Papers by Author: Hai Peng Liu

Abstract: 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.

Abstract: In MEMS, the size of micro-structure is usually in the micron and even nanoscale. It's easier to form capillary phenomenon than the macroscopic system. In view of this phenomenon, this article is based on the micro-mechanical gyroscope as the research object, to analyze the occurrence of capillary condensation of adhesion phenomenon. Firstly, we derive the Kelvin equation for capillary condensation, and then combination of the Kelvin equation introduce the capillary condensation of the adhesion phenomenon; Secondly, it analyzes the dynamics characteristics of its structure existing the liquid bridge, and analyzes the causes of the liquid bridge; Finally, it analyzes the capillary adhesion phenomena on the performance of the micro-mechanical gyroscope,as well as how to avoid the generation of capillary condensation adhesion.

Abstract: 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.

Abstract: The micro-machined gyroscope is a kind of typical micro-electro-mechanical sensor, its typical working mode is electrostatic drive and comb capacitive detection. As for as the transverse detection capacitance structure now commonly used, we find out that the relationship between capacitance variation and displacement is nonlinear through analyzing its detection capacitance. This nonlinearity will greatly affect the dynamic performance of micro-machined gyroscope.

Abstract: 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.

Abstract: 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.

Abstract: The stability and accuracy of the drive mode are important for the performance of vibrating MEMS gyroscope. At present, the PI-like controller is always used in the control of the drive mode of vibrating MEMS gyroscope. The PI-like control has good effect on rejecting the literal disturbance, but it can’t reject the time-dependent disturbance well. The disturbance for the MEMS gyroscope is so uncertain that the stability and accuracy of the PI-like control for the gyro are comparatively low. In this paper, an ADRC method for vibrating MEMS gyroscope drive is introduced, and it is proved that this method can rapidly and stably control the MEMS gyro drive mode by simulation and comparing with the PI-like method.