阅读说明：本技术 用于运行有压缩空气供应设施和空气弹簧设施的气动系统的方法和装置和有压缩空气供应设施和空气弹簧设施的气动系统及车辆 (Method and device for operating a pneumatic system with a compressed air supply and an air spring system, and pneumatic system and vehicle with a compressed air supply and an air spring system ) 是由 约尔格·沙尔彭贝格 马蒂亚斯·哈恩 费蒂·奥默尔·耶尔马兹 于 2018-09-26 设计创作，主要内容包括：本发明涉及用于运行具有压缩空气供应设施(10)和空气弹簧设施(90)的气动系统(100)的方法,其中,气动系统(100)具有：具有压力存储器容积(VD)的压力存储器(120)；和/或具有空气干燥器容积(VL)的空气干燥器(61)；通路(95)和能经由阀块(97)的阀(93、93.1、93.2、93.3、93.4)选择性地以导气的方式与通路(95)连接的至少一个空气弹簧(92、92.1、92.2、92.3、92.4),空气弹簧具有配属给空气弹簧(92、92.1、92.2、92.3、92.4)的多个气囊容积(91V、91.1V、91.2V、91.3V、91.4V)；其中,方法具有以下步骤：-确定至少一个空气弹簧(92、92.1、92.2、92.3、92.4)的至少一个偏移量(92A、92.1A、92.2A、92.3A、92.4A),-基于至少一个偏移量(92A、92.1A、92.2A、92.3A、92.4A)确定至少一个空气弹簧(92、92.1、92.2、92.2、92.3、92.4)的弹簧气囊(91、91.1、91.2、91.3、91.4)的至少一个气囊容积(91V、91.1V、91.2V、91.3V、91.4V)。根据本发明设置的是：-基于平衡容积(VBIL)周围的质量流量平衡(BIL),给出针对容积(91V、91.1V、91.2V、91.3V、91.4V、VD、VL)的气动的等效模型(PEM),-基于气动的等效模型(PEM)计算容积(VBIL、91V、91.1V、91.2V、91.3V、91.4V、VD、VL)的至少一个压力值(P、PL、PV、PS、PE、PF1、PF2、PF3、PF4)。(The invention relates to a method for operating a pneumatic system (100) having a compressed air supply (10) and an air spring system (90), wherein the pneumatic system (100) has a pressure accumulator (120) having a pressure accumulator Volume (VD) and/or an air dryer (61) having an air dryer volume (V L), a passage (95) and at least one air spring (92, 92.1, 92.2, 92.3, 92.4) which can be connected to the passage (95) selectively in an air-conducting manner via a valve (93, 93.1, 93.2, 93.3, 93.4) of a valve block (97), the air spring having a plurality of air spring volumes (91V, 91.1V, 91.2V, 91.3V, 91.4) assigned to the air spring (92, 92.1, 92.2, 92.3, 92.4), the air spring volume (91V, 91.1V, 91.2V, 91.3V, 91.4V) being based on a pneumatic pressure value (V, V3, 92, 92.92, 91.2, 91.3, 92, 91.2V, 91.4) of a pneumatic air spring (92, 91.2, 91.3, 92, 91.2V, 92, 91.2, 92, 91.4, a 3, 92.2, 92.4, a 3, a 3, 92.4, a 3, a 3, a 3, a, b.)

1. Method for operating a pneumatic system (100) having a compressed air supply (10) and an air spring system (90), wherein the pneumatic system (100) has:

a pressure accumulator (120) having a pressure accumulator Volume (VD), in particular an air dryer (61) having an air dryer volume (V L),

-a passage (95) and at least one air spring (92, 92.1, 92.2, 92.3, 92.4) which can be selectively connected in an air-conducting manner to the passage (95) via a valve (93, 93.1, 93.2, 93.3, 93.4) of a valve block (97), which has a plurality of air bag volumes (91V, 91.1V, 91.2V, 91.3V, 91.4V) which are assigned to the air springs (92, 92.1, 92.2, 92.3, 92.4), and which has the following steps:

-determining at least one offset (92A, 92.1A, 92.2A, 92.3A, 92.4A) of the at least one air spring (92, 92.1, 92.2, 92.3, 92.4),

-determining at least one air bag volume (91V, 91.1V, 91.2V, 91.3V, 91.4V) of a spring air bag (91, 91.1V, 91.2V, 91.3V, 91.4) of the at least one air spring (92, 92.1, 92.2, 92.3, 92.4) based on the at least one offset (92A, 92.1A, 92.2A, 92.3A, 92.4A),

it is characterized in that the preparation method is characterized in that,

-based on a mass flow balance (BI L) for balancing a volume (VBI L), giving a Pneumatic Equivalent Model (PEM) for the volume (91V, 91.1V, 91.2V, 91.3V, 91.4V, VD, V L),

-calculating at least one pressure value (P, P L, PV, PS, PE, PF1, PF2, PF3, PF4) of a volume (VBI L, 91V, 91.1V, 91.2V, 91.3V, 91.4V, VD, V L) based on the Pneumatic Equivalent Model (PEM).

