Abstract An aircraft cabin air pressure controller includes a digital integrator having a 1023 counter and a counter which is adjustable for counts of 1022, 1023, or 1024. The two counters are used with a set-reset flip-flop to form a pulsewidth modulator. The digital integrator can cause an increase in the width of the pulsewidth modulated signal by counting to 1024, can cause a decrease in the width of the pulsewidth modulated signal by counting to 1022, or it can hold the width of the signal by counting to 1023, which is the same count as given by the reference counter. The rate of pressure change created by the system is governed by the occurrence of special counts in the variable counter, the counter counting to 1023, many, many times between each command which causes the counter to either count to 1022 or to 1024, under the control of a manually adjustable rate clock. The output of the digital integrator is filtered and passed into a summing network together with an actual cabin pressure signal so as to generate an error signal for controlling the pressurization system. In addition, the error signal is fed into a 60-foot limiter that prevents the error signal from varying from the actual cabin pressure by more than the pressure equivalent to 60 feet of altitude at sea level density. Whenever a 60-foot limit is reached, control of the digital integrator is taken over by an automatic tracking circuit which causes the digital integrator to generate a pressure reference signal at a rate of change which is much faster than the maximum permissible manual rate of pressure change. Thus, the 60-foot limit controls the actual pressure error signal by analog means, and additionally provides digital control for automatic tracking of the digital integrator so that it will be brought into correspondence with the pressure command which is integrally forced on the system by the 60-foot limiter. The 60-foot limiter comprises a digital indicating analog clamp having a pair of differentially operable, complementary transistors in the feedback loop such that when the error signal exceeds a given magnitude, an appropriate one of the transistors will conduct, which inserts a small resistor in parallel with a large feedback resistor, and which also provides a digital output signal indicating that the maximum error signal has in fact been exceeded.
Inventors
👤 Thomas E Gardner
Bibliographic Details
Application Number—
JurisdictionUS
Data Sourcegoogle_patents
Last Synchronized2026-10-29 18:54
CPC Classifications
G; G05; G05D; G05D16/00; G05D16/20
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
161 words
An aircraft cabin pressurization control system generating a pressure reference control signal comprising: a cabin pressure transducer for generating an actual cabin pressure signal; means including an integrator for generating a pressure reference signal; means responsive to the magnitude of pressure error signal in excess of predetermined limits for generating automatic tracking control signals; control means for causing said integrator to increase, decrease or hold the value of pressure reference signal being generated thereby, said control means including a manually operable uphold-down switch, said control means also including means responsive to said automatic tracking signals for simulating the up and down operation of said manual switch; means for deriving a pressure error signal in response to the difference between said actual cabin pressure signal and said reference pressure signal; said pressure error signal means including a clamp responsive to a pressure error signal in excess of said given magnitude for preventing said pressure error signal from substantially exceeding said given magnitude.
Claim 2
Dependent Claim
161 words
An aircraft cabin pressurization control system generating a pressure reference control signal comprising: a cabin pressure transducer for generating an actual cabin pressure signal; means including an integrator for generating a pressure reference signal; means responsive to the magnitude of pressure error signal in excess of predetermined limits for generating automatic tracking control signals; control means for causing said integrator to increase, decrease or hold the value of pressure reference signal being generated thereby, said control means including a manually operable uphold-down switch, said control means also including means responsive to said automatic tracking signals for simulating the up and down operation of said manual switch; means for deriving a pressure error signal in response to the difference between said actual cabin pressure signal and said reference pressure signal; said pressure error signal means including a clamp responsive to a pressure error signal in excess of said given magnitude for preventing said pressure error signal from substantially exceeding said given magnitude.
Claim 3
Dependent Claim
131 words
An aircraft cabin pressurization control system generating a pressure reference control signal comprising: a cabin pressure transducer for generating an actual cabin pressure signal; means including a digital integrator for generating a pressure reference signal; means responsive to the magnitude of pressure error signal in excess of predetermined limits for generating automatic tracking control signals; control means for causing said integrator to increase, decrease or hold the value of pressure reference signal being generated thereby, said control means including a manually operable up-hold-down switch, said control means also including means responsive to said automatic tracking signals for simulating the up and down operation of said manual switch; and means for deriving a pressure error signal in response to the difference between said actual cabin pressure signal and said reference pressure signal.
Claim 4
Dependent Claim
131 words
An aircraft cabin pressurization control system generating a pressure reference control signal comprising: a cabin pressure transducer for generating an actual cabin pressure signal; means including a digital integrator for generating a pressure reference signal; means responsive to the magnitude of pressure error signal in excess of predetermined limits for generating automatic tracking control signals; control means for causing said integrator to increase, decrease or hold the value of pressure reference signal being generated thereby, said control means including a manually operable up-hold-down switch, said control means also including means responsive to said automatic tracking signals for simulating the up and down operation of said manual switch; and means for deriving a pressure error signal in response to the difference between said actual cabin pressure signal and said reference pressure signal.