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The article contains the results of research and development of a system for active noise damping of an automobile engine. The main source of noise from a running engine is exhaust noise. The frequency spectrum of this sound has a pronounced low-frequency character, which explains its weak absorption when the sound is propagating in open spaces. A possible solution to this problem is to use an active system for suppressing the resonant frequencies of the muffler using strain gauges to read the primary information about the dynamic processes that determine the noise level. It is for such active noise suppression systems that the authors develop a high-temperature pressure sensor based on strain gauges made of silicon whiskers. Such strain gauges have unique mechanical properties, are characterized by high sensitivity and the ability to operate in various amplitude-frequency and temperature ranges up to 500°C. The study of the dynamic characteristics of pressure sensors made it possible to confirm the quality of its electromechanical part and determine that the measurement error of the sensor is ±0.5 in the temperature range of 20 to 500°C. The active noise suppression system is a buffer tank whose volume changes in accordance with signals from pressure sensors. This design makes it possible to dynamically change the resonant frequency of the buffer capacitance depending on the operating modes of the engine, which leads to a decrease in its noise characteristics. Using the developed additional resonator chamber with a variable volume in the exhaust muffler of an internal combustion engine made it possible to reduce resonance phenomena in the zone of low-frequency pulsations of the exhaust gas pressure from 57 to 43 Hz with a frequency drift in the range of 310 to 350 Hz, which significantly improved its noise characteristics.

One of the promising directions of development of information and measuring systems for monitoring and diagnostics is the use of intelligent sensors of various physical quantities, in particular pressure, temperature, deformation, acceleration, etc. The main functional feature that distinguishes such sensors is the possibility of signal processing directly in the measuring zone, which involves the temperature compensation of the output signal, linearization of the transformation function. Along with primary converters, intelligent sensors include analog-to-digital and digital-to-analog converters, microcontroller, memory-storage device, input/output interfaces. However, the technologies used today for the creation of existing microelectronic sensors are quite complex and require special process equipment and materials, that leads to an increase in their value. The aim of this work is to develop an information and measurement system for use in conjunction with mechanical sensors based on strain gauges made of silicon whiskers in terms to provide a higher efficiency. The deformation and temperature characteristics of sensors of mechanical quantities (pressure, force and deformation) with strain gauges on the basis of p-type Si whiskers (ρ=0.005-0.02 Ω·cm) in the temperature range from -60 to +60°C were analyzed. It has been established that at a deformation level of &plusm;6·10–4 relative units, the high values of sensitivity and linearity of strain gauge characteristics are maintained, and the hysteresis effect due to the characteristics of elastic elements is shown to the smallest extent. It is shown that the temperature dependence of relative change in the resistance of strain gauge resistors based on p-Si whiskers with resistivity of 0.005 Ω·cm is characterized by the smallest nonlinearity. This simplifies the problem of compensation of the temperature errors, which are typical for such sensors. The temperature coefficient of resistance for strain gauges was found to be 0.15%/°N. The information and measuring system was developed on the basis of pressure sensor with strain gauges made of silicon whiskers (ρ=0.005 Ω·cm). This pressure sensor provides the simultaneous measurement of pressure and temperature in the ranges 0...100 kPa and –60...+60°N, respectively. The measuring channel of the developed system was based on the AVR ATmega328P microcontroller, which provides the ability to create modern high-precision distributed data gathering and display systems. As a result of testing, satisfactory results were obtained regarding stability, sensitivity and measurement ranges of the developed information and measuring system. The main measurement error did not exceed 0.1%. The measuring circuit can be easily adapted to a new task without making any significant changes to its hardware, the function of the device is easily adjusted by changing the work program.

Sensitive element of multifunctional sensor for measuring temperature, strain and magnetic field induction has been developed based on the studies of electrical conductivity and magnetoresistance of silicon and germanium microcrystals in the temperature range 4.2—70 K, strain ±1.5*10–3 rel.un. and magnetic fields of 0—14 T. The feature of the sensitive element is the using of the p- and n-type conductivity germanium microcrystals as mechanical and magnetic field sensors, respectively, and the p-type silicon microcrystal — as temperature sensor. That allows providing the compensation of temperature influence on piezoresistance and on sensitivity to the magnetic field.

