Abstract: Disclosed is an AC electric motor with oscillating rotary output, a permanent magnet rotor having radially magnetized magnets, and feedback control of oscillation amplitude. Amplitude control is accomplished without a separate amplitude sensor by using an accurate model of the motor as a basis for calculation of amplitude from measurements of motor voltage and current. The motor has high efficiency, low inertia, and uses a relatively small volume of permanent magnet per unit power output.

Abstract: A common and inexpensive integrated 555 timing circuit is used to vary the timing of triac firing pulses in response to a control voltage. A trigger pulse generator generates a pulse at each zero cross-over of an AC line. This pulse initiates a variable, one shot pulse generator which generates a rectangular pulse. The rectangular pulse terminates following a time interval which is controlled by the magnitude of a control input signal. A pulse forming circuit generates a triac firing pulse at the termination of the rectangular pulse from the one shot pulse generator.

Abstract: A method of measuring the distance at closest approach between the piston of a free piston compressor and the cylinder head. The method derives measurements of both the alternating and average components of piston position from direct measurements of the voltage and current applied to the linear permanent magnet motor that drives the piston, and thus eliminates any requirement for an additional position sensor located within the compressor.

Abstract: An electrical circuit and method for generating a continuous train of width modulated pulses. A square wave is generated and a delay circuit provides a delayed analog of the square wave. A controllable duration one-shot multivibrator generates a modulating pulse having a duration proportional to the sum of the absolute value of the modulating signal and a constant offset. The constant offset is chosen so that, in the absence of a modulating signal, the offset provides the largest control signal to the one-shot multivibrator which causes an output modulating pulse from the multivibrator equal in duration to the minimum duration which the multivibrator intrinsically is capable of obtaining. The polarity of the modulating signal is detected, a logical OR operation is performed upon the delayed square wave and the modulating pulse and an EXCLUSIVE OR operation is performed upon the combination of the result of the OR operation and the polarity detector output logic level.

Abstract: A method of measuring the distance at closest approach between the piston of a free piston compressor and the cylinder head. The method derives measurements of both the alternating and average components of piston position from direct measurements of the voltage and current applied to the linear permanent magnet motor that drives the piston, and thus eliminates any requirement for an additional position sensor located within the compressor.

Abstract: The displacement of a Stirling cycle cryocooler is controlled as a function of temperature by controlling the amplitude of the fundamental component of an AC signal which is applied to the motor at its operating frequency. A pulse train is generated, having a frequency which is a harmonic of the operating frequency. The duty cycle of the pulse train is modulated between 50% and 100% as a function of the temperature. The modulated pulse train is applied to the motor during one-half of the load's operating period and the complement of the pulse train is applied to the load during the other half of its operating period. Modulating the duty cycle of the pulse train (and consequently simultaneously of its complement) as a function of temperature variably controls the amplitude of the fundamental component of the drive voltage and therefore variably controls the displacement of the motor and, as a consequence, of the cryocooler piston.

Abstract: Disclosed is an improvement to Integral Monitoring of two-frequency Instrument Landing System Localizer transmitting antenna arrays, by means of which the Clearance signal can be precisely separated from the combined Course and Clearance output of an Integral Monitor recombiner and monitored as if it existed alone. A first detector detects a composite Clearance and Course signal input, and sends an output to a separation filter which does not pass frequencies of 0, 90 or 150 hertz, but does pass frequencies of the difference between Course and Clearance frequencies (.DELTA.f), .DELTA.f.+-.90 hertz, and .DELTA.f.+-.150 hertz. The output of the filter is input to a second detector which measures the difference between the percentages of 90 and 150 hertz amplitude modulations of an amplitude modulated carrier having a frequency .DELTA.f.

Abstract: The invention relates to thermomechanical transducers drivingly linked to a linear motor or alternator, preferably a free piston Stirling engine in which the piston is drivingly linked to the field magnet of an alternator. There are symmetric and coaxial secondary magnets attached at opposite ends of the field magnet. The field magnet is polarized radially in one direction and the secondary magnets are polarized radially in the opposite direction. When the field magnet is displaced from a centered position, the secondary magnets have an oppositely directed axial net force exerted upon them. This causes a centering bias on the field magnet and therefore a centering of the piston in the Stirling engine or cooler.A secondary effect produced by the magnetic spring of the secondary magnets is amplitude limiting during load reduction on the Stirling engine. Amplitude limiting is a result of increased spring constant of the magnetic spring past a certain amplitude.

Abstract: A new linear position transducer is disclosed which is substantially identical to the transducer described and illustrated in U.S. Pat. No. 4,667,158, except that the tubular layer contained between the coil and the outer shield comprises a silicon steel foil wrapped around the coil which has the effect of reducing the reluctance of this space to a low value. An electrical insulator is applied to one side of the silicon steel foil to prevent the creation of a current path between the coil and the outer shield of the transducer.

