scholarly journals Fast Telemetry and Communication Scheme Based on Doppler Diversity Reception under Large Dynamic Doppler for Hypersonic Vehicles

Electronics ◽  
2019 ◽  
Vol 8 (7) ◽  
pp. 781 ◽  
Author(s):  
Lei Shi ◽  
Lei Zhao ◽  
Chao Zhang ◽  
Bo Yao
Keyword(s):  
High Speed ◽  
Doppler Frequency ◽  
Frequency Offset ◽  
Rate Of Change ◽  
Hypersonic Vehicles ◽  
Diversity Reception ◽  
Communication Signals ◽  
Doppler Diversity ◽  
Communication Time ◽  
Tracking Module

Large dynamic Doppler caused by high-speed flight of hypersonic vehicles brings a great challenge to acquisition, tracking and correct demodulation of telemetry and communication signals. Different from receiving schemes of existing telemetry and communications, a novel communication method based on Doppler diversity reception for hypersonic vehicles was proposed in this study. Firstly, the proposed method offers a coarse acquisition of Doppler frequency offset and its rate-of-change by fast-coarse acquisition method, and then decreases the large Doppler frequency offset into a certain range through compensation. Finally, signals with residual Doppler frequency offset are processed directly by Doppler diversity reception method without a complicated tracing method. Different from the traditional receiving scheme with acquisition and tracking module, the proposed scheme lowers requirements on acquisition accuracy and neglects the accurate tracking module, thus shortening telemetry and communication time significantly for hypersonic vehicles. Simulation results demonstrate that the proposed method can achieve satisfactory performance when the residual Doppler is no higher than 1 kHz with normalized Doppler frequency offset and when the normalized artificial frequency shift is 0.01 and 0.4 respectively.

Realization of the Detecting Method for Aircraft Digital Image Transmission System Based on Multi-Processor

2012 ◽  
Vol 490-495 ◽  
pp. 2352-2356
Author(s):  
Feng Yang Duan ◽  
Li Min Chang ◽  
Ye Zhan
Keyword(s):  
High Speed ◽  
Data Communication ◽  
Image Data ◽  
Doppler Frequency ◽  
Image Transmission ◽  
Frequency Synthesis ◽  
Image Block ◽  
Direct Digital Frequency Synthesis ◽  
Display Module ◽  
Communication Signals

The technologies of image block, pyramid and multi-threading were used in this program to design the high-speed image generation display module and the processes of image data scheduling and mapping and solve the problems of large-capacity image data modeling and high-speed displaying. The technology of direct digital frequency synthesis (DDS) was used to design the Doppler shifting signal generation module and the multi-processor parallel system architecture, which can analog the Doppler frequency shifting of the data communication signals and solve the problem of the authenticity of communication signals during the simulated flight.

scholarly journals Kinematic parameters of goats walking on different slopes and biomimetic walking mechanisms

2017 ◽  
Author(s):  
Fu Zhang ◽  
Yafei Wang ◽  
Wei Wang ◽  
Keyword(s):  
Experimental Data ◽  
Theoretical Basis ◽  
High Speed ◽  
Rate Of Change ◽  
Kinematic Parameters ◽  
High Speed Video ◽  
Experimental Image ◽  
Displacement Speed ◽  
Walking Mechanism ◽  
Uphill Walking

A comparative analysis of the kinematic parameters of a goat on different slopes was conducted to study the kinematic parameters of goats on different slopes with walking mechanics. The uphill walking processes on different slopes (0°, 5°, 10°, 15°, 20°, 25° and 30°) were recorded by a high speed video system (VRI Phantom M110). The experimental image results were processed and analyzed using PCC and MATLAB software. The kinematic parameters were obtained from the goat walking on different slopes; these parameters are the changes of centroid with displacement, speed with time, and acceleration with time. As the gradient in the uphill process increases, the range of centroid fluctuation ranges from 0.079 to 0.59 and the rate of change ranges from 0.4 to 2.2 m/s, while the acceleration of the goat slope decreases. The present research can provide theoretical basis and experimental data for the design of a biomimetic agricultural slope walking mechanism.