This research investigates complex studies of electrical conductivity and magnetoresistance of both strain and non-strain samples of p-type Si whiskers with different degrees of doping with boron and nickel in a wide temperature range from 4.2 to 300 K. It is established that the greatest manifestation of the piezoresistive effect is observed in the vicinity of concentrations which correspond to the metal-insulator transition. Investigation of the magnetoresistance of crystals was carried out in the range of fields with induction up to 14 T. Whiskers of silicon with a doping concentration of boron of 5·1018 cm-3 can be used as a sensitive element for two-functional deformation and magnetic field sensors in difficult operating conditions. Microwires for research were grown by chemical transport reactions with the crystallographic orientation and with the concentration of charge carriers, which corresponds to the vicinity of metal-insulator transition (5·1018 см-3). The nickel doping was conducted by the low-temperature diffusion from the precipitated film on the surface of the crystal. The uniaxial strain of Si microcrystals was carried out by fixing them on substrates with the different coefficient of thermal. The metallic-type temperature dependence on the resistivity is typical for heavily doped silicon microcrystals (with the bor concenctation >5·1018 сm-3) for both deformed and non deformed samples. Significant influence of the deformation on characteristics of microcrystals wasn't found. The maximum magnetoresistance of such samples doesn't exceed 4% in magnetic fields with induction of 14 T at the temperature of liquefied helium. The resistivity of Si crystals with ρ300К = 0.012 Оhm·сm (which corresponds to the dielectric side of MIT) is reduced in several times at the the temperature of liquefied helium and under the uniaxial deformation. Decreasing of boron concentration reduces this effect. This is also confirmed by the calculation of the experimental data temperature dependence of gauge factor for these samples in helium temperatures. The gauge factor is K4.2K=165 at the compressive strain ε=–5.29·10-3 RVUs. It is also found that the deformation of these samples has significant impact on characteristics of the magnetoresistance and the value of the magnetoresistance decreased almost in 3 times. The undeformed samples of Si p-type microwire doped with nickel and boron concentration in the vicinity of dielectric side to MIT can be used as the sensing element of magnetic field. The significant magnetic field dependence on magnetoresistance is observed in such crystals wich can reach a value of 250% at 14 T.

Currently, silicon and germanium, the most common materials in the production of discrete semiconductor devices and integrated circuits, do not always meet all the requirements to the sensing elements of mechanical quantities sensors. Therefore, it is logical to research the properties of other semiconductor materials that could be used as sensing elements in such sensors. A3B5 semiconductor compounds seem promising for such purpose. Effect of hydrostatic pressure up to 5000 bar on the resistance of n-type antimonide gallium whiskers doped by Se or Te was studied. Coefficient of hydrostatic pressure for this crystals was determined, it equals Kh = (16,5—20,0)•10–5 bar–1 at 20°N. Temperature dependence of resistance and coefficient Kh for this crystals in the temperature range ±60°N was studied. Design of the developed hydrostatic pressure sensor based on GaSb whiskers and its characteristics are presented. The possibility to decrease the temperature dependence of sensitive element resistance by mounting GaSb whiskers on the substrates fabricated from materials with different temperature coefficient of expansion was examined. It was shown that mounting of GaSb crystals on Cu substrate gives the optimal result, in this case the temperature coefficient decrease to 0,05%•°N–1, that leads to decrease of output temperature dependence. The main advantages of developed pressure sensor are: the simplified design in comparison with pressure sensors with strain gauges mounted on spring elements; the high sensitivity to pressure that is constant in the wide pressure range; the improvement of sensors metrological characteristics owing to hysteresis absence. The possible application fields of developed sensors are measuring of high and extremely high pressure, chemical and oil industries, measuring of pressure in oil bore-holes, investigation of explosive processes.

