to drive its bending deformation,which has the advantages of small volume,mass and large output displacement;The electrostatic adsorption method is used between the soft unit and the target surface.Under the deformation of SMA wire driving soft unit,the electrostatic adsorption electrode can better fit the target surface,further increase the adsorption force,and the adsorption also has the advantage of switching.Therefore,the design,preparation and feasibility of soft electrostatic adsorption unit driven by SMA wire are studied in this paper.The research contents are as follows:The electric thermal mechanical coupling model of SMA wire is established.Based on the mechanism of phase transformation of SMA wire,the constitutive model of SMA wire between temperature,stress and strain is established by usin g Taylor expansion and thermodynamics law;Through the heat balance equation,the relationship between temperature,current and power on time is established;Combined with the two models,the electrical thermal mechanical coupling model of SMA is established,and the relationship between the power on time and the output strain and stress of SMA is derived;Through the constant load SMA wire shrinkage experiment,the undetermined parameters in the model were obtained by curve fitting method.In order to verify the correctness of the mathematical model,repeated experiments are carried out to replace the load on the SMA wire.The correctness of the electrical thermal mechanical coupling model of SMA wire is verified by comparing the experimental and simulation results.A double-layer soft element driven by SMA wire is designed and fabricated.The factors influencing the bending angle are analyzed and verified by experiments.In order to make the soft unit complete the action of fitting and separating the target surface,a single-layer soft unit embedded with SMA wire was designed,and its preparation process was discussed.It was found that it could not complete the recovery after bending.After improvement,a soft unit embedded with double-layer SMA wire was designed,which could bend in two directions.In order to improve the bending angle of the soft element,the deformation model of the double-layer soft element is analyzed.It is found that the length of the soft element and the distance between the SMA wire and the neutral layer have influence on the bending angle of the soft element.According to the above three factors,three groups of bending angle experiments were carried out to verify the correctness of the deformation model.At the same time,by comparing the trend of the bending time curve of the soft element and the strain time curve of the SMA wire,the applicability of the electrical thermal mechanical coupling model of the SMA wire in the soft element is verified.The integrated soft electrostatic adsorption unit was designed and prepared,and the adsorption separation reabsorption experiment of the soft electrostatic adsorption unit for the target surface was completed.In order to improve the adsorption force between the surface of software unit and the target surface,the electrostatic adsorption electrode was designed on the surface.Based on the principle of electrostatic adsorption,the mathematical model of electrostatic adsorption force was deduced.The main factors affecting the adsorption f orce were the loading voltage and the adsorption insulating layer material.Therefore,the carbon coated electrode was prepared by using silica gel as the adsorption insulation layer of the adsorption electrode,which improved the friction between the adsorption electrode and the target surface.Three kinds of high-voltage modules,including traditional high-voltage module,piezoelectric high-voltage module and photovoltaic generation module,are selected and compared.The piezoelectric boost module produces the largest lateral force due to the highest voltage,and the volume and mass of photovoltaic generation module are much smaller than the other two modules.The soft electrostatic adsorption unit was prepared by combining the soft unit with carbon coated electrode.The adsorption separation reabsorption experiment of the soft electrostatic adsorption unit was carried out,and its feasibility was verified.Based on SMA wire driven soft electrostatic adsorption unit,a soft foot wall climbing robot is designed and analyzed.The soft electrostatic adsorption unit is applied to the foot of the wall climbing robot,and the adsorption separation reabsorption of the soft foot and the wall is completed under the cooperation of SMA wire driving soft unit bending and electrostatic adsorption.Stm32f103c8t6,Bluetooth module and mobile phone are used to control the robot,and the straight line,turn and interrupt procedures of the wall climbing robot are designed.The feasibility of the wall climbing robot based on SMA wire driven soft electrostatic adsorption unit is verified by building a wall climbing experimental platform and testing the robot prototype crawling on marble,glass and epoxy plate.