2. The method according to claim 1, characterized in that at least one pressure value (P, P L, PV, PS, PE, PF1, PF2, PF3, PF4) is calculated upon a state change (ZA) of the pneumatic system (100),

-wherein the state change (ZA) is a change of the at least one offset (92A, 92.1A, 92.2A, 92.3A, 92.4A), or is a regulation process (RV) of the air spring arrangement (90), or is a switching process (SV) of at least one valve (93, 93.1, 93.2, 93.3, 93.4, 240, 250).

3. The method according to claim 1 or 2,

-said at least one pressure value (P, P L, PV, PS, PE, PF1, PF2, PF3, PF4) is corrected by means of a pressure value (PMESS) measured by a pressure sensor (94).

4. Method according to claim 3, characterized in that the measured pressure value (PMESS) is measured by means of the pressure sensor (94) in a time period (TFREI) in which no regulating process (RV) of the air spring system (90) takes place.

5. Method according to claim 3, characterized in that the measured pressure value (PMESS) is measured during the regulation process (RV) by means of a pressure sensor (94).

6. Method according to any of the preceding claims, characterized in that the at least one offset (92A, 92.1A, 92.2A, 92.3A, 92.4A) is measured by means of a height sensor (H.1, h.2, H.3, H4).

7. Method according to any of the preceding claims, characterized in that the Pneumatic Equivalent Model (PEM) is formed by:

-determining an initial Pressure (PI) present in the equilibrium volume (VBI L),

-determining at least one single initial pressure (P L, PV, PS, PE, PF1, PF2, PF3, PF4) in at least one single volume (V L, VV, VD, U, 91.1V, 91.2V, 91.3V, 91.4V), in particular in a single volume (V L, VV, VD, U, 91.1V, 91.2V, 91.3V, 91.4V) that is not part of the equilibrium volume (VBI L),

-determining all air mass flows (MB, MB1, MB2, MB3, MB4, MS, MZ) flowing into or out of the balancing volume (VBI L),

-determining the total air Mass (MG) present in the equilibrium volume (VBI L) and/or determining at least one individual air mass (M L1, M L2, M L3, M L4, M L S, M LL) in a volume (91V, 91.1V, 91.2V, 91.3V, 91.4V, VD, V L),

-calculating the pressure (P, P L, PV, PS, PE, PF1, PF2, PF3, PF4) based on a gas equation (GG), in particular an ideal gas equation (GGI), using the air mass (MG, M L1, M L2, M L3, M L4, M L S, M LL), the volume (VBI L, 91V, 91.1V, 91.2V, 91.3V, 91.4V, VD, V L) and the measured temperature (T).

8. The method according to claim 7, characterized in that the determination of all air mass flows (MB, MB1, MB2, MB3, MB4, MS, MZ) flowing into the balancing volume (VBI L) or flowing out of the balancing volume (VBI L) further has the steps of:

-determining by calculating at least one balloon air mass flow (MB, MB1, MB2, MB3, MB4) by means of a perforated plate equation (BG) taking into account at least one spring balloon pressure (PF1, PF2, PF3, PF4) and at least one effective spring balloon flow cross section (AF1, AF2, AF3, AF4), and/or

-determining by calculating at least one storage air mass flow (MS) by means of the perforated plate equation (BG) taking into account at least one storage Pressure (PS) and at least one effective storage flow cross section (AS), and/or

-determining by calculating a conveying section air mass flow (MZ) by means of an orifice plate equation (BG) taking into account at least one air dryer pressure (P L) and at least one effective conveying section flow cross section (AZ),

balancing the total air Mass (MG) taking into account all air mass flows (MB, MB1, MB2, MB3, MB4, MS, MZ).

9. The method according to claim 7 or 8, characterized in that the determination of the air dryer pressure (P L) further has the steps of:

-determining by calculating the compressor air mass flow (MV) by means of the perforated plate equation (BG) taking into account at least one compressor Pressure (PV) and at least one effective compressor flow cross section (AV), and/or

-determining by calculating the bleed air mass flow (ME) by means of the orifice plate equation (BG) taking into account the at least one bleed Pressure (PE) and the at least one effective bleed flow cross section (AE).

10. Method according to any of claims 7 to 9, characterized in that the determination of the initial Pressure (PI) present in the equilibrium volume (VBI L) is made on the basis of the measured Pressure (PMESS).

11. Method according to any of claims 7 to 9, characterized in that the determination of the initial Pressure (PI) present in the equilibrium volume (VBI L) is made on the basis of the calculated pressure (P) of the previous application cycle (Z) of the Pneumatic Equivalent Model (PEM).

12. Method according to any of claims 7-11, characterized in that the compressor Pressure (PV) and/or the compressor air mass flow (MV) are known from a displacement characteristic curve (24).

13. Method according to claim 12, characterized in that the displacement characteristic curve (24) is adapted as a function of an ambient parameter (UP), in particular an ambient Pressure (PU) of the atmosphere and/or a booster supply voltage (UK).

