Fraunhofer-Institut für Optronik, Systemtechnik und Bildauswertung IOSB

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  • Publication
    DecaWave ultra-wideband warm-up error correction
    ( 2021)
    Sidorenko, Juri
    ;
    Schatz, Volker
    ;
    Scherer-Negenborn, Norbert
    ;
    Arens, Michael
    ;
    Hugentobler, Urs
    In the field of indoor localization, ultra-wideband (UWB) technology is no longer dispensable. The market demands that the UWB hardware has to be cheap, precise and accurate. These requirements lead to the popularity of the DecaWave UWB system. The great majority of the publications about this system deals with the correction of the signal power, hardware delay or clock drift. It has traditionally been assumed that this error only appears at the beginning of the operation and is caused by the warm-up process of the crystal. In this article, we show that the warm-up error is influenced by the same error source as the signal power. To our knowledge, no scientific publication has explicitly examined the warm-up error before. This work aims to close this gap and, moreover, to present a solution which does not require any external measuring equipment and only has to be carried out once. It is shown that the empirically obtained warm-up correction curve increases the accuracy for the twoway- ranging (TWR) significantly.
  • Publication
    Self-Calibration for the Time Difference of Arrival Positioning
    ( 2020)
    Sidorenko, Juri
    ;
    Schatz, Volker
    ;
    Bulatov, Dimitri
    ;
    Scherer-Negenborn, Norbert
    ;
    Arens, Michael
    ;
    Hugentobler, Urs
    The time-difference-of-arrival (TDOA) self-calibration is an important topic for many applications, such as indoor navigation. One of the most common methods is to perform nonlinear optimization. Unfortunately, optimization often gets stuck in a local minimum. Here, we propose a method of dimension lifting by adding an additional variable into the l2 norm of the objective function. Next to the usual numerical optimization, a partially-analytical method is suggested, which overdetermines the system of equations proportionally to the number of measurements. The effect of dimension lifting on the TDOA self-calibration is verified by experiments with synthetic and real measurements. In both cases, self-calibration is performed for two very common and often combined localization systems, the DecaWave Ultra-Wideband (UWB) and the Abatec Local Position Measurement (LPM) system. The results show that our approach significantly reduces the risk of becoming trapped in a local minimum.
  • Publication
    Error corrections for ultra-wideband ranging
    ( 2020)
    Sidorenko, Juri
    ;
    Schatz, Volker
    ;
    Scherer-Negenborn, Norbert
    ;
    Arens, Michael
    ;
    Hugentobler, Urs
    Precise indoor localization is a major challenge in the field of localization. In this work we investigate multiple error corrections for the ultra-wideband (UWB) technology, in particular the DecaWave DW1000 transceiver. Both the time-of-arrival (TOA) and the time-difference-of-arrival (TDOA) methods are considered. Various clock-drift correction methods for TOA from the literature are reviewed and compared experimentally. The best performing method is extended to TDOA, corrections for the signal power dependence and the hardware delay are added, and two additional enhancements suggested. These are compared to each other and to TOA in positioning experiments.
  • Publication
    Self-Calibration for the Time-of-Arrival Positioning
    ( 2020)
    Sidorenko, Juri
    ;
    Schatz, Volker
    ;
    Bulatov, Dimitri
    ;
    Scherer-Negenborn, Norbert
    ;
    Arens, Michael
    ;
    Hugentobler, Urs
    Self-calibration of time-of-arrival positioning systems is made difficult by the non-linearity of the relevant set of equations. This work applies dimension lifting to this problem. The objective function is extended by an additional dimension to allow the dynamics of the optimization to avoid local minima. Next to the usual numerical optimization, a partially analytical method is suggested, which makes the system of equations overdetermined proportionally to the number of measurements. Results with the lifted objective function are compared to those with the unmodified objective function. For evaluation purposes, the fractions of convergence to local minima are determined, for both synthetic data with random geometrical constellations and real measurements with a reasonable constellation of base stations. It is shown that the lifted objective function provides improved convergence in all cases, often significantly so.