High precision ultrasonic positioning using phase correlation

Three dimensional (3D) positioning systems are used in many applications across a wide variety of fields, including entertainment, sports science and medical treatment. Among the medical applications, emerging areas include: gait analysis, rehabilitation, medical robotics and biofeedback systems. Traditionally, these positioning systems use optical motion capture techniques. The main disadvantages of this method include its cost and setup complexity. In this paper we present a new technique for 3D positioning for medical applications using ultrasonic transmitters and receivers and a phase correlation approach for measuring the time-of-flight of these signals in the presence of multipath distortion. Our experimental results show the precision provided by the proposed system is comparable with the alternative optical systems and is acceptable for medical applications which require this high precision. However, the system cost and complexity of the proposed ultrasonic system is expected to be much less than for an equivalent optical system.