Controller, cabin pressure control system and method of controlling cabin pressure

A cabin pressure control system, especially for use in an aircraft, comprising

• a first pressure sensor (12) for measuring the actual pressure inside the cabin (30),
• a controller (11) with an input unit (33) for receiving information about pressure of an atmosphere or for receiving information about a pressure differential between actual cabin pressure and atmosphere pressure and information about additional critical parameters,
• said controller (11) comprising a channel (15) for calculating a control cabin pressure based on the pressure differential between the cabin pressure and the atmosphere pressure and additional critical parameters and for generating an associated channel output signal (40) in order to keep the actual cabin pressure near the control cabin pressure in a closed loop control,
• at least one outflow valve (17) with an associated actuator (35) actuatable by an output signal (20;
• 21) from said controller (11),
• characterized in that
• said cabin pressure control system (10) comprises a second sensor (13) for measuring actual cabin pressure, in that
• said controller (11) comprises a pressure differential safety function (22) calculating an output signal (41) depending only on the pressure differential between actual cabin pressure and atmosphere pressure, which is connected to said second sensor (13), and in that
• said safety function (22) comprises a control (32) for comparing the two output signals (40, 41) and selecting the output signal (41) generated by the safety function (22) if the output signal (40) from said channel control (31) is found inaccurate.

A method of controlling the actual pressure inside a cabin (30), especially in an aircraft cabin, comprising the following steps:

• measuring the actual pressure inside said cabin (30),
• measuring the actual pressure in a surrounding atmosphere,
• calculating the pressure differential between said actual pressure and said atmosphere pressure, or, as alternative, measuring the pressure differential between said actual pressure and an atmosphere pressure,
• calculating a control cabin pressure based on the pressure differential between the cabin pressure and the atmosphere pressure and additional critical parameters, and
• generating a first output signal (40) depending on the calculated control pressure in order to keep the actual cabin pressure near the control cabin pressure in a closed loop control,
• characterized by the steps of
• generating a second output signal (41) depending only on the pressure differential between the actual cabin pressure and atmosphere pressure, said pressure differential being obtained independent from the pressure differential for generating said first output signal (40),
• comparing said two output signals (40, 41) and selecting the second output signal (41) if said first output signal (40) is found inaccurate.