Key Engineering Materials Vol. 613

Abstract: As applied to the dimensional inspection the peculiarities of 3D objects image formation with clear shadow projection under their illumination by quasi-monochromatic partially coherent light based on the constructive theory of 3D objects formation using a model of equivalent diaphragms are studied. Two threshold algorithms for determining the position of 3D objects geometric boundaries under their inspection by optical shadow method according to their thickness as well as the light source angular size and the projection system aperture diaphragm are developed. These algorithms are based on the application of true (calculated) threshold or standard one using the corrective component to threshold. It has been shown theoretically and experimentally that their use can significantly improve the measurement accuracy of extended objects. The obtained results under the development of measuring systems for industrial inspection of ceramic details allowed us to reduce the measurement error.

Abstract: In order to measure the parallelism of two thin parallel beams in multi-axis interferometers and differential interferometers, the autocollimation principle was used by locating a CCD at the focal plane of collimation lens, the two beams converge on CCD image plane at different points when they are not parallel, and the distance between the two converging points is used to calculate the parallelism of the two beams. To achieve high accuracy and low system error, the CCD defocus and tilt should be strictly controlled according to the accuracy requirement. A centroid algorithm with grey threshold was used to reduce the influence of image noise. A beam-selected structure was designed to let the two beams converge to the CCD image plane in sequence to avoid superposition of beam spots. An experimental setup is built to verify the validity of the method. Experimental results show that the system has a centroid position resolution of 0.05 arcsec and a centroid position stability of 0.4 arcsec. It is therefore concluded that the method can be used to measure parallelism that is more than few arcsecs for two thin beams. Moreover, the measuring accuracy of this method can be improved when higher centroid position stability is achieved.

Abstract: It is proposed in this paper to use phase only liquid crystal spatial light modulators to realize non-mechanical lateral and axial confocal microscopic laser scanning. With a phase only liquid crystal spatial light modulator used as a scanner to realize laser beam deflection, a confocal microscopic lateral beam scanning system is designed. A zoom illuminating lens is formed by incorporating a liquid crystal spatial light modulator along the confocal illumination light path, and thus the focus of the objective lens is axially shifted to realize the axial non-mechanical scanning. The theoretical analyses indicate that phase only liquid crystal spatial light modulators can be used to realize non-mechanical 3D confocal microscopic laser scanning.

Abstract: The article is devoted to the suggested technique of on-line uncertainty calculation in non-contact temperature measurements, which can be used as a basic algorithm for smart measuring systems, e.g. intelligent radiation thermometers. As the initial data for uncertainty evaluation we use a priori information about heat detector characteristics, calibration curves along with their related uncertainties, estimated ambient temperature and external information of correction factor that should be inputted in a probabilistic form. We suggest utilizing models based on a characteristic function, in order to evaluate the combined uncertainty. In our opinion, the discussed principles are applicable for lots of other areas of measurement, especially, where it is critical to improve effectiveness of subsequent decision-making.

Abstract: With an increasing concern about renewable resource, piezoelectricity has gained significant importance in research for extracting renewable resource from the environment. In this work, a piezoelectric energy harvester is developed, which composed of polyvinylidene fluoride (PVDF) and a fan structure, to generate electric power from wind energy. The voltage/power responses were evaluated when subjected to various wind speeds. Three laminated piezoelectric PVDF specimens were tested in this study. A series of experiments demonstrated a peak voltage 21.6v and a maximum power density 5.64mw/cm³ is generated respectively when the wind speed is 9m/s.

