55 research outputs found

    Output Overvoltage in DC-DC Switching Converters in Case of Sudden Unloading

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    In present time the high efficiency switching DC/DC converters, e.g. buck and boost are often used. This work describes some problems of DC-DC converters, which can occur, when the load is suddenly disconnected or simultaneous disconnection of the load and the capacitor at the output. The results were derived both by simulation but also by measurement. A special measuring system has been developed for these measurements, which enables the realization of fault conditions. Therefore, measurements were performed on 2 different types of DC-DC converters. The results of simulations and measuring are presented in the work. Error conditions usually cause an overvoltage that can damage the equipment connected to the converter. A solution how to prevent overvoltage and thus damage connected systems is also described

    Home Blood Pressure Monitors For 21st Century

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    Home blood pressure monitors will play increasingly important role in 21st century healthcare. Improvements in their accuracy and reliability will be necessary. In this paper we described their function and suggested several improvements. The improvements include static accuracy check, a public database of cuff pulse waves, utilization of cuff pulse waves for several hemodynamic variables, and wider cuff for wrist monitors

    Recursive Sine Wave Digital Oscillator with New Method Used for Amplitude Control

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    This work describes the control of the amplitude of the output signal (or amplitude stabilization) in digital sine recursive oscillators. As in the case of analog oscillators, it is also necessary to control the amplitude of digital oscillators with a sine wave. If the amplitude is not controlled, exponential increase or decay of the oscillation amplitude occurred, even if floating-point arithmetic is used. An example of digital sine recursive oscillator control with quadrature outputs, simulation results and design results are given in detail. Oscillator amplitude control is performed in a completely new way with a simple and fast algorithm for finding the maximum (minimum) and amplitude correction in case the amplitude differs from the desired value. The advantage is that the oscillator can be simply implemented by a program in the microcontrolle

    STANOVENÍ POHYBOVÉ AKTIVITY NA ZÁKLADĚ VÝSLEDKŮ ZÁTĚŽOVÉHO VYŠETŘENÍ

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    PHYSICAL ACTIVITY PRESCRIPTION BASED ON STRESS TEST EXAMINATION. KARD training program was developed for long-term training for competitive athletes, leisure time activities and also for patients. The training program has been based on results acquired from bicycle or treadmill ergometer. Cardiopulmonary exercise testing analysis allows to diagnose of training or rehabilitation effects. On the basis of testing results the program enables selecting alternatives of long-term physical activity that optimally suits each individual. The program is able to set the type, intensity, duration and frequency of the exercise units. The physician can modify the program which is important for patients especially. On the result of the stress test cardiopulmonary examination and physician recommendation the patient can do physical activity in home, without physician supervision, e.g. only heart rate measuring is used

    Using pulse width modulation with carrier frequency changing for transmission of two separate signals

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    Oxide Precipitation Hardened (OPH) alloys are a new generation of Oxide Dispersion Strengthened (ODS) alloys which have outstanding mechanical properties based on using appropriate heat treatment (HT). The production consists of mechanical alloying, which leads to a ductile matrix and hard oxide dispersion; however, the initial state shows a fine grain structure and basic mechanical properties. The composition, production process parameters, and HT affect the hardness of the OPH. In order to obtain a better understanding of the hardness of OPH alloys, three machine learning techniques were developed using ANN, ANFIS and SVMR to simulate the hardness. Moreover, the importance and intensity of the impact of each parameter on the hardness of OPH alloys were discussed. Based on the experimental results achieved by the authors, the composition of OPH alloys (Al, Mo, Fe, Cr, Ta, Y, and O), HT conditions, and Mechanical Alloying (MA) was used to train the models as inputs. The validity of the models was measured by different statistical criteria such as R, k, k′, m, n, and Rm. The mean absolute error for prediction of the hardness values at the test set was about 32 HV (ANFIS model), 37 HV (ANN model), and 44 HV (SVMR model). The results demonstrated that the ANFIS model predicts more accurately than the other methods. The sensitivity analysis and the influence of valid parameters were studied for the ANFIS model. It was revealed that HT temperature has a great effect on the hardness of the OPH alloys

    Digital sinusoidal recursive oscillators with quadrature and three phase outputs

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    Digital oscillators are essential parts in many applications. They are used in communications, control, radar, in digital signal processing and music synthesis. Flexibility, and low cost are the main advantages of such type of oscillators. Moreover, he parameters of a digitally generated sine signal are easy to control. Nowadays a Direct Digital Synthesis oscillators (DDS) with sine look-up table are most often used as a conventional method for generating sinusoidal waveforms, but recursive digital oscillators with quadrature or three phase outputs can be also used in different applications. Because of the finite word-length and therefore quantization it can be therefore some problems with amplitude stabilization and amplitude changing. In this paper, examples of quadrature outputs and three phase outputs are analyzed, simulated and constructed by microcontroller

    Simple amplitude control and frequency correction of recursive sine wave digital oscillators

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    This work describes one of the possibilities of amplitude control in recursive sinusoidal digital oscillators with integer arithmetic. As in the case of analog oscillators, it is also necessary to control the amplitude of digital oscillators with a sine wave. If the amplitude is not controlled, exponential increase or decay of the oscillation amplitude over time can occurs, even if floating-point arithmetic is used. This phenomenon is even more evident when using integer arithmetic. In this paper, various types of digital oscillators and their properties with partial use of integer arithmetic are presented. The results of amplitude control simulations are presented, but the oscillators were also implemented in a microcontroller and their function was verified. Moreover the frequency correction is described
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