Abstract: A displacement measuring transducer performs a direct conversion of changes in physical position, particularly angular position, into a digital form suitable for input to a digital microprocessor. The transducer is of the inductive type. Two inductance legs are connected at a common input to form a three-terminal bridge device. To sense positional changes, a step voltage is applied to the input and the transient response at the output of each leg is sampled periodically. Digital circuitry compares the responses of each leg to a fixed reference voltage and produces a binary digital count proportional to the motion sensed by the transducer. This transducer provides high resolution and low noise over a wide dynamic range. It also allows temperature compensation and scale factor calibration.

Abstract: A tow target system for use with a remotely piloted aircraft, including deployment of the target(s) from wing launchers on a tow line, braking of the tow line, release of target and tow line from the aircraft, and parachute recovery of the jettisoned target. A dual tow reel and two tow target launchers are provided on the carrier aircraft for sequential operation of more than one towed target. Signals received from the ground control only the target deployment from its carrier and the later jettisoning of the towed target when desired. The braking system has automatically operative control means for pay-out speed, slowing, and stopping of the reels at predetermined line lengths. The parachute recovery is automatically initiated by aerodynamic control forces when target release is commanded.

Abstract: A router is mounted in a resilient support within a housing mounted on the end of a robot arm to permit substantial lateral movement of the router relative to the housing in any radial direction as the router traverses a template; the router being concentrically positioned within the housing in a resilient support positioned midway between the ends of the router.

Abstract: A frame integrator for integrating each of the outputs of an array of radiation detectors whose output is obtained by the charge-injection-device technique. An array of analog integrators is connected using row and column interconnection techniques with an array of radiation detectors. The output from each radiation detector is sampled periodically and the detector returned to its unexposed condition to avoid saturation of the detector. The analog integrator associated with each detector integrates the sampled output of the detector to increase the effective sensitivity of the detector and to reduce the noise in the output. Each analog integrator consists of a precharged capacitor which is discharged through a field effect transistor in an amount proportional to the output of the associated radiation detector.

Abstract: A plurality of acoustical transducers such as microphones are placed in appropriate array so that they are capable of detecting sonic energy emanating from an acoustical source such as an aircraft or a ground vehicle. The outputs of the transducers are sequentially sampled and multiplexed together, the time multiplexed signals then being converted from analog to digital form in an analog/digital converter. The output of the analog/digital converter is fed to a fast Fourier transformer (FFT), which transforms these signals to Fourier transform coefficients represented as real and imaginary (cosine and sine) components. The output of the fast Fourier transformer is fed to a digital processor. In this processor, the power and phase of each frequency bin for each microphone output is determined and the phase differences between signals received by pairs of microphones for each frequency bin of interest are determined.

Abstract: A passive ring resonator laser gyro includes a thin film, passive waveguide adapted to provide a closed, substantially circular propagation path for optical signals. Couplers are provided for coupling coherent optical signals in opposite directions in the waveguide. Frequency controllers for each of the counter-rotating optical signals are adapted to adjust the frequencies of the respective signals in the waveguide to achieve resonance along the optical path encountered by each of the signals. Detectors provide signals representative of the frequency shifts of the two counter-rotating optical signals in the waveguide. These signals are nulled by servos which apply correcting frequencies to the frequency controllers. A difference network generates a rate signal corresponding to the difference in frequency between the signals applied to the controllers. The rate signal is representative of the angular rotation rate of the waveguide.

Abstract: Apparatus for early detection of fatigue cracks in aircraft structure surrounding fasteners and the like.An ultrasonic scanner manipulating apparatus is provided with various types of replaceable tips which are used to establish the center of a given fastener, adjustable support legs which provide stability and maintain a proper distance for an ultrasonic transmitting/receiving head assembly to be rotated 360.degree. about the centerline of the fastener, and a liquid filled boot attached to the transmitting/receiving head assembly to assure a reliable signal path between the head and the structure being evaluated.

Abstract: A two degree of freedom gyro having an axial gap, permanent magnet motor. The gyro motor includes a stator having two sets of series connected coils wound in quadrature. The motor further includes a rotor which is adapted for continuous rotation about a spin axis, and for rotational displacements about the two orthogonal input axes. The rotor includes a set of permanent magnets supported so that the moment of each of the magnets is substantially parallel to the spin axis, with the magnetic moment of adjacent magnets being oppositely directed. The rotor is positioned with respect to the stator so that flux from the magnets is coupled to the coils. The rotor also includes a return ring for establishing a magnetic flux return path for completing a circuitous path for flux passing through the coil. An excitation network for the coils detects back emf in the respective coils, and generates control signals for driving alternating currents in the respective sets of coils. The alternating currents have a 90.degree.

Abstract: An improved power drill having means for sensing when the drill bit has penetrated through the workpiece and for then retracting the drill bit from the workpiece. An electrical signal responsive to the axial force between the drill and the drill bit is used to sense when the drill bit pierces the workpiece. A sudden decrease in the axial force triggers a mechanism for retracting the drill bit from the workpiece. Means are included to detect broken bits, missing bits and previously drilled holes.

Abstract: Disclosed is a circuit to compensate for switching speed variations of semiconductors arranged to apply fixed current pulses to a passive load. The circuit monitors changes in the voltage transients created at each current reversal and adjusts the turn-on time of the semiconductor devices to compensate for instability in the turn-off speed of the semiconductors.

