Fundamentals and Practices of Sensing Technologies by Dr. Keiji Taniguchi,
Hon. Professor of Xi’ an Dr. Masahiro Ueda, Professor of Faculty of Education and Regional Studies Dr. Ningfeng Zeng, an Engineer of Sysmex Corporation (A Global Medical Instrument
Corporation), Dr. Kazuhiko Ishikawa, Assistant Professor Faculty of Education and
Regional Studies, [Editor’s Note: This paper is presented as Part II of a series of chapters from the new book “Fundamentals and Practices of Sensing Technologies”; subsequent chapters will be featured in upcoming issues of this Journal.] 【Example 1.7】An example of a block diagram for a sensing system using vision sensors and actuators is shown in Fig.1.15. 【Example 1.8】A photograph of 60(GHz) Band Communication System which can use for sensing systems is shown in Fig.1.16.
1.1.8 Examples for Sensing Systems A. Power Train Control for Automotive Engine (13) From environmental problems, exhaust emissions from automotive engines have to be reduced to lower and lower levels. For this reason, multiple sensors and actuators are recently used for engine control as shown in Fig.1.17(a). In this figure, several of sensors are used for measurements such as crankshaft position, intake mass air- flow, manifold pressure, coolant and cylinder head temperatures, and heated exhaust gas oxygen (HEGO, located both before and after the catalytic converter). Furthermore, some of actuators are also used for controls such as throttle valve, exhaust gas recirculation (EGR), ignition plug and fuel injector.
CommentsECU ( Engine Control Unit): ①:mass air flow sensor ②:throttle valve actuator ③:fuel injection actuator ④:cylinder head temperature sensor ⑤:crankshaft position sensor ⑥:manifold pressure sensor ⑦:camshaft position sensor and actuator ⑧:ignition actuator ⑨:EGR (Exhaust Gas Recirculation)actuator ⑩:HEGO(Heated Exhaust Gas Oxygen)sensors ⑪:coolant temperature sensor
In a gasoline engine, the precise air-fuel ratio (A/F) regulation for emission control is necessary to achieve the high simultaneous conversion efficiencies in the catalytic converter. Dynamic A/F control, closed-loop regulation of A/F for high catalyst performance, is needed for lower emission control. Figure
1.17(b) shows the relationships between mean A/F and conversion efficiencies
for the hydrocarbon (HC), the oxide of nitrogen ( From this figure, it is evident that precise A/F regulation is needed for this purpose. B.Surgical Robot System(14) A surgical robot system as shown in Fig.1.18 helps to save lives in remote communities, battle fields, disaster-strikes areas, etc.. It consists of a surgical robot, a video camera, communication systems, an unmanned air vehicle, a surgical console and video monitor, two gasoline generators. C. Accelerometer as System- on- Chip System Figure1.19 (a) shows the electrode configuration of an accelerometer which the changes of a different capacitance with two sets of fixed and movable electrodes are sensed independently(15) . Furthermore, Fig.19 (b) shows the ADXL335 block diagram of the 3-axis accelerometer(16) .
1.2 Transduction Principles for Physical Sensors 1.2.1 Transduction Principles The most important point in selecting transducers and sensors is based on its transduction principle. Some transduction principles, which are frequently used as transducers or sensors, are shown in the following figures, and their explanations are, also, briefly described as follows: A. Thermo-EMF Transduction The measurand: B. ResistiveTransductionThe measurands: C. Relactive Transduction The measurand:
Fig.1.22 Relactive transduction D. Capacitive Transduction The measurands: E. Photoconductive Transduction The measurand: F. Piezoelectric Transduction The measurand: G. Potentiometric Transduction As shown
in Fig. 1.26(a), the measurand: the rotation angle into the change Figure1.26 (b) shows a photograph of a rotary sensor. This sensor is used for animal robot, switch for automotive, motor drive unit, radio control equipment, car audio (navigation system, changer), etc..
These details mentioned above will be described in chapter 2. 1.2.2 Relationship between Measurement Object and Sensing Device Figure 1.27 shows the relationship between measurement objects and sensing devices.