The article presents the design of a pressure-temperature sensor based on p-type silicon whiskers, doped with boron, with a resistivity of 0,005 Ohm?cm. The sensor is operable in a temperature range from –100 to +200°C and at pressures from 0 to 20 MPa. The sensor is designed for a wide range of applications.

Studies aimed at the creating of piezoresistive pressure sensors based on silicon whiskers, operating at high temperatures were carried out. Using the glass adhesive for strain gauges mounting on spring elements of covar alloy gave the possibility to elevate the sensor’s operating temperature range. Several modifications of pressure sensors based on the proposed strain-unit design were developed.

The characteristics of semiconductor strain gauges based on boron doped р-type silicon whiskers under high energy electron irradiation were studied. Strain gauges were irradiated at room temperature by electrons with energies 4,2—14 MeV and different doses 5·1016—1·1018 el/cm2. The main parameters of irradiated strain gauges: resistance, its temperature dependence and resistance change vs strain at –196…+100°C and –269…+20°C temperature ranges were measured. There are determined the values of electron irradiation energy and dose at which the radiation stability of strain gauges could be ensured.

To create low-temperature strain gauges based on p-type silicon whiskers tensoresistive characteristics of these crystals in 4,2—300 K temperature range were studied. On the basis of p-type Si whiskers with different resistivity the strain gauges for different materials operating at cryogenic temperatures with extremely high gauge factor at 4,2 K were developed, as well as strain gauges operating at liquid helium temperatures in high magnetic fields.

The developed universal construction of tensoresistive pressure transducer for cryogenic liquids (liquid nitrogen and liquid helium) is described. The study of strain gauges characteristics on the basis of p-type Si whiskers with different boron concentration, mounted on the invar spring elements (beams), in the wide ranges of strain ε=±1,2·10-3 and temperature 4,2-300 К for transducers simulation were carried out. It was shown that using heavily doped silicon strain gages gives the possibility to develop pressure transducers for liquid nitrogen and liquid helium based on the classic piezoresistance. The significant increasing of the pressure transducers sensitivity for liquid helium could be achieved by using the strain gages on the basis of silicon with boron concentration in the vicinity of metal-insulator transition based on the non-classic piezoresitance. Developed pressure transducers for cryogenic liquids with strain gauges on the basis of doped p-type Si whiskers are presented.

Purpose: The article contains the results of research and development of a system for active noise damping of an automobile engine. The proposed system of active noise suppression can significantly reduce the sound pressure level in the frequency band up to 500 Hz. The robotic principle of the developed system is based on the addition of an additional buffer tank with a variable volume in the silencer system. The use of high-temperature sensors with strain gauges based on silicon microcrystals to obtain information on the parameters of sound vibrations arising during the exhaust gas outflow made it possible to create a control system for changing the volume of the buffer tank. The results of testing the proposed system of active noise suppression of an internal combustion engine are presented. Design/methodology/approach: The active noise suppression system based on the Helmholtz resonator used tools to control general noise levels, experimental tests, complex mathematical modelling of acoustic processes in Solidworks, taking into account the conditions of propagation and attenuation of sound energy by intermediate closed volumes. Findings: The use of an additional resonator chamber with variable volume in the exhaust muffler of the internal combustion engine allowed to reduce the resonant phenomena in the zone of low-frequency pulsations of exhaust gas pressure from 57 Hz to 43 Hz at frequency drift in the range of 310...350 Hz, which significantly improved its noise characteristics. Research limitations/implications: For further research, to improve the characteristics of the active noise suppression system, it is advisable to consider the use of several in additional cameras of the Helmholtz resonator and to clarify the algorithm of the controller in transient modes of engine operation. Practical implications: The developed design of active noise reduction is simpler in comparison with analogs and allows reducing the noise of exhaust gases in a low-frequency range. Originality/value: To reduce the noise, a variable-volume Helmholtz resonator was used, the efficiency of which is provided by high-temperature sensors of the original design. [ABSTRACT FROM AUTHOR]