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  • 1
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    Pointing and Scanning Control of Optical Instruments using Rotating Unbalanced Masses (1996)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Correct pointing direction and scanning motions are essential in the operation of many flight payloads, such as balloon-borne telescopes and space-based X- ray and gamma-ray telescopes. Rotating unbalanced mass (RUM) devices have been recently proposed, implemented and successfully tested to produce a variety of scanning motions. Linear scans, raster scans, and circular scans have been successfully generated on a gimbaled payload using pairs of RUM devices. Theoretical analysis, computer simulations, and experiments have also been used to study the feasibility of using RUM devices to control instrument pointing direction, in addition to generating scanning motion. Dynamic modeling of a gimbaled payload equipped with a pair of RUM devices has been studied, and preliminary testing indicates that the pointing control is indeed feasible. However, there is also great potential for significant performance improvements through more advanced control system analysis, modeling and design. In this paper, modeling and control methods are described to achieve simultaneous scanning and pointing control of a gimbaled payload using rotating unbalance mass (RUM) devices. The model development work builds upon the results of Polites et al. and also some modeling approaches from robotics research. Results of some preliminary experiments are discussed and some nonlinear control methods will be proposed.
    Keywords: Mechanical Engineering
    Type: NASA-TM-112521 , NAS 1.15:112521 , AAS-97-065
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  • 2
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    System providing limit switch function with simultaneous absolute position output (2006)
    In:  CASI
    Details
    Publication Date: 2019-08-15
    Description: A limit and position sensing system includes a sensor assembly and an emitter. The sensor assembly includes first and second electrical conductors arranged in opposing parallel planes. The first electrical conductor is coiled outwardly from either end thereof in a clockwise fashion to form a first coil region and a second coil region. The second electrical conductor forms a single coil with portions of the single coil's rings lying between the first end and second end of the first electrical conductor being parallel to an axis of the first electrical conductor's plane. Ferromagnetic material is aligned with the first and second electrical conductors and spans beyond (a) the first and second ends of the first electrical conductor, and (b) the portions of the rings of the second electrical conductor's single coil that lie between the first end and second end of the first electrical conductor. The emitter is spaced apart from the sensor assembly and transmits a periodic electromagnetic wave towards the sensor assembly.
    Keywords: Electronics and Electrical Engineering
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  • 3
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    Motor Controller System For Large Dynamic Range of Motor Operation (2006)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: A motor controller system uses a rotary sensor with a plurality of signal conditioning units, coupled to the rotary sensor. Each of these units, which is associated with a particular range of motor output shaft rotation rates, generate a feedback signal indicative of the position of the motor s output shaft. A controller (i) converts a selected motor output shaft rotation rate to a corresponding incremental amount of rotational movement for a selected fixed time period, (ii) selects, at periodic completions of the selected fixed time period, the feedback signal from one of the signal conditioning units for which the particular range of motor output shaft rotation rates associated therewith encompasses the selected motor output shaft rotation rate, and (iii) generates a motor drive signal based on a difference between the incremental amount of rotational movement and the feedback signal from the selected one of the signal conditioning Units.
    Keywords: Mechanical Engineering
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  • 4
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    Reconfigurable Sensor Monitoring System (2017)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: A reconfigurable sensor monitoring system includes software tunable filters, each of which is programmable to condition one type of analog signal. A processor coupled to the software tunable filters receives each type of analog signal so-conditioned.
    Keywords: Electronics and Electrical Engineering
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  • 5
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    Systems, Methods and Apparatus for Position Sensor Digital Conditioning Electronics (2012)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Systems, methods and apparatus are provided through which in some implementations determine the amplitude of an amplitude modulated signal, modulated by the position of an object being sensed. In some aspects, the apparatus accepts an excitation signal and the amplitude modulated signal and divides the amplitude modulated by the excitation signal to produce an output signal that is proportional to the position of the object being sensed. In other aspects, the division is performed only when the excitation signal is non-zero, such as close to the peaks in the excitation signal. In other aspects, the excitation signal and amplitude modulated signal are degraded due to an air gap and the degraded signals are used to correct for amplitude fluctuations due to the air gap, and produce an output signal, tolerant of the air gaps, that is proportional to the position of the object being sensed.