14. Method according to any one of claims 9 to 13, characterized in that the bleeder Pressure (PE) is given by the ambient Pressure (PU) of the atmosphere.

15. Method according to any of the preceding claims, characterized in that compressed air (D L) is generated by the compressor (21) if the determined pressure (P) or the measured Pressure (PMESS) lies below a minimum pressure value (PMIN).

16. Method according to any of the preceding claims, characterized in that compressed air (D L) is discharged via the bleed air interface (3) if the determined pressure (P) or the measured Pressure (PMESS) lies above a maximum pressure value (PMAX).

17. Device (300) for controlling and regulating a pneumatic system (100), wherein the device (300) is configured for performing a method according to any one of claims 1 to 16 and has a pressure determination unit (94C) and a pressure regulator (304).

18. Pneumatic system (100) having a compressed air supply (10) and an air spring arrangement (90) and having a device (300) for controlling and regulating the pneumatic system (100) according to claim 17, wherein the pneumatic system (100) further has:

-a pressure reservoir (120),

a passage (95) and at least one air spring (92, 92.1, 92.2, 92.3, 92.4) which can be selectively connected to the passage (95) in an air-conducting manner via a valve (93, 93.1, 93.2, 93.3, 93.4) of a valve block (97), having a passage (95) and having at least one air spring (92, 92.1, 92.2, 92.3, 92.4)

A pressure determination unit (94C) and a pressure regulator (304),

-a device (300) for controlling and regulating a pneumatic system (100) according to claim 17.

19. Vehicle (1000), in particular passenger motor vehicle (PKW), having a pneumatic system according to claim 18 and/or a device (300) for controlling and regulating a pneumatic system (100) according to claim 17.

Technical Field

The invention relates to a method for operating a pneumatic system according to the preamble of claim 1. The invention also relates to a device for controlling and regulating a pneumatic system, a pneumatic system having a compressed air supply and an air spring system, and a vehicle.

Background

Methods for operating a pneumatic system, in particular for the measured determination of the pressure in a pneumatic system, are known. In particular in pneumatic systems with compressed air supply and air spring systems, it is desirable during this time to reduce the dependency on the measurement by the pressure sensor for the purpose of pressure determination, in order to reduce the costs in particular in terms of equipment and to minimize the measurement times which do not provide the functionality of the system.

The process described at the outset is known from EP 1744915B 1. In particular, the method is used when the pressure in the air reservoir is greater than the pressure in the air spring and the throughputs in the throttle check valve and in the air dryer are in the subcritical range. First, a closed control chamber, most suitably the crankshaft housing of the supercharger and the air dryer, is selected within the air supply facility. The control chamber is at a defined pressure level. It is therefore expedient to connect the control chamber to the atmosphere by means of a two-position, two-way valve, so that atmospheric pressure builds up in the control chamber. Thus, the pressure in the control chamber is known. Subsequently, the two-position, two-way valve is opened for a defined period of time, thereby allowing a quantity of compressed air to flow from the higher pressure air spring into the reduced pressure control chamber until the pressure equalizes. In this case, the travel distance covered by the air spring is measured. From this journey, the loading state of the vehicle is deduced. The pressure in the air spring is inferred via simulation using this loading state and the previously known drop in the air spring. The average volume flow through the throttle check valve and the air dryer is then known, wherein it is assumed that the pressure in the air reservoir is above this pressure. For this purpose, the two-position two-way valve is opened for a defined time, so that a quantity of compressed air flows from the air accumulator via the air dryer into the air spring. In this case, the travel distance covered by the air spring is measured and the volume change is calculated therefrom. The volume flow from the air reservoir to the air spring is therefore also known. Using the known pressure in the air spring and the average volume flow and using the easily known external temperature, all variable variables are known in order to calculate the pressure in the air reservoir, wherein the facility-specific constants and the standard temperature and the standard pressure are included in the calculation.

The compressed air quantity of the air supply is calculated using the pressure in the air accumulator and the known volume in the air accumulator, which are thus known, and using the known pressure in the air spring and using the volume calculated via the distance traveled by the air spring, and is compared with the compressed air quantity tolerance band. In the case of an excess of the minimum permissible compressed air quantity, a corresponding quantity of compressed air is filled into the air supply, and in the case of an excess of the maximum permissible compressed air quantity, a corresponding quantity of compressed air is discharged from the air supply. The air supply facility is thus made to contain again an amount of compressed air within the compressed air amount band for the design situation.

In this respect, a method for air quantity control in a closed air supply of a chassis is described, in which a demand or surplus for a required compressed air quantity of the air supply for a design situation is calculated and the air supply is filled or discharged within a defined time.