Abstract: A compensation winding for improving the linearity of a displacement transducer. The displacement transducer is the type having an electrically conducting non-ferromagnetic wall which moves in telescoping relation with the coil and is excited by a signal at a sufficiently high frequency that skin effect on the wall permits displacement of the wall to vary the reluctance of the coil flux path and thereby vary its inductance proportionally to displacement of the wall. The compensation winding is wound in telescoped, coaxial relationship to the coil in a fixed position. The compensation winding has a pitch which is a decreasing function of the distance from the end of the coil which is nearest the wall when the wall and the coil are in their least overlapping relationship.

Abstract: A linear displacement transducer has an elongated current conducting, tubular coil which is mounted to an end cap in a hydraulic or pneumatic cylinder and extends into a hole bored in the piston/piston rod unit within the cylinder. An electrically conducting, nonferromagnetic tube lines the wall of the bore and reciprocates axially with the piston/piston rod unit varying its overlap of the coil and thereby varying the inductance of the coil at an applied frequency. An AC electrical energy source is connected to apply an AC signal to the coil, the frequency of this signal being at least high enough that the skin depth in the tubular wall is less than the physical depth of the tubular wall. A detector circuit means is connected to the coil for detecting a signal which is proportional to the coil inductance and therefore is proportional to the displacement of the piston/piston rod unit within the cylinder.

Abstract: Disclosed is a radiofrequency distributor for a two frequency Instrument Landing System Localizer transmitting antenna array, for the purpose of driving each antenna with predetermined modulated radiofrequency currents of four different types, the distributor consisting of a combination of quarter wavelength power dividers and bidirectional couplers.

Abstract: The relative displacement of two bodies is measured by moving an electrically conducting, non-ferromagnetic wall means in proportion to the relative movement of the bodies in order to increase its overlapping, telescoping relationship to a first current conducting coil while simultaneously decreasing its overlapping, telescoping relationship to a second current conducting coil. Each of the coils are excited with an AC signal at a frequency which is at least high enough that the skin depth of the wall means is less than the physical depth of the wall means. A signal is detected which is proportional to the difference in the amplitude of the voltages across the two coils which results in improved sensitivity while improving linearity and substantially reducing temperature dependence.

Abstract: A temperature compensation structure for a displacement transducer of the type having a coil and an electrically conducting, non-ferromagnetic wall moving in telescoping relationship with the coil and excited by a signal at a sufficiently high frequency so that skin effect in the wall permits wall displacement to vary the reluctance of the coil flux path and thereby vary its inductance proportionally to displacement. The improvement provides temperature compensation for and essentially eliminates variation in the electrical scale factor which is caused by change in the temperature of the transducer. The improvement is to interpose between the coil and the core of the transducer a wall which has a thickness which is small compared to the skin depth of the wall material at the operating frequency of the device.

Abstract: Disclosed are a transducer for converting linear motion of a core into a proportional change in inductance by means of skin effect, and bridge processing circuitry for stable conversion of changing inductance into a proportional voltage.

Abstract: A linear alternator capable of delivering multi-phase power and yet being driven by a free piston Stirling engine. The alternator has a permanent magnet mounted to the power piston of the free piston Stirling engine and an armature coil member mounted radially outwardly from the piston cylinder for generating one phase. A body, such as a second piston mounted in the same cylinder, is drivingly linked through a spring to be driven by the power piston. A second permanent magnet is mounted to the body and a second armature coil member is formed outwardly of the cylinder disposed outwardly from the body to provide the second phase. Proper design selection of the mass of the body and the spring constant of the spring, together with all other springs connected to the body, causes the body to be driven in phase quadrature with the power piston so that the voltage outputs of the two phases are in quadrature.

Abstract: A load regulator for a linear alternator driven by a free piston Stirling engine. A substantially constant output voltage is maintained across the useful load by shunting a portion of the armature output current of the alternator through a variable energy absorbing conductance and varying that conductance in proportion to changes in the output voltage of the alternator in order to maintain a constant total armature power output. The regulator may be made more efficient by forming the armature coil as a plurality of series connected coils by one or more taps and then switching the number of series coil turns in connection to the load approximately in inverse proportion to the square root of the steady state power demand of the load so that the total armature output power is switched between discrete levels while the output voltage is maintained constant for all those levels by the variable impedance.

Abstract: An improved integral monitor for the Instrument Landing System Localizer is disclosed, which uses resistive networks and transmission lines to generate analogs of radiated signal at three specified angles from runway centerline.

Abstract: An electromechanical transducer particularly useful as a linear alternator driven by a free-piston Stirling engine is disclosed. A relatively high permeability material is formed into a flux loop having at least a pair of spaced gaps formed transversely through the loop. The gaps are aligned along a reciprocation path for a magnet which is mechanically mounted for reciprocation between alternate positions within the gaps. The magnet has a magnetization vector transverse to the reciprocation path and is drivingly linked to a mechanical energy input or output for operation respectively as an alternator or motor. The armature coil is wound around a portion of the flux loop.

Abstract: In an antenna array for radiating Instrument Landing System localizer signals, a method for reducing the required number of antenna elements by the combination of average element to element spacing exceeding one wavelength and end-fire directive antenna elements which suppress spurious radiation that would otherwise occur.