中英文资料翻译参考文献Monitoring the Tire Pressure at Cars Using Passive SAW SensorsAbstract：In our paper we present the application of surface acoustic wave (SAW) sensors to the continuous manitaring of the tire pressure in road ve hicles. With these, the tire pressure can be read out in every phase of driving. We show the implemented prototype setup for measurement of the tire pressu re, the applied SAW sensors, improved versions and the interrogation setup. The problems in practical application are discussed. Experimental result s measuring the tire pressure during test rides are presented.INTRODUCTIONOperating a road vehicle, a malfunction of the tires in motion due to a tire puncture can cause serious accidents and endanger human life. Furthermore, nowadays manufacturers of cars try to save the spare wheel in vehicles. Usually it only costs weight and space, therefore it yields a higher fuel consumption,although it will be required less than one time in more than ten years of a car's life. This only can be done, if the air pressure in the tires can be measured even during driving. Currently used sensors contain active components, powered by a Lithium battery. The mass of these sensor assemblies is about 20 grams causing high dynamic load. A few years ago,wirelessIy interrogable SAW devices far sensor applications were invented. [1，2, 3]. Using an one port SAW delay line connected to an antenna only, an RF interrogation signal is fed into and the sensor response,carrying thesensor information is retransmitted wirelessly to the interrogator. These sensors are capable for measurement of temperature, mechanical load, force and displacement, etc. The advantage is, that SAW sensors are totally passive devices and contain neither power supply nor semiconductors. They withstand temperatures up to several hundreds of degree centigrades, their lifetime is much longer than that of battery powered systems.Further,in vehicles strong electromagnetic pollution is generated by ignition systems etc.SAW sensors operate without risk of damage even in rough environments. First we discuss pressure measurement employing SAW sensors with wireless interrogation.We present some types of sensor assemblies and the interrogation system.Next we discuss the implementation into thecar and thenwepresent experimentally results.Finally a brief summary concludes the content of the paper.SAW PRESSURE SENSORSThe electrical behaviour of a passive SAW pressure sensor always is that of a one port delay line with multiple reflectors or a resonator,respectively. In the delay linecase,the interrogator transmits a burst signal,the sensor responds with a chain of bursts,one for every reflector arranged at the substrate's surface.The differential delay between two or more response signals is evaluated.To measure some physical value,the parameter has to be converted into a change of sensor's surface length or surface acoustic wave's velocity,respectively.The delay ri of the response of areflector i is the ratio of SAW propagation length Li on the substrate's surface and propagation velocityv,.Affecting the sensor with a measurand causes a scaling of the sensor's response to be observed as individual delay shifts Ari of the response signals si originating frotmhe reflectors i.Mechanical measurands can be collected by loading the sensor mechanically.Apart from stretching and compressing,utilized for wireless measurement of torque,etc.the SAW sensor's substrate can be bent.Pressure can affect the sensor by bending a membrane,shifting the edge of a sensor fixed on theother side.Here the sensor is loaded to be bent due to a shift of the center of a membrane loaded by the pressure.On the other hand the sensor can directly be fitted to the membrane or a piezoelectric membrane representing the SAW substrate can be used.Figure 1 shows these methods.Fig.1:a)Membrane converting pressureto shift bendingthe SAW sensor(SAWS)b)SAW sensor fitted to the membraneThe next step is to cover the sensor membrane by a cap consisting of a spacer frame and a quartz cover plate.This yieldsanintegratedpressure chamber SAW sensor[4](fig.2).Fig.2:Integrated pressure chamber SAW sensorThecover protects theSAW generating metallic structure from oxidation and thesurface from dust.The cavity can befiIledwith a gas at reference pressure.If the cavity is evacuated,absolute pressure values can bemeasured.Measurement is made byinterrogationusing simple RF burst signals.The response impulses are evaluated in magnitude and phase.Bending the membrane due to pressure loadyields a phase shift of for instance 100 degree for lo4 Pascal.With this theairpressure in car tires can be measuredwith a resolutioonf approx.IO'Pascal(0.01 Bar).To reduce the amount of data to process,for the implementation in cars the resolution was reduced to 50 mBar.IMPLEMENTATIONThe first prototype used for the experimental measuremenwtsas a pressure chamber with a membrane made of brass.The sensor unit was fitted to a hub cap andwas connected to the valve by a pressure assembly(fig.3).Fig.3:First prototype of pressure