Although the approach according to the prior art according to EP 1744915B 1 reduces the outlay in that the method described there takes care even completely without a pressure sensor. But still show some disadvantages. This concept still needs to be improved in terms of reliability of pressure values that may only be approximately calculated, in particular. The lowering and lifting process of the vehicle required for the pressure calculation is not very efficient, because the functionality of level adjustment cannot be provided in this time, and because the measuring process would lead to a pressure loss. The lowering and lifting process also causes the vehicle height to change.

It is desirable to specify a method, a device for controlling and regulating a pneumatic system and a pneumatic system having a compressed air supply and an air spring system, which are improved with regard to the reliability and efficiency of the pressure determination, in particular the availability of the system.

Disclosure of Invention

The invention is based on the object of specifying a method and a pneumatic system which are improved in the above-described respect and which have a compressed air supply and an air spring system, wherein the pressure in the pneumatic system is reliably and effectively determined. In particular, the dependence on measurements made on sensors should be reduced.

This object is achieved in a method-related manner by the invention having claim 1.

The invention is based on the consideration that it is generally advantageous to reduce the number of sensors for pressure determination, in particular in order to save costs and reduce expenditure on the equipment.

The invention is also based on the idea that, on the other hand, a reduction in the number of pressure sensors, in particular to one pressure sensor, can lead to the possibility of different pressure measurements being carried out in succession by switching the component to be measured on in succession, which can be associated with disadvantages.

The invention is based on a method for operating a pneumatic system having a compressed air supply and an air spring system, wherein the pneumatic system has: a pressure accumulator with a pressure accumulator volume and/or an air dryer with an air dryer volume, a passage and at least one air spring which can be selectively connected in an air-conducting manner to the passage via a valve of a valve block and has a plurality of airbag volumes assigned to the air spring.

The invention is based on the idea that sequential pressure measurements of all components, such as the spring bellows and the pressure reservoir, result in a longer duration of the measurement. During this measurement duration, the functionality of the system will not be available. This limitation of the usability of the system is then noticeable to the user, in particular to the driver of the vehicle, when measuring between partial transitions. In particular, the measurement is carried out at this point in time in order to minimize air losses and thus pressure losses that would otherwise occur as a result of the components being switched on in sequence. This measurement lasts for several seconds, for example between the lifting of the rear axle and the lifting of the front axle, and is perceived by the driver.

The invention is also based on the idea that sequential pressure measurements result in that the valves of the pneumatic system have to be designed for a significantly higher number of switching processes, since each component is switched on for each measurement. This results in structural expenditure and in particular a corresponding increase in costs. Switching on all the components to be measured leads to pressure losses which on the one hand lead to undesirable horizontal losses in the vehicle and on the other hand have to be compensated for by corresponding additional work, in particular a compressor. The invention also makes it possible, in relation to the initially mentioned prior art, to recognize that in particular the parasitic volumes of the air dryer and the lines can lead to undesirable flooding during the pressure measurement. This occurs, for example, when the vehicle is lifted by means of compressed air from the pressure accumulator and the pressure in the air dryer is therefore higher than the pressure in the component to be measured subsequently. In this case, air flows from the parasitic volume into the component to be measured and causes an undesired level change.

The inventive concept provides the basis for an improved pressure measurement with advantages over the prior art described above, that is to say with advantages over only one pressure measurement and also with advantages over a purely computationally performed pressure calculation only once, whereby the problems described above are partially or completely eliminated.

The method according to the invention also has the following steps:

-determining at least one offset of at least one air spring,

-determining at least one spring bellows volume of a spring bellows of at least one air spring on the basis of the at least one offset.

The method according to the invention therefore also has the further steps according to the invention:

-giving an equivalent model for the pneumatics of the volumes based on the mass flow balance around the balancing volume.

-calculating at least one pressure value of the volume based on the pneumatic equivalent model.

In particular, the dependence on the measurement, in particular the sequential measurement, by the sensor is reduced by the computational determination of the pressure on the one hand, which is based on the pneumatic equivalent model, and on the other hand, taking into account the switching process of the valve which is carried out for adjusting the air spring system. Furthermore, the calculation of the pressure at each switching or regulating operation of the pneumatic system results in the current pressure value being available not only at the time of the measurement, respectively, but also (at least in an approximate form) at each change of state of the pneumatic system, in particular at each switching or regulating operation.

In particular, the determination of the pressure by calculation (in the context of the above-mentioned problems) makes it possible to reduce the number of measurements or even to cancel them completely. In this way, the system availability of the air spring system is thus increased. Furthermore, the number of switching processes required in the valves of the pneumatic system is thereby reduced, and the structural outlay or the cost of the valves is therefore simplified. Air losses due to the measurement and the compensation work required thereby, in particular of the compressor, are also avoided. Finally, reducing or eliminating the measurement results in reducing or completely avoiding the flooding of the compressed air from the parasitic volume.

The concept of the invention makes it possible to measure the gas pressure actually present in the passage at times when no pneumatic system, in particular an air spring system, is required. The pressure determined by the pneumatic-based equivalent model may then be corrected based on the measurements. In this way, the usability of the air spring system is not impaired.