    Keywords: Electronics and Electrical Engineering
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  • 6
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    Arc-Tangent Circuit for Continuous Linear Output (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: A device suitable for determining arc-tangent of an angle theta is provided. Circuitry generates a first square wave at a frequency omega(t) and a second square wave at the frequency omega(t) but shifted by a phase difference equal to the angle theta. A pulse width modulation signal generator processes the first and second square waves to generate a pulse width modulation signal having a frequency of omega(t) and having a pulse width that is a function of the phase difference theta. The pulse width modulation signal is converted to a DC voltage that is a linear representation of the phase difference theta.
    Keywords: Electronics and Electrical Engineering
    Format: text
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  • 7
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    Miniature housing with standard addressable interface for smart sensors and drive electronics (2006)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: A miniature assembly is disclosed which includes a housing assembly with a cover configured to be sealably secured to a box-like receptacle. The receptacle comprises openings on opposing sides for the seating therein of communications connectors. Enclosed within housing is custom-sized circuit board for supporting, at least, a standard communications interface and at least one electronic device.
    Keywords: Electronics and Electrical Engineering
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  • 8
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    Multi-speed multi-phase resolver converter (1995)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: A multiphase converter circuit generates a plurality of sinusoidal outputs of displaced phase and given speed value from the output of an angular resolver system attachable to a motor excited by these multi-phase outputs, the resolver system having a lower speed value than that of the motor. The angular resolver system provides in parallel format sequential digital numbers indicative of the amount of rotation of the shaft of an angular position sensor associated with the angular resolver system. These numbers are used to excite simultaneously identical addresses of a plurality of addressable memory systems, each memory system having stored therein at sequential addresses sequential values of a sinusoidal wavetrain of a given number of sinusoids. The stored wavetrain values represent sinusoids displaced from each other in phase according to the number of output phases desired. A digital-to-analog converter associated with each memory system converts each accessed word to a corresponding analog value to generate attendant to rotation of the angular resolver a sinusoidal wave of proper phase at each of the plurality of outputs. By properly orienting the angular resolver system with respect to the rotor of the motor, essentially ripple-free torque is supplied to the rotor. The angular resolver system may employ an analog resolver feeding an integrated circuit resolver-to-digital converter to produce the requisite digital values serving as addresses. Alternative versions employing incremental or absolute encoders are also described.
    Keywords: Electronics and Electrical Engineering
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  • 9
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    Resolver to 360.degree. linear analog converter and method (2000)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The converter produces a linear analog signal that is linearly proportional to a shaft angle of a resolver over 360.degree.. An excitation cosine signal supplied to the resolver and a response cosine signal received from the output windings of the resolver are converted to logic level signals. Digital logic is performed on the logic level signals in a programmable digital logic device to produce a logic level pulse-width modulated signal. The logic level pulse-width modulated signal is used to control a switch to switch between two reference voltage levels to produce a pulse-width modulated signal, which is filtered and buffered to produce the linear analog signal.
    Keywords: Electronics and Electrical Engineering
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  • 10
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    Position Sensing for Rotor in Hybrid Stepper Motor (2011)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: A method and system are provided for sensing the position of a rotor in a hybrid stepper motor. First and second Hall sensors are positioned in a spaced-apart relationship with the first and second armatures of the rotor such that the first and second Hall sensors generate electrical outputs that are 90.degree. out of phase with one another as the rotor rotates. The electrical outputs are adjusted relative to a reference, and the amplitude of the electrical outputs is further adjusted to account for spacing differences between the rotor and each of the first and second Hall sensors.
    Keywords: Mechanical Engineering
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