Abstract: A self-tuning controller, for dynamic control of the servo valve and the actuator (mass, column, pad) of a seismic source vibrator, includes a state variable feedback network associated with a model reference for the servo valve and the actuator. The model references provide controllable states of the servo valve and actuator that would otherwise be inaccessible. The models run on-line and have the same inputs as the servo valve and the actuator. A Kalman filter provides a full order observer that compares accessible states between each model and the servo valve and actuator, and updates the model states in dependence on the difference.

Abstract: An electronic system automatically produces representations of three-dimensional recommended horizons from processed seismic data. Significant events, in the form of turnings, are identified in all of the digitized traces that make up the processed seismic data. Pairs of significant events in adjacent traces are determined. The system determines these pairs through a mutual nearest neighbor technique, together with a technique for detecting similar signs. The system measures the curvature of the path formed by the paired turnings in successive digital traces and terminates the path at any point where the curvature exceeds a predetermined limit. The system then looks for three-dimensional continuity by looking for a closed loop of at least four turnings making up four pairs of turnings. These techniques yield at least one horizon represented in a first format.

Abstract: A computer system automatically determines pairs of significant turnings related to the same seismic event in adjacent seismic traces of a three-dimensional seismic volume, wherein a turning is defined as a zero-crossing in the Nth derivative of the seismic trace. The times of the turnings of a first trace are compared with the times of the turnings of a second trace, and vice versa. The mutual smallest differences between times of turnings is detected and those turnings having the smallest mutual differences are paired, thereby designating the turnings that are mutual nearest neighbors, provided that the signs of the (N+1)th derivatives are the same (positive or negative). The system has the capability to compare the signs. The system repeats the comparison and pairing throughout the three-dimensional seismic volume.

Abstract: A seismic energy source air gun has a body with an air chamber formed therein that opens 360 degrees around the periphery of the body. A sleeve-type shuttle covers the opening in a pre-fire condition. When the air gun is fired, the shuttle moves rapidly away from the opening providing a large area for compressed air held in the chamber to escape. This very quick release maximizes the acoustic output. The movement of the shuttle is ultimately controlled by a solenoid which, when activated, causes the shuttle to move away from the 360 degree opening and when deactivated permits the shuttle to move back into the pre-fire position over the 360 degree opening.

Abstract: A vibrator seismic source has a sweep generator for providing a pilot signal and sensors for generating a feedback signal representative of the force imparted to the ground by the vibrator pad. Circuitry is incorporated for separating the fundamental signal from the feedback signal and for separating the distortion from the feedback signal. Means are provided for generating a control signal for controlling the action of the vibrator, the control signal being reduced or increased by the difference between the pilot signal and the fundamental signal, and further reduced by the distortion, if any. A threshold circuit is employed to ignore distortion below the threshold level and a threshold circuit is provided to ignore differences in amplitude between the pilot and fundamental signals when the difference is below the threshold. Additionally, the control system employs a phase detector circuit that outputs any phase difference between the feedback and pilot signals.

Abstract: An electronic thermal printer has a thermal printhead to which is applied a train of pulses which is pulse width modulated. A power switch connects and disconnects the printhead from a DC power source. The pulse train is integrated, scaled and applied as an input to a comparator circuit. The thermal printhead has a temperature sensing diode whose output is applied, as a reference voltage, to the other input of the comparator. During a print cycle, the output of the temperature sensing diode is cut off and the reference voltage is capacitively stored and held as the reference voltage. The output of the comparator circuit clears a latch circuit whose input is provided by a system clock and whose output is connected to control the power switch. The comparator provides an output when the integrated voltage reaches the reference voltage, clearing the latch. Since the latch is supplied with signals from the system clock, a constant frequency is maintained.

Abstract: A PSK integrated circuit modem employs multi-mode filters in its switched capacitor circuitry for providing a plurality of filter response to accomodate a plurality of modem protocols. Each capacitor is selectively connected or disconnected from the circuit by a transistor switch, and selectively connected and disconnected from the circuit voltage reference by a transistor switch. The switches operate out of phase with each other so that when any capacitor is connected in the circuit, it is disconnected from the reference voltage and when any capacitor is disconnected from the circuit, it is connected to the reference voltage. The modem switch minimizes the effect of stray capacitance from the unselected capacitors and their associated transistor switches that have been turned off.