According to the inventive concept, a continuously updated determination of the pressure can be achieved in a coordinated manner without the disadvantages of practical, in particular sequential, measurements. Since the information already provided, in particular the loading situation of the vehicle and the information about the spring bellows, such as the current offset of the associated air spring and thus the contour of the spring bellows, can be advantageously used when the pressure is determined in a computational manner according to the concept of the invention.

Advantageous developments of the invention, which are found in the dependent claims and specify advantageous possibilities, are achieved in the context of the task and with regard to further advantages.

In particular, it is provided that at least one pressure value is calculated when a state of the pneumatic system changes, wherein the state change is a change or a regulation process of at least one offset of the air spring system or a switching process of at least one valve. The change in state can be caused, for example, by a change in the loading state of the vehicle, for example, an occupant entering the vehicle, the height of the vehicle being reduced due to the additional mass and thus at least one offset of the air spring being changed. However, the change in state can also be caused by further changes in the surroundings and operating parameters, for example a changing atmospheric pressure or a changing ambient temperature.

For different purposes, for example, for calculating the availability when lifting from the pressure store, the control of the air suspension system requires the pressure in the air spring bellows and in the pressure store. In particular, the pressure in the air spring bellows depends primarily on the static wheel load (vehicle empty mass plus variable vehicle loading) and the contour of the spring bellows. By detecting all parameters describing the state of the pneumatic system, in particular by sensors installed in the pneumatic system and in the vehicle, a state change can be detected regularly, in particular continuously or quasi-continuously. Suitable sensors for this purpose are, in particular, height sensors, temperature sensors and/or pressure sensors.

In a further development of the invention, in which the calculation of the pressure value determined by means of the pneumatic equivalent model is always kept up to date by means of practically continuous detection of the relevant state changes of the pneumatic system, the switching process of the pneumatic system, in particular in the form of a valve switching process which is carried out automatically in the context of a control process of the pneumatic system, but also a manually triggered switching process, also represents a change in the state of the pneumatic system. The pressure value determined in a computational manner is therefore advantageously as close as possible to the actually present pressure value.

It is advantageously provided that at least one pressure value is corrected by means of the pressure value measured by the pressure sensor. In particular, this may mean that the computationally determined pressure value may be compared with the measurably determined value for correction. In particular, the pressure values determined in a computational manner can be replaced by pressure values determined in a measurement manner at regular or irregular intervals.

In this refinement, an advantageous compromise can be achieved between the pressure values which are always up to date and which describe the state of the pneumatic system at least approximately and which are determined in a computational manner and the pressure values which are determined only over a relatively long time interval but are determined in a precisely measured manner.

In particular, it is provided that the measured pressure value is measured by means of a pressure sensor during a time period in which no adjustment process of the air spring system is carried out. In particular, this can mean that the pressure actually present in the total volume is determined in a sensing manner by means of the pressure sensor, in order to carry out a correction, in particular based on a pneumatic equivalent model, in a computational manner, in particular using the physical measured variable. In this refinement, the measurement is carried out in particular during periods in which the function of the compressed air supply facility is not required. This means that, in particular, no lifting or lowering operation of the vehicle has to be carried out during this time. This refinement advantageously makes it possible to decouple the measured compressed air value from the provision or the computational determination of the pressure value by the pneumatic-based equivalent model. For processes which require a current value of the pressure prevailing in the total volume, in particular for the control process of the air spring system, a computationally determined pressure can therefore be used instead of a measured pressure, and thus measurement can advantageously be avoided.

This advantageously results in the disadvantage mentioned at the outset that the availability of compressed air supply facilities is limited due to the measurement of compressed air values, in particular the sequential measurement of a plurality of compressed air values, being reduced or even completely avoided.

In particular, it is provided that the measured pressure value is measured by means of a pressure sensor during the setting process. In particular, this may mean that the measurement that is to take place in reverse, in particular a pressure measurement that is carried out within the scope of the regulating process of the pneumatic system, may advantageously be used in this case (as opposed to a measurement that is triggered specifically for correcting the computationally determined pressure value) in order to determine the actual pressure and thus for correcting the computationally determined pressure value. Such a measurement can be carried out, for example, during the lifting of the vehicle by the supercharger or during the filling of the pressure accumulator.

It is advantageously provided that the at least one offset is measured by means of a height sensor. In this case, it is particularly advantageous to use existing sensors, which are used in particular for determining the vehicle height at the respective air spring, for determining the offset of the air spring and thus for determining the airbag volume.

