Indoor Positioning Method Research Using Ultrasonic And Dead Reckoning

With the development of the Internet of things(IoT)and smart space,the target location problem has been paid more attention to and its technology has been developed rapidly.Positioning system can be divided into outdoor location and indoor location according to the application environments.The satellite positioning technology is generally employed in outdoor positioning system and indoor positioning systems(IPS)are developed using various methods.For indoor location,the major research directions are as follows: infrared ray,radio frequency identification(RFID),Bluetooth,WiFi,Ultrawideband(UWB)and so on.Compared with those techniques,The processing of ultrasonic signal can be much easier and has advantage of simple and low-cost hardware.The IPS based on ultrasonic is adopted as the research project in this paper,based on the analysis and comparison of all IPS technologies.On the other hand,with the development of wireless sensor networks(WSN)and intelligent terminals in recent years,wireless networks have covered many shopping malls and offices.Since they cut the communication wiring costs and obtain large-scale applications,the existing wireless networks can be used for communication in different WSN nodes.An IPS is designed and implemented in this thesis,by combining ultrasonic and WSN technologies.In particular,the following aspects are studied in this thesis:Firstly,in the IPS based on ultrasonic and WSN,the distance values between a positioning target(PT)and anchor nodes are measured,by using time-of-flight(ToF)and speed of ultrasonic in the air.Then,the coordinates of the PT can be calculated by means of the distance values and coordinates of the anchor nodes.The ToF is the most important factor in the positioning process.The maximum of the ultrasonic envelope signal(UES)is regarded as the time of arrival(ToA)in this thesis.Considering noises existing in practical system,the digital lock-in amplifying technique is used to detect the UES,which makes the signal spectrum moving and puts the useful signal to the vicinity of the direct-current signal.Then the noises and disturbances can be removed by the digital low pass filter.The simulation and application experiments show that the digital lock-in amplifying method can detect the UES and filter noises off effectively,and the system precision and stability can be improved.An envelope detection method based on the least square method is proposed,which can also detect the UES and remove noises without a digital filter because the least square method has a good noise reduction function,and also the UES has no time delay caused by the filter.Many simulation and application experiments for this method are carried out with analysis.Secondly,the IPS only based on ultrasonic cannot meet the needs of practice applications.So,the combined positioning system based on ultrasonic and dead reckoning is studied.A method of measuring the rotation angle of the driving wheel of a mobile robot is proposed for implementation of dead reckoning,which has some advantages,such as high measurement accuracy and low cost.The extended Kalman filter(EKF)is used to fuse ultrasonic data and dead reckoning data to improve the location accuracy.Then the combined positioning algorithm based on unscented Kalman filter(UKF)is analysed and discussed to reduce linearization error which is existed in EKF.Sina the data communication is accomplished by a wireless network in IPS,there usually are data transmission delay and packer loss.The EKF with one step delay and missing measurements are respectively studied.Then their applications in the combined positioning system are analysed and discussed.Lastly,two networked control experimental platforms are developed in this PHD project.The procedures of implementing the two platforms are introduced: one is the real-time networked control platform based on the eCos operating system and a low power embedded microprocessor,and the other is a networked control platform based on android intelligent terminals and wireless actuators.When the position information of a mobile robot measured using the combined positioning system developed in this thesis is fed back to the controller,a path tracking control experiment for a wheeled mobile robot is successfully carried out.