Three sources, three receivers, six degrees of freedom: An ultrasonic sensor for pose estimation & motion capture

Motion capture systems have become a common utility in a wide variety of fields and rely on various underlying principles to estimate the pose of one or multiple mobile objects. The most popular applications for pose estimation systems can be found in the entertainment sector where it is used for computer animation purposes or in sports for performance measurements. These systems present millimeter accuracy but also come with a high cost. We wish to reduce the cost of such a motion capture system while retaining the high accuracy by using an embedded ultrasonic measurement system. The proposed system comprises of one or multiple mobile nodes containing a small microphone array (at least 3 microphones) which receives multiple simultaneously emitted coded and broadband ultrasonic transmissions from at least three fixed transmitters. Using this technique, the complete pose (six degrees-of-freedom) of every mobile sensor can be estimated while retaining the low-cost aspect of the system. Motion capture systems which combine low cost with high accuracy open many new fields of application such as physiotherapy practices.