Abstract:An autonomous vehicle operates in a dynamically changing environment, where multiple sensors must work in a cooperative mode. In these scenarios reliability of the communication protocol carries a lot of importance in real time data transfer. In this paper, CAN communication is used to demonstrate sensor integration using a LIDAR and a camera. Also demonstrated is a novel method for object detection, obstacle avoidance and navigation of an autonomous RC vehicle.

Abstract:In order to test the static and dynamic performance of a Global Positioning System (GPS) receiver, a GPS signal simulator is required to generate real satellite signals in various environments. The software simulator is widely used because of the advantages of being flexible and reprogrammable. Therefore, a digital intermediate frequency GPS signal software simulator which implemented using MATLAB software is proposed. It is a method to calculate the satellite ephemeris parameters by using the anchor point, satellite elevation angle and azimuth angle, and to achieve navigation information transmission delay by modifying the C/A code frequency based on analyzing the positional relationship between the satellite and the receiver. The simulation results show that the simulator is correct and effective. When the receiver is stationary and the satellite is moving, the receiver positioning error is less than 1 m.

Abstract:Recently, the fault diagnosis of the ball mill mostly depends on the experience of workers, which brings about a lot of uncertainty for fault diagnosis. In addition, the cost of labor is getting higher, so that the research of ball mill fault diagnosis based on machine learning has become increasingly valuable. The current fault diagnosis methods are mostly judging based on instantaneous data, which makes it difficult to reflect the ball mill indicators and the occurrence of time-related correlation (such as hysteresis effect). This paper presents a ball mill fault diagnosis method based on Gate Recursion Unit (GRU), which analyzes the fault data in the form of time series and compares with other common methods such as neural network, Autoencoder and Long Short-Term Memory (LSTM). After comparison, it is concluded that the fault diagnosis method based on GRU ball mill has the lowest error rate as 4.85%.

Abstract:To improve the efficiency of MEMS piezoelectric vibration energy harvesters (PVEHs), the bulk lead zirconate titanate (PZT) has been used to substitute the thin film PZT for the higher mechanical-electrical coupling coefficients. The expensive equipment of micromachining set a high entry barrier on the research of PVEHs with high efficiency. To solve this issue, this paper developed an efficient PVEH with bulk PZT using common precision machining, whose dimensions and electrical outputs are comparable to the MEMS devices. After numerically analyzing the effects of the length ratio of the proof mass to the harvester on the output power, a compact PVEH consisting of a cantilevered uni-morph and a tungsten proof mass was designed. Simulations show that the mechanical damping ratio and the thickness have little effects on the optimized length ratio. By using a uni-morph with the copper structural layer of about 80-90μm and the bulk PZT-5H layer of 139μm, a low-cost harvester prototype was assembled. The key parameters of the prototype were experimentally identified and compared with the theoretical predictions. Under the harmonic base excitation of 0.4g (where g = 9.8m/s2) at 160 Hz, the maximum output power of the prototype is about 76.7μW, with the normalized power density of about 3.35mW/cm3/g2. Under base excitation of 0.4g at 159Hz, the prototype charged a 680μF capacitor from 0 to 4.84V in about 154 seconds.

Abstract:The acoustic vibration characteristics of landmines are investigated by means of modal analysis. According to the mechanical structure of landmines, a certain number of points are marked on the landmine shell to analyze its multi-modal vibration characteristics, based on laser self-mixing interferometer and taking 69 plastic landmine as an example, the vibration detection experiment system is built to show the results of analytical method of multi-modal testing. The first and second order natural frequencies of the bricks are 38 HZ and 106 HZ, 112HZ and 232HZ for plastic landmines, and 74HZ and 290HZ for metal landmines. The first and second order natural frequencies of the bricks are far smaller than those of plastic landmines and metal landmines. This indicates that landmines show multi-modal vibration characteristics under external excitation, which are significantly different from those of bricks. The findings can be used for further research on acoustic landmines detection technology.

Abstract:The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity are increased, and the costs are decreased. The process parameters of relay production lines are studied based on the long-and-short-term memory network. Then, the Keras deep learning framework is utilized to build up a short-term relay quality prediction algorithm for the semi-finished product. A simulation model is used to study prediction algorithm. The simulation results show that the average prediction absolute error of the fraction is less than 5%. This work displays great application potential in the relay production lines.

Abstract:Hole-drilling method is a commonly used method for measuring residual stress. The calibration coefficients in ASTM E837-13a would cause large errors due to the plasticity deformation of materials. In the study, calibration coefficients were modified in the plasticity deformation stage based on the distortion energy theory. The calibration experiment of calibration coefficients was simulated by the finite element model, and the plasticity modification formulas of 7075 aluminum alloy were obtained. From the results of uniaxial tensile loading test, the measuring errors of high residual stress are significantly reduced from -4.071% ~ 53.440% to -5.140% ~ 0.609% after the plasticity modification. This work provides an effective way to expand the application of hole-drilling method.

Abstract:The air-kerma is one of the most important physical quantities in ionizing radiation dosimetry. The measurement of air-kerma rate in narrow-spectrum series is the basis to determine the radiation dose at protection level. In this article, the absolute measurement method is used to derive the standard air-kerma rate of the ISO 4037 narrow-spectrum series that ranges from 60 kV to 150 kV by a primary standard ionization chamber, it is used in direct comparison for air kerma. The indirect method is used to obtain the air-kerma rate by a secondary standard transfer ionization chamber named A5 chamber with calibration factors of the corresponding reference qualities. The results are very similar comparing between absolute and indirect methods for air-kerma rate, all the differences are within ±3.3%.