Digital Encoder Designing for Mobile Robot Control

In this paper we present the design of a quadrature decoder/counter interface IC (ASIC) that performs the decoding, counting, and bus interface function in digital motor control systems, employing an Altra FLEX 10KA, 2s150fg456 Xilinx device. The ASIC contains a pair of digital filters, a quadrature decoder, an up/down counter, a latch and inhibit circuit, and an 8-bit bus interface to a digital processing system. The design of digital of the digital filter is based on the finite state machine model with datapath (FSMD). A novel scheme for detecting the motor rotation direction is also proposed. The ASIC can be applied to a digital motor control system forgetting the rotation speed or position of the motor, which is quipped with an optical encoder. The data acquisition can be extended to 16-bit integer format by two continuos reading cycles. Simulation and experimental tests are shown to verify the ASIC function properly.DOI:http://dx.doi.org/10.11591/ijece.v4i4.550

Evaluation of the Frequency of Occupational Hazards Among a Group of Iranian General Dentists and its Prevention Criteria

Objective: To evaluate the frequency of occupational hazards and the criteria for their prevention among Iranian dentists. Material and Methods: This cross-sectional study was conducted on 187 general dentists in Kerman. The data collection tool was a questionnaire including personal information (gender, age, marital status, condition and place and years of employment, and the average of weekly working hours) and a valid and reliable questionnaire of occupational hazards, including 24 questions about occupational hazards (6 domain) and nine questions about criteria for the prevention of the risks of dentistry. The t-test, chi-square, and linear regression were used. Results: 92 (49.2%) were men. The mean and standard deviation of the score of occupational hazards was 27.04±16.21 out of 96, and the criteria of prevention were 22.00±7.28 out of 36. Regression analysis showed significant correlations between single statuses, years of occupational and type of employment, weekly work hours and occupational hazards, participation in occupational injury identification courses, and hepatitis vaccination. In addition, there were significant correlations between gender, age, weekly work hours, and preventive measures. Moreover, 3.2% of dentists were in a high-risk group and 26.2% were weak in preventive measures. Conclusion: A total of 32.6% of dentists are at moderate risk of occupational hazards, and 10.7% meet the prevention criteria properly. It is recommended to hold training classes to identify occupational hazards and the criteria for their prevention among dentists

Stock Return, Consumer Confidence, Purchasing Managers Index And Economic Fluctuations

This paper empirically investigates, in the context of vector autoregression and error-correction methodology, the link between three confidence measures of consumers, investors, businesses, and economic fluctuations. Using quarterly data for the United Sates from 1980 to 2005, we found that the hypothesis that these confidence measures do not Granger-cause GDP was rejected, even after controlling for other macroeconomic variables. Forecast Variance decompositions of GDP suggest that consumer confidence, stock return, and purchasing manger’s index, account for large variations in GDP. Overall, the results reconfirm the views that these measures play important roles in economic fluctuations

Auto generation of the center of gravity of tubular structures during crush deformation

Displacement of the center of gravity (COG) of tubular structures with various polygonal cross-sections is numerically investigated under an axial crush using the program code of ANSYS/LS-DYNA. A subroutine is developed using this code to calculate the COG of the deformed shape, during and after the crush. The effect of wall thickness on displacement of the COG is also investigated. Displacement of the COG decreases as the number of edges increases; it is a reasonable symmetric-deformed shape for the number of edges beyond eight. An even number of edges leads to a more symmetric displacement of the COG. The effect of the number of polygonal edges on symmetric deformation of the COG becomes more prominent as the initial wall thickness decreases. The higher number of edges stabilizes the deformed shape and the value of the mass moment of inertia of the deformed shape about the y axis (Iyy). The value of the mass moment of inertia about the x-z axes (Ixz) in comparison with I yy can be neglected in the case of dealing with an axial crush along the y direction

Stress analysis of periodic notches by using the strain energy density approach

This research focuses on the stress analysis of periodic notches by using the strain energy density approach. Bolts, screws and rotary-shouldered connections, as examples of periodic notched components, play an important role in the performance of the machinery. The contents are related to two-dimensional (2D), as well as three-dimensional (3D) modeling of periodic notches both in the case of round and sharp notches. The analyses are based on the numerical modeling of periodic notches with linear elastic assumption of the material. The simple analytical expressions for the notch stress intensity factors (NSIFs) of periodic sharp notches, as well as theoretical stress concentration factors (SCFs) of periodic blunt notches are obtained. Using the strain energy density (SED) approach, the coarse mesh in the finite element models is used and compared with the results obtained from the fine meshing. In fact, using SED approach, the averaged strain energy in a control volume allows using the coarse meshes in order to determine the NSIFs and SCFs of notched components precisely. In the case of 3D analysis, the thickness effects with particular attention on coupling modes, which due to Poisson effect are automatically generated, are studied. These modes can have a significant effect on the structural integrity of mechanical components. In addition, two collaborative industry projects with: Officine Meccaniche Zanetti s.r.l. and Omera s.r.l. are successfully implemented