Ambulatory Estimation of Relative Foot Positions using Ultrasound

D. Weenk, Michiel van der Coelen, Arno A.G. Geessink, Frank J. van der Hoek, Bart Verstoep, H.G. Kortier, Fokke van Meulen, Bernhard J.F. van Beijnum, Petrus H. Veltink

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    The recording of human movement is used for biomedical applications like physical therapy and sports training. Over the last few years inertial sensors have been proven to be a useful ambulatory alternative to traditional optical systems. An example of a successful application is the instrumented shoe, which contains two 6D force/moment sensors beneath the heel and the forefoot and two inertial sensors rigidly attached to the force/moment sensors [1]. These shoes can be used for ambulatory assessment of walking kinetics and kinematics. The relative position of the feet is currently not measured directly but estimated from double integration of feet accelerations. However, this method immediately leads to large position errors (drift) when the estimated inertial accelerations are inaccurate. In this study we investigated the ambulatory estimation of the relative positions of the feet using ultrasound transducers. On one shoe we mounted a 400PT120 Air Ultrasonic Ceramic Transducer (13 mm diameter, 10 mm height, 85º beam angle) sending a 40 kHz pulse to a similar transducer on the other shoe. Using the time of flight, the distance is estimated. Under static conditions a mean error of 5.7 ±0.8 mm was obtained over a range of 5 till 75 cm [2]. From this pilot study we concluded that the distance between the feet can be estimated ambulatory using small and low-cost ultrasound transducers. Future research includes the use of multiple transducers on each foot for a distance measure during different daily-life activities. Also the relative positions of the feet will be investigated by fusing the distance estimates with inertial sensor data.
    Original languageUndefined
    Title of host publicationFourth Dutch Conference on Bio-Medical Engineering
    Place of PublicationEgmond aan Zee, The Netherlands
    Number of pages1
    ISBN (Print)not assigned
    Publication statusPublished - 24 Jan 2013
    Event4th Dutch Bio-Medical Engineering Conference, BME 2013 - Hotel Zuiderduin, Egmond aan Zee, Netherlands
    Duration: 24 Jan 201325 Jan 2013
    Conference number: 4

    Publication series



    Conference4th Dutch Bio-Medical Engineering Conference, BME 2013
    Abbreviated titleBME
    CityEgmond aan Zee
    OtherFourth Dutch BME Conference
    Internet address


    • EWI-23013
    • METIS-296274
    • IR-83739
    • BSS-Biomechatronics and rehabilitation technology

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