Abstract: A method for suppressing distortion and removing selected signals from a feedback path in a closed-loop control system is provided. Improvements lie in the manner in which control signals for a vector controller are generated and in the addition of a reference network element which broadens effective cancellation bandwidth. Control signals for the vector controller are derived from various sensors which measure such parameters as temperature, signal level, distortion, etc. Sensor outputs are compared to those stored in a look-up table. Based upon this comparison, a processor decides which set of control signal values will yield improved cancellation of the selected signals. The bandwidth over which cancellation of the selected signals can be achieved is related to how closely the reference signal matches that of the selected signals in the feedback path. Match is controlled by passing the reference signal through a reference network which shapes its amplitude and/or phase.

Abstract: A spray controller accepts a spray pressure input and a pressure control input, and provides a pressure control output. The controller includes an amplifier and pressure transducer, and its pressure control output is the product of the amplifier's gain and the sum of (a) a preset calibration voltage and (b) the product of the pressure transducer's gain and electrical response. The pressure control input controls the gain of the transducer to vary the pressure control output.

Abstract: A spray controller includes a governor which limits the current applied to an electric motor that operates a spray system pump. The controller accepts pressure sensing and pressure setting signals and provides a pulse train output to drive the motor whenever the sensor signal indicates that the output pressure is less than the "set" pressure. The governor accepts the spray pressure setting signal and limits the width of the pulse train as a function of the desired pressure setting, thus limiting the motor's current and speed. In the preferred embodiment, the motor's speed is restricted at lower pressure settings, but is allowed to operate at maximum speed at higher pressure settings.

Abstract: An adaptive feedback system provides a means and method for removing selected signals from the feedback path, for compensating for changes in electrical characteristics of the feed forward and feedback paths so as to maintain negative feedback, and for prevention of closed-loop oscillation. Application to the suppression of amplifier distortion is emphasized. Cancellation techniques are employed to remove the desired output signal from the feedback path leaving only distortion to be negatively fed back. By this means, in-band distortion such as intermodulation products and noise can be suppressed without reduction in effective amplifier gain. Adaptive feedback compensation is used to assure negative feedback of a selected spectral band even when transfer characteristics of the forward and/or feedback paths vary due to such factors as changing input-signal parameters, component value drift due to environmental conditions, etc.