Abstract: Pre-stressed piezoelectric unimorphs show enhanced actuation displacements and high efficiency of energy harvesting compared with conventional unimorphs. A method to increase the amount of stored energy by injecting elastic energy to energy harvesting system consisting of the THUNDER device is described in this paper. A stretching spring is mounted on the two tabs of THUNDER device in order to inject energy to the system. The mechanical stress applied on THUNDER device results in an increase in the initial stored mechanical and elastic energy, which contribute to the improved response of the modified device. In experiment, two different springs were added on the THUNDER device: one's initial length is 17mm with k=45N/m and another is 33mm with k=145N/m. For the THUNDER device with a spring of k=145N/m and a proof mass of 8.2g, the maximum open circuit V_RMS was 29.4V, and output power of 4.53mW was obtained by a load resistor of 90 kΩ at vibration frequency of 51Hz. Compared with standard device, the energy density or the output power at resonance frequency increased by 74.4%. The displacement performance of the modified devices was larger than that of the standard device. Through measurements and analysis, after a stretching spring was attached to the THUNDER device, dielectric constant did not change obviously, while d₃₁ increased a lot. We can conclude that the improvement of energy harvesting is mainly due to the increase of d₃₁ and stress distribution in the THUNDER device. Furthermore, the use of an initial energy injection mechanism based on a nonlinear approach can artificially enhance the conversion abilities of piezoelectric materials.

Abstract: A small deformable mirror which realizes concave shape as well as convex shape has been developed. In addition, this deformable mirror was developed to realize long term stability. For this purpose, a new push-pull actuator using two multilayered piezoelectric actuators aligned inline was designed. In this process, a practical method for simulating the property of piezoelectric actuator in the finite element method was proposed. From the experimental results, it was confirmed that newly developed deformable mirror has the ability to make complex profiles. Furthermore, efficiency of proposed simulation method was also confirmed.

Abstract: Equipment technical state monitoring systems contain hundreds of vibration and temperature sensors for real-time health monitoring of machinery. Monitoring systems reliability should significantly exceed the units stock reliability, being protected from accidents and incidents.The paper considers the approach to monitoring systems reliability growth, primarily by means of providing control (monitoring) of measuring-converter path technical condition. Sensors are the weakest point, due not only to wear, but also to damage, caused by repair personnel when servicing equipment. The self-diagnostics method for channels with piezoelectric transducers and the choice of optimal self-diagnostics circuits parameters have been suggested. The results of practical implementation have been provided as well.

Abstract: A real-time temperature measurement system was designed for end-face sliding friction pairs with an infrared (IR) probe and IR thermography installed on it. The approximate temperature of contact surface was measured by the probe while non-contact surface’s temperature distribution was determined with the IR thermography. Two experiments with constant load but varied rotational speeds were carried out, and a preliminary study was made to analyze the variation of temperature in the friction process. Furthermore, the probe data was used as thermal load to calculate the temperature field by the FEM model and the result was verified using IR images. The experimental results showed that the infrared measurement system can detect and record the interface-temperature variation accurately. The probe data showed a good dynamic performance with the variation of friction coefficient. In addition, the calculated temperature field showed good accordance with the IR thermography data.

Abstract: The performance of a fire sensor has a significant effect on fire detection. Today’s fire alarm systems, such as smoke and heat sensors, however are generally limited to a close proximity to the fire; and cannot provide additional information about fire circumstances. Thus, it is essential to design a suite of low-cost networked sensors that provide the capability of performing distributed measurement and control in real time. In this work, a wireless sensor system was developed for fire detection. The purpose of this paper is to analyze the integration of traditional fire sensors into intelligent fire management systems by using the smart transducer concept. An automated video processing sensor for fire smoke monitoring applications is integrated into an surveillance network as a case study and supported sensor fusion assessment to improve the resistance to nuisance alarms. The proposed sensor system for fire detection was developed to reconcile issues related to proliferation and interoperability, and the architecture can support a smart transducer interface (IEEE 1451). The proposed embedded system for STIM (smart transducer interface module) and NCAP (network capable application processor) will be implemented with DSP. To realize the self-identification of transducers and plug-and-play connections, a transducer electronic data sheet (TEDS) is also stored inside the DSP. The acquired sensor data are pre-processed and applied to discriminate nuisance sources. The IEEE 1451 standard has been integrated into an automatic video-based fire smoke detection system. The proposed architecture has been tested on an experimental setup with the purpose of monitoring fire incidents successfully.