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A method and apparatus for controlling a valve/actuator plant by generating a plurality of independent correcting control signals each responsive to a plurality of respective input signals and at least one of these input signals being the set point signal. The plurality of independent correcting con

A method and apparatus for controlling a valve/actuator plant by generating a plurality of independent correcting control signals each responsive to a plurality of respective input signals and at least one of these input signals being the set point signal. The plurality of independent correcting control signals includes a pneumatic flow signal. The correcting control signals may be derived from all linear control signals, all non-linear control signals, or a combination of linear control signals and non-linear control signals.

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A method and apparatus for controlling a valve/actuator plant by generating a plurality of independent correcting control signals each responsive to a plurality of respective input signals and at least one of these input signals being the set point signal. The plurality of independent correcting con

A method and apparatus for controlling a valve/actuator plant by generating a plurality of independent correcting control signals each responsive to a plurality of respective input signals and at least one of these input signals being the set point signal. The plurality of independent correcting control signals includes a pneumatic flow signal. The correcting control signals may be derived from all linear control signals, all non-linear control signals, or a combination of linear control signals and non-linear control signals. egister values. 6. The apparatus of claim 4, wherein said compare timer has a variable interrupt rate defining a frequency of said pulse width modulated signal. 7. The apparatus of claim 2, further comprising a flow sensor generating a flow signal which varies in response to inhalation and exhalation by a user, and a trigger circuit providing a trigger signal to said microcontroller in response to said flow signal, said microcontroller adjusting the frequency and amplitude of said motor control signal to switch between said inhalation and exhalation modes in response to said trigger signal. 8. The apparatus of claim 2, wherein said microcontroller includes memory programmed to hold minimum amplitude values for a set of frequencies corresponding to specific gas pressures, and wherein said microcontroller retrieves a stored amplitude value from memory when switching from one frequency to another. 9. The apparatus of claim 2, wherein said blower control system changes the frequency and amplitude of the motor control signal by adjusting the frequency and amplitude in unitary increments based on a slope of frequency versus amplitude. 10. The apparatus of claim 2, wherein said blower control system changes the frequency and amplitude of the motor control signal using a Bresenham algorithm. 11. The apparatus of claim 1, wherein a first frequency and amplitude of said motor control signal cause said impeller to operate at said first speed and a second frequency and amplitude of said motor control signal cause said impeller to operate at a second speed, wherein said first speed is greater than said second speed, and wherein said blower control system increases the speed of said impeller from said first speed to said second speed by adding an excess amplitude to said motor control signal, increasing the frequency and amplitude of the signal based on a difference between the first frequency and amplitude and the second frequency and amplitude, and removing the excess amplitude. 12. The apparatus of claim 11, wherein the excess amplitude is equal to the ratio of the second frequency to an acceleration constant. 13. The apparatus of claim 12, wherein the motor control system includes memory programmed to hold acceleration constants for various frequencies. 14. A method of generating bilevel positive airway pressure for respiratory therapy using a gas flow generator having a blower powered by an alternating current (AC) motor, said method comprising the steps of: applying a motor control signal having an amplitude and a frequency to the motor to produce a blower speed; determining whether a speed change is required for the blower; determining a target amplitude and a target frequency corresponding to a target speed; and adjusting the amplitude and frequency of the motor control signal until the amplitude and frequency correspond with the target amplitude and the target frequency, wherein one of the amplitude and frequency is incremented during a first interval and the other is incremented during a second interval which is a multiple of the first interval. 15. The method of claim 14, wherein the second interval is based upon a comparison of a differential change in amplitude and a differential change in frequency needed to move from the amplitude and frequency to the target amplitude and frequency. 16. The method of claim 14, wherein a Bresenham algorithm is used to adjust amplitude and frequency of the motor control signal. 17. The method of claim 14, further comprising the steps of adding excess amplitude before said adjusting step, and removing the excess amplitude after said adjusting step. 18. The method of claim 17, wherein the excess amplitude is equal to a ratio of the target frequency to an acceleration constant. 19. The method of claim 18, further comprising the step of retrieving the acceleration constant from a memory device. 20. The method of claim 14, wherein the applying step includes using a microcontroller to generat