Abstract: A backward-wave Raman amplifier or pulse compressor for compressing laser pulses. A laser pulse, or pump beam, of relatively long duration enters one end of the compressor. A short, initiating Stokes-Raman pulse enters the other end of the compressor and absorbs energy from the pump beam as the Stokes-Raman pulse traverses the compressor. The cross-sectional area of the Stokes-Raman pulse within the compressor increases linearly with distance traversed through the compressor so that the energy density within the pulse remains substantially constant as the pulse traverses the compressor and receives energy from the pump beam which traverses the compressor in the opposite direction. The cross section of the pump beam also varies linearly with distance within the compressor so as to coincide substantially with the cross section of the Stokes-Raman pulse and thus achieve efficient compression.

Abstract: A dynamically tuned free rotor gyro is equipped with a set of three case-fixed torquers equally spaced circumferentially about the drive axis beneath the rotor. Three pickoffs are arranged diametrically opposite the corresponding torquers beneath the rotor. The outputs of the three pickoffs are combined to produce a vector rebalance signal, which is nulled by the effect of the torquers. The vector rebalance signal is resolved into three separate control signals for the corresponding torquer drive circuits.

Abstract: A lightweight composite structure including a continuous filament member laced through the structure to provide a plurality of tension members integral with the structure. The preferred method of manufacture is to layup and cure two or more composite structural members, such as "I" beams, with each cured "I" beam having a plurality of holes extended through its upstanding leg, its top and bottom T-cap portions. Next, an uncured composite skin panel is laced to the top T-cap portion of the "I" beams, utilizing the holes provided through the upstanding legs of the "I" beams. The laced composite structure is then cured using pressures and temperatures well known to those skilled in the art.

Abstract: A system of modulation and demodulation for the transmission of binary data in the presence of multipath. The binary data modulates the phase of the carrier and the same binary data, after a delay of ".delta." bits, also modulates the frequency of the carrier. Following reception, the binary data is obtained either by frequency demodulation or by a method of coherent phase shift demodulation wherein the mark or the space frequency is selected for detection of each bit in accord with the bit received "n" bits previously. The system selects between the demodulation methods to obtain one which operates satisfactorily in the instant electromagnetic environment.

Abstract: A closed loop control system for maintaining a force transducer assembly in a balanced position is disclosed. The control system has a feedback loop control circuit for providing a force rebalance signal at one of a plurality of predetermined discrete amplitude values during each of a plurality of successive equal duration time intervals. The signal has a constant amplitude during each interval. The control circuit further provides a respective digital representation for each amplitude value of the rebalance signal for each of the successive time intervals. Thereby, a precise determination of the value of the time-force product can be generated with the concomitant determination of the forces acting upon the force responsive transducer. The control system is particularly useful for non-linear transducers, such as square law devices where the time-force product is difficult to determine with continuously variable amplitude values.

Abstract: A device for translating the frequency of the energy contained in a laser beam. Higher order Raman scattering is utilized to convert the energy in a laser beam into a collimated beam of radiation at a frequency removed from that of the original beam by an amount corresponding to the frequency shift exhibited by higher order Raman scattering processes. A Raman cell is utilized as a saturated amplifier at power density levels below that required for oscillation, so as to obtain efficient conversion. By selecting the path length within the Raman cell, nearly all of the energy exiting the cell is caused to appear in a single, higher order Stokes wave.

Abstract: An axial gap, permanent magnet motor. The motor includes a stator affixed to a motor housing. The stator has two sets of series connected coils wound in quadrature. Each set of coils is disposed in an annular configuration about a spin reference axis, with the principal axis of each coil being substantially parallel to the reference axis. The motor further includes a rotor which is adapted for continuous rotation about a spin axis. The rotor includes a set of permanent magnets and a member for supporting the magnets in a substantially annular configuration about the spin axis. The magnetic moment of each of the magnets is substantially parallel to the spin axis, with the magnetic moment of adjacent magnets being oppositely directed. The rotor is positioned with respect to the stator with the configuration of magnets being adjacent to the configuration of coils so that flux from the magnets is coupled to the coils.

Abstract: A solenoid torquer system with flux rate feed-back. The system includes a torquer coil and an associated core, and a device adapted to drive a current through the coil having an amplitude proportional to the difference between a coil current command signal and the actual current in the coil. A flux rate servo loop includes a sensor coil coupled to the core to provide a signal representative of the flux rate in the core. This flux rate signal is compared with a flux rate command signal having a ternary width-modulated form. The resultant difference signal is used as the current command signal. The system network provides a precise flux level, or force.

Abstract: An ultrasonic phased array imaging system having a received signal encoding and correlating system. Pulse echoes picked up by each of the plurality of transducers are passed by a timed gate signal only during a predetermined time interval when a return signal from a focal point is expected to arrive. The return signal is also encoded by a chirp waveform. All gated chirp signals are fed to a dispersive transversal filter where their sum occurs simultaneously.

Abstract: A laser which utilizes a saturable absorber within a second resonator to obtain mode-locking for the production of short pulses. A second resonator which contains the saturable absorber and operates at the lasing frequency of the absorber intensifies the radiation from the absorber. The intensified radiation interacts with the absorber to reduce its effective lifetime and thus shorten its recovery time following saturation. The reduced lifetime absorber interacts with a laser amplifier to mode-lock the amplifier, thus producing short pulses of laser energy.