Abstract: Protection apparatus for an AC or DC motor (4) and a static drive (8), including a static inverter or a static drive (8). An I.sup.2 T signal is modified to take account of the frequency with which the switching elements of the drive (8) are switching their load current (at 42) and other factors. The modified I.sup.2 T signal is lowpass filtered in a filter whose cutoff frequency is also a function of the drive's switching frequency. The resulting drive protection signal is compared with a predetermined threshold. An I.sup.2 T signal is also modified to take account of the speed of the motor and other factors, then filtered, to provide a motor-related signal (at 90). Upon occurrence of an overload both the drive-related signal and the motor-related signal are indpendently capable of turning off the system by tripping a line contactor (6).

Abstract: Apparatus for automatically steering a farm crop vehicle into rows of corn by sensing the locations of the rows ahead of the vehicle on both sides of the vehicle. The apparatus senses the plants of each row by means of contact sensors that touch the plants as the crop vehicle approaches them. The data thus obtained are processed by an on-board microcontroller to determine the lateral location of the crop vehicle relative to the rows. Also, the frequencies of encountering plants in laterally spaced-apart rows provided information regarding turning of the vehicle, i.e., incipient changes of lateral position. This is used to produce a further feedback signal that improves the automatic steering, especially where the rows are curved. Having the turning-feedback signal in the servo loop also permits higher loop gain without instability, which reduces tracking error even further.

Abstract: The depth of a cavity or chamber (10') is measured by using the chamber as the resonator of an electronic oscillator (24) whose oscillations are coupled to fluid in the cavity by transducers (12, 13). Both the variable-depth main chamber (10') and a reference chamber (117) of fixed depth are measured. Variations in the data obtained from the chambers are caused by factors affecting the velocity of propagation of sound in the fluid. An accurate measurement of the depth of the main chamber is obtained by compensating direct data (at 42) obtained from the main chamber (10'), using, data (at 43) obtained from the fixed-depth reference chamber (117). In one embodiment an inertance orifice (121) is utilized between the two chambers. The fluid inertance of the orifice, together with the compliance of the fluid in the main chamber (10'), form a resonant system whose anti-resonant frequency is a measure of the dimensions of the main chamber. (Inertance is the acoustical equivalent of inductance.

Abstract: A cavity such as a chamber (10) of a hydraulic cylinder (2) containing a movable piston (4) is equipped with transducers (12) for transmitting alternating pressure signals into a fluid in the chamber and for receiving signals from it. The fluid chamber acts as a resonant tank circuit for determining the frequency of an external electronic oscillator (24). The frequency of oscillation of the circuit indicates the depth of the cavity, i.e., the position of the piston in the cylinder. Multiple modes of oscillation are employed (34, 36) in the same chamber to provide high accuracy and resolution of ambiguities. In one embodiment chambers (10', 66) on both sides of the piston (4') of a double-acting cylinder (2') are measured, and the readings are combined (76) to reduce errors that would otherwise result from changes in temperature, pressure, viscosity and other parameters unrelated to the position of the piston.

Abstract: A controller for an electric clamp closes the clamp rapidly at first, then runs at a slower speed while contacting the workpiece, and speeds up again after contacting it, to close with full clamping force. Arrival of the clamp at the position for slowing down is directly detected by means of a proximity sensor, as are arrivals at other positions. The speed of operation is relatively insensitive to the voltage of its AC electrical power source because an open-loop compensating signal controls the pulse duration of rectified DC pulses that drive the motor. The controller has dynamic braking that is applied between individual pulses of pulse trains of motor current; this results in sigfificant increase in swings of current values for a given motor speed, that reduces harmful effects of mechanical friction. Two jogging speeds are selectable.

Abstract: A displacement gauge or gauge for detecting misalignment (3) employs four magnetic coils (24N, etc.) 90.degree. apart, (each) energized by an oscillator (36N, etc.), to sense the dislocation of a machine part, such as a post (12), near their center. A nominal position of the part (9 or 12) relative to a reference component (6) of the machine is first established. Subsequent displacements are detected and are indicated if they exceed a predetermined threshold magnitude.Signals from the four coils are combined in such a way that the magnitude of the radius of a displacement of the part (9 or 12) from the nominal position is ascertained approximately, irrespective of the direction of displacement from the reference part (6). The combination signal (at 64) is the greatest of (a) the absolute value of a north/south displacement signal, (b) the absolute value of an east/west displacement signal, and (c) 0.

