High-performance inline RF MEMS switch for application in 5G mobile networks

This article presents the results of the design and analysis of a radio-frequency switch made using microelectromechanical systems technology. The device is the capacitive switch with a hybrid type of contact, in which the movable electrode of the structure – the metal membrane is part of the microwave signal line of the coplanar waveguide. The switch design is characterized by a high capacitance ratio and low contact resistance. The zig-zag elastic suspension is used to reduce the value of the pull-down voltage – 2 V and the switching time ∼ 7 us. The central resonant frequency of the switch is 3.8 GHz. In this case, in the open state, the value of the insertion loss is not more than -0.2 dB and the isolation value in the close state is not less than -55 dB. The effective frequency range is the S-band, as well as the C-, X- and Ku-band, in which the isolation value is at least -30 dB. The presented inline RF MEMS switch is suitable for use in various types of ground and satellite communications, in particular for devices and systems of 5G mobile networks.

Nonlinear Dynamics of Electrostatic Comb-drive with Variable Gap Under Harmonic Excitation

This paper provides an extensive study of the nonlinear dynamics of a variable gap electrostatic comb-drive. The amplitude- and phase-frequency response, as well as the amplitude- and phase-force response of the comb-drive were obtained and analyzed with and without taking into account the cubic nonlinearity of the suspension. A significant variation in the frequency and force response is demonstrated in the presence of nonlinearity of the elastic suspension. Using numerical methods of bifurcation theory, solutions are obtained that correspond to the resonance peak of the frequency response when the constant and variable components of the voltages change. The result obtained makes it possible to determine the range of excitation voltage values that provide the required vibration amplitude in the resonant mode. The influence of the second stationary electrode on the dynamics of the system is estimated. The significant influence of this factor on the resonant-mode characteristics is revealed.

Моделирование динамического воздействия авиационного двигателя на крыло самолета при отрыве лопатки вентилятора

One of the requirements for a projected aircraft is the ability to continue flying and land in the event of a breakdown of one of the engines. One of the calculated cases of engine breakdown is a fan blade breakaway. This phenomenon causes large vibrations of both the engine itself and the aircraft structure.Design model and method for studying engine vibrations with damage in the form of blade breakaway have been developed; numerical studies of unsteady vibrations of an engine suspended on a pylon have been carried out. Herewith, the following load options are considered: engine operation with fan imbalance before shutdown, which is performed by the pilot; sharp braking and jamming of the fan rotor as a result of breakage of the front elastic support of the rotor, which can occur when the blade breaks off; braking the rotor after turning off the engine.The front bearing of the rotor is ball the bearing installed in elastic elements "squirrel wheel". The ball bearing is modeled as a rigid joint. Outside the elastic element, there are two thin-walled shells, which are intermediate load-bearing elements. With an increase in the imbalance of the fan rotor, the gap in the oil damper closes, the damper housing sits on the shells, switching on their rigidity to work. Thus, the stiffness characteristic of the support is bilinear. The stiffness coefficients of the elastic element "squirrel wheel" and the front support shells are determined by the method of numerical simulation. The fan rotor is modeled as a solid body on bearing supports. The stator of the engine is modeled by a rigid body on an elastic suspension. The pylon and the elastic engine mount elements are modeled by beams of variable cross-section operating simultaneously in tension, torsion and bending.A numerical analysis of the transient vibration processes of the D-436-148FM engine on the pylon of the An-178 airplane is carried out. The most dangerous case of damage as the breakdown of the bearing support after the fan blade breakaway is investigated. The results of the calculations are the graphs of the forces in the bearing arrangements and in the hinges of the engine mounting depended on time.

Comparative Effect between Silesian Suspension and Total Elastic Suspension on GRF Loading in Subjects with Trans-Femoral Prosthesis: A Biomechanical Study

Background: The major function of all Suspension systems is Prosthesis retention. The suspension system prevents rotation, translation and vertical movement of the prosthesis in relation to the residual limb. The Silesian suspension and TES system that are commonly prescribed for Transfemoral amputees are believed to provide a better suspension. Nevertheless, their effect on Transfemoral amputees’ gait performance has not yet been fully investigated. The main intention of this study was to understand the potential effects of the Silesian suspension and TES systems on Transfemoral amputees on gait kinetics. Aim & Objective: To find out the effect of two types of suspension system on Gait Kinetics in subject with unilateral transfemoral amputee. Study Design: Two group post-test Comparative Experimental study design. (Quasi Experimental). Methods: 30 subjects with two different suspension systems such as Silesian suspension (Group-A) and Total Elastic Suspension (Group-B) was included in this study by convenient sampling method. All subjects walked with Endo skeletal design Trans femoral Prostheses gait training given called after 3 weeks. After that data regarding gait kinetics parameters was evaluated by Kistler Force Plate in dynamic position. Result: The results revealed that there is significant difference in gait kinetics parameters that GRF (Fx) mean shows no significantly difference between Group-A and Group-B (p= 0.582), GRF (Fy) mean shows non-significantly difference between Group-A and Group B (p=0.163) and GRF (Fz) mean shows non-significantly difference between Group-A and Group-B. Conclusion: The findings concluded that the study support the hypothesis that there were significant difference with two different suspension system on kinetic gait parameters. Key words: Transfemoral prosthesis, TES, Silesian suspension, Gait Kinetics.