chamber formeasurement of tire pressureFor serial manufacture the sensor system~have tobe much smaller and able to be integrated in the tire.Therefore we implemented the integrated pressure chamber(fig.2)into the tire.The sensor was fixed to the rim,the metallic valve shaft was used as the sensor's antenna(fig.4).Fig.4:Integrated pressure chamber fixed to the rim,valve used as antennaFoirmproved implementation a sensor assembly only fitted to the valve was developed(fig.5).The total mass of the unit is only a few grams,the dynamic load is small even driving at high speed.Fig.5:Pressure sensor forfitting into the valve shaftThcear based interrogation system uses space diversity to distinguish the sensors in the tires.Therefore below every car wing an antenna has to be employed.We used coaxial cables,hut it is difficult and expensive to use them in cars.Our investigationsshow the applicability of twisted pair wires too.Fig.6:Interrogation antenna on carFor measurement we developed a small sized interrogation system transmitting bursts and looking for the phase shift between the response signal bursts.The system was controlled by a one chip microcontroller and abisle to display the measurement result on aLCD display.In fig.7 a photograph of the system is shown.Fig.7:System for wireless interrogation of passiveSAW sensors(50 x 100 x 160 mm’)MEASUREMENTRESULTSTo test our sensors and our system we made a lot of test rides within the area and around the city of Vienna.The interrogation system was coupled to alaptop computer.The pressure values were measured and recorded to a file. Thefigures 8 and 9 show characteristic behaviour of tire pressure for different driving conditions. Due to the shocks from a rugged lane,in the left part of fig.8 the absolute pressure value swings around the mean value by the least significant bit,0.05 Bar.The narrow higher peaks of tire pressure belong to braking maneuvers(the sensor was mounted toa front wheel).The longer increase of tire pressure and the following period of decay is due to riding over a curbstone.The system showed high reliability even when driving in a heavy snow storm. tire pressure[Bar]Fig.8:Tire pressure for different driving conditionsIn figure 9 the pressure in the right front wheel can be observed zoomed in time while passing a two track grade crossing with an adjacent water channel across the lane.Due to the dilapidated arrangement of the grade crossing,hard shocks are transmitted to thecar body causing hard pressure shocks in the tires.Fig.9:Tire pressure crossing a grade crossing withtwo tracks and a water channel across the laneDISCUSSIONSAW sensors with wirelessly interrogation are free of maintenance and withstand high thermal and mechanical load.The measurement performance is comparable to that of competitors.The effort in car based system is higher for SAW sensors,since theactive sensor units transmit preconditioned digital information containing pressure valueand sensor The major advantage of SAW devices in identification. applications,where high revolutions per time occur, is their low mass.The centrifugal force is m.v*/r,with the mass m,the velocity v and the radius r.To minimize dynamic mechanical load,the mass of a system applied to rotating parts should be as low as possible.Whereas conventional sensor units for tire pressure measurements have a mass of approx.20 grams,the integrated pressure sensor itself(fig.5) has a mass of less than one gram.The complete SAW sensor unit's mass in worst case is only a few grams.Conventional systems are powered by a Lithium battery.In case of a worntire,since the battery cannot be checked,the sensor should be replaced too,yielding problems of waste disposal.For a system integrated in the car electronic,it is needless to display the pressure of each tire continuously.Here,only a malfunction should trigger an alert.The system's display can be canceled,reducing system's cost.CONCLUSIONTheadvantagews of passive SAW sensors make thwemell suited for vehicular applications.Especially for measurement of tire pressure low mass and the fact thatthey are free of maintenance makethem to be superior over the competitors.The SAW sensors for pressure measurement,the implementation in tires and the system for interrogation were discussed.Experimental results out of a lot of measurement rides were presented.REFERENCES[l]Reindl,F.Muller,C.Ruppel,WE.Bulst and F.Seifert,Passive surface wave sensors which can be.wirelessly interrogated,International Patent Appl WO 93/13495(1992).[2]Seifert F.,Bulst W.E.,Ruppel C.,Mechanical sensors based on surface acoustic waves,Sensors andActuators,A44(1994)231-239[3]G.Scholl,T.Ostertag,L.Reindl,H.Scherr,0.Sczesny,U.Wolff,Wireless SAW Sensors for Remote Measurement of Physical Parameters,Proc.IEEE Intern.Workshopon Commercial Radio Sensors and Communication Techniques,1997,pp.51-58.[4]H.Scherr,G.Scholl,F.Seifert,R.Weigel,Quartz Pressure Sensor Based on SAW Reflective Delay Line,Proc.IEEE Ultrasonics Symposium 1996,pp.347-350.译文轮胎压力监测在汽车使用被动声表面波传感器摘要：在我们的文件，我们目前的应用表面声波（声表面波）传感器不断的轮胎压力在道路车辆。