Abstract: A multi-mode fiber optic sensor and method for optically sensing a physical perturbation includes a multi-mode optical fiber segment that accepts coherent monochromatic radiation from a suitable source. As the radiation is propagated in the fiber the various modes form a complex interference pattern that changes in response to a physical perturbation of the fiber. A detector provides an output signal to a signal processor that analyzes the signal as a function of the change in intensity to provide an information signal that is functionally related to the perturbation.

Abstract: A rotating shaft torsional displacement and speed detector provides a light beam which impinges on one or both ends of the rotating shaft. Different combinations of beam altering materials such as reflecting and non-reflecting surfaces, wave retarding plates, and linear polarizers are attached to the front shaft end and rear shaft end. These beam altering materials change either the polarization or magnitude of the light beam in a predictable manner that allows for the detection of shaft speed and torsional displacement of the front shaft end with respect to the rear shaft end.

Abstract: The method of the invention provides for actuating at least one actuator, such as a piezoelectric transducer in response to movement of a waveguide, such as an optical fiber. In a preferred embodiment of the invention, both the piezoelectric member and the optical fiber are connected to a structure. The connection is such that movement of the structure is detected by corresponding variations in and/or back scattering from light transmitted into the optical fiber. The piezoelectric member is actuated in response to the movement of the structural member as detected by the variations in the light in passing through the optical fiber. The actuation of the piezoelectric member may effect a dampening of the initial structural movement. Alternatively, monitoring the light passing through the fiber may be used as feed back on the position of the structural member, which in turn may be used to reposition the structural member by further actuation of a piezoelectric member.

Abstract: Apparatus for the ratiometric measurement of a quantity of liquid in a tank includes first and second capacitors disposed in a tank and responsive to an AC excitation signal. The output signal from the first capacitor corresponds to the quantity of liquid in a tank, while the output signal of the second capacitor corresponds to an empty tank condition. First and second rectifiers are respectively coupled to the first and second capacitors. Preferably, the rectifiers are each a diode pair of opposite polarity diodes. The output signal from each rectifier is thus a current signal. A first current-to-voltage converter is coupled to both the first and second rectifiers and provides a first voltage signal corresponding to the first and second rectified signals. A second current-to-voltage converter is coupled to the second rectifier and provides a second voltage signal corresponding to the second rectified signal.

Abstract: An optical frequency domain distributed strain sensor for determining the strain distribution along an optical fiber includes an optical source that provides a polarization controlled optical interrogation signal having a frequency that varies in a recurring linear manner. The interrogation signal is injected into a sensor fiber embedded within a composite structure that places the fiber under strain. A portion of the interrogation signal is backscattered from the sensing fiber as a consequence of the strain experienced by the fiber and is mixed with a reference signal to produce beat frequency signals. The frequency of the beat signals is directly related the to position of backscatter in the sensing fiber while the amplitude of each beat frequency signal is directly related to the integrated strain-induced birefringence up to the backscatter point.

Abstract: A speed sensor for sensing the rotational speed of an N bladed fan in a turbo-machine application includes a polarization-preserving optical circuit positioned adjacent the locus described by the remote ends of the blades. First and second sets of sensing segments of the optical circuit are spaced apart from one another by an angular spacing equal to that of the blades and with the first set of sensing segments angularly offset from the second set and with the first and second sets cross-coupled to transpose the polarization modes. The orthogonal polarization modes of optical energy launched into the optical circuit are subjected to phase shifts as the optical fiber is perturbed by pressure variations caused by the moving fan blades with the cumulative phase shift in each portion of the optical circuit subtracted as a consequence of the cross-coupling and the resulting light output having an intensity or other characteristics that vary as a function of the rotational speed of the fan.

