Design And Study Of Vibration Displacement Sensor Based On Quasi Zero Stiffness

In some scenes,such as vibration isolation of vehicle-mounted precision instruments,active suspension of automobiles,and micro-vibration control of drones,it is often necessary to measure and feed back absolute displacement vibration signals in real time.there are some common features of these scenarios: fistly,there is no or difficult to find absolute coordinate references.Secondly,it contains significant low-frequency vibration,and the third is to require the sensor itself to be small and lightweight.Obviously,the displacement sensor that requires an absolute stationary reference frame can't be used in these scenarios.Using the accelerometer to obtain an absolute displacement vibration signal through two integrations makes it difficult to balance real-time feedback and ensure that the signal is not distorted in the low frequency band.So far,there are no mature products of absolute displacement vibration sensors that fully meet the requirements of above scenarios.Therefore,it is necessary to study and develop small volume,light-weight vibration sensors that can directly measure low-frequency absolute displacement signals.In this paper,a quasi-zero stiffness(QZS)structure with negative magnetic stiffness and positive stiffness in parallel is used to construct a vertical vibration displacement sensor.Research is focused on the model construction and principle analysis,dynamic characteristics,and physical structure implementation methods of the sensor system.First,the principle of vibration displacement sensor based on negative magnetic stiffness is introduced.The system stiffness characteristics of the sensor are analyzed based on the calculation and verification of the magnetic force and stiffness of the magnetic negative stiffness spring.Secondly,after establishing the mechanical model of the sensor,the dynamic characteristics in the measurement direction are discussed,and the response characteristics of the lateral excitation are also analyzed.At the same time,the characteristics of the sensor in the frequency domain,amplitude domain and time domain are analyzed.Finally,the detailed structure of the sensor using two mechanical quantity-electricity conversion methods of capacitance and resistance strain gauges is introduced,and the characteristics and specific performance of these two sensors are analyzed and compared.And then,built a test platform to verify the theoretical analysis and design effect of the sensor.On this basis,the structure of the sensor is improved,and the possible performance of the sensor is analyzed.The research results show that when the sum of the linear equivalent stiffness of the negative magnetic stiffness and the stiffness of the flexble spring is equal to zero,the vibration displacement sensing system has measurement performance;Coulomb damping,viscous damping,non-linear stiffness coefficient,and measured signal amplitude all have an effect on sensor sensitivity.As the amplitude of the measurement signal increases,the nonlinear error of the sensor gradually becomes larger.Therefore,the sensor system is not suitable for the measurement of larger displacement amplitudes.Transverse excitation will cause the sensor inertial mass to translate and rotate relative to the housing,causing deformation of the diaphragm spring,but the mass will not move in the axial direction.Compared with resistance strain gauges,the use of capacitors as the conversion elements has a larger inertial mass of the inertial mass of the sensor,a larger axial dimension,a smaller measurement amplitude range,but a stronger lateral anti-interference capability.The performance test results of the new-type vibration displacement sensor sample show that the sensitivity trend,nonlinear error and lateral sensitivity are consistent or similar to the theoretical analysis result,indicating the accuracy of the theoretical analysis and design effect.By adjusting the structural parameters,the sensor can realize the measurement of low-frequency absolute displacement signals above 1.2 Hz.