Research Of Velocity Wireless Measurement Method Based On Three Dimensional Acceleration Sensor

The rapid development of computer,network technology, semiconductor materials and electronic manufacturing technology had promoted the development of MEMS(Micro-Electro-Mechanical System),SoC(System on Chip),wireless communication and low power embedded technology.The thesis designd a velocity wireless measurement method,which was based on the ZigBee wireless transmission technology, CC2530 chip and ADXL345 three-dimensional acceleration sensor.The measurement method implemented the velocity measurement of the large machine with a low speed intermittent motion in industrial environment.The thesis discussed variety of wireless communication technologices which were gradually matured in recent years, and the applicabilities and advantages of ZigBee technology in the velocity wireless measurement of large machine with a low speed intermittent motion.Then the velocity measurement method based on ZigBee wireless transmission technology was studied, this method used the three axis acceleration sensor to measure the motion acceleration and the velocity was calculated by time integration. In order to ensure the measurement accuracy, the error sources of the accelerometer were analyzed, and the appropriate error model was established.The thesis studied the Kalman filtering algorithm and Sage-Husa algorithm, which could effectively filter the random error. According to the advantages and disadvantages of these two algorithms and combined with the actual situation of the working environment, this thesis presented an noise adaptive Kalman filtering algorithm,and the improved algorithm could effectively restrain the influence of random error and reduce the processing time.Because ADXL345 was a high sensitivity three axis accelerometer, the device jitter or the change of the sensor installation position would cause the sensor to produce the drift output,which could not be eliminated by filtering. These tiny drift outputs would be accumulated into the velocity calculation, which would lead to increasing bias in the calculation result, this was called the accumulation error. The thesis analyzed several common accumulation error compensation algorithm and summarized their respective advantages and disadvantages, and combined with the actual situation of the measuring object,the thesis designed a multi-axis accumulated error adaptive compensation algorithm.The algorithm could dynamically estimate the motion state of each direction axis,and made effective error compensation.Finally, the overall design of system was introduced, and the experimental analysis were carried out.The experimental results show that, the filtering precision of the improved noise adaptive Calman filtering algorithm was higher about 20% than that of the Calman algorithm,and the filter time consuming was lower than that of Sage-Husa algorithm. After using the multi?axis accumulation error adaptive compensation algorithm, the velocity was more close to the real velocity.