Dynamic Quality of an Aerostatic Thrust Bearing with a Microgroove and Support Center on Elastic Suspension

The disadvantage of aerostatic bearings is their low dynamic quality. The negative impact on the dynamic characteristics of the bearing is exerted by the volume of air contained in the bearing gap, pockets, and microgrooves located at the outlet of the feeding diaphragms. Reducing the volume of air in the flow path is a resource for increasing the dynamic quality of the aerostatic bearing. This article presents an improved design of an axial aerostatic bearing with simple diaphragms, an annular microgroove, and an elastic suspension of the movable center of the supporting disk. A mathematical model is presented and a methodology for calculating the static characteristics of a bearing and dynamic quality indicators is described. The calculations were carried out using dimensionless quantities, which made it possible to reduce the number of variable parameters. A new method for solving linearized and Laplace-transformed boundary value problems for transformants of air pressure dynamic functions in the bearing layer was applied, which made it possible to obtain a numerical solution of problems sufficient for practice accuracy. The optimization of the criteria for the dynamic quality of the bearing was carried out. It is shown that the use of an elastic suspension of the support center improves its dynamic characteristics by reducing the volume of compressed air in the bearing layer and choosing the optimal volume of the microgroove.

The Staple-Shape Plate Springs Engineering Calculation Method

The new types of elastic devices – staple-shape plate spring and leaf spring - have been developed at the Kyiv National University of Construction and Architecture. The staple-shape plate spring is an elastic plate where the ends are deflected from its middle part in the same direction and are made in the form of consoles equipped with hinge attachments. The middle part of the plate as a parallel to the line of the load action is designed with variable length section. In each section, the axis, relative to which the moment of the section inertia is a maximum, is perpendicular to the spring bending plane, designed as the equal resistance beam. This article substantiates the feasibility of using a staple-shape plate spring to improve the elastic suspension of truck cabs. The recommendations for choosing the most promising mass production directions, as well as the engineering calculation methods of such springs, have been developed. Objects of the study are devices intended for machines and their components dynamic loads shock absorption, differing in having a bracket shape and being a subject to bending in the plane of the highest rigidity of their cross sections, as well as shock absorbers using these springs, in particular KamAZ cabs suspension. This research implementation allows significantly reducing the metal consumption and elastic devices manufacture complexity, as well as can be useful in the design and operation of elastic car suspensions.Keywords: elastic device, staple-shaped plate spring, leaf spring, elastic suspension

Theoretical Investigation on Performance Characteristics of Aerostatic Journal Bearings with Active Displacement Compensator

Active aerostatic bearings are capable of providing negative compliance, which can be successfully used to automatically compensate for deformation of the machine tool system in order to reduce the time and improve the quality of metalworking. The article considers an aerostatic radial bearing with external combined throttling systems and an elastic displacement compensator, which is an alternative to aerostatic bearings with air flow rate compensators. The results of the mathematical modeling and theoretical research of stationary and nonstationary modes of operation of bearings with slotted and diaphragm throttling systems are presented. A counter-matrix sweep method has been developed for solving linear and nonlinear boundary value problems in partial derivatives with respect to the function of the square of the pressure in the bearing gap and inter-throttling bearing cavities for any values of the relative shaft eccentricity. A numerical method is proposed for calculating the dynamic quality criteria, and the transfer function of the dynamic compliance of a bearing with small displacements is considered as a linear automatic control system with distributed parameters. An experimental verification of the theoretical characteristics of the bearing was carried out, which showed a satisfactory correspondence among the compared data. It is shown that bearings with a throttle system have the best quantitative and qualitative load characteristics. The possibility of optimal determination of the values of a number of important parameters that provide the bearing with optimal performance and a high stability margin is established. It is shown that bearings with an elastic suspension of the movable sleeve allow one to compensate for significant movements, which can be larger than the size of the air gap by an order of magnitude or more. In these conditions, similar bearings with air flow compensators would be obviously inoperative.