Abstract: A displacement sensor or displacment gauge (3) for detecting misalignment measures the dislocation of a machine part, such as a post (12), by means of four magnetic coils (24N, etc.) deployed 90.degree. apart around the post and each energized by an oscillator (36N, etc.). A reference position of the machine part (12) relative to another component (6) of the machine is first established. Subsequent displacement is detected and excessive displacement is indicated if it exceeds a predetermined threshold magnitude.Signals from the four coils are processed combined in such a way that the magnitude of the radius of a displacement of the machine part (12) from the reference position is ascertained and provided irrespective of the direction of the displacement.

Abstract: A controller for a batter-drive DC motor controls the average motor current by switching a series-connected FET on and off with a pulse-width-modulated gate signal. Motor speed is changed by chaning the duty cycle of the signl, which is generated by an oscillator. An undervoltage protection circuit senses the battery voltage and compares it with a reference system that has hysteresis. An overload protection circuit senses the motor current, integrates the sensed signal, and comprares the result with a Zener reference diode that is connected in an amplifier circuit for positive feedback. The oscillators's pulse-width-modulated output, the undervoltage protection circuits's output, and the overload protection circuit's output are input to a "NOR" Logic gate, whose output drives the gate of the FET.

Abstract: A closed-loop torque demand power steering system suitable for large off-highway and other vehicles has no mechanical linkages or hydraulic connections entering into the driver's cab. A torque demand signal is produced electronically without any separate electromechanical torque sensor. Upon starting, the system provides synchronization between steering and steering wheels without initial corrective motion of either member. During operation the direction of the steered wheels does not drift relative to the position of the steering wheel. The circuit includes protection against spurious steering signals that might otherwise occur if the steering is moved back and forth mechanically on a transition boundary of a position sensor. In the event of certain types of failure of its primary steering system it automatically changes over to an open-loop secondary steering system that is controllable by the same steering wheel, and that has components in common with the primary system.

Abstract: An optical gauge measures the shape of a target object by scanning a laser beam over it, (and/or measures the radial velocity of the target), by measuring the Doppler frequency shift of the reflected wave. The Doppler-shifted frequency is demodulated by a phase locked loop, which has a limited hold-in frequency range within which it is capable of staying locked on. With this invention, if the reflected wave's frequency gets close to exceeding the hold-in range of the phase locked loop, the gauge adjusts the drive frequency of an acoustooptical modulator that modulates the outbound target beam. This offsets the frequency of the target beam and keeps the return signal within the hold-in range of the phase locked loop.

Abstract: A laser distance gauge measures the distance and shape of a target by alternately performing (a) a Doppler shift measurement during optical scanning of the target's surface and/or motion of the target and (b) a chirp measurement with a chirp frequency laser signal. To ascertain changes in radial distance from the gauge to the target, the Doppler shift information is integrated and the result is combined with absolute distance measurements made in the chirp mode. A single CW laser, which operates single frequency, serves for both types of measurement. A computer changes the gauge from Doppler mode to chirp mode when the Doppler shift reaches a predetermined amount. When a chirp measurement of absolute distance is completed it reverts to Doppler mode.

Abstract: A power steering system suitable for large off-highway and other vehicles has no mechanical linkages or hydraulic connections entering into the driver's cab. Torque demand signals are produced in an electromechanical torque sensor that measures the deflections of a torsional spring. The system provides synchronization between steering and steered wheels upon starting, without initial corrective motion of either member. During operation, the direction of the steered wheels does not drift with respect to the position of the steering wheel. In the event of certain types of failures of its primary steering system the apparatus automatically changes over to an open-loop secondary steering system that is controllable by the same steering wheel, and that has components in common with the closed-loop primary system.

Abstract: A laser distance measuring apparatus in which source beams from two lasers are combined and focused on a target. One beam is continuous wave and one has periodic narrow pulse envelopes. After reflection the composite reflected beam is redivided in a diffraction grating and compared with two respective reference beams by means of two photodetectors. Doppler data are provided, as well as separate high resolution and low resolution range output data. Integration of the Doppler data in a computer, and combination of the three data signals there, enable an unusually complete and accurate record of the shape of the target even if the shape has many severe discontinuities, as in the case of a turbine rotor. An alternative embodiment provides for switching the pulse time of flight portion of the system to utilize various harmonics of the pulse envelope waveform.