Fig.1.27 Relationship between interested
objects and sensing devices The elements numbered by①,②,③,④, and⑤ express energy sources, interested objects, preprocess operation, measurands, and sensing devices, respectively. Some preprocesses are required for the effective extraction of the measurands from an interested object. We show here such an example. For example, the important points shown in example1. 1(See Fig. 1. 4), are as follows: (1) The selection of DC and RF current sources. (2) For obtaining higher sensitivity, the optimal design of an orifice in the flow chamber as shown in Fig. 1.28. This figure shows us that in location①, white blood cells flow randomly, but in location ②, they flow with continuously some spaced intervals along the center of stream line. This method is well known as sheath flowing techniques. (3) A chemical processing for extracting efficiently measurands from the interested objects. This technique is shown in Fig.1.8.
1.2.3 Configurations of Transducers and Sensors Figure1.29 shows the relationship between a measurand and an active transducer, where no power supply is required. The thermocouple is a representative example (See Fig.2.3).
Fig. 1.29
Configuration of an active transducer B. Passive TransducerFigure 1.30 shows the relationship between a measurand and a passive transducer, where a power supply is required for the conversion into a voltage. The representative example is a resistive temperature transducer used as a transduction element(See Fig. 2.7). 1.2.4 Active and Passive Sensors A. Active Sensor Figure 1.31 shows the relationship between a measurand and an active sensor, where no power supply is required for a transduction element. The representative examples are a diaphragm used as a sensing element and a piezo electric element used as a transduction element (See Fig. 3.16).
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B. Passive SensorFigure 1.32 shows the relationship between a measurand and a passive sensor, where a power supply is required for a conversion. The representative examples are a diaphragm used as a sensing element and a relactive element used as a transduction one (See Fig. 2.14).
Fig. 1.32 Configuration of a passive sensor 1.2.5 Example of Photo Sensing System (6 ), (17) ,(18) Figure 1.33 shows the configuration of an automated hematology analyzer using a laser diode as a light generation source and two photodiodes as sensing devices. In this figure, a mechanism of the generation of sheath flow is shown in Fig. 1.28. Figure 1.34 shows the scattering models of laser beam caused by a white blood cell. Some definitions used in Fig.1.35 are shown in Fig.1.34. By using the method shown in Fig.1.7, white blood cells are measured by using the photodiode-sensors set-up in the following different channels. Figure 1.35 shows the two- dimensional scatter-grams for WBC five differential counts. (1) In the DIFF channel, lymphocytes, monocytes, eosinophils ,and eutrophils+basophils are clustered by the chemical processing using the reagent 1, and
then they are measured by the intensity scattering beam which depends on the inner structure of the white blood cell, and the intensity diameter of the white blood cell . They can be, then ,classified and counted from the WBC/DIFF scatter-gram shown in Fig.1.35(a). (2) In the WBC/BASO channel, basophils are separated from red cell ghosts and other white blood cells by the chemical processing using the reagent 2. As a result, the normal white blood cells are classified into five categories: neutrophils, eosinophils, basophils, lymphocytes and monocytes, as is shown in Fig.1.35.
1.3 Radar Sensors 1.3.1 Outlines of Radar Sensors Radar (radio detection and ranging) sensors including sonar (sound navigation and ranging) sensors can determine the range, velocity, and direction of an object. There are two types of radar sensors: active radar sensors and passive ones. Firstly, we deal with the active radar sensors. An active radar sensor which radiates a beam of radio wave energy toward the object, receives an echo signal from the object and analyzes its echo signal. There are three types of radio wave radiations: the pulse modulated wave radiation, the continuous wave (CW) radiation, and the frequency modulated wave radiation. 1.3.2 Pulsed Radar Sensors (19) Figure 1.36 (a) shows a block diagram of the pulsed radar sensor. It consists of a transmitter, an antenna, a transmit/receive electronic switch (T/R switch), a receiver, and a PPI (plan position indication) display scope. The operation of this sensor is as follows: (1) The transmitter sends a narrow width pulsed RF power signal from the antenna toward the object. (2) The receiver receives the echo signal from the object, and the echo signal is, finally, displayed on the PPI scope after a proper signal processing. Fig.1. 36(b) shows the relationship between the transmitting signal and its receiving signal. A
range for the object location can be determined by measuring a round-trip time
of the transmitting signal. The range
where the round-trip time for the transmitting signal, respectively. For the radio wave
propagation in a vacuum, whereas for acoustic wave
radiations, and Next, we will describe several items which express abilities of radar sensors. (1) The
range resolution
where (2) The smallest range Fig. 1. 36(b):
where (3) The
maximum range where (4)
The detectable maximum range
where For example, the radar cross
section is approximately The derivation of Eq.(1.8) is described in problem 1.3. 【Example 1.9 】Determine
the range Using Eq.(1.4),
【Example1.10】In the pulsed radar sensor shown in Fig. 1.36, we let
Determine the following values: (1) where (1) (3) (4) (5)
(6) In the modulator shown in Fig. 1.37 (a), the carrier waveform, the modulation waveform, and the modulated waveform are shown in Figs. 1.37 (b), 1.37(c), and 1.37(d), respectively.