Abstract: A PSK modem has a transmitter for converting received digital signals into corresponding PSK output signals and a receiver for receiving PSK signals and converting into corresponding digital signals. The receiver has a dual-integrator voltage controlled oscillator in which, during any given cycle of oscillations, one-half of the circuit is integrating toward the threshold voltage while the other half is idle. When the output of the integrating half reaches the threshold voltage, a control flip-flop toggles and the formerly idle integrator half begins to integrate, allowing the other half to stabilize before the next cycle of oscillation.

Abstract: A device interface controller provides a sophisticated communication link between a central processor and peripheral digital apparatus. The device interface controller provides simultaneous read and write operations with the peripheral digital apparatus. The device interface controller communicates with the peripheral digital apparatus, providing data to that apparatus and receiving data from that apparatus, as well as commanding the apparatus to perform functions peculiar to the selected device.

Abstract: A video data acquisition system includes a vision system having a video camera for taking pictures of articles. The video acquisition system is adapted to acquire, digitize and select signals within a predetermined amplitude range as representations of pixels of the images of the pictures arranged in rows, columns and diagonal lines, and further adapted to provide a total count of pixels in rows, columns and diagonal lines. A hand-held application module for directing the operation of the vision system has teaching capabilities in conjunction with the system for causing the video camera to take repeated pictures of an article within its field of view in various positions to provide identity of the article. The video acquisition system includes means for computing the area and perimeter of the article and for computing the maximum moments and minimum moments, thereby providing an identification of the article and its orientation.

Abstract: A PSK modem has a transmitter for converting input digital data into corresponding PSK signals modulated on a first carrier for transmission out and a receiver for receiving PSK signals and for converting those PSK signals into corresponding digital signals wherein the receiver has a phase locked loop used in demodulating the input PSK signal. The phase locked loop includes a low pass filter and an integrator connected in a circuit configuration so that the low pass filter output overrides the integrator output even if the output of the integrator is equal in magnitude to either of its input signals, thereby allowing the loop to lock. The integrator then adjusts itself slowly to reduce the DC output of the low pass filter and the steady state phase to 0. This permits the loop to free run in the absence of an input signal without losing lock.

Abstract: A seismic cable assembly having an acoustically transparent tubular enclosure has at least one hydrophone electrically connected and positioned within the cable assembly enclosure. The hydrophone is made up of a pair of formed, electrically conductive plates that fit against an insulating seal which also forms a fluid seal, providing a sealed chamber defined by the inside surfaces of the conductive plates. A pair of piezoelectric elements are interconnected and positioned within the sealed chamber, one element mechanically and electrically connected to the inside surface of one of the conductive plates and the other piezoelectric element mechanically and electrically connected to the inside surface of the other conductive plate. When pressure is applied to the conductive plates, they deform, causing the piezoelectric elements to flex. When the elements flex, an electrical output is presented on the conductive plates which serve as terminals.

Abstract: An extended range sample and hold circuit for use in systems such as floating point amplifiers is disclosed. An input differential amplifier receives a varying analog signal which is passed by a transistor sample switch during a predetermined sample period to an integrating differential amplifier having a sample capacitor across its output and inverting input. The charge on the sample capacitor follows the input analog signal. The output of the integrating differential amplifier is connected to a nonlinear circuit which in turn is connected to the noninverting input of an output differential amplifier. The nonlinear circuit provides a resistive path for small signals so that a fraction of the voltage across the sample capacitor is presented at the input to the output differential amplifier. As the signal becomes larger, a nonlinear portion of the circuit provides a signal at the input to the output differential amplifier that approaches the charge on the sample capacitor at one extreme.

