Research On Omni-directional Tilt Sensor Of Magnetic Fluid

Magnetic fluid is widely used in many different fields due to its characteristics,but its application in tilt sensor is still on the development stage.The omni-directional and wide range tilt sensors based on magnetic fluid meet the requirements of tilt sensor development.However,the current research on magnetic fluid tilt sensor is mostly focused on single-axis tilt sensor and research on the omni-directional tilt is not yet more.At the same time,most of conversion elements of magnetic fluid tilt sensor are using the coils based on the method of electromagnetic induction principle,the method needs to be equipped with complex acquisition system.The Tunnel Magnetoresistive sensor can measure magnetic field,which has the characteristics of high sensitivity,good linearity and wide linear range.In this paper,a magnetic fluid omni-directional tilt sensor with Tunnel Magnetoresistive sensor as conversion element is designed by using the principle of gravity pendulum.The main research contents are as follows:(1)The structure of the magnetic fluid omni-directional tilt sensor is designed.The sensitive element of the tilt sensor is composed of magnetic fluid and stacked permanent magnet.Using Tunnel Magnetoresistive sensor as a conversion element and then,tilt angle signal is converted into electrical signal by detecting the magnetic field.The tilt sensor has advantages of omni-directional measurement and wide range.(2)The magnetic field of a cylindrical permanent magnet is analyzed.The method of calculating levitation height of permanent magnets immersed in magnetic fluid is proposed by measuring magnetic field intensity then.The levitation height of four kinds of stacked permanent magnets is measured by experiment.(3)The analysis of magnetic field distribution of stacked permanent magnets by use of finite method.It is determined that the d-type stacked permanent magnets with decreasing radius can not only increase stability of the tilt sensor,but can also extend the linear range of sensor.(4)A magnetic fluid omni-directional tilt sensor signal acquisition system is designed,and the output characteristic curve equation of acquisition system is obtained by Helmholtz coil experiment.The measurement accuracy of the acquisition system is tested by soldering experiment,results show that the acquisition system resolution is up to 0.01 Gs within range of ±300Gs,the accuracy is higher than 0.3%,the system has a high precision which can meet the design needs of magnetic fluid omni-directional tilt sensor.(5)The input /output characteristic curves are obtained by static experiment of magnetic fluid omni-directional tilt sensor.The performance parameters of tilt sensor and formula of tilt angle are deduced.Through contrast experiment with gyroscope,the tilt sensor is tested.The test results show that the measured value of magnetic fluid omni-directional tilt sensor is consistent with that on gyroscope experiment within allowable range of error.The tilt sensor can measure the tilt angle in omni-directional.The sensor can measure the tilt angle in range of 10 ° ~ 170 ° with sensitivity 24 mV /(°)proximately.