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Introduction to Optimal and Robust Control
Published in Chunling Du, Lihua Xie, Modeling and Control of Vibration in Mechanical Systems, 2018
Mathematical relations and operations can be handled by digital microprocessor only when they are expressed as a finite set of numbers rather than as functions having an infinite number of possible values. Thus any measured continuous signal must be converted to a set of pulses by sampling, which is the process used to measure a continuous-time variable at separated instants of time. The infinite set of numbers represented by the smooth curve is replaced by a finite set of numbers. Each pulse amplitude is then rounded off to one of a finite number of levels depending on the characteristics of the converter. The process is called quantization. Thus a digital device is one in which signals are quantized in both time and amplitude. In an analog device, signals are analog; that is, they are continuous in time and are not quantized in amplitude. The device that performs the sampling, quantization, and converting to binary form is an analog to digital (A/D) converter.
Number Systems, Conversions and Codes
Published in Dale Patrick, Stephen Fardo, Vigyan ‘Vigs’ Chandra, Electronic Digital System Fundamentals, 2020
Dale Patrick, Stephen Fardo, Vigyan ‘Vigs’ Chandra
A general discussion of electronics is primarily centered around analog applications. An analog device is one in which a quantity is represented on a continuous scale. Temperature, for example, can be determined by the position of a column of mercury. Voltage, current, and resistance can be determined by the movement of a coil of wire that interacts with a magnetic field. Analog devices are usually concerned with continuously changing values. An analog value could be any one of an infinite number of values. Radio, television, and stereo sound systems deal primarily with manipulation of analog data.
Whole-body vibration exposure in unfavourable seated postures: apparent mass and seat-to-head transmissibility measurements in the fore-and-aft, lateral, and vertical directions
Published in Ergonomics, 2023
Figure 2 shows the head, thorax, and pelvic inclinations corresponding to the angles The time variations of these angles were measured by a system developed specifically for this experiment. It worked on the same principle and gave the same results as the CUELA system developed by IFA (Hermanns et al. 2008; Ellegast, Hermanns, and Schiefer 2009). It was composed of inertial measurement units (MPU9250—InvenSense) and 3 axial accelerometers (ADXL345—Analog Device) placed on clothing for the thorax and at the back of the skull for the head. Their size was ∼3 × 2 cm. Their thickness was <1 cm. They were fixed with Velcro strips and connected by flexible wires. These sensors were not sensitive to the moderate pressure caused by sitting or leaning back. The system was controlled by the Matlab software and its Data Acquisition Toolbox (Mathworks). The sampling frequency was 50 Hz. The precision was 5° during shocks or vibrations of high amplitude and low frequency. A graphical interface allowed to initialise the measurements, to record the data, and to warn the experimenter of the maximum deviations of the subject's position from the instruction. All degrees of freedom were initialised at 0° at the beginning of each session while subjects adopted the sitting position defined by ISO 2631-1 (ISO-2631-1 1997) (Figure 1). Subjects were seated on a rigid seat without a backrest. They adopted a relaxed posture and placed their hands on their legs. The height of the footrest was adjusted so that their feet rested flat.
Voltage-tunable immittance functions: Linear voltage-controlled quadrature oscillator implementation
Published in International Journal of Electronics Letters, 2023
Proposed designs simply utilise the voltage-control aspect of the readily usable AD-835/534 multiplier (Analog device Datasheet, 2017) devices where these are then coupled with readily available current feedback amplifiers (CFA-AD844; Analog devices, 1990; Macromodel AD-844; 1992);the circuit topologies are shown in Figure 1 and the corresponding design values are shown in Table 2. Analysis indicates that effects of the parasitic capacitances (3.3< Cy,z (pF) < 6) (Macromodel of AD-844AN, 1992) of the CFA and its roll-off poles (Gift & Maundy, 2005; Nandi et al., 2009; Tammam et al., 2014) are quite negligible to the derived values of L and D. Subsequently, frequency-selective features of the proposed immittances had been studied with appropriate design of bandpass-LC and band-reject-rD type filters; these are listed in Table 3, with the effects of parasitic capacitors (Cz,p) on the stability factor (SF) in Table 4.
CMOS voltage and current feedback opamps: a comparison between two similar topologies
Published in International Journal of Electronics Letters, 2021
Hervé Barthélemy, Valentin Gies, Stéphane Meillère, Rémy Vauché, Edith Kussener, Manon Fourniol
In this sub-section, it is proposed to provide a comparison between the CFOA and the VFOA presented in Figures (5 and 6) plus Figure 7 with the help of simulation results. Table 2 summarizes the sizes of all transistors for the CFOA and the VFOA. Table 2 also includes our estimation (post-layout) of the drain and source area and perimeters of each transistor in order to take into account, during simulation, the reverse junction capacitance effects. All Simulations have been performed using LTSPICE (Antognetti and Massobrio, 1990, Analog Device) and the typical CMOS 0.35 μm BSIM3V3 transistor models from AMS (Multi-Project Circuits,) for VDD = 3.3 V and VSS = 0 V. The DC common mode voltage is then equal to VDD/2 = 1.65 V. The DC bias current I01 is set to 50μA for the CFOA and 75μA for the VFOA while I02 = I01/2. All simulations were performed with infinite loading impedance (node out) and the compensation capacitances C1 and C2 have been set from simulations. In this paper, the value of C1 = C2 = CC has been increased until there is no resonance.