Abstract: A compound floating point amplifier for amplifying an analog signal for presentation to an analog-to-digital converter has two amplifying sections to achieve a wide dynamic range. A signal representative of the rate of change (slew) is derived from a differentiating circuit. The analog signal and the slew rate signal are combined and if both are below a predetermined threshold level, a single step amplification is made in a dual gain amplifier. If both signals are not below the threshold, then there is unity gain through the dual gain amplifier. A sample and hold circuit receives the output of the dual gain amplifier and stores it. Subsequently, the stored voltage is impressed on a binary ladder attenuator which provides a digital word output indicating the required amplification. The voltage stored in the sample and hold circuit is also impressed on a binary gain amplifier system and amplified in accordance with the digital word from the binary ladder attenuator.

Abstract: A data display device has a manual input keyboard device that is infinitely adjustable with respect to its supporting surface between predetermined limits. The angular displacement mechanism that provides this adjustment is made up of a fixed arbor attached to the keyboard device and a rotating arbor attached to a foot. The arbors are axially aligned and rotatably connected together by a clutch coil spring. A manually operable push button mechanism on the keyboard device is linked to the tang of the coil spring so that when depressed, the tang is moved in a direction to unwind the coil spring, thereby permitting the locating arbor to rotate with respect to the fixed arbor, moving the foot away from the keyboard device. A tilt torsion spring is anchored to the movable arbor and connected to the keyboard device to cause the rotatable arbor to rotate when the push button is actuated thus moving the foot with respect to the keyboard device.

Abstract: A digital data transmission system for transmitting digital data from digital data handling hardware over a transmission line by analog signal representation and for receiving analog signal representation for reception of digital signals by the digital data handling hardware, incorporates an integrated circuit PSK modem. The modem has a transmitter which includes an encoder for encoding digital data into a first format for conversion to corresponding PSK signals and a transmitter modulator, implemented in switched capacitor circuits, for phase modulating a first carrier frequency according to the first format. The modem has a receiver that includes a demodulator, implemented in switched capacitor circuits, for demodulating PSK signals on a second carrier frequency to provide a second format for conversion to corresponding digital signals, and an encoder for encoding the second format into corresponding digital signals.

Abstract: A seismic vibrator source having an hydraulic vibrator coupled to vibrate a ground pad is provided with one or more force transducers such as, for example, load cells, strain gauges, or piezoelectric elements for measuring the force applied to the earth. Signals indicative of the pressure force are applied to a controller for the hydraulic vibrator to adjust control signals to prevent decoupling of the ground pad from the earth during ground seismic operations.

Abstract: A hand-held application module directs the operation of a programmable manipulator controlled by digital computing means. The module identifies points to which the end effector of the programmable manipulator shall move, programs the programmable manipulator to direct the precise operations relative to the points, selectively runs to one or more points to debug the entered program and retrieves statements for display in its alpha-numeric display facility. Program statements and parameters may be deleted from the program, and program statements and parameters may be added to the program. Entry of commands is made through a keyboard and data is displayed on an alpha-numeric display.

Abstract: A system displays data in a first and second alphabet selectable by the operator, the second alphabet being of the kind in which the characters differ in form according to their position in the context. The system receives data in the form of a sequence of standard binary code bytes representing alpha-numeric characters in the first alphabet, alpha-numeric characters in the second alphabet in which the characters are presented in one of the various forms possible for them in accordance with their position in the context, punctuation marks in the two alphabets, and editing functions. A display unit is connected to a ROM, both controlled by a processing unit wherein the ROM contains all of the characters of the first alphabet and all of the forms of all of the characters of the second alphabet including the form transmitted in the standard binary code and corresponding forms, depending upon their respective positions in the context.

Abstract: A multicopy impact printer has a wire matrix stored energy printhead having circuitry for reducing the power requirement of the printhead. A permanent magnet is incorporated in the printhead to flex leaf springs each of which is attached to the corresponding activation end of a respective one of a plurality of print members. A coil is provided for each print member, being activated when selected, to provide a magnetic field in opposition to the magnetic field of the permanent magnet and of an amplitude sufficient to release the flexed leaf spring. The opposing field diverts the field of the magnetic coil into paths away from the activated coil, thereby increasing its intensity and requiring more current in other selected coils to release the corresponding flexed leaf springs. A common coil is connected at one end to one end of each of the printer element coils and wound and positioned to provide a field in opposition to that of the permanent magnet.