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Proceedings Paper

Managing piezoelectric sensor jitter: kinematic position tracking applications
Author(s): Malome T. Khomo
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Paper Abstract

Piezo-acoustic distance tracking sensors have challenges of reporting true distance readings. Challenges include directional anisotropy signal loss in transmission power and in receiver sensitivity, distance-related attenuation of signal and the phase shifts that result in jittery values, some preceding, and others succeeding the expected distance readings. There also exist signal time losses arising from dead time associated with processor latency, with carrier signal pulse length and with voltage rise-time delays in pulse detection. Together these factors cause distance under-reporting, and more critically, makes each reported value uncertain, which is unacceptable in distance-critical applications.

Piezo-inertial accelerometers have equivalent if not more severe challenges in tri-axial configurations, for instance where a rotational tilt may happen under linear accelerative force. In the absence of tensor component adaptation to change of orientation, signal is lost until the next axial sensor detects it.

Study paper focusses on piezo-acoustic transducers UCD1007 and 400SR160 (40kHz), used in a face-to-face configuration over a 600mm range. Within that range 10 successive phase shift wave fronts were identified, but it took 15 reconstructed wave fronts to uniquely identify a continuous end-to-end jitter-free and slippage-free kinematic data stream from the jittery sensor data. The additional 5 degrees of freedom were consumed by the 5-stage filter applied. The technique has remarkable combinatorial and projective geometry implications for digital sensor design. It is possible for the procedure to be applicable in 3-axis accelerometers and adapted into firmware for truly kinematic device driver interfaces so long as the reporting rates are matched with the user interface refresh rates.

It is shown that acoustic transducer sensors require phase loop locking for kinematic continuity whereas gravimetric accelerometers demand better measurement time consistence in sensor values for induced kinematic phase locking.

Paper Details

Date Published: 3 February 2017
PDF: 8 pages
Proc. SPIE 10036, Fourth Conference on Sensors, MEMS, and Electro-Optic Systems, 100360M (3 February 2017); doi: 10.1117/12.2242736
Show Author Affiliations
Malome T. Khomo, Univ. of Limpopo (South Africa)

Published in SPIE Proceedings Vol. 10036:
Fourth Conference on Sensors, MEMS, and Electro-Optic Systems
Monuko du Plessis, Editor(s)

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