Meiling Wang

Transfer function of fluidic system in liquid-circular angular accelerometer

In this paper, a new kind of liquid-circular angular accelerometer is studied. Based on electrokinetic phenomenon, this angular accelerometer is designed with a porous transducer and fluid mass. Due to the existence of electrical double layer between transducer and fluid mass, this angular accelerometer is able to convert angular acceleration input to electrical signal. The whole system is composed of fluidic system and molecular electronic system. Theoretical analysis and several experiments are implemented to obtain transfer function model of fluidic system. The flow in transducer satisfies the Darcy Law in the experiment and angular velocity input is proved to have no effect on the output. A prototype is designed to compare the output of theoretical model and experiments. All of the experiments prove that the fluidic system of this liquid-circular angular accelerometer can be seen as a first-order system, especially when the frequency of input is less than 30Hz and its transfer function is derived.

Modeling for Fluid Transients in Liquid-Circular Angular Accelerometer

Liquid-circular angular accelerometer is generally designed with the circular tube, the fluid mass, and the porous transducer. With the consideration of the fluid compressibility, a novel theoretical model of the fluidic system of this sensor is developed based on the theory of fluid transients for the first time. Simulation and experiments are conducted to prove the validity of the proposed model and the model manifests satisfactory performance to calculate the natural frequency, the resonances, the bandwidth, and the low-frequency gain of the fluidic system. Moreover, the influences of several structure parameters are analyzed by using the proposed model. The wave speed in the fluid mass affects the bandwidth of the fluidic system grossly, while the radius of the circular tube has effects on both the gain and the bandwidth. Besides, the liquid resistance of the transducer and the cross-sectional area of the circular tube are found to exert analogous influences on the frequency response of the fluidic system.

Dynamic Fluid in a Porous Transducer-Based Angular Accelerometer

This paper presents a theoretical model of the dynamics of liquid flow in an angular accelerometer comprising a porous transducer in a circular tube of liquid. Wave speed and dynamic permeability of the transducer are considered to describe the relation between angular acceleration and the differential pressure on the transducer. The permeability and streaming potential coupling coefficient of the transducer are determined in the experiments, and special prototypes are utilized to validate the theoretical model in both the frequency and time domains. The model is applied to analyze the influence of structural parameters on the frequency response and the transient response of the fluidic system. It is shown that the radius of the circular tube and the wave speed affect the low frequency gain, as well as the bandwidth of the sensor. The hydrodynamic resistance of the transducer and the cross-section radius of the circular tube can be used to control the transient performance. The proposed model provides the basic techniques to achieve the optimization of the angular accelerometer together with the methodology to control the wave speed and the hydrodynamic resistance of the transducer.

Electrokinetic experiments of porous transducer in liquid circular angular accelerometer

This paper is aimed to improve the accuracy and bandwidth of liquid circular angular accelerometer through analyzing the electrokinetic property of the embedded porous transducer. The transducer sintered by glass microspheres is utilized to measure the streaming potential and the streaming current in the sensor. By using SurPASS, a series of electrokinetic experiments are conducted on different transducer samples. We show that the streaming potential coupling coefficient (SPC) and streaming current coupling coefficient (SCC) can be calculated from the measured streaming potentials and streaming currents for solvent with different concentration, pH, and ion species and for porous transducers with different permeability. The further experimental results show that these two coefficients decrease as the conductivity increases while they increase with the increasing permeability. In addition, we also show that the surface conductance is more influential than the solution conductivity at the low solution salinity. This electrokinetic study is beneficial to select the suitable porous transducer and solvent such that the SPC or SCC is high, which contributes to improving the detection of weak signals, obviously increasing the accuracy of accelerometer and expanding the bandwidth.

Particle detection of porous media using scanning electron microscope images

Porous media have a wide range of applications in the field of material science and geology. The achievement of the shape parameters of a porous medium gives great significance to the reconstruction of the medium and the calculation of physical parameters such as porosity and permeability. A kind of particular porous media are focused on in the paper which are composed of randomly packed spheres made of glass. A modified Hough transform method using scanning electron microscope (SEM) images is proposed to detect the particles that compose the medium. The raw gray level image is preprocessed using a Gaussian filter. Then a modified vote mechanism is applied to transform the edge points obtained by gradient map into the accumulation array of the center locations. After a non-maximum suppression, final circle centers are picked up and their radii are estimated. The method is conducted on several SEM images, indicating the method can achieve a remarkable accuracy of ~75%.