【作者】 杨永；

【导师】 赵美蓉； 郑叶龙；

【作者基本信息】 天津大学 ， 仪器科学与技术， 2023， 博士

【摘要】 微小力值测量在工程和科学领域中具有广阔的应用前景,但同时也面临诸多挑战。微力测量的精度取决于微力传感器的分辨力和环境扰动的大小。针对微力测量易受环境噪声干扰导致测不了的难题,本文提出阴影法并引入粘弹性材料提高系统阻尼比来抑制环境噪声影响。针对微力测量溯源困难导致测不准的难题,本文基于静电力天平将微力溯源至国际单位制。此外,本文还对微力测量的关键技术——微位移测量与微力测量的重要应用——触觉传感,开展了一系列的理论分析、数值模拟与实验研究。创新工作主要包括:(1)建立并完善阴影法的数学模型。受到水黾在水面上滑行时在太阳的照射下在池塘底部形成阴影的启发,将阴影与水黾腿压弯水面的深度建立联系。首先分析弯曲液面形貌并建立其控制方程,然后建立其三维模型并利用光学仿真和数值模拟阴影的形成,最后对阴影法进行建模,在理论上证明阴影直径变化与压深成正比关系。(2)基于阴影法提出微位移测量方法。模拟水黾超疏水腿压弯水面,设计平行四边形机构带动超疏水刚性圆柱体单自由度法向运动。然后,采用Zernike正交矩对阴影边缘进行亚像素拟合,得到亚像素精度的阴影直径以提高测量分辨力。最后,经过标定实验证明阴影直径变化与压深成正比,传感器的分辨力为62.1 nm,测量范围为50μm,重复性误差为155 nm,非线性误差为1.58%,其相对合成标准不确定度为1.61%。(3)基于阴影法提出微力测量方法。针对微力测量过程中易受环境噪声干扰的难题,受到蝎子腿部狭缝感受器的启发,引入粘弹性材料,基于接触力学将阴影法应用于微小力值测量。系统阻尼比可达0.22,可以有效抑制环境扰动的影响。首先基于降维法求解刚性圆柱体与弹性半空间的接触力学模型,其次对系统等效刚度进行建模以降低系统刚度来提高分辨力,然后建立以弹性半空间为变形元件的阴影法模型。最后,针对微力溯源困难的问题,采用静电力天平将力值溯源至国际单位制。经过标定实验证明阴影直径变化与待测微力成正比,传感器的分辨力为0.86μN,测量范围为392.4μN,重复性误差为3.53μN,非线性误差为1.12%,其相对合成标准不确定度为1.95%。与刚度类似而阻尼比较小的悬臂梁相比,基于阴影法的微力传感器降低了约96.6%的扰动影响。(4)基于阴影法提出触觉传感方法。针对机械手难以实现滑动预测的难题,基于阴影法提出一种具有不等高圆顶阵列的图像式触觉传感器,可以在滑移发生之前预测滑移。首先基于接触力学建立传感器测量法向力与切向力的数学模型,其次基于阴影法建立阴影图像与待测力之间的关系,然后提出五圆顶中心对称分布结构的不等高圆顶阵列,利用大小圆顶之间的滑动摩擦力差别,无需训练集即可巧妙地实现滑动预测。最后经过标定实验,触觉传感器法向和切向分辨力均可达到10 m N,最大相对合成标准不确定度分别为5.47%和4.78%。与数据驱动的技术相比,该滑动预测技术具有效率高、复杂度低、无需训练数据集等优点。更多还原

【Abstract】 Micro-force measurement has vast prospects for applications in engineering and scientific fields,but it also faces numerous challenges.The precision of micro-force measurement depends on the force sensor resolution and the environmental disturbance magnitude.Aiming at the difficulties of being easily disturbed by environmental disturbance,this dissertation proposes the shadow method and introduces the viscoelastic material to increase the system damping ratio and suppress the environmental disturbance.To tackle the issue of traceability in microforce measurement,an electrostatic force balance is utilized to trace microforce to the International System of Units.In addition,a series of theoretical analyses,simulations,and experimental research are conducted on the key technology(Micro-displacement Measurement)of and the important application(Tactile Sensing)of micro-force measurement.The main innovative work includes:(1)The mathematical model of the shadow method is established and improved.The shadow method was inspired by the shadow formed by the superhydrophobic legs of the water strider when walking on the water under sunlight.The shadows are related to the depth of the water striders’legs from the water surface.First,establish the governing equation of the bent water surface,then conduct optical simulation and numerical simulation to simulate the shadow formation,and finally model the shadow method.It is theoretically proved that the change of shadow diameter is proportional to the depth from the water surface.(2)A micro-displacement measurement method is proposed based on the shadow method.To imitate the water strider’s superhydrophobic legs bending the water surface,design a parallelogram mechanism to drive the superhydrophobic rigid cylinder to move in the single-degree-of-freedom normal direction.Then,the Zernike moment is used to perform sub-pixel fitting on the shadow edge,and the shadow diameter with sub-pixel accuracy is obtained to improve the resolution.Finally,the calibration results show that the change in shadow diameter is proportional to the depth.The resolution,measurement range,repeatability,and linearity error of the sensor are 62.1 nm,50μm,155 nm,and 1.58%,respectively.The relative combined uncertainty is 1.61%.(3)A micro-force measurement method is proposed based on the shadow method.Inspired by the viscoelastic material near the slit sense organ of the scorpion used to separate the useful signals from the environmental noise,the transparent viscoelastic polymer is used as the sensitive element in the micro-force sensor,whose damping ratio of 0.22 can effectively suppress environmental disturbances,improving the measurement precision.First,the normal contact between the rigid cylinder and the elastic half-space is solved by the method of dimensionality reduction.Second,the equivalent stiffness of the system is modeled to improve the resolution.Then,the shadow method model with the elastic half-space as the deformation element is established.Finally,to overcome the difficulty in micro-force traceability,an electrostatic force balance is used to trace the micro force to the International System of Units.The calibration results show that the change in shadow diameter is proportional to the micro-force to be measured.The resolution,measurement range,repeatability,and linearity error of the sensor are 0.86μN,392.4μN,3.53μN,and1.12%,respectively.The relative combined uncertainty is 1.95%.Compared with micro-force sensors based on the cantilever,the sensor is capable of the reduction of the disturbance influence by approximately 96.6%.(4)A tactile sensing method is proposed based on the shadow method.Aiming at the problem that it is difficult for manipulators to predict slippage,a vision-based tactile sensor with an unequal-height dome array is proposed based on the shadow method,which can predict slippage before it occurs.First,based on contact mechanics,the mathematical model measuring the normal force and the tangential force is established.Second,the relationship between the shadow image and the measured force is established based on the shadow method.Then,the five-dome centrosymmetric distribution structure is designed for slippage prediction subtly by the sliding time difference between the large and small domes.Finally,after calibration experiments,the resolutions could both reach 10 m N with maximum relative uncertainties of approximately 5.47%and 4.78%in normal force and tangential measurements,respectively.Compared with data-driven methods,this slippage prediction technique has the advantages of high efficiency,low complexity,and no need for training datasets.更多还原