Method for controlling the pressure of an air bellows

A method for regulating the pressure of an air bellows belonging to a pressure-regulated air suspension, wherein the determination of a pressure resulting from a venting process inside the air bellows takes place with the aid of a learning algorithm programmed in an associated computing device as well as via a pressure measuring sensor and a height measuring sensor, the computing device being assigned to a control device for controlling switching processes of valves in the air suspension, wherein the pressure measuring sensor is arranged at a distance from the air bellows in a feed line leading to the air bellows, through which an air mass flow can be delivered under pressure from the air bellows, wherein a valve, which is configured to be switched between a shut-off setting and an open setting for filling or venting the air bellows, is provided in the feed line and the pressure measuring sensor is arranged between the valve and the air bellows, the method comprising:

• before the valve is opened in order to vent the air bellows:
• a) taking a first measurement of a first pressure p0 at the pressure measuring sensor, and
• b) taking a first measurement of a current first height h0 of the air bellows by the height measuring sensor;
• and,
• c) determining, on a basis of a characteristic curve determined by predefined starting values, in which a dimensionless characteristic number KV as a variable representative of a bellows volume V is plotted against a height of the air bellows, an assumed starting air mass m0 in the air bellows takes place with the first pressure p0, the first height h0 and with a characteristic number KV0 obtained for the first height h0 from the characteristic curve as a variable representative of a bellows volume V0;
• opening the valve in order to vent the air bellows;
• while the valve is open, respectively in a number of successive cycles within the cycle times:
• d) taking a measurement of a further pressure p1 at the pressure measuring sensor;
• wherein
• e) from the difference between the pressure p1 measured in step d) and the pressure p0 measured in step a), ascertaining a flow rate of air at a bellows outlet corresponding to the pressure difference (p0−p1) with the aid of the learning algorithm and air mass flow in the feed line between the air bellows and the valve is ascertained therefrom, the air mass flow being multiplied by a correction factor kvent that takes into account a friction loss in the feed line;
• after which:
• f) integrating the air mass flow ascertained in step e) and provided with a correction factor over a cycle time to give a differential air mass and subtracted from the assumed starting air mass m0 in the air bellows, which was determined in step c), to give a bellows air mass mB assumed after the cycle time;
• g) taking a further measurement of a current height h1 of the air bellows by the height measuring sensor and ascertaining a new filling pressure pB to be assumed in the air bellows and resulting from an air mass discharge during the preceding cycle with the aid of the algorithm from a characteristic number KV1 ascertained for the height h1 with the aid of the characteristic curve as a variable representative of a bellows volume V1 and the bellows air mass mB ascertained in step f);
• h) repeating steps d) to g) within each further individual cycle time, the ascertained bellows air mass mB respectively ascertained in the preceding cycle being used as the basis in step f) as a new starting air mass m0=mB respectively contained in the air bellows;
• wherein the new filling pressure pB respectively ascertained in the steps d) to h) is provided as an input signal of an electronic regulating device for venting the air bellows, the valve being closed by a regulating device, and the determination of the bellows pressure for the venting process being ended, after a predefined target pressure in the air bellows is reached.

A device for regulating the pressure of at least one air bellows belonging to a pressure-regulated air suspension, wherein a determination of a filling pressure that can be generated inside the air bellows by a filling process takes place with the aid of a programmed learning algorithm, the device comprising:

• a control device for controlling switching processes and valves as well as a computing device assigned to the control device with the programmed learning algorithm;
• a pressure measuring sensor and a height measuring sensor assigned to the at least one air bellows;
• said pressure measuring sensor for measuring the air bellows pressure being arranged at a valve arranged in a feed line to the at least one air bellows and at a distance from the at least one air bellows;
• an air mass flow can be delivered under pressure in the feed line into the air bellows or from the air bellows and the valve is configured as a directional control valve and is configured to be switched to a shut-off setting, an inflation setting and a venting setting in order to fill or vent the air bellows via the feed line, wherein the pressure measuring sensor is arranged at a valve outlet of the valve which leads to the feed line to the air bellows.