Abstract: An optically powered sensor system includes a plurality of sensors connected to a system optical bus that communicates with a system controller. Optical energy is transmitted along the bus for distribution to all sensors in the system with return pulses from the various sensors transmitted on the bus to the system controller. Each sensor includes a photodiode array for converting optical energy transmitted system-wide by the controller into electrical energy for storage in a storage capacitor associated with each sensor. A transducer, such as a thermistor, and a fixed-value reference, such as a resistor, are connected to a pulse encoder and, in response to power switched from the capacitor, the pulse encoder produces a series of short-duration pulses having a pulse spacing that is dependent upon the fixed value of the reference and the parameter-affected value of the transducer. The pulses are used to drive an optical source for transmitting optical pulses from the sensor to the system controller.

Abstract: A method of measuring aircraft fuel quantity and density in a fuel container using an ultrasonic transducer; a stillwell liquid fuel; a computer control, an indicator and an altitude sensor. The computer control includes a central processing unit connected to each of the ultrasonic transducers. The altitude sensor is connected to the central processing unit. The indicator means is connected to the central processing unit. The stillwell is supported by the container. Each ultrasonic transducer is supported within the stillwell by the container. The liquid fuel is supported within the container. An ultrasonic signal is transmitted from the transducer within the stillwell. The reflected ulrasonic signal is received by the transducer within the stillwell. The round-trip time period from sending to reciving the signal is measured. The quantity of fuel in the container is determined from the round-trip time period and stored data on the container volume in the central processing unit.

Abstract: Apparatus for use with a densitometer having a probe with an output and a probe driver for driving the probe includes a loop circuit coupled between the probe output and the probe driver. An amplifying circuit is coupled in the loop circuit to amplify the signal provided by the probe. A phase/gain control device is also coupled in the loop circuit between the amplifying device and the probe driver. The phase/gain control device controls the loop circuit to provide a loop gain of at least one and a substantially zero degree phase shift between the probe driver and the probe output signal. The amplifying device includes an op-amp which is preferably coupled to a shielded cable carrying the probe output signal. The shield conductor and one input of the op-amp are held at ground potential, and the op-amp acts to hold the center conductor at ground potential also. With the center conductor held at ground potential, the output signal from the probe varies with current, not voltage.

Abstract: Apparatus and method for self-referencing and multiplexing light intensity modulating fiber optic sensors provides a pulsed or chirped source light beam. The light beam is propagated through an input fiber optic cable into at least a first loop path. In the first loop path, the source light beam is modulated in accordance with a detected phenomenon to provide a modulated light beam. In the first loop path, a coupler splits-off (a) a portion of the source light beam, and (b) a portion of the modulated light beam. The split off portions are directed through an output fiber optic cable to a photo detector which thus receives a pulse train having a modulated pulse and an unmodulated pulse. The output of the photo detector is supplied to a processor which forms a ratio of the modulated and unmodulated pulses and provides an output signal which varies in accordance with the detected phenomenon but is relatively insensitive to optical transmission losses and optical source drift.

Abstract: The present invention provides an improved alternator system in which the magnetic flux modulating sleeve is carried by the rotor and rotates with the rotor. The position of the sleeve on the rotor is adapted to be adjusted during operation of the alternator while the rotor and sleeve are rotating. The repositioning of the sleeve on the rotor during rotation beneficially provides a more constant voltage output during load and speed variations. Concurrent rotor and sleeve rotation reduces eddy current losses in the magnetic circuit and increases alternator efficiency. The alternator of the invention is estimated to provide a constant voltage for a 10:1 variation in either electrical load (in OHMS) or rotor angular velocity (revolutions per minute, RPM), or a combined 10:1 variation of electrical load and rotor angular velocity.

Abstract: An actuator system for positioning a flight control surface on an aircraft in which a primary braking device provides a continuous braking action to the actuator screw shaft by means of a load bearing disc brake wheel and a pair of rachet wheels contiguous therewith, the torque between the disc brake wheel and the rachet wheel (which ever wheel is being racheted by the load bearing disc) is proportional to the load on the screw shaft (and hence the actuator for the flight control surface). A Hall-effect device is mounted above the pawls associated with the rachet wheels for measuring the movement of the pawls in a closed loop circuit for the purpose of determining not only a faultlessly running braking condition but also to indicate whether a faulty condition exists, as well as what kind of fault is being detected.