Advantageously, the pneumatic equivalent model is formed by the following steps: determining an initial pressure present in the equilibrium volume; determining at least one individual initial pressure in at least one individual volume not belonging to the equilibrium volume; determining all mass air flows into or out of the balancing volume; determining the total air mass present in the balancing volume and/or determining at least one individual air mass present in the volume; the pressure is calculated using the air mass, volume and measured temperature based on gas equations, especially ideal gas equations. In particular, this means that an equivalent pneumatic model is formed by balancing all the air mass flows into and out of the balancing volume, wherein the volume of the balancing volume is known or determinable and the pressure present in the balancing volume can therefore be determined on the basis of a gas equation, in particular an ideal gas equation. For this purpose, the temperature, in particular in the compensation volume, is also measured or otherwise determined, in particular approximately. In this way, according to the inventive concept, it is advantageously possible to achieve a determination of the pressure present in the equalizing volume. Furthermore, it should be noted that the term "formation of an equivalent model" should equally be understood as an application of the equivalent model or as an update of the input variables of the equations of the model. In each computational determination of the pressure, the basic relationship is therefore not reconstructed, but only the state-describing parameters, in particular the offset of the air spring for describing the compensation volume, are updated.

Within the scope of a particularly preferred development, it is provided that the determination of the total air flow into or out of the equalization volume further comprises the following steps: the at least one spring bellows air flow is determined by calculating the at least one spring bellows air flow by means of an orifice equation, taking into account the at least one spring bellows pressure and the at least one effective spring bellows flow cross section, and/or the at least one storage air mass flow is determined by calculating the at least one storage air mass flow by means of an orifice equation, taking into account the at least one storage pressure and the at least one effective storage flow cross section, and/or the delivery air mass flow is determined by calculating the delivery air mass flow by means of an orifice equation, taking into account the at least one air dryer pressure and the at least one effective delivery flow cross section, and the total air flow is balanced taking into account all air mass flows.

In particular, this means, in particular, that all the air mass flows into and out of the balancing volume are balanced for the purpose of balancing. This does not necessarily mean that the air mass flow inevitably occurs at each throttle or at the location described by the orifice plate equation in each aerodynamic equivalent module at each balancing. Instead, it is possible or even expedient to carry out the balancing and thus the recalculation of the pressure after each switching operation of the valve in order to update the pneumatic equivalent model and always maintain the calculated value of the pressure at the actual pressure as close as possible to the respective state. The calculated determination of the mass flow and the calculated determination of the pressure based on the mass flow according to the inventive concept, which are carried out in particular permanently in conjunction with the current level value and the air mass in the respective volume, advantageously reduce the dependency on the sensor. This relates in particular to the time dependence of the pressure measurement. A particularly preferred embodiment of the calculated determination of the mass flow and the subsequent calculated determination of the pressure is set forth in the accompanying description as an exemplary system of orifice plate equations.

In particular, it is provided that the determination of the air dryer pressure further comprises the following steps: determining by calculating the compressor air mass flow by means of the perforated-plate equation taking into account the at least one compressor pressure and the at least one effective compressor flow cross section; the determination is carried out by calculating the bleed air mass flow by means of the orifice equation, taking into account the at least one bleed pressure and the at least one effective bleed flow cross section. In particular, this can mean that the compressor as input and the bleed air connection as output of the balancing volume as control volume are combined for simplicity in a pneumatically equivalent module, in particular in the region of a further mass flow balancing. In this way, the calculation of the pressure based on the pneumatic equivalent model is advantageously simplified.

It is advantageously provided that the determination of the initial pressure prevailing in the compensation volume is carried out on the basis of the measured pressure. In particular, this means that the measured pressure is used as an input variable for the computational determination of the pressure by means of a pneumatic equivalent model. This has the advantage that the value can be determined for a period of time before the calculation, in particular during a period of time when the function of the compressed air supply facility is not required. The determination of the current pressure value in a computational manner can also be carried out to a value which is as current as possible and which deviates in particular slightly from the pressure actually present in the balancing volume and/or the individual volumes.

Within the scope of a particularly preferred development, it is provided that the determination of the initial pressure prevailing in the compensation volume is carried out on the basis of the calculated pressure of the previous application cycle of the pneumatic equivalent model. In particular, this means that values are used as input variables for the computational determination of the pressure, which is also determined computationally, and more precisely in particular in previous applications of pneumatic equivalent models. In this way, it is possible to tolerate, however, adding up the possible deviations of the pressure actually present in the compensation volume over one or more preceding calculations. However, this risk can be reduced or suppressed by the quality of the pneumatic equivalent model, taking into account systematic deviations between the model and the actual situation by means of correction factors and, in particular, measuring the actual pressure prevailing in the compensation volume for the purpose of correction. In this way, the dependence on measurements made in a sensing manner is advantageously reduced.

In particular, it is provided that the compressor pressure and/or the compressor air mass flow are determined by means of a displacement characteristic curve. In particular, this means that the delivery output of the compressor, in particular the pressure-dependent volume flow, can be determined by means of known relationships which are described in the form of delivery quantity characteristic curves. On the basis of this, the air mass flow delivered by the compressor can be determined in an advantageously simplified manner when balancing the total air mass.

In the context of a particularly preferred development, it is provided that the displacement characteristic is adapted as a function of ambient parameters, in particular the ambient pressure of the atmosphere and/or the booster supply voltage. In particular, this means that the relationship between the volume flow and the pressure described in the displacement characteristic is adapted as a function of ambient parameters which depend on the compressor. This is done in particular when determining the air mass flow in order to take into account the compressor power which is influenced by the changing ambient parameters. In this way, the result of the calculation is advantageously improved, in particular in that it is made closer to reality.

