Evaluation of ultra-wideband technology for use in 3D locating systems

Abstract

A high-powered (5 Watt peak power) ultra-wideband (UWB) ranging system was evaluated for use as the basis of a 3-Dimensional (3D) locating system by comparing tracking results to a ground truth system. The UWB ranging system is composed of five ranging radios. One radio is connected to a computer and the others communicate to it wirelessly. The distance between any two of the radios is determined using a time-of-flight (TOF) algorithm provided with the system from the manufacturer. Four of the radios were placed at known locations and the fifth radio was placed at an unknown location to be tracked. The distance from each of these four fixed radios to the fifth radio was continuously measured and different tracking algorithms were implemented to calculate the unknown radio's 3D position in real-time. The algorithms tested utilized trilateration. multilateration, error minimization, and low-pass filtering. Position-versus-time data were obtained from each algorithm and compared to position-versus-time data obtained from a 3D ground truth locating system known to have an uncertainty of approximately 5 mm. Both moving and stationary tests were performed for each algorithm. During moving experiments, the tracked radio was moved along a predetermined path by an experimenter holding the radio while walking. During stationary experiments, the tracked radio remained at a single location while 1000 positions were measured by the various algorithms. The tests took place in an indoor laboratory environment which was free of obstruction in order to promote optimum performance of both the UWB and ground truth tracking systems. By analyzing the data from the UWB and ground truth systems, the error of the UWB system's 3D location measurement was expressed as a function of time.