scholarly journals Research on Safety Technology for High-Speed Interruption for Mining Flameproof Movable Substation

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 934
Author(s):  
Yanwen Wang ◽  
Le Wang ◽  
Sven G. Bilén ◽  
Yan Gao
Keyword(s):  
Solid State ◽  
High Speed ◽  
Single Phase ◽  
Low Voltage ◽  
Short Circuit ◽  
Rate Of Change ◽  
Simulation Experiments ◽  
Gas Detonation ◽  
Ultra High Speed ◽  
Short Circuit Fault

Due to the working condition of low-voltage cabling from the mining flameproof movable substation to the loads of the mining face being poor, it is easy to cause various external mechanical damages to the cable sheaths. Furthermore, a single-phase earth leakage fault or short-circuit fault can occur when the low-voltage cable sheaths are damaged, and electric sparks caused by these faults can lead to a gas explosion. As the gas detonation time caused by the above faults is usually more than 5 ms, the high-speed interruption solid-state switch which controls the cables must cut off the current within 3 ms. This requires the action time of the solid-state switch to be less than 1 ms, and at the same time, the sampling and calculation time of the relay protection must be less than 2 ms. Based on these problems, this paper proposes the use of a high-speed solid-state circuit breaker (SSCB) topology at the neutral point of transformer, and analyzes the conduction mechanism and shut-off mechanism of the current of the SSCB. It presents an ultra-high-speed algorithm based on pattern recognition of single-phase earth leakage fault protection, and an ultra-high-speed algorithm of short-circuit fault which is based on the rate-of-change of the current. Finally, through computer simulation experiments and semi-physical simulation experiments, the feasibility of the above three technologies is verified to ensure that when a single-phase earth leakage fault or short-circuit fault occurs in the low-voltage cable, the solid-state switch which is installed in the mining flameproof movable substation will cut off the current within 3 ms.

Sound and turbulence modulation by particles in high-speed shear flows

2019 ◽  
Vol 875 ◽  
pp. 254-285 ◽  
Author(s):  
David A. Buchta ◽  
Gregory Shallcross ◽  
Jesse Capecelatro
Keyword(s):  
Gas Phase ◽  
High Speed ◽  
Pressure Fluctuations ◽  
Sound Radiation ◽  
Rate Of Change ◽  
Intensity Increase ◽  
Mass Loading ◽  
Local Pressure ◽  
Time Rate ◽  
Particle Laden Flows

High-speed free-shear-flow turbulence, laden with droplets or particles, can radiate weaker pressure fluctuations than its unladen counterpart. In this study, Eulerian–Lagrangian simulations of high-speed temporally evolving shear layers laden with monodisperse, adiabatic, inertial particles are used to examine particle–turbulence interactions and their effect on radiated pressure fluctuations. An evolution equation for gas-phase pressure intensity is formulated for particle-laden flows, and local mechanisms of pressure changes are quantified over a range of Mach numbers and particle mass loadings. Particle–turbulence interactions alter the local pressure intensity directly via volume displacement (due to the flow of finite-size particles) and drag coupling (due to local slip velocity between phases), and indirectly through significant turbulence changes. The sound radiation intensity near subsonic mixing layers increases with mass loading, consistent with existing low Mach number theory. For supersonic flows, sound levels decrease with mass loading, consistent with trends observed in previous experiments. Particle-laden cases exhibit reduced turbulent kinetic energy compared to single-phase flow, providing one source of their sound changes; however, the subsonic flow does not support such an obvious source-to-sound decomposition to explain its sound intensity increase. Despite its decrease in turbulence intensity, the louder particle-laden subsonic flows show an increase in the magnitude and time-rate-of-change of fluid dilatation, providing a mechanism for its increased sound radiation. Contrasting this, the quieter supersonic particle-laden flows exhibit decreased gas-phase dilatation yet its time-rate-of-change is relatively insensitive to mass loading, supporting such a connection.

Sign in / Sign up

Export Citation Format

Share Document