US 7,454,254 B2Granted

Aircraft cabin pressure control system and method for reducing outflow valve actuator induced cabin pressure oscillations

AssigneeHoneywell International Inc.

InventorGerard L. McCoy

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Abstract

A cabin pressure control system and method that reduces or inhibits gear train backlash and the concomitant cabin pressure oscillations associated therewith. The cabin pressure control system includes a variable proportional-integral (PI) controller that implements a proportional function with a variable gain term and an integrator function with variable saturation limit. The proportional function gain term is increased, and the integrator saturation limits are decreased, at relatively low cabin error rate magnitudes. Increasing the proportional function gain term at relatively low cabin error rate magnitudes offsets potential backlash effects from the gear train. Decreasing the integrator saturation limits at relatively low cabin rate error magnitudes reduces potentially excessive integrator wind-up levels, which reduces the likelihood of producing limit-cycling and the potential for cabin pressure oscillations.

Claims14

Dependent claims

An aircraft cabin pressure control system controller circuit, comprising:

a comparator configured to receive a cabin pressure rate-of-change command signal and a sensed cabin pressure rate-of-change signal and operable, in response thereto, to supply a cabin rate error signal representative of a difference between the cabin pressure rate-of-change command signal and the sensed cabin pressure rate-of-change signal;
and
a variable gain proportional-integral (PI) controller coupled to receive the cabin rate error signal and operable, in response thereto, to generate an actuator command signal and determine a magnitude of the cabin rate error, the variable gain PI controller including a proportional function and an integrator function, the proportional function having a variable gain term, the integrator function having a variable upper saturation limit and a variable lower saturation limit, the variable gain PI controller further operable, upon receipt of the cabin rate error signal,
to vary the proportional function gain term between a maximum gain value and a minimum gain value when the cabin rate error magnitude is between zero and a first predetermined magnitude,
to vary the integrator function upper and lower saturation limits between minimum and maximum saturation limit magnitudes when the cabin rate error magnitude is between zero and a second predetermined magnitude and maintains the integrator function upper and lower saturation limits at the maximum saturation limit magnitude when the cabin rate error magnitude is above the second predetermined magnitude,
to vary the integrator function upper and lower saturation limit magnitudes between the minimum saturation limit magnitude and an intermediate saturation limit magnitude as a first function of cabin rate error magnitude when the cabin rate error magnitude is between zero and a third predetermined magnitude that is less than the second predetermined magnitude, and
to vary the integrator function upper and lower saturation limits between the intermediate saturation limit magnitude and the maximum saturation limit magnitude as a second function of cabin rate error magnitude when the cabin rate error magnitude is between the third predetermined magnitude and the second predetermined magnitude.

4 more elements

An aircraft cabin pressure control system, comprising:

a cabin pressure sensor configured to sense aircraft cabin pressure and supply a cabin pressure signal representative thereof;
and
a control unit coupled to receive the cabin pressure signal and one or more signals representative of aircraft operational mode and operable, in response thereto, to supply actuator control signals, the controller circuit including:
a rate circuit coupled to receive the cabin pressure signal and operable, in response thereto, to supply a signal representative of sensed cabin pressure rate-of-change,
a comparator configured to receive a cabin pressure rate-of-change command signal and the sensed cabin pressure rate-of-change signal and operable, in response thereto, to supply a cabin rate error signal representative of a difference between the cabin pressure rate-of-change command signal and the sensed cabin pressure rate-of-change signal, and
a variable gain proportional-integral (PI) controller coupled to receive the cabin rate error signal and operable, in response thereto, to generate the actuator control signals and determine a magnitude of the cabin rate error, the variable gain PI controller including a proportional function and an integrator function, the proportional function having a variable gain term including a phase lead term defined by ((z−b)/z), the integrator function having an integrator term defined by (Tz/(z−1)), a variable upper saturation limit and a variable lower saturation limit, the variable gain PI controller further operable, upon receipt of the cabin rate error signal,
to vary the proportional function gain term, between a maximum gain value and a minimum gain value only when the cabin rate error magnitude is between zero and a first predetermined magnitude,
to vary the integrator function upper and lower saturation limits between minimum and maximum saturation limit magnitudes only when the cabin rate error magnitude is between zero and a second predetermined magnitude,
to maintain the integrator function upper and lower saturation limits at the maximum saturation limit magnitude when the cabin rate error magnitude is above the second predetermined magnitude,
to vary the integrator function upper and lower saturation limit magnitudes between the minimum saturation limit magnitude and an intermediate saturation limit magnitude as a first function of cabin rate error magnitude when the cabin rate error magnitude is between zero and a third predetermined magnitude that is less than the second predetermined magnitude, and
to vary the integrator function upper and lower saturation limits between the intermediate saturation limit magnitude and the maximum saturation limit magnitude as a second function of cabin rate error magnitude when the cabin rate error magnitude is between the third predetermined magnitude and the second predetermined magnitude.

8 more elements

A method of generating aircraft cabin pressure control system outflow valve actuator control signals, comprising the steps of:

comparing a commanded cabin pressure rate-of-change command and an actual cabin pressure rate-of-change signal to determine a magnitude of a cabin rate error;
selectively varying a proportional function gain term between a maximum gain value and a minimum gain value only when the cabin rate error magnitude is between zero and a first predetermined magnitude;
selectively varying an integrator function upper saturation limit and lower saturation limit between minimum and maximum saturation limit magnitudes only when the cabin rate error magnitude is between zero and a second predetermined magnitude;
maintaining the integrator function upper and lower saturation limits at the maximum saturation limit magnitude when the cabin rate error magnitude is above the second predetermined magnitude;
varying the integrator function upper and lower saturation limit magnitudes between the minimum saturation limit magnitude and an intermediate saturation limit magnitude as a first function of cabin rate error magnitude when the cabin rate error magnitude is between zero and a third predetermined magnitude that is less than the second predetermined magnitude;
varying the integrator function upper and lower saturation limits between the intermediate saturation limit magnitude and the maximum saturation limit magnitude as a second function of cabin rate error magnitude when the cabin rate error magnitude is between the third predetermined magnitude and the second predetermined magnitude;
processing the cabin rate error through the proportional function to determine a proportional cabin rate error that is proportional to the gain term;
processing the cabin rate error through the integrator function to determine an integrated cabin rate error that is not greater than the upper saturation limit or less than the lower saturation limit;
and
generating the actuator control signals from the proportional cabin rate error and the integrated cabin rate error.

7 more elements

Dependencies are inferred from the claim text.