Abstract: Method and apparatus for compensating a phototransducer system for fiber optic transmission losses and optical source power fluctuations includes generating a broadband source light beam having a plurality of spectral components. The source light beam is transmitted to a polarizer which polarizes the light beam and directs it to a multiple wave retardation device. The retardation device retards the spectral components of the polarized light beam. The retarded light beam is injected into a photoelastic transducer which modulates the polarizations of the retarded light beam in accordance with pressure applied to the transducer. Each spectral component of the retarded light beam will be modulated by the transducer. However, the broadband light beam will remain, in sum, relatively invariant to the applied pressure. The modulated light beam is then passed through an analyzer, injected into a fiber optic cable, and transmitted to a beam splitter.

Abstract: Apparatus and method for compensating a photo sensor for fiber optic cable lead/connector losses and optical source power fluctuations includes a specially selected broadband optical source used in conjunction with a photoelastic fiber optic transducer that uses a polarizer and an analyzer that only polarize a portion of the broadband signal. The portion of the signal that is not polarized is simply transmitted through the photoelastic element and emerges with no modulation. The portion of the signal that is polarized is modulated according to the stress on the photoelastic element. After transmitting the output light beam through a single fiber optic cable, the beam is separated into two parts. The first part is filtered so as to transmit only that portion of the broadband signal that is not affected by the polarizer and analyzer and hence is not modulated. The filtered first part is converted to an electrical signal by a photo detector.

Abstract: Method and apparatus for deriving a correction factor used in calculating corrected liquid (e.g., fuel) quantity of a tank having a probe capacitance which varies in accordance with the quantity of liquid contained within the tank. The correction factor reduces sensing diode voltage drop errors and stray capacitance errors (affecting the capacitance of the probe) through use of a switchable high/low amplitude Lo-Z oscillator. All oscillator outputs are "low" amplitude relative to the output amplitudes of conventional devices. Signal processing is effected by inputting raw data (both reference and probe-sensed signals) to an analog-to-digital sampling circuit, which raw data are used for deriving the correction factor. The correction factor is then applied to the raw data to determine a corrected liquid quantity indication. Recalibration of the correction factor periodically permits automatic adaption to changing error magnitudes (i.e.

Abstract: What is proposed is an electro-impulse de-icing device for use in an airfoil of an aircraft that includes a system having an energy storage device connected via a triggering device to a set of coils each embodying a coil construction in the form of a spirally wound ribbon coil member whose planar dimension is pressed against an interior surface in the leading edge of the airfoil, and wherein the coil sets are arranged in a linear manner along the long axis of the airfoil and are energized simultaneously and sequentially via an interlocking pattern from the wing tips or from the fuselage of the aircraft with each coil set being triggered twice from about three to five seconds apart.

Abstract: An opto-acoustic fuel quantity gauging system, including: a tank; an ultrasonic energy source; an optical power source; a fiber optic cable; an ultrasonic sensor; an optical detector and a signal conditioning circuit. The ultrasonic energy source is connected to the tank. The ultrasonic energy sensor is connected to the tank. The optical power source is connected to the fiber optic cable. The ultrasonic energy source is connected to the fiber optic cable. The ultrasonic energy sensor is connected to the optical detector by the fiber optic cable. The circuit is connected to the optical detector.

Abstract: A foil-backed acrylic transfer adhesive tearband structurally joins and hermetically seals a split instrument housing assembly. The tearband is formed by an acrylic transfer adhesive layer affixed to one side of a metallic foil strip layer.

Abstract: A decoupling device for gear motors used in cargo conveyor belt systems in which a coupler member is free to move axially on the output shaft of the gear motor to cooperate with the final gear of the gear train in the motor housing. A spring member maintains the coupler in engagement with the final gear via the corresponding jaw structures. Disengagement of the respective jaw structures is accomplished by axially moving the coupler member along the output shaft by means of a self-securing pivotally mounted yoke which engages the coupler for transmitting axial motion thereto. The yoke is pivoted by means of a cam follower device mounted for pivotal movement exteriorly of the gear housing to thereby rotate to one of two positions, thus connecting or disconnecting the aforementioned respective jaw structures on the output shaft.