Shi Qiao Gao

Simulation of the Dynamic Characteristics of the Coupled System Structure

The human body forms a complex dynamic system with more than one natural frequency and provides considerable damping capacities. Therefore, the coupled system of a structure and the occupants can hardly be described with its basic dynamic characteristics considering only the mass of the occupants. Depending on the natural frequency of the empty structure, the human body dominantly acts like a mass, a mass and a damper or a damper. If the natural frequency of the empty stand increases 3 Hz, the human body induces considerable damping into the coupled system. In the limit, the dynamic characteristics can be described based on the average values of the characteristics of the human body.

One Kind of Flight Control System Design for Separation Section in Cruise Missile

Separation section is the most complex and dramatic stage in disturbing the cruise missile during the entire flight trajectory. The characteristic of low-altitude, low-speed, non-aileron flight separation of the missile propelled by rocket was analyzed in this paper. Classic engineering methods and neural network dynamic inversion methods was used to design control system, and two different control methods were compared.

The Dynamic Characteristics of a Couple System by Pedestrian Bridge and Walking Persons

The human body forms a complex dynamic system with more than one natural frequency and provides considerable damping capacities. In a simplified approach active persons can be modeled as external loads. While this approach may be sufficient for an activity like jumping, it has been shown already that for a bobbing person some interaction effects may occur. The question arises if also pedestrians are able to influence the dynamic characteristics of the structure they are actually crossing. Observations during a mass event with several thousand persons crossing a 66 m long bridge indicate that the damping capacity of the coupled structure may have increased. In this paper a single beam experiment was operated. The basic idea is to use a known background excitation induced by a shaker. It can be seen that both natural frequency and damping ratio have been changed comparing with empty structure. The change with passive person is stronger that an active person. Meanwhile, the linear sweep method which was used in measurement provides a good result for the analysis of dynamic properties of a structure.

Study on the Energy Harvesting Performance of PE Cantilever Beam

Harvesting ambient vibration energy through piezoelectric (PE) means is a popular energy harvesting technique. The merit of applying PE means to supply energy for microelectronic devices is that they can reduce the battery weight and possibly make the device self-powered by harvesting mechanical energy. This investigation will examine the energy generating performance of miniature PE cantilever beam through theoretical modeling, simulation and experiment testing. Through the theoretical analysis of the piezoelectric energy harvesting structure, the expression of open circuit voltage output is obtained. Using ANSYS software, the working performance of piezoelectric cantilever beam is analyzed. On the basis of theoretical analysis and simulation optimization, a set of experimental system is established to test the energy harvesting performance of the piezoelectric cantilever beam. The testing result shows that the harvested energy by the piezoelectric cantilever beam could supply electrical power to some micro electrical devices.

Corner Effect of Micro-Comb Capacitive Structure

The comb-shaped capacitive micro-machined gyroscope employing an electrostatic comb drive and capacitive sensing structure is a typical type of MEMS sensor. Because of design and processing limitation and other factors, there are problems related to parallelism, dimensional accuracy and shape accuracy of the fabricated comb capacitor. These problems induce error into the calculation of the capacitance of the comb capacitor. The capacitance of the comb capacitor can be better calculated by the modeling the corner effect with various equipotential lines.

Joint Doa-Frequency Estimation for Coherent Signal Identification

The problem of spatial temporal spectrum technique for coherent signal identification is studied in this paper. Spatial smoothing scheme is firstly introduced to spatial temporal signal processing to eliminate the singularity of array output covariance matrix, and then spatial temporal spectral analysis technique is used to realize the joint DOA and frequency estimation. Simulation results show the proposed method can indentify all the signal sources correctly even when they are full coherent.

A Space Time Autoaggressive Method Based on Parameters Estimation for Airborne MIMO Radar

The clutter distribution of an airborne multiple input and multiple output (MIMO) radar in non-homogeneous environment varies with ranges and samples in different range gates are not independent identically distributed vectors, so that the statistical space time adaptive processing (STAP) methods degrade heavily. A clutter suppression method for airborne MIMO radar in non-homogeneous environments is studied in this paper. Firstly, Space time autoaggressive (STAR) method is introduced to airborne MIMO radar for clutter suppression and then an AR model parameters estimation method for STAR is proposed to decrease the complexity of traditional method. Simulation results show the proposed method can estimate parameters exactly and rapidly with only few training samples and be fit for clutter suppression in non-homogeneous environments.

An Elevation Cosine Derivation Based Updating STAP Method for Non-Sidelooking Uniform Linear Array

The clutter distribution of airborne radar with non-sidelooking uniform linear array antennas varies with ranges and interference in different range gates are not independent identically distributed vectors, so the performance of statistical STAP methods degrade heavily. In this paper, the range dependency problem is studied and a clutter nonstationarity reducing method is proposed. This method involves in the pre-processing of elevation cosine based vector extending and subsequently statistical STAP technique. Simulation results show the proposed method can reduce the clutter dispersion significantly and outperform conventional compensation methods.

Influence of Package on Micro-Accelerometer Sensitivity

Package is one of the key technologies for micro-accelerometer. This paper researched the influence of package on the sensitivity of self-designed piezoresistive accelerometer. Based on the designed package method, the effect of thickness and elastic modulus of die adhesive, package shell materials and signal connection wires on the sensitivity of the sensor were studied by theory analysis, simulation and experimental test. According to results, the sensitivity of micro-accelerometer would be increased with the increasing thickness of die adhesive and decreased with increasing elastic modulus and the quantity of the die adhesive; besides, compared with accelerometer packaged by ceramic shell, the sensitivity of accelerometer packaged with the stainless steel shell was much bigger; meanwhile, the output sensitivity of the sensor varied with length of signal connection wire.

Structure Design and Simulation Analysis of Multiple Micro Piezoelectric Cantilevers

In order to effectively capture the environment vibration energy, convert it into electricity and supply energy for the microelectronics devices, multiple micro piezoelectric cantilevers are designed. It is composed of more than one piezoelectric cantilever array, which broaden the resonant frequency band of the piezoelectric vibrator, and it can produce resonance or similar to the resonance in a frequency range. Compared to a single piezoelectric cantilever, multiple piezoelectric cantilevers can effectively broaden the resonant frequency and improve the piezoelectric power generation capacity. The simulation results show that the finite element method can provide important theoretical guidance for the structural design of multiple micro piezoelectric cantilevers.