Theory And Experiment Research On A Novel Ferrofluid Inertial Sensor

Application of new functional materials in sensor technology is one of the main directions to the development of sensor technology.Ferrofluid,as a new functional material with both magnetism and fluidity,can be used to construct novel sensors or sensors with unique performance by taken advantage of its unique properties.It is one of the important ferrofluid application fields.In this paper,a novel inertial sensor based on ferrofluid was proposed and theoretical and experimental studies were carried out.This paper is funded by National Natural Science Foundation.The main works of this paper is as follows:1.A novel ferrofluid inertial sensor was proposed.Its inertial mass was a composite structure core which is composed of two permanent magnets and one iron core.The inertial mass can be suspeneded by ferrofluid in the middle of a circular tube shell;the elastic recovery force is the magnetic repulsion force;the damping force is the gas damping and the ferrofluid viscosity damping force when the composite core slides within the shell.2.Research on the buoyant properties of permanent magnets immersed in ferrofluid.The formulas of surface stress tensor and body stress of ferrofluid under the action of magnetic field were deduced,and then the equation of magnetic buoyant force suffered by the non-magnetic object immersed in ferrofluid was obtained.For the given sensor structure,the principle of the levitation force and restoring force is analyzed by simplified model;factors influncing the permanent magnet suspension in tube shell were discussed,and the interacted process between the cylindrical permanet magnet and ferrofluid is observed.The suspension properties of the sensor core in the tube shell is obtained by experimental method.3.The mechanical property between the permanent magnet was discussed,and the calculation formula of the magnetic repulsion force between the two permanent magnets was derived.The characteristic curves between magnetic repulsion force and the distance were obtained by numerical calculation and experimental measurement,and the suitable working range for the sensor is given.A comparative analysis of the existing structures and methods for the core displacement detection were discussed,put forward more reasonable core displacement detection structure.The sensor core displacement detection mechanism by inductive coil and its characteristics were analyzed.The signal conversion and conditioning circuit was designed.4.Studied the principle of the novel ferrofluid inertial sensor used to tilt measurement,established the corresponding mathematical model,obtained its static and dynamic response properties,and then the work conditions for tilt measurement and its static sensitivity formula was given;The principle of the novel ferrofluid inertial sensor used for acceleration measurement was also studied,established the corresponding mathematical model,and then obtained restrictive conditions for acceleration measurement according to its dynamic response.5.Base on the novel ferrofluid inertial sensor model,Two experimental prototype sensors were designed and fabricated,one with the basic strcture and the other with the improved structure.A series of experiments were carried out to determine the static performance and dynamic performance of the sensors on the experimental platform which was specifically designed for the sensor tests.The experimental results were in agreement with the theoretical analysis and verified correctness of the working mechanism of the sensor.