An Ultra-wideband And Inertial Positioning System

Ultra-Wideband(UWB) Ranging and Communication Modules(RCM) allow reliable distance measurements and data transmission in a wide variety of applications, a typical one being Unmanned Aerial Vehicle(UAV) or Unmanned Ground Vehicle(UGV) positioning with a precision far surpassing that of a GPS system, or in GPS denied areas. Several modules can be combined to provide a 2D or 3D position, as well as attitude.The work presented here has three main parts: the first is interfacing with, characterizing and evaluating the UWB modules used.The second part focuses on implementing high precision distance measurements using a couple of modules with different filtering methods and different parameters, and comparing the results. This yielded precisions of a few millimeters, with sampling frequencies largely dependent on the parameters used.The third and most important part is the design and building of a 2D positioning and heading determination system combining UWB measurements from four modules and inertial measurements. This was done by using a geometrical method for determining positions, velocities and heading from the UWB measurements, and getting accelerations and angular velocities from an Inertial Measurement Unit(IMU). Then a 3D(2D position + heading) Kalman filter was used in conjunction with modified median filtering for noise reduction. Precisions of a few millimeters and less than 0.5 degrees were reached that way, with a sampling frequency of 8 to 11 Hz. All the processing is done in real time either on a microcontroller or a computer through a bluetooth link.A mobile platform has also been set up to simplify measurements taken on the system and be used for future extensions of the system.