Research On High-precision Indoor Three-dimensional Positioning Technology Based On Ultrasound

With the progress of the information age and the development of the Internet of Things technology,the demand for obtaining location information in indoor environments is increasing.Due to the wide variety of indoor positioning technologies and the different positioning accuracy and applicable scenarios,there is no universal high-precision indoor positioning technology solution.For some common application scenarios,such as the need for three-dimensional positioning of employees or robots in large warehouses,obtaining vehicle location information in underground parking lots,and obtaining personal location information in large airports or hospitals,high-performance positioning technology can not only provide convenience for people,but also significantly improve work or production efficiency,with high application value and commercial value.This paper is based on the research of ultrasonic positioning technology,with the purpose of improving the current positioning accuracy of this technology.The main work and innovation points of selecting an ultrasonic ranging and active positioning scheme to locate targets in indoor visual range environments are as follows.Firstly,a signal transit time calculation method based on the ultrasonic sensor model is proposed to solve the accuracy problem of the distance calculation between the target point and the base station.Based on the equivalent circuit of the ultrasonic sensor,the transfer function model of the signal at the receiving end is established to make the original signal used in the calculation of the ultrasonic transit time more consistent with the actual situation.For this purpose,a digital phase locked amplifier and a transit time calculation and correction method are designed.Simulation experiments have verified that the calculation error of the transit time of the algorithm in a noiseless environment is 3.10×10^-6s。Then,an improved Time Of Arrival（TOA）optimization algorithm is proposed to solve the target location problem with known ranging information.Based on the TOA algorithm,this algorithm derives an analytical form for further optimizing the positioning results under known distances and initial estimated positions in detail.It not only has iterative convergence characteristics,but also has the advantage of small computational complexity of the analytical algorithm.Through simulation experiments,it is verified that this algorithm not only greatly improves the positioning accuracy based on the TOA algorithm,but also has better performance,uses fewer base stations,and is less affected by the target location compared to the Chan algorithm and Fang algorithm based on the arrival time difference.With a ranging error of 1cm as the standard deviation,the positioning accuracy of the algorithm for spatial independent positions is 1.66 cm,and the positioning accuracy for a given reference trajectory is 1.93 cm.Finally,a comprehensive simulation experimental model of ultrasonic indoor three-dimensional positioning is built to verify the feasibility and accuracy of the entire ultrasonic positioning algorithm.According to the limitations of practical application scenarios,two base station layout schemes,closed and open,are given.The experiment generates the original ultrasonic signal received by each base station in an environment where the temperature and noise are determined,taking into account the ultrasonic attenuation characteristics.Further,a signal transit time algorithm based on the ultrasonic sensor model is used,and the distance between the current position of the target trajectory and each base station is obtained by combining the ultrasonic speed.On this basis,the improved TOA optimization algorithm,Chan algorithm,Fang algorithm,and TOA algorithm are used to calculate the location and compare the positioning results.The experimental results show that compared to the other three algorithms,the improved TOA optimization algorithm has the highest positioning accuracy,and is less affected by the base station layout scheme and spatial location.The accuracy under the closed base station layout scheme is 1.44 cm,and the accuracy under the open base station layout scheme is 1.98 cm.