Research On Force Measurement Technology Based On Negative Poisson’s Ratio Structure

Force measurement plays an important role in evaluating the state and performance of electromechanical systems,and has direct application value and research significance.The force sensor is the most common device used to measure force.Under the design and manufacturing technology conditions of the existing sensor,the components of most force sensors are in contact with each other.This mutual contact brings many constraints to the design and fabrication of sensors,and also causes mutual interference and noise transmission between components.To this end,this paper proposes a force measurement technology based on a negative Poisson’s ratio structure,which mainly consists of three parts: a light source,a negative Poisson’s ratio structure,and a photocell.Components,the three parts are independent of each other,avoiding mutual interference between measurement components.The specific research work is as follows:(1)This paper selects the negative Poisson’s ratio structure represented by the concave hexagonal structure as the research object,and conducts a theoretical analysis on it.First,the calculation formulas of porosity and Poisson’s ratio are deduced,indicating that both porosity and Poisson’s ratio depend on the concave angle θ of the unit cell structure,the length l of the connecting rod,the length h of the unit cell,and the wall thickness d of the unit cell.Secondly,using the single variable principle,the effects of different unit cell structure parameters on the porosity were calculated respectively.The research results show that the change of porosity is achieved by changing the concave angle of the unit cell structure by external force,and the increase of pressure leads to the decrease of the concave angle,thereby reducing the porosity;the unit cell structure parameters not only determine the structure of the porosity The size of the porosity also determines the change rate of the porosity with the external force.Finally,aiming at the calculation of the porosity of the deformed negative Poisson’s ratio structure,a calculation method for calculating the porosity of the deformed negative Poisson’s ratio structure is introduced.(2)The feasibility of the structural force measurement technology based on negative Poisson’s ratio is verified through theoretical analysis and experimental research.Firstly,the components of the technology and their main functions in the technology are described,and the working principle of the measurement technology and the relationship between the static characteristics such as range and sensitivity and the structural parameters of negative Poisson’s ratio are analyzed.Theoretical analysis results show that when the light source,photocell and force are constant,the measuring range increases with the increase of the concave angle,the length of the connecting rod,and the length of the unit cell,and decreases with the increase of the wall thickness of the unit cell;the sensitivity increases with the length of the connecting rod,It increases with the increase of unit cell length,and decreases with the increase of unit cell wall thickness and concave angle.On the basis of theoretical analysis,a measurement technology experiment bench was built,with liquid photosensitive resin as the base material,and SLA 3D printing technology was used to complete the structure manufacturing,and the experimental research of positive and negative Poisson’s ratio structures in this measurement technology was carried out.The results show that the force measurement technique based on the negative Poisson’s ratio structure has a sensitivity of 0.04 m V/N and a linearity of 8.17%;while the measurement technique based on a positive Poisson’s ratio structure has a sensitivity of 0.02 m V/N and a linearity of 14.78 %.Compared with the positive Poisson’s ratio structure,adopting the negative Poisson’s ratio structure improves the sensitivity and linearity of the force measurement technique proposed in this paper.(3)In order to further improve the sensitivity of the force measurement technology,the paper optimizes the design of the negative Poisson’s ratio structure.The negative Poisson’s ratio structure was simulated and analyzed using ANSYS Workbench,and the porosity of the negative Poisson’s ratio structure was calculated using Open CV image processing technology,and the relationship between the change rate of the porosity with the force and the unit cell structure parameters was obtained.change rule.The optimal design method is used to design the optimization scheme,which effectively improves the optimization efficiency.Taking the theoretical analysis results as a reference,the optimization results are verified experimentally on the test bench.The results show that the sensitivity of the measurement technology using the optimized negative Poisson’s ratio structure has been greatly improved compared with the measurement technology based on the structure before optimization.