18,123 research outputs found

    Low speed phaselock speed control system

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    A motor speed control system for an electronically commutated brushless dc motor is provided which includes a phaselock loop with bidirectional torque control for locking the frequency output of a high density encoder, responsive to actual speed conditions, to a reference frequency signal, corresponding to the desired speed. The system includes a phase comparator, which produces an output in accordance with the difference in phase between the reference and encoder frequency signals, and an integrator-digital-to-analog converter unit, which converts the comparator output into an analog error signal voltage. Compensation circuitry, including a biasing means, is provided to convert the analog error signal voltage to a bidirectional error signal voltage which is utilized by an absolute value amplifier, rotational decoder, power amplifier-commutators, and an arrangement of commutation circuitry

    A mismatch-insensitive high-accuracy high-speed continuous-time current comparator in low voltage CMOS

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    This paper presents a CMOS current comparator which employs nonlinear feedback to obtain high-accuracy (down to 1.5 pA) and high-speed for low input currents (8 ns@50 nA). This structure is much faster for low currents (below 10 /spl mu/A) than other previous nonlinear feedback comparators. Particularly, when compared to the fastest current comparator reported up to now, the new one operates at more that 100 times faster for a 1 nA current, with smaller area occupation and similar power consumption. In addition, the new comparator is virtually insensitive to mismatch and capable of operating with supply voltages as low as 1 V

    Progress of analog-hybrid computation

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    Review of fast analog/hybrid computer systems, integrated operational amplifiers, electronic mode-control switches, digital attenuators, and packaging technique

    Design and testing of an aerospace dew point hygrometer final report

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    Small sensor hygrometer for measuring dew point in manned spacecraf

    Induction motor control system with voltage controlled oscillator circuit

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    A voltage controlled oscillator circuit is reported in which there are employed first and second differential amplifiers. The first differential amplifier, being employed as an integrator, develops equal and opposite slopes proportional to an input voltage, and the second differential amplifier functions as a comparator to detect equal amplitude positive and negative selected limits and provides switching signals which gate a transistor switch. The integrating differential amplifier is switched between charging and discharging modes to provide an output of the first differential amplifier which upon the application of wave shaping provides a substantially sinusoidal output signal. A two phased version with a second integrator provides a second 90 deg phase shifted output for induction motor control

    A new nonlinear time-domain op-amp macromodel using threshold functions and digitally controlled network elements

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    A general-purpose nonlinear macromodel for the time-domain simulation of integrated circuit operational amplifiers (op amps), either bipolar or MOS, is presented. Three main differences exist between the macromodel and those previously reported in the literature for the time domain. First, all the op-amp nonlinearities are simulated using threshold elements and digital components, thus making them well suited for a mixed electrical/logical simulator. Secondly, the macromodel exhibits a superior performance in those cases where the op amp is driven by a large signal. Finally, the macromodel is advantageous in terms of CPU time. Several examples are included illustrating all of these advantages. The main application of this macromodel is for the accurate simulation of the analog part of a combined analog/digital integrated circui

    Hybrid computer Monte-Carlo techniques

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    Hybrid analog-digital computer systems for Monte Carlo method application

    Design and testing of an aerospace dew point hygrometer Final report

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    Thermoelectrically cooled miniature dew point hygrometer system for spacecraft instrumentation system

    A closed-loop digitally controlled MEMS gyroscope with unconstrained Sigma-Delta force-feedback

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    In this paper, we describe the system architecture and prototype measurements of a MEMS gyroscope system with a resolution of 0.025 degrees/s/root Hz. The architecture makes extensive use of control loops, which are mostly in the digital domain. For the primary mode both the amplitude and the resonance frequency are tracked and controlled. The secondary mode readout is based on unconstrained Sigma Delta force-feedback, which does not require a compensation filter in the loop and thus allows more beneficial quantization noise shaping than prior designs of the same order. Due to the force-feedback, the gyroscope has ample dynamic range to correct the quadrature error in the digital domain. The largely digital setup also gives a lot of flexibility in characterization and testing, where system identification techniques have been used to characterize the sensors. This way, a parasitic direct electrical coupling between actuation and readout of the mass-spring systems was estimated and corrected in the digital domain. Special care is also given to the capacitive readout circuit, which operates in continuous time
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