The paper describes how laser interferometry can be used to respond to the increasing demands from industry and elsewhere that the traceability of vibration and shock measurements to SI units be established or improved. As an example of the top level of a hierarchic traceability system, the paper focuses on six different national standard devices using laser interferometry to ensure the realization and dissemination of the three translational motion quantities: acceleration, velocity and displacement, and the three rotational motion quantities: angular acceleration, angular velocity and rotation angle, in wide measurement ranges with sinusoidal, shock-shaped and other user-defined time histories. The application of the methods to the primary calibration of transducers (including laser interferometers as calibration objects) is demonstrated. The high accuracy of the primary calibration facilities serves, among other things, to investigate the behaviour of special laser vibrometers intended to be qualified as reference laser vibrometers applicable as a sub-system of calibration equipment, e.g., in a service calibration laboratory.
Schlagwörter: Beschleunigungsaufnehmer, Referenznormale, Absolutkalibrierung, Interferometersignale, Signalverarbeitung Es wird ein für die Absolutkalibrierung von Beschleunigungsaufnehmer-Referenznormalen geeignetes Verfahren zur zeitdiskreten Regelung sinusförmiger Schwingwegverläufe im breiten Schwingwegamplitudenbereich von 50 μm bis 500 mm vorgestellt. Dieses Verfahren erlaubt gleichzeitig die Echt-Zeit-Bestimmung der Schwingungsparameter Weg-Amplitude und Nullphasenwinkel und daraus abgeleiteter Größen durch Anwendung der Methode der kleinsten Abweichungsquadrate. Die Grundlage für Regelung und Messung bildet die Rekonstruktion der Schwingung als zeitdiskrete Phasensequenz aus dem Fotoempfän-gerausgangssignal eines Michelsoninterferometers. Über Simulationsrechnungen werden die maximalen Meßabweichungen unter dem Einfluß verschiedener Störquellen und die maximal erreichbare Unterdrückung nichtlinearer Verzerrungen analysiert. Die Leistungsfähigkeit der vorgeschlagenen Verfahren in der Praxis wird mittels eines DSP-basierten Meßsy-stems an einem Tieffrequenz-Langhuberreger mit einem Arbeitsfrequenzbereich von 0,1Hz bis 20 Hz nachgewiesen.
Time-discrete control of steady motionforms using real-time processing of interferometer signalsA method for time-discrete control of sinusoidal vibration in the wide displacement amplitude range of 50 μηι to 0.5 m which is applicable to absolute calibration of reference standard accelerometers is presented. The least square sum method used for the real-time identification of the motion parameters allows the amplitude and initial phase angle of the displacement and derived motion quantities to be accurately measured. The motion control and measurement method is based on the reconstruction of the vibration as sequence of discrete phase values derived from the photodetector output signal of a Michelson interferometer. The maximum error components for different disturbing sources and the maximum achievable suppression of non-linear distortions are analyzed by computer simulation. The performance of the method 116 under the practical conditions was investigated by means of a DSP-based measuring system in combination with a low-frequency long-stroke vibration exciter in the operational range of 0.1 Hz to 20 Hz.
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