Within the scope of a particularly preferred development, it is provided that the pressure of the air bleed is given by the ambient pressure of the atmosphere. In particular, this means that when using a pneumatic equivalent model and in particular when determining the bleed air mass flow, the ambient pressure, in particular the air pressure prevailing outside the vehicle, will be used when using the orifice plate equation. For example, the value may be measured, for example, by a further sensor which does not necessarily belong to the compressed air supply facility, or determined, in particular, on the basis of other measured values and information, such as the current geographic height of the vehicle, which is an approximate determination.

In particular, it is provided that compressed air is generated by the compressor if the determined pressure or the measured pressure lies below a minimum pressure value. In particular, this means that in the method according to the inventive concept, in particular the pressure value is determined computationally and/or from a combination of calculations and measurements, and the measures for increasing the pressure are carried out in the sense of a regulating circuit at a minimum value below the critical value on the basis of the determined value. Such measures are, in particular, the generation of compressed air for filling the pressure accumulator in order to provide a sufficient quantity of compressed air for carrying out the desired level adjustment process of the air spring system. In this way, the availability and reliability of the pneumatic system and in particular of the compressed air supply is advantageously increased.

It is advantageously provided that the compressed air is discharged via the bleed air connection if the determined pressure or the measured pressure lies above a maximum pressure value. Analogously to the above-described development, it is specifically intended that, in the method according to the inventive concept, the pressure value is determined, in particular in a computational manner and/or from a combination of calculations and measurements, and the measures for reducing the pressure are carried out in the sense of a control loop when a critical minimum value is exceeded on the basis of the determined value. Such measures are in particular the discharge of compressed air via the bleed air connection. In this way, critical pressure states which may be caused by a supercritical air pressure within the compensation volume are advantageously avoided.

The object is achieved by the invention with a device for controlling and regulating a pneumatic system for carrying out the method according to the inventive concept, which has a pressure determination unit and a pressure regulator. The object is achieved by the invention with a pneumatic system which is designed for carrying out the method according to the inventive concept and has a compressed air supply and an air spring system, wherein the pneumatic system has: a pressure accumulator, a passage and at least one air spring which is selectively connected in an air-conducting manner to the passage via a valve of a valve block, a device for controlling and regulating a pneumatic system according to the inventive concept.

In relation to vehicles, this object is achieved by the invention having a vehicle, in particular a passenger vehicle, having a pneumatic system and a device for controlling and regulating the pneumatic system, which device has a pressure determination unit and a pressure regulator for carrying out the method according to the inventive concept.

The device for controlling and regulating a pneumatic system having a pressure determination unit and a pressure regulator is configured for carrying out the method according to the invention. The advantages of the method are advantageously used in the device according to the invention for controlling and regulating a pneumatic system. This is achieved in particular by a pressure determination unit which performs a pressure determination on the basis of a pneumatic equivalent model and can thus achieve a pressure determination and a pressure regulation with the advantages already mentioned in connection with the method.

According to the invention, a pneumatic system having a compressed air supply and an air spring system is configured to carry out the method, wherein the pneumatic system has:

a pressure accumulator, in particular in a compressed air supply system and/or in an air spring system,

a passage and at least one air spring selectively connected to the passage in an air-conducting manner via a valve of the valve block,

the device for controlling and regulating a pneumatic system according to the invention.

The pneumatic system according to the invention also utilizes the advantages of the method in an advantageous manner. Which enables pressure determination and pressure regulation by means of a pressure determination based on a pneumatic equivalent model with the advantages already mentioned in connection with the method. This is particularly advantageous in passenger vehicles, since the computationally performed determination can reduce the dependency on the measurements performed in a sensing manner, and thus can reduce or avoid measurements that particularly lead to waiting times that can be perceived by the user of the vehicle.

Embodiments of the invention are described below with the aid of the figures. The figures for illustration are not shown to scale, but are embodied in schematic and/or slightly modified form. For additional content on the teachings that can be seen directly from the figures, reference is made to the relevant prior art. It is contemplated herein that details of the invention may be made without departing from the general concept of the invention. The features of the invention disclosed in the figures and in the claims can be of importance for the development of the invention, both individually and in any combination. Furthermore, all combinations of at least two of the features disclosed in the description, the drawings and the claims fall within the scope of the invention. The general idea of the invention is not limited to the exact form or details of the preferred embodiments shown and described below, nor to the subject matter which is limited compared to the subject matter claimed in the claims. For a given measurement range, values within the mentioned limit ranges should also be disclosed as limit values and can be used as desired and can be protected by rights. For the sake of clarity, identical or similar parts or parts with identical or similar functions are provided with the same reference signs.

