By a News Reporter-Staff News Editor at Journal of Technology -- Investigators discuss new findings in Sensor Research. According to news reporting out of Lausanne, Switzerland, by VerticalNews editors, research stated, "In this paper, we present a method for automated calibration of an implanted anisotropic magnetoresistive (AMR) sensor for measuring the internal-external rotation in a prosthetic knee without using any reference measurement. The measurement system consists of a permanent magnet and a 2-D AMR sensor configured and embedded into the prosthesis."
Our news journalists obtained a quote from the research from the School of Life Science, "Using the physical relation between the measurements of channels of sensor, we proposed a reference-free calibration method through the optimization. The parameters of the measurement model of the sensor obtained via the calibration were directly used in an angle estimator. Two different optimization approaches were tested, and the resultant estimates were compared with the reference angle with the expected +/- standard deviation of error of -1.69 degrees +/- 0.65 degrees and -1.17 degrees +/- 1.13 degrees. The reference-free calibrated estimators were also compared with the reference-dependent least-square estimators. This latter comparison showed an offset error difference among the estimators while the coefficients of determination for the both reference-free and reference-dependent estimators were high, i.e., larger than 0.91. The good performances were maintained even when using a small portion of data for the optimization. The sensor-magnet misalignment effect was also investigated."
According to the news editors, the research concluded: "The misalignment slightly worsened the mean error of the estimates, but neither dramatically affected the variance of error nor the coefficient of determination."
For more information on this research see: Reference-Free Automated Magnetic Sensor Calibration for Angle Estimation in Smart Knee Prostheses. IEEE Sensors Journal, 2014;14(6):1788-1796. IEEE Sensors Journal can be contacted at: Ieee-Inst Electrical Electronics Engineers Inc, 445 Hoes Lane, Piscataway, NJ 08855-4141, USA. (Institute of Electrical and Electronics Engineers - www.ieee.org/; IEEE Sensors Journal - ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=7361)
Our news journalists report that additional information may be obtained by contacting A. Arami, Ecole Polytechnic Fed Lausanne, Sch Life Sci, CH-1015 Lausanne, Switzerland. Additional authors for this research include J.D. Rechenmann and K. Aminian.
Keywords for this news article include: Europe, Lausanne, Switzerland, Sensor Research
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