Research On RF Synchronization And UKF Algorithm For Indoor Ultrasonic Location System

Ultrasound location is an important accurate location method for the moving objects in the indoor environment. In many complex and severe indoor environments, it can provide more accurate coordinates information for the moving staff or mobile terminal which need to know their own locations, thus it will ulteriorly achieve intelligent operation services based on the location information.However, during the actual operation, there are many factors influencing the location accuracy. The separation layout of ultrasonic transmitter and receiver can cause ranging time delay, this paper set RF synchronization between the ultrasonic transmitter and receiver to increase the timing synchronism, thereby to improve the accuracy of distance measurement time. In addition, since measurements will be disturbed by a variety of random noises in the environment, then it results in the positioning coordinate values to be untrue, this paper uses unscented Kalman filtering(UKF) to reduce the noise error, and then it will further improve the system's location accuracy.The main research works completed by the author include:1. The paper studied the domestic& international situation and development tendency of indoor positioning system, and analyzed the domestic& international application of RF technology. Given the requirements of centimeter level measurement accuracy range, it proposed the positioning scheme based on RF and ultrasonic technology.2. It used the programmable, low-cost, low power CC1100 chip to design RF transceiver modules, and the transmitting frequency is 433MHz band which needn't to apply for the frequency range permission. The module can be independently configured as the transmitter or receiver module, to implement RF synchronization when executing the ultrasonic ranging.3. It designed system control module for RF modules using ATmegal6L SingleChip, and the SCM can achieve SPI communication control for RF modules by in-system programming.4. This paper completed RF module hardware design and circuit board production, as well as software programming. Then the author did ID identifier code experiment to distinguish different RF modules, and also wirelessly monitored the systematic temperature. These experiments proved RF synchronization function, and wirelessly transmitted the coordinate information of nodes.5. The system used the trilateration principle, redundant nodes to analyze positioning scheme. While computing 3D coordinates of the moving objects using the least square method, this paper made use of the unscented Kalman filtering algorithm to reduce signal interference caused by random noises in the environment, and got filtering estimates of the target trajectory's continuous measurements. Meanwhile, the author did MATLAB simulation for the extend Kalman filtering (EKF)and UKF algorithms. Compared with EKF algorithm, the experiments showed that UKF has the best estimated effect, simultaneously, the estimated and actual trajectories have the best fitting degree. More important is, this paper realized algorithm optimization.