Abstract: An apparatus and method for determining a linear position from a linear variable differential transformer (LVDT) including a primary coil driven by an excitation signal, and two secondary coils coupled to two correlated signals. The method includes converting the correlated signals to a digital estimate, for each of the correlated signals, and evaluating an amplitude of the correlated signals to determine the linear position. The process of converting the correlated signals comprises comparing the correlated signal to an analog feedback signal to generate a comparison result and incrementally adjusting the digital estimate in response to sampling the comparison result at an estimation frequency.

Abstract: An apparatus and method for determining a linear position from a linear variable differential transformer (LVDT) including a primary coil driven by an excitation signal, and two secondary coils coupled to two correlated signals. The method includes converting the correlated signals to a digital estimate, for each of the correlated signals, and evaluating an amplitude of the correlated signals to determine the linear position. The process of converting the correlated signals comprises comparing the correlated signal to an analog feedback signal to generate a comparison result and incrementally adjusting the digital estimate in response to sampling the comparison result at an estimation frequency.

Abstract: An apparatus and method for determining an angular position of a shaft are disclosed, which comprise resolving an excitation signal at an excitation frequency into at least two orthogonal signals, converting the orthogonal signals to a digital estimate, for each of the orthogonal signals, and evaluating an amplitude and a polarity of the orthogonal signals to determine the angular position. The process of converting the orthogonal signals comprises comparing the orthogonal signal to an analog feedback signal to generate a comparison result and incrementally adjusting the digital estimate in response to sampling the comparison result at an estimation frequency. The converting process also includes converting the digital estimate to the analog feedback signal, collecting a digital estimate history at a sample frequency that is a binary multiple of the excitation frequency, and analyzing the digital estimate history to determine the amplitude and the polarity substantially near the excitation frequency.

Abstract: A watchdog timer circuit includes a cyclic counter having an overflow signal that functions as a reset pulse to a microprocessor. The timer circuit includes a feature for selectively supplanting the overflow signal to enable in situ programming of the microprocessor.

Abstract: A controlled fuel flow system from variable flow solid fuel gas generator to secondary combustor is provided, which system includes a hot gas valve which is operated by an electronic controller. The valve is mounted between the gas generator and the secondary combustor, which valve has in the throat thereof a pivotable blade that moves to relatively blocking and unblocking positions therein and a nozzle downstream of such blade which communicates with the secondary combustor. A first pressure transducer is mounted in the gas generator and a second pressure transducer is mounted downstream of such blade near or in the nozzle. Actuator means are also provided to pivot such blade between relatively blocked and unblocked settings as guided by electronic gas flow controller logic. The secondary combustor has one or more air ducts therein and the above system is mounted, e.g., in a variable flow ducted rocket.