Abstract: An image sorting system such as an airborne defense system for receiving and classifying enemy radar signals according to frequency, azimuth angle of arrival, etc. It employs a RAM that is addressed by the frequency and azimuth values of each received signal. If the addressed storage location in the RAM is empty, a number is assigned and stored there to represent the radar that is producing the received signals. The RAM represents a map of the aircraft's environment. Hash addressing, chaining of overlapping radar signals, pipelining to facilitate the blocking of superfluous pulse Doppler signals, etc. enable rapid reliable sorting and identification of hundreds of radar or other signals in the area.

Abstract: A controller for a battery-driven DC motor controls the average motor current by switching a series-connected FET on and off with a pulse-width-modulated gate signal. Motor speed is changed by changing the duty cycle of the signal, which is generated by an oscillator. An undervoltage protection circuit senses the battery voltage and compares it with a reference system that has hysteresis. An overload protection circuit senses the motor current, integrates the sensed signal, and compares the result with a Zener reference diode that is connected in an amplifier circuit for positive feedback. The oscillator's pulse-width-modulated output, the undervoltage protection circuit's output, and the overload protection circuit's output are input to a "NOR" logic gate, whose output drives the gate of the FET.

Abstract: A field-oriented controller for a 3 phase induction motor is powered by a dc power source through a static inverter. Current reference signals are compared with current feedback to produce error signals. They are amplified by a proportional plus integral amplifier, whose output goes to a threshold comparator having negligible hysteresis. Flip-flops, through which the threshold comparators' gating signal outputs are fed, are clocked at a fixed frequency to introduce pseudo-randomness into the gating times. This reduces apparent acoustic noise of the motor. Asymmetrical anti-overlap delays for the gating signals are made long enough to serve also as the principal means for limiting the maximum frequency of gating. Locking circuitry overrides the proportional integral error signal in one phase at a time, and holds the inverter's gating in one switching state throughout the approximate middle 60.degree. interval of each phase. During each such 60.degree.

Abstract: A closed loop optical gauge directs a laser beam toward an object whose radial velocity, instantaneous position, and/or shape are to be measured, and utilizes the Doppler frequency shift of the reflected beam to make measurements. A reference sample of the original direct beam has its frequency shifted by an acoustooptical modulator. A closed loop system is created by sensing the difference in frequency between the reflected beam and the shifted reference beam. The amount of frequency modulation is then controlled so that the frequency of the shifted reference beam continuouly tracks that of the reflected beam, preferably with a fixed offset of frequency. The output can be integrated with respect to time to obtain position or shape information.Absolute distance to the object is measured by transmitting a train of pulses of light toward the object and receiving reflected light pulses back.

Abstract: An active inertial isolation system is disclosed generally for any inertial body, and also for bodies subject to structural resonance, and further particularly for a microlithography system (2) for processing semiconductor wafers (4) subject to a submicron design rule. One or more linear forcers (94, 76, 74, 94' 76', FIGS. 18 and 19) are provided for applying a force between the body or worktable (6) and a reaction mass RM (202, 204, 206, 210). One or more accelerometers (98, 78) sense acceleration of the body (6) and apply force against sensed acceleration regardless of the position or variation of position of the body (6) relative to the reaction mass RM. The reaction mass RM may be supported relative to the linear forcer, and/or be a part thereof or rigidly fixed thereto, or the reaction mass RM may be supported relative to a reference such as a sidewall or the floor.

Abstract: A hybrid laser distance gauge utilizes complementary simultaneous measurements based upon both Doppler and time of flight principles. A complete record can be produced of the location and shape of a target object even when the object has severe discontinuities such as the edges of a turbine blade. Measurements by the two principles are made by using many optical elements in common.The Doppler measurements have an open loop optical/electronic arrangement in which the Doppler shift is converted to a voltage by a phase locked loop. The time of flight measurements are made at one or more harmonic frequencies of a mode locked pulse envelope wave train, for unusually accurate and unambiguous distance data.

Abstract: An AC power/step-down transformer suitable for use in switchgear for controlling electrical apparatus such as an indicator lamp has low core cost and permits economical assembly, as no interleaving of laminations is required. Its magnetic circuit comprises simple rectangular coil core assemblies whose ends are either fitted into holes in upper and lower plate assemblies or abutted against them. There are two primary and two secondary coil core assemblies, spaced apart to permit pushrods to pass between them for actuation of a back-mounted switch. A primary winding is placed around both of the primary coil core assemblies, and a secondary winding is placed around both of the secondary coil core assemblies.