Abstract: Control moment gyros in an array are rotated to reorient a satellite. Gyro angle is selected from one of three values based upon whether the stored angular momentum for the desired angle is below a singularity free value, greater than the singularity free value or is greater than the maximum available stored angular momentum.

Abstract: Control moment gyros in an array are rotated to reorient a satellite by an attitude signal. If the signal causes a gyro to have position that will produce a singularity in attitude control, a disturbance is introduced into the signal to avoid the singularity.

Abstract: Control moment gyros in an array are rotated to reorient a satellite. A pseudo inverse control is employed that adds a term to a Moore-Penrose pseudo inverse to prevent a singularity.

Abstract: A method and apparatus for preventing false nulls in an optical delay line by causing the input optical beam to be frequency modulated or variably time delayed so that the components of the optical signal in the output cannot be of equal magnitude and of opposite phase.

Abstract: A calibrate and run bias voltage control method for an optical delay system utilizing a plurality of voltage controlled switches which may experience bias drift wherein during calibration an output optical power error signal of the system is monitored while rapidly changing the bias voltages to the switches according to a desired algorithm and setting the bias voltages at a the level achieved when the output error signal falls below a predetermined tolerance level.

Abstract: A feedback system for use in controlling control moment gyroscopes that are used in positioning a spacecraft where the relative rate of rotation is determined from the difference between the rotation rate of the gimbals of the CMGs and the rotation rate of the frame about the gimbal axis. The inertial reference units on the spacecraft are utilized as the source of measured rates of rotation of the three spacecraft axes with respect to a predetermined axis and these are converted to the rates of rotation of the frame about the individual CMG gimbal axes.

Abstract: A valve assembly has a valve body (10) which houses a pivotally mounted valve closure member (14) in the form of a valve closure flap secured to upper and lower spindles (16, 17). The valve housing is formed from two sections (20, 22) which are releasably secured together by means of an annular clamp (24) which engages with a peripheral upstanding rib (36) formed by the alignment of a flange (34) on one face of each of the valve housing sections.The valve closure member is located in the vicinity of the junction of the two valve housing portions. The provision of a clamp permits the valve assembly to be dismantled extremely quickly in the event of service or repair of the valve assembly.

Abstract: An electrical generator provides an output at a main stator winding which is excited by a main rotor winding. The main rotor winding is connected via a rectifier to a main exciter rotor winding which is excited by a main exciter field winding. A control circuit controls excitation of the main exciter field winding so as to stabilise the generator output voltage. The control circuit includes a detector for detecting excessive generator output voltage and a transistor switch for connecting a resistor in the current recirculation path of the main exciter field winding so as to prevent transient over-voltages caused by sudden load reductions.

Abstract: The invention is a utility tray assembly that is capable of being mounted on a support member of a ladder, such as a shelf or a step. The assembly includes a tray having parallel side walls, parallel end walls disposed normal to the side walls, and a bottom defining a plane and disposed normal to the side walls and the end walls. The end walls have slots therein extending in a direction parallel to the plane of the bottom. The assembly further includes a strap having a body portion and opposing end portions. Each of the end portions includes a slot extending in a direction parallel with the longitudinal axis of the strap. A fastener is associated with each end wall and is insertable through the slots in the end wall and the strap for securing the end portions of the strap to the tray end walls in such a manner that the support member of the ladder is captured between the body portion of the strap and the undersurface of the tray bottom.

Abstract: Apparatus and method for controlling a plurality of pulse width modulated devices from a single controller including condition sensors to input the controller, a logic unit to determine the error between the sensed values and the desired values of the conditions and a direct memory access unit which is digitally coded with the error values, the pulse width modulated device being connected to receive the outputs of the direct memory access unit and operable to control the conditions.

Abstract: A system used with a system having a carrier delay to determine the phase of a signal before the delay and to recover the signal after the delay. Two signals at different frequencies are sent through the system having a carrier delay. One signal will be the signal that contains the phase information. The other signal is a reference signal to generate a reference for the first signal.

Abstract: A changeable sign comprises an enclosed outer housing and inner changeable number display areas. The number display areas are comprised of vertically spaced sections, each including a plurality of rotatable horizontal flaps. The flaps are rotated by motors which may be controlled on-site or remotely using telephone, pager or radio remote controllers. Different arrangements of number displays may be provided to display the time, temperature, single digit numbers, multiple digit numbers and decimals as well as other characters. The sign has a compact construction and is weather resistant.

Abstract: A novel bias circuit provides precise base emitter voltage(V.sub.BE) which tracks the temperature coefficient of an RF transistor using low cost devices. The bias circuit includes a precision current source which injects current through a P-N junction device to derive a temperature compensating reference voltage thereacross. The P-N junction device is isolated from current fluctuations using a current isolation circuit coupled between the P-N junction device and the base of the RF transistor. The diode is thereby isolated from and unaffected by changes in the base current of the RF transistor. Multiple RF transistors are biased from the single P-N junction device by replicating only a trimming potentiometer and the current isolation circuitry for each additional RF transistor to be biased.

Abstract: A chemical energy power plant includes control of steam temperature to prevent turbine damage while allowing throttling of the power output level and rapid response to commands for changed power output level.

Abstract: A control circuit for a brushless DC motor providing positive control in all four quadrants of motor operation. The circuit provides control of motor current, thereby controlling motor torque, in response to an applied current command signal, relying solely on feedback signals of motor current and rotor angle. The heart of the system is a level dependent logic stage which selectively controls the states of the switches applying power to the motor windings in accordance with a current error signal developed by reference to the feedback current signal. The control circuit causes the motor current to correspond to any applied current command and works at any motor speed and torque for rotation in either direction.

Abstract: A control system for a permanent-magnet motor (10) driven by a multiphase line-commutated inverter (12) is provided with integrators (24) for integrating the back EMF of each phase of the motor for use in generating system control signals for an inverter gate logic (30) using a sync and firing angle (.alpha.) control generator (26) connected to the outputs of the integrators. A precision full-wave rectifier (16) provides a speed control feedback signal to a phase-delay rectifier (14) via a gain and loop compensation circuit (20) and to the integrators for adaptive control of the attenuation of low frequencies by the integrators as a function of motor speed, whereby as the motor speed increases, the attenuation of low frequency components by the integrators is increased to offset the gain of the integrators to spurious low frequencies. While the attenuation may be a continuous linear function of speed, a switch (Q.sub.1) is employed to provide a step change in attenuation at 40% of speed.