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Liu H.,Beijing Institute of Technology | Cai Z.-C.,Beijing Institute of Technology | Zhu L.-J.,Science Research Institute of China North Industries Group Corporation | Xiang C.-L.,Beijing Institute of Technology | Huo C.-J.,Beijing Institute of Technology
Binggong Xuebao/Acta Armamentarii | Year: 2012

A nonlinear simple single stage planetary gears dynamic model that contained multiple backlashes and multiple time-varying parameters was established, wherein the backlash, time-varying mesh stiffness and its engaging phase difference, gear mesh composite errors and time-varying planet position angle were considered. According to different input rotational speed and torque, operational terms were categorized into four work conditions. The vibration behaviors were described in detail by frequency spectrum, dynamic load coefficient and load sharing coefficient. The results demonstrate that the changes of nonlinear vibration behaviors represent diverse characteristics in different work conditions. The change of nonlinear behavior that is generated by ascending rotational speed worsens vibration more clearly in light load condition than heavy load condition. At the same time, the change that is brought by increased load improves vibration more obviously in high speed state than low speed state. The change of nonlinear behavior is staged similar in frequency spectrum, each vibration characteristic parameters also have staged similar character that is consistent with frequency spectrum. It provides reference for the design of planetary gears in complicated work conditions. Source

Feng Y.,Beijing Institute of Technology | Feng Y.,Science Research Institute of China North Industries Group Corporation | Tao R.,Beijing Institute of Technology | Wang Y.,Beijing Institute of Technology
Science China Information Sciences | Year: 2012

The signal feature of propeller cavitation noise during acceleration or deceleration procedure can be used to passively detect and classify moving vessels and underwater vehicles in the port regions. By analyzing the chirp periodicity of the variation of propeller wake velocity under acceleration situation, this paper presents a time domain expression of the modulation envelope signal of the accelerating propeller noise, treating the signal as a Gaussian-shaped chirp periodic pulse train with increasing trend and fluctuating pulse amplitude. The paper investigates the characteristics of simplified fractional Fourier transform (SFRFT) spectrum of the chirp periodic signal, and thus obtains the relation between the chirp periodic signal and its chirp harmonics under the conditions of underwater passive detection. Furthermore, the experimental data of the cavitation tunnel satisfy the results obtained by simulation, which verifies the correctness of the proposed signal model. © 2011 Science China Press and Springer-Verlag Berlin Heidelberg. Source

Hu C.,Beijing Institute of Technology | Liu Z.-P.,Beijing Institute of Technology | Zeng T.,Beijing Institute of Technology | Fu B.-B.,Science Research Institute of China North Industries Group Corporation | Zhu Y.,China Academy of Space Technology
Binggong Xuebao/Acta Armamentarii | Year: 2010

The geosynchronous earth orbit synthetic aperture radar (GEO SAR) running in high orbit can capture high resolution radar image in hundreds or thousands of kilometers and offer a very effective way for target reconnaissance and accurate attack in wide swath. The large orbit height brings a lot of advantages, and causes a lot of imaging difficulties for GEO SAR. The conventional lower orbit SAR secondary range compression algorithms are based on the linear trajectory model or the Fresnel approximation. It will cause high order phase error of hundreds radians and result in severe spatial-variance in range direction when it is used in GEO SAR, thus the accurate focusing is difficult to be implemented under the conditions of long synthetic aperture time and large scene. An improved secondary range compression (SRC) algorithm to adapt the GEO SAR imaging requirements at perigee was proposed. Based on the accurate satellite curve trajectory model, the chirp rate of azimuth reference function was analytically derived, and its variance was adaptively compensated and the spatial-variance in range direction was overcome. Under the conditions of 100 seconds in synthetic aperture time and 40 km in distance, the simulation results verify the effectiveness of the algorithm proposed in this paper, and the highly accurate imaging can be implemented in GEO SAR. Source

Zhiyu S.,Beijing Institute of Technology | Yuan F.,Science Research Institute of China North Industries Group Corporation | Dongyang F.,Beijing Institute of Technology | Shunshan F.,Beijing Institute of Technology
Advanced Science Letters | Year: 2012

Small cylindrical object navigating near free-surface is subject to wave disturbance. Wave disturbance can dramatically influence the depth control of the near-surface navigating object. In order to diminish the wave disturbance, a self-regulating fuzzy depth control method based on the adaptive fuzzy control theory is proposed to keep the small cylindrical object navigate at the expected depth under free-surface. The near-surface dynamic model of the cylindrical object is introduced with the first and second order wave forces, and the fuzzy depth control model is presented. Hardware-in-loop simulation is designed to testify the validity of the control method. The results obtained by a series of hardware-in-loop simulations demonstrate that the self-tuning fuzzy depth control method performs well in stabilizing the near-surface navigating small cylindrical object and in keeping it in the expected depth under free-surface disturbances. © 2012 American Scientific Publishers All rights reserved. Source

Shao Z.Y.,Beijing Institute of Technology | Feng Y.,Science Research Institute of China North Industries Group Corporation | Jin J.,Academy of Armored force Engineering | Bian J.N.,Beijing Institute of Technology
Advanced Materials Research | Year: 2014

The Unmanned Underwater Vehicle (UUV) is used more and more widely in military and non-military areas. Since UUV's navigation and motion control system is highly complex, a Hardware-In-the-Loop Simulation (HILS) system is designed and implemented to help research and development of its navigation and motion control system. The HILS system is mainly composed of real-time simulation computer, main control compute, GPS/Beidou satellite signal simulator, three-axis turntable, actuator load simulator, water pressure simulator, acceleration simulation unit, visual computer and interface devices. Performance specifications are allocated to each components of the HILS system according to dynamic characteristics of the UUV under complicated disturbances. Proximity between the results of the UUV's HILS and sea trial demonstrates the validity of the HILS system elementarily. © (2014) Trans Tech Publications, Switzerland. Source

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