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Micro-sensors use micro-machining technology to encapsulate micron-sized sensing elements, signal processors, and data processing devices on a single chip. Due to its small size, low price, and ease of integration, micro-sensors can significantly improve system test accuracy. At present, the technology has gradually matured, and various miniature sensors such as detection mechanical quantities, magnetic quantities, and thermal quantities can be produced. Multifunction means that a sensor can detect two or more characteristic parameters or chemical parameters, thereby reducing the number of automotive sensors and improving the reliability of the system. Intelligence is the combination of sensors and large-scale integrated circuits with intelligent functions.
Due to the important role of automotive sensors in automotive electronic control systems and the rapidly growing market demand, countries all over the world attach great importance to their theoretical research, new material applications, and new product development. Here are some new products in this area.
Second, ion detection system Mitsubishi (Mitsubishi Electronics) is developing a vehicle ion detection system. This system can monitor the combustion of each cylinder of the engine by detecting ions. When the combustible mixture continues to burn, ionization occurs near the combustion peak. By placing a biased probe into the cylinder, the ion flow associated with the ionization condition can be measured.
This information control system, which can reflect various combustion conditions of the engine, consists of a spark plug with a probe, an ignition coil with a test attachment, and an electronic module that processes the ion flow signal. It can determine the ignition, combustion, and explosion of each cylinder. Earthquake situation. A further function will be to monitor the mixture conditions of the engine, ie to control the air-fuel ratio of each cylinder based on the combustion conditions shown by the ion flow.
Third, the quick start of the oxygen sensor When the engine is cold, the CO and HC emitted by the engine are the most. This requires the oxygen sensor to start as soon as possible and enter the closed-loop control state. NGK Spark Plugs Co., Ltd. has developed a new type of oxygen sensor that can achieve closed-loop control within 15 seconds. By narrowing the heating zone and reducing the impedance, the heating device of the sensor is improved. Due to the use of new materials and a new temperature control system, the life of the heater is similar to the existing type, and the low-temperature characteristics are improved.
Fourth, the side slip sensor Bosch company developed a two-way sensor, which is composed of piezoelectric crystal linear accelerometer combination. This combination is more conducive to sensor setup, signal processing, and packaging. This sensor has two micromachined signal generators and each corresponding to the reference plane of the measured acceleration direction, and the corresponding force can be measured corresponding to an independent signal of a reference plane. A very high Q factor makes the sensor package available under normal pressure.
Fifth, the piezoelectric resonant angular velocity sensor Mitsubishi Electric Corporation developed this sensor is a glass-silicon-glass structure, and its resonant part is a silicon beam made by etching method. Excited by an external oscillator, its resonant frequency is approximately 4KHz. The thickness of the beam is the same as that of the silicon wafer. Its width and length are determined by etching. The connection between the silicon beam and the glass support was made using an anodic welding process under vacuum to ensure that the natural frequency change was small.
The variation of the angular velocity can be measured based on the change in capacitance between the metal electrodes on the glass holders on both sides of the beam caused by the variation of the vibration frequency of the silicon beam. The sensor circuit consists of a capacitor voltage (C-V) converter and a synchronous demodulator. The C-V converter is a conversion capacitor comparator (ASIC). When the measurement range is ±200°/s, the nonlinearity is ±1%.
Sixth, high pressure sensor Denso Company develops a kind of immersed high pressure sensor. These sensors can be used to detect the pressure of oil, hydraulic systems, gasoline and air-conditioning refrigerants, such as brake hydraulic control systems, air conditioner compressors and power steering pumps at idle, fuel control systems, suspension control systems, and automatic transmissions. Hydraulic shift system. The pressure of these systems varies from 2 to 20 MPa, while the sensor can withstand 38 MPa.
The sensor is encapsulated with a resin glue instead of the commonly used metal and glass to form a sufficiently large oil molecular channel, and an optimal design for the size of the outer shape and the sealing between the elements is achieved. All components including pressure sensing elements and amplifier circuits are concentrated on a single chip.
7. Direct thermal detection sensor The GM R&D center is testing a direct thermal detection system to suppress the deployment of side airbags at the rear-end adult seat (RFIS). The temperature of the occupant seat surface is compared with the driver's seat performance temperature. If the two are different and differ from each other by a predetermined value, the deployment of the airbag is suppressed. The temperature of the occupant seat is determined by a thermistor mounted on the seat surface. A direct thermal or non-direct thermal thermistor can be used.
In fact, this kind of suppression system can use a variety of detection methods. When the operation of the direct thermal detector is not reliable enough, other methods can be used to improve the reliability of the system. It has been suggested to configure other sensors, such as measuring body weight, capacitance, vibration, using ultrasound, microwaves, optics, and infrared rays. It is also proposed to configure multiple detection devices for a suppression system to make it more reliable.
