Research On MEMS Multi-dimensional Tactile Sensing Technology

Tactile sensors can detect information such as pressure,friction,slip,temperature,and object shape,and are widely used in smart electronic devices,medical devices,and the robotics industry.It can not only detect information such as contact pressure and relative slip,but also extract the shape,size and stiffness information of the contacted object,and accurately extract the physical characteristics of the object.Aiming at the defects of existing tactile sensors such as difficulty in decoupling and single function,this paper designs a MEMS multi-dimensional tactile sensor based on its own structure decoupling,which can realize the accurate detection of three-dimensional force and two-dimensional torque signals,and the multi-signal output is almost Without coupling,the main innovation lies in the design of special electrode structure and layout,which realizes the detection and decoupling of multi-dimensional tactile signals.The main research contents of this paper are as follows:In order to realize multi-parameter tactile signal detection,this paper designs a tactile sensor based on capacitive multi-dimensional signal perception.Its structure mainly includes a central mass block,a U-shaped beam,a detection electrode mass block,a fixed anchor point,a glass electrode plate and a metal electrode fixed on the glass substrate.The central mass block is used as a signal sensitive unit to sense external tactile signals;the U-shaped beam is used to support the central mass block and connect it to the fixed anchor point;the sensor electrode layers are sputtered on the glass substrate and the silicon-based anchor point respectively.The sensing principle of the sensor mainly includes: the external tangential force is detected by changing the area of the grid capacitor plate;the external normal force is detected by changing the distance between the parallel plate capacitors;the external torque is detected by changing the distance between the inclined plate and the substrate.The decoupling principle is: when the tangential force signal acts on the designed sensor,only the area facing the capacitor is changed;while the small maximum range torque signal only changes the distance between the plates,which is realized from the sensing mechanism through the device structure.Decoupling of tangential force and moment signals.In order to illustrate the device performance,this paper uses ANSYS software to carry out modal simulation of the multi-dimensional tactile sensor.The simulation results show that the first-order resonant frequency of the tactile sensor is greater than 5000 Hz,which has a wide operating frequency band and good anti-resonance performance.The first five modal shapes of the tactile sensor are consistent with the displacement states of the triaxial force and the two-dimensional moment,meeting the initial design requirements.The second-order resonant frequency is close to the third-order resonant frequency,and the corresponding mode shapes are rotation along the X-axis and along the Y-axis,respectively.Therefore,the tactile sensor has the same sensitivity to the torque detection of the X-axis and the Y-axis.Similarly,the fourth-order resonant frequency is close to the fifth-order resonant frequency,and the corresponding mode shapes are translation along the Y axis and translation along the X axis,respectively,so the tactile sensor has the same sensitivity for force detection in the X and Y directions.In order to optimize the performance of the tactile sensor,the displacement simulation and structural optimization of the sensitive element of the tactile sensor were carried out by using COMSOL software under the action of the external excitation signal.The simulation results show that:(1)increasing the width of the U-shaped beam can increase the maximum detection range,but it will reduce the sensitivity;(2)increasing the length of the U-shaped beam can improve the sensitivity by reducing the elastic coefficient,but reduce the maximum detection range.(3)Reducing the thickness of bulk silicon to a certain extent can improve the device sensitivity.According to the design requirements and simulation results,the detection sensitivities of the optimized tactile sensor tangential force,normal force and moment are 163.3 f F/N,2.4 f F/m N,5.7 f F/m N m,and the corresponding maximum range is 1.05 N,80 m N,0.26 m N m.For small MEMS devices,the effect of capacitive edge effects on the output performance of the device is not negligible.In order to reduce the influence,this paper uses the electromagnetic field analysis software ANSYS Electronics Desktop to simulate the edge effect of gate differential capacitors.The comparative analysis results show that the edge effect of a group of gate differential capacitors is smaller than that of parallel plate capacitors,and the differential structure can effectively improve the gate type.The overall nonlinearity of the type capacitor;appropriate reduction of the plate spacing can also improve the linearity of the capacitor.Finally,according to the theoretical analysis and simulation optimization results,this paper designs the specific process flow of the MEMS multi-dimensional tactile sensor,and draws the device processing layout.