Drawings

Additional advantages, features and details of the present invention will be apparent from the following description of preferred embodiments, taken in conjunction with the accompanying drawings. Wherein:

fig. 1 shows a preferred embodiment of a pneumatic system with a compressed air supply and an air spring system;

FIG. 2 shows a schematic diagram of an equivalent model of pneumatics;

FIG. 3 shows a schematic flow chart for determining a pressure value by means of a pneumatic equivalent model;

FIG. 4 shows the switching state of the pneumatic system and the time profile of the measured and calculated pressures;

fig. 5 shows a very simplified illustration of a vehicle with a pneumatic system.

Detailed Description

Fig. 1 shows a preferred embodiment of a pneumatic system 100 with a compressed air supply 10 and an air spring system 90. The compressed air supply system 10 has a compressed air supply 1, a compressed air connection 2 to the air spring system 90, and a bleed air connection 3 to the environment U, in which an ambient pressure PU of the atmosphere is present. Furthermore, the compressed air supply 10 comprises a pneumatic main line 60 between the compressed air supply 1 and the compressed air connection 2. The pneumatic main circuit 60 has an air dryer 61 and a first throttle 62. The bleed air line 70 of the compressed air supply system 10 connects the compressed air supply 1 to the bleed air connection 3 via the second throttle 63 and the bleed air valve 240. The main port 12 of the air spring system 90 is connected to the compressed air port 2 via a supply line 96.

Furthermore, a control valve 241 is connected to the purge valve 240, so that the compressed air in the pneumatic main line 60 can be used to adjust the position of the purge valve when the control valve 241 is in the corresponding position. Here, the first throttle 62 ensures that a sufficiently high dynamic pressure is always formed in front of the first throttle 62 in order to open the valve 240. In this way, the valve can be brought from the blocking position shown into a regeneration position in which air can flow from the compressed air supply 1 via the bleed line 70 to the bleed air connection 3. In this way, the air dryer 61 can be flowed through against the actual direction of conveyance by means of compressed air from the pressure accumulator for regeneration purposes.

As is clearly visible on the right-hand side of fig. 1, an air spring system 90 of the vehicle is provided, the air spring system 90 has a passage 95, to which in each case a respective directional control valve 93.1, 93.2, 93.3, 93.4 can be pneumatically separated connected an air bag branch line, which leads to the air bags 91.1, 91.2, 91.3, 91.4 of the air springs 92.1, 92.2, 92.3, 92.4, respectively, in the present case, in total four directional control valves 93.1, 93.2, 93.3, 93.4 are arranged in the valve block 97, depending on the pressure or air quantity in the air bags 91.1, 91.2, 91.3, 91.4, the air springs 92.1, 92.2, 92.3, 92.4 are offset by an offset amount 92A, 92.1A, 92.2A, 92.3A, 92.4a pressure sensor 94 is connected to the passage 95, in the present case, the pressure sensor 94 is connected via a pressure sensor 94, via a sensor 94, a L, a pressure sensor 94, a pressure sensor 300, a pressure sensor 94, a pressure regulator unit, a pressure.

Furthermore, the compressed air supply 10 currently has a pressure accumulator 120. The pressure accumulator 120 is connected in a gas-conducting manner to the channel main interface 12 via the pressure accumulator supply line 82. The connection may be selectively interrupted via a pressure accumulator valve 250.

In the present case, compressor structure 21 is driven by motor M and draws air via bleed air interface 3 for the purpose of compressing compressed air D L, an air filter 68 is arranged between compressor structure 21 and bleed air interface 3.

Fig. 2 shows a schematic diagram of a pneumatic equivalent model PEM according to the concept of the invention. In this case, the pneumatic system, which is shown in simplified form in fig. 1, is constructed, in particular, as a system of volumes and throttle elements as a basis for a model for the computational pressure determination.

In the present case, the valve block 97 forms with its valve block volume VV a compensating volume VBI L which takes into account all the main mass flows, in which four spring bellows 91.1, 91.2, 91.3, 91.4 of the total air mass MG. are present, which are coupled to the valve block 97, in the pneumatic equivalent module PEM the lines and valves leading to the respective spring bellows are taken into account in a simplified manner by means of the restrictors D1, D2, D3, D4, respectively, the lines and valves leading from the valve block 97 to the pressure accumulator 120, in particular the pressure accumulator valve 250 and the pressure accumulator supply line 82, are taken into account by means of the restrictor D5, when the respective directional control valve 93.1, 93.2, 93.3, 93.4 is in the open position, the movement of the bellows mass flows MB1, MB2, MB3, MB4 takes place by means of the respective restrictors D1, D2, D3, D D4., depending on the respective pressure ratio, from the respective air spring bellows 97 to the respective air spring bellows 91.90, 91.3, 91.4, which leads to a lowering in the respective direction, or to a lowering of the respective spring in the opposite direction.

Similarly to the bladder mass flows MB1, MB2, MB3, MB4, the pressure accumulator air mass flow MS moves through the throttle D5 when the pressure accumulator valve 250 is in the open position. When the pressure accumulator 120 is filled, the pressure accumulator air mass flow MS