Eight, when the engine oil viscosity sensor when the oil is replaced is generally based on the manufacturer's time or mileage. A few manufacturers adopted a more advanced method to calculate the oil change interval by recording engine speed and temperature. LucasVarity is developing a piezo-vibration viscometer sensor whose working principle is similar to vibrating viscometers. Vibrators (balls, sheets, or rods) will vibrate when their vibratory frequencies decay. Therefore, depending on the shape of the vibrator, some parameters of viscosity and density can be measured. A vibratory viscometer vibrator is a quartz rod, which can be excited by torsional vibration. By measuring the amplitude and resonant frequency width corresponding to the liquid viscosity, the viscosity can be determined (accurately, the combined value of viscosity and density). . Visible viscometer is a device that determines the viscosity by measuring the shear wave transmitted by the liquid. However, because the shear waveform at the contact point of the sensing element and the liquid may be distorted, the correspondence between the test value and the liquid may be poor.
The viscosity sensor provides an interface to improve the contact relationship between the sensing element and the liquid, the principle of which is similar to the ultrasonic transducers we are familiar with on biomedical and marine vessels.
At the heart of the sensor is a piezo-electric transducer that produces tangential motion when voltage is applied across it. The electrode is deposited on the surface of the piezoelectric crystal using a metal evaporation deposition method, and then the entire body is coated with an insulating layer.
A sweeper determines the resonant frequency of the sensing element through the alternating voltage generated by the oscillator. Because at the time of resonance, the resistance of the sensing element reaches a maximum value, and as the viscosity of the liquid changes, the value of the bee changes accordingly and is converted into a voltage signal by the peak detection circuit.
The thickness of the insulating layer is determined according to the range of the measured viscosity, since the shear wave reflected from the liquid interface must be completely absorbed by the insulating layer, so the thickness of the insulating layer is about a quarter wavelength.
Nine, magnetic velocity sensor SST Technology Co., Ltd. developed an integrated sensor, which is a magnetic sensitive speed sensor that combines high magnetoresistive (GMR) materials and semiconductor devices. High reluctance materials are characterized by changes in their electrical resistance as the magnetic field changes. The semiconductor device is composed of a signal processor and a voltage regulator fabricated on the same BICMOS circuit board. The high reluctance material is first deposited on a BICMOS substrate, and the photoresist is used to make it into a resistor. The foil is connected to a BICMOS circuit through an aluminum foil, and then a layer of alloy is coated on the periphery to gather magnetic lines of force.
This kind of sensor is a bipolar structure. A square-wave pulse signal is output by level conversion. Its output frequency is the same as the rotation frequency of the teeth of the soft magnetic signal, and the excitation mechanism is a permanent magnet. Since the sensor's signal processing circuit is DC-coupled, zero-speed conditions can be handled. And it has high sensitivity so that it can work under a large air gap.
The ABS sensor using the above technology has a bipolar structure in which the zero-speed processing and the output signal change between two levels, and the pulse frequency is the same as the rotation frequency of the signal teeth or magnetic poles. In the allowable temperature and operating frequency range, the ratio of the bandwidth is (50±10)%, and when the gear module is 2.5, the air gap characteristic can reach 3mm.
Tenth, the development trend of the sensor technology of the car The sensor technology of the car of the future, the general development trend is multi-functionalization, integration, intellectualization. Multifunctionalization means that one sensor can detect two or more characteristic parameters or chemical parameters. Integration refers to the use of IC manufacturing technology and fine processing technology to produce IC sensors. Intelligence refers to the combination of sensors and large-scale integrated circuits, with MPU, and intelligent functions. The recently developed automotive sensors have the following features: digital signal output, linearized microprocessor compensation, sensor signal sharing and processing, sensor indirect measurement, composite sensor signal processing, IC and fine processing.
Fiber Sensor has developed hundreds of types such as temperature, pressure, position, rotation speed, liquid level, flow rate, vibration and gyro. Due to the characteristics of high sensitivity, small size, light weight, bendability, good insulation, no electromagnetic interference, wide frequency band, low loss and other characteristics, the optical fiber sensor will be widely applied to automobiles in the future.
In order to improve the safety and comfort of automobiles, sensors such as biological measurements are also being studied. For example, sensors are used in devices such as driver's blindness obstacle measurement, maintaining two-vehicle distance, and automatic collision protection.
The computer interface of the sensor signal output and control system is also an important research topic. The smart car sensor with A/D, D/A, I/O drive, buffer RAM, program ROM, MPU, and linearity, temperature compensation, and corresponding control program attracts attention and will make every element of the car system The number of devices has been greatly reduced, resulting in lower system costs, reduced size and reduced quality, and making the entire system more simple and reliable.
In short, the development of automotive sensor technology is not only the development of the sensor itself, but also focuses on the development of interchangeability, durability, and reliability of the sensor.
New vehicle sensor and analysis of development trend
I. INTRODUCTION As an important information source for automotive electronic control systems, automotive sensors provide real-time, accurate measurement and control of various information such as temperature, pressure, position, rotational speed, acceleration, and vibration. The key to measuring the level of modern limousine control systems is the number and level of sensors. At present, about a hundred sensors are installed on a domestic ordinary family car, and there are as many as 200 sensors on a luxury sedan. The overall development trend of automotive sensor technology in the future is miniaturization, multi-functionalization and intelligence.