N. Korobova

Error angle determination of the star sensor with liquid cooling

Design studies method of star sensor thermal stability with liquid cooling using modern CAD has been described. Optimal operation of two circuits for liquid cooling structure of star sensor has been chosen using a mathematical model for calculating the convective heat transfer coefficient. Study defined the angular displacement of the star sensor with liquid cooling (~ 0.3 arc seconds), which is acceptable for star sensors with 1 arc seconds accuracy. At this level of scientific investigation the developed 3D model of the star sensor assembly comprising a thermally stabilizing ground test equipment allows to determine the angular error due to the temperature loads and optimal parameters liquid of cooling system (for example, the flow rate of fluid , geometrical parameters of cooling circuits , etc.). In the future, this model should be improved, which will consider the impact of other factors (e.g. gravity, vibration, etc.) on the performance of the star sensor.

Research and development of capacitive transducer with linear acceleration

Paper presents the study results and modeling of functional characteristics of the linear acceleration transducers, enabling sensors creation with the specified parameters. Sensing element made for linear acceleration transducer with torsion cruciform section has been proposed on the based design and technological principles. It allows minimizing the impact of cross-acceleration and gives the maximum of center mass displacement for high sensors sensitivity in the given dimensions. The range of measured acceleration from ± 0.2g to ± 50g was provided by changing the torsion bar thickness n = 34 ÷ 56 microns. The transducers frequency range of linear acceleration 100-150 Hz depends on the gas pressure P = 700-800Pa in which the sensor element was located. Methods converting displacement of sensing element in the sensor output have been provided. On their basis the linear acceleration transducers with analog output signal having a predetermined frequency range and high linearity of the transformation (nonlinearity 0.2-1.5%) was developed. Also the linear acceleration transducers with digital signal consuming little (no more than 850 μA), low noisy (standard deviation to 0.1mg/rt-Hz) and high sensitivity (up to 0.1mg) to the accelerations was made. Errors in manufacturing process of sensitive elements and operating environment temperature affect the changes in the characteristics of the linear acceleration transducers. It has been established that different plate thickness up to 3.6% leads to the scale factor error to 4.7%. Irreproducibility of depth anisotropic etching of silicon up to 6.6% introduces an error in the output signal of 2.9 ... 13.8mg.

Comb structure analysis of the capacitive sensitive element in MEMS-accelerometer

In this paper analysis of comb design for the sensing element MEMS accelerometer with longitudinal displacement of the inertial mass under the influence of acceleration to obtain the necessary parameters for the further construction of an electronic circuit for removal and signal processing has been done. Fixed on the stator the inertia mass has the ability to move under the influence of acceleration along the longitudinal structure. As a result the distance between the fixed and movable combs, and hence the capacitance in the capacitors have been changed. Measuring the difference of these capacitances you can estimate the value of the applied acceleration. Furthermore, managing combs that should apply an electrostatic force for artificial deviation of the inertial mass may be used for the initial sensitive elements culling. Also in this case there is a change of capacitances, which can be measured by the comb and make a decision about the spoilage presence or absence.

Providing of MEMS inclinometer operation under external influencing factors

Research data of accelerometer noise parameters were used to calculate possible resolution. The layout scheme has been developed for design creation. Engineering calculations allow evaluating the reliability and the ability for MEMS inclinometer operation under external influencing factors. Protection technology has been developed to ensure reliable inclinometer operation from external influencing factors.

Anomalous dependence of carbon nanotubes work function on humidity

The impact of humidity on the single- and multi-walled carbon nanotubes field emission characteristics, such as work function and emission current, was studied. The behavior of carbon nanotubes on Si, Al, stainless steel and polyethylene naphthalate substrates during humidity changing was compared with pristine metals and other materials without nanotubes. Work function of the samples was measured in ambient conditions and in humidity range of 25-100 %. The strong correlation between work function and humidity of carbon nanotubes was found and strong anticorrelation was observed for control samples without CNT.

Some important aspects in the glass structure of chalcogenide systems

There are two ways to solve the glass-formation prognosis problem in the absence of a unified concept of glass-formation that connects its structural-chemical, kinetic, and thermodynamic aspects. Structural-chemical and energetic factors of glass-formation, together with the relaxation conditions of glass- forming ability with increase in atomic numbers of elements have been considered as a starting point for the development of the structural-energetic concept of glass formation.

Packaging problem in microelectronics due to stress and fracture at the “metal-ceramic” interface

The packaging of the integrated circuits requires knowledge of ceramics and metals to accommodate the fabrication of modules that are used to construct subsystems and entire systems from extremely small components. Stress analysis was conducted for a linear work-hardening metal cylinder embedded in an infinite composite ceramics (Al2O3 - SiO2) matrix. Sticking between metal and ceramic was established at high temperature and stresses developed during cooling to room temperature. It was noted that pore clusters were capable of initiating ductile rupture, by means of plastic instability, in the presence of appreciable tri-axiality.

Preparation and some properties of pure and doped barium titanate thin films

The article describes the research and development results of thin pure and doped barium titanate films with control orientation deposited on Pt substrates by electrophoretic deposition and sol-gel technique. Film temperature dependences of the electrical properties were investigated. Results showed that pure films had semiconductive behavior after heat-treatment in vacuum at 700-1000 °C. It was found that resistance to the degradation of dielectric properties can be improved by small doping (0.1-0.5 mole%) of La2O3.

Features design and manufacturing technology in microelectromechanical encapsulated devices

Research methodology for measuring the natural frequency of the inner and outer frames of micromechanical oscillating system with an electrostatic actuator in filling spaces inside corps with nitrogen, and verification methodology of a micromechanical sensor element (SE) on the basis of rotation angle measurement has been developed. Developed new technical solution was consisted in that for correcting errors in the form of etched shapes compensator topology with special configuration has been used. It was possible to obtain the moving parts of MEMS with etched rectangular shape figures and with a large etching depth about 400 microns. Hydrogenated silicon surface layers were investigated by IR - spectroscopy. It was shown that substrate temperature plays a primary role in the formation of hydrogen-defect layer in silicon. The behavior of the low-frequency band in the region of stretching vibrations of Si-H during annealing has been analyzed. The dependence character of the resonance frequency of the movable (SE) part of MEMS torsion type vs temperature has been investigated. It was found that when the temperature changes from 25 to 80 °C, so natural SE frequency does not change more than 1%. The dependence of the quality factor and the natural frequency of the moving SE part from the inside corps pressure on the various modes of oscillation was investigated.

Calculation of the dynamic characteristics of micro-mirror element based on thermal micro-actuators

Paper presents a structure of a micro-mirror element driven by thermal micro-actuators. Micro-mirror dimensions are 100x100 um and it was manufactured by a surface micromachining using microelectronics technologies. Thermal microactuator is a bimorph structure consisting of aluminum and silicon dioxide layers with a polysilicon heater between them. The description of manufacturing process for micro-mirror element is given. The micro-mirror motion is achieved by passing an electric current through the heater. The actuator structure is heated and rotates the mirror. The processes of heating and cooling of thermal micro-actuator structure directly affects the characteristics of manufactured micro-mirror, thus the studying of these processes is essential. The report proposes a method for calculating the heating and cooling time, taking into account the influence of the structure geometry, electrical characteristics of external influence and the environment conditions. Also a method for the experimental determination of the dynamic characteristics is proposed, along with the method of electro-thermal analogy. The results of calculation are in good agreement with the experimental data, which allows one to use it to determine the dynamic characteristics of micro-devices based on thermal microactuators.