Study On The Principle Atructure And Performance Piezoelectric Fluidic Angle Velocity Sensor

The principle of piezoelectric fluidic angle velocity sensor is measuring the angle velocity by changes in the resistance of hot wires. The changes are caused by Coriolis' force which made the airflow departed from the central axis of the sense organ. The sensor is a solid-state inertia device with the function of gyroscope while without the wheel part of traditional gyroscope nor the append system of piezoelectric gyroscope.The operational of piezoelectric fluidic angle velocity sensor and the measure principle of detecting circuit are analyzed in this paper. The numerical simulation model and boundary conditions are supposed on the basis of academic analysis and working condition of sensor located in the detection system. With calculation in basal equation of piezoelectricity and numerical simulation, the motion state of airflow in the airtight cavity is simulated on the control of basal equation of hydrodynamics. The motion of airflow is driven by the imperforate and piezoelectric twin diaphragms. After analyzed the results of simulation, the conclusions are drawn in this paper. The conclusions indicate that:(1) The without-slippage-velocity boundary condition with periodic variation was supplied to the motion of airflow by the oscillation of piezoelectric pump.(2) The motion of airflow in cavity is simulated according to the velocity boundary condition. Under static state, the velocity of airflow in cavity is increased with the increase of the driven voltage of pump. The difference of the velocities on the two hot wires is increased with the driven voltage at the same inlet angle velocity. The output voltage of sampling circuit is increased too.(3) The different locations of fixed hot wires lead to the changes of output of detecting circuit. The better and steadier output voltage will be received with same inlet angle velocity, if the distance between the exit of channels 3 and the hotwires is from 4.5mm to 5mm, and space between the hotwires is from 3mm to 4mm.(4) The structure of channel 3 has great influence on the velocity of airflow in jet room. The result of simulation indicated: Under static state, the resultant velocity of airflow in jet room of model 3 is twice over the velocity of the former model. Under dynamic state, the difference of airflow velocity between the two hot wires in jet room of model 3 is sixth times more than the same velocity of the former model. The increase of airflow velocity under static state makes the difference of airflow velocity enhance.(5) The fitting polynomial, which describes the relation between the different inlet angle velocity and the airflow velocity of hot wire, is obtained with the results of simulation.(6) In measuring system, the location fixed sensor influences the output of sensor. The distance between the center axes of measuring system and the location fixed sensor show direct proportion with the error of output. The result of experiment indicated that when the distance is 8cm, the error of output is 1.07°/s.Citing the classical thermodynamics formulae that measured the velocity of airflow using resistance temperature under the force convection condition, the equations are detruded following the measuring principle. They are equation of resistance of hot wire - airflow velocity(as I_w is invariable), equation of output voltage of Wheatstone bridge - airflow velocity, equation of temperature of hot wire - airflow velocity and output voltage of Wheatstone bridge - temperature of hot wire.At last, the equation between output voltage of sensor and inlet angle velocity is obtained.Otherwise, circuitries are also optimized in this article. One is appended tuning circuit which keeps steady matching between pump and the driver circuit, the other is driver circuit which is designed to improve the driven power.In the end, the signal processing circuit and the method of data processing are introduced in this paper. The electrical performance testing at normal temperature and environment temperature testing on completed sensor has been finished. The results of testing are satisfied with the demand of the design.It's the first time that set the airflow velocity in cavity as masterstroke and linker which links the piezoelectric pump, the motion of airflow in cavity and the output voltage of Wheatstone bridge made up of hot wires together. The whole calculation method is build up.