Study On Metrological Traceability Of Automobile Emissions And Ultrasonic Field Based On Opto-electronic Hybrid Technology

Measurement is one of the most important sources for us to acquire information,and thus it must be reliable and traceable. A core concept in measurement ismetrological traceability, defined as the property of the result of a measurement or thevalue of a standard whereby it can be related to stated references, usually national orinternational standards, through an unbroken chain of comparisons, all having stateduncertainties. And this will unite unit and value. At present, livelihood measurement,such as those applied in environmental protection and medical care, is being paidgreat attention. Since photo-electronic hybrid technology has advantages in highprecision, long distance, wide range, non-contact measurement, easy for controllingand storing information and realizing automatic operation, it becomes an importantmeans of metrological traceability.This paper is a systematic study of the traceability of chassis dynamometers forautomobile emissions testing with photo-electronic hybrid technology. First of all, thispaper proposed a way to calibrate chassis dynamometers for automobile emissionstesting. Based on photoelectric technology, a standard instrument called coast-downtime tester is devised for calibration. Besides, the paper studies characteristicparameters of coast-down time tester and a way to calibrate coast-down time tester,and traceability system for chassis dynamometers for automobile emissions testing isestablished. Secondly, according to current situation of safety inspection to the outputof medical ultrasound equipment, a three-dimensional digital schlieren–technique isproposed to measure parameters of ultrasonic field, such as the maximum value of theultrasound instantaneous peak intensity, negative acoustic peak pressure, acousticintensity of beam. A device is designed and analyzed theoretically to measureultrasonic field using three-dimensional digital optical technology. The feasibility ofthis method is confirmed by experimental data. The main work in this paper isreported as the following:By analyzing structure and technical specifications of chassis dynamometers forautomobile emissions testing, the paper gives the characteristic parameters, calibrationmethods, standard set-ups and environmental conditions of ‘chassis dynamometers forautomobile emissions testing’ for the periodic calibration. Coast-down testing withtwice constant-force loading method, a new way to get the DIW (DynamometerInertia Weight) of chassis dynamometers, is proposed. To prevent cheating whenusing software of ‘chassis dynamometers for automobile emissions testing’ during thecalibration of coast-down time with constant-force loading, a preloading method isused and its theoretical formula is derived. Finally, the calibration method is proved tobe reasonable and accurate by experimental data and analysis of uncertainty of measurement results. The method can satisfy calibration and traceability requirementsof chassis dynamometers for automobile emissions testing.In this paper, according to the methods that we have proposed for calibration ofchassis dynamometers for automobile emissions testing, especially taking intoaccount its traceability, a coast-down time tester based on photoelectric technology isdeveloped as calibration standard equipment, and an on-line real-time data samplingprocessing system which can get speed, time interval, force value and otherparameters of chassis dynamometer in real-time is developed. Two high-speed opticalisolations that can isolate signals produced by optical encoder system effectively areused to increase the anti-interference ability and work stability of the coast-down timetester. Quadruple frequency circuit is devised to improve the measurement accuracy. Amethod that uses cross mean value three times to measure coast-down time is firstproposed in this paper. This method can not only satisfy accuracy requirements ofspeed determination, but also reduce the timing error caused by speed determinationtime. Making a study of the experimental data, the paper confirms that the coast-downtime tester with contact-type sampler can synchronize with ‘chassis dynamometers forautomobile emissions testing’ and their speed difference is less than0.02%, and theMPE of coast-down time is less than±3ms. The uncertainty of the measurementresult of coast-down time calibration is less than one-third of the MPE（maximumpermissible errors）of coast-down time that is prescribed in performance requirementsto chassis dynamometers. The uncertainty fully meets calibration requirements ofchassis dynamometers for automobile emissions testing.In order to better the traceability system of automobile emissions testing, theparameters that represent characterization are proposed for coast-down time tester. Atmeanwhile the calibration methods, standard set-ups and environmental conditions ofthe calibration are determined. By analysing the experimental data and uncertainty,the calibration methods proposed in this paper are proved to be correct and reasonable.It can satisfy calibration and traceability requirements.In order to solve traceability issues of safety inspection to the output of medicalultrasound equipment, a method using optical three-dimensional digital fringetechnology is proposed to research ultrasonic field. A measuring system is studiedand designed, which adopts iterative algorithm to calculate the phase distribution ofthe plane that ultrasonic pulse just passed the sound field through light intensitydistribution image obtained by CCD. When the ultrasonic transducer is rotated from0to180degrees along the axis that is perpendicular to the direction of propagationincidence pulse light waves, many phase distribution slices are gained. Thenthree-dimensional phase distribution map is reconstructed based on chromatographyalgorithm, and three-dimensional sound pressure distribution of pulsed ultrasound field can be gained according to the relationship between phase, refractive index andpressure distribution. Finally, the characterization security parameters of medicalultrasound equipment’s output can be obtained. The improved theory of GS iterativealgorithm and Radon filtered back projection reconstruction algorithm ofthree-dimensional phase images are researched. In addition, the methods of samplingfrequency and filter choosing in the process of three-dimensional reconstruction aredetermined. The relation between refractive index and sound pressure is derived andcalculated. Finally, an experiment device based on optical three-dimensional digitalstripe technology is set up to research ultrasonic sound field and to obtain preliminaryexperimental results. Comparing with the results by hydrophone scanning method,data analysis shows that the consistency of these results is satisfactory. It is provedthat3D stripes imaging technology method is feasible in both theory and practice. Thestudies in this paper provide a basis for further realization of optical safety inspectionto the output of medical ultrasound equipment.