Importance

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Abstract

A pressure control servo system for regulating cabin pressure in jet airplanes. In the preferred embodiment, the system comprises a first summing network, which sums data from a air data computer (ADC), a flight deck (FD), and a flight management computer (FMC), which produces a pressure reference signal, P.sub.R, indicative thereof. The summing network is connected to both a derivative path, and a proportional path. The derivative path comprises a proportional gain shaper, a derivative, an altitude dependent gain, and a gain multiplier. The proportional path comprises an integral gain shaper, an altitude dependent gain, a gain multiplier, and a rate limit. The outputs of the derivative and proportional paths are then connected to a second summing network, which sums those signals. Then, this summed output passes through a common digital integrator with a limit and a rate limit. The output of the common integrator is eventually compared to an actual pressure reference signal to a corresponding position signal, which then drives an outflow valve. This valve regulates the amount of air exhausted from an aircraft's cabin. The outflow valve moves, causing a change in cabin pressure. This change in cabin pressure is then measured and a signal is accordingly sent back to the first summation network. The gain shapers allow the gains to vary as a function of the magnitude of pressure error. The gain is decreased for small errors. This design provides increased stability for small disturbances, without sacrificing the response to large disturbances.

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First Claim