Figure 1. 37(e) is the angular frequency spectrum
of the modulated waveform shown in Fig.1.37(d). The
angular frequency in the continuous carrier wave is carrier wave frequency)as is evident from Fig.1.37(a). The angular frequency spectrum of modulated wave has, however the wide range of the spectrum for the pulsed modulation, as shown in Fig. 1.37(e). The
relationship between the modulated signal is expressed as follows: 【Example1.11】Find the Fourier
transform of Changing 【Example1.12】Find the Fourier
transform of Using the Euler’s
formula: Example 1.11, we obtain the following relation:
Figure. 1.38 shows
a simplified block diagram of a CW radar sensor. When the transmitting signal with the carrier
frequency In
this situation, the Doppler frequency shift
where 【Example 1.13】When Using
Eq. (1.9), 1.3.4 FM Radar Sensor (19) The CW radar sensor described previously, can’t measure the range between the object and the radar sensor. For a solution of this problem, the frequency of carrier wave is varied as a function of the time in a FM-CW radar sensor. The
block diagram of the FM-CW radar sensor is shown in Fig. 1.39, and the
relationship between the transmitting signal and the receiving signal are also
shown in Fig.1.40, respectively. Figure.1.40 (a) shows the frequency variation
in the case that the object is moving with the speed of The details described above are explained as follows: (1) The frequency of the carrier wave in the FM-CW radar sensor is expressed as a function of the time in the following form: where (2) The
values (3) The receiving signal is
expressed as: (4) The value (5) The values
The range follows:
In the case of the object moving with a speed of the relationship between the transmitting and receiving frequencies is expressed as follows: (6) Up chirp frequency: (7) Down chirp frequency: (8) From (5), (6), and (7) described above, the range
(9)Doppler
frequency: (10)
Speed of the object: 【Example 1.14】In the FM-CW radar sensor shown in Fig. 1.39, we let
Then
we obtained following data: Determine the range between the object and the radar sensor, and the speed of the object. From
Fig.1.40 (a),
Using
Eq.(1.12), .
1.3.5 Examples of Radar Sensors for Automotive Use (20) Radio waves, infrared rays, ultrasonic waves, and visible light rays are used as energy sources in the sensing systems for automotive uses. Figure. 1.41 shows an example of the architectures of automotive wave sensors for holding securely cars from collisions.
①:Long range sensor using a carrier frequency of 77(GHz). Maximum range is approximately 150(m). ②:Infrared sensor. Maximum range is approximately 120(m). ③:Image sensors. Maximum range is approximately 80(m). ④:Short range sensors using a carrier frequency of 24(GHz). Maximum range is approximately 20(m). ⑤:Sonar sensors, (Maximum range is approximately 3(m)) Details are described in Chapter 3.
Fig. 1.41 Architectures of wave sensors for
holding securely cars from collisions(17) References: (13) J.A.Cook,D.McNamara,K.V.Prasad:Control, Computing and Communications: Technologies for the Twenty-First Century Model T, Proceedings of the IEEE, Vol.95, No.2, pp.334-355 (2007) (14) J.Rosen, B. Hannaford : DOC at a DISTANCE, IEEE Spectrum,pp.28-33 (Oct.,2006) (15) O.Brand: Microsensor Integration Into Systems-on-Chip, Proceedings of the IEEE , Vol.94, No.6, pp.1160-1176 (2006) (16) Datasheet, ADXL-203, Analog Devices, (17)Overview of Automated Hematology analyzer SF-3000TM,Product Development Division, Sysmex Corporation, Sysmex Journal,Vol.18, pp.11-22(1995) [ BWW Society Home Page ] © 2009 The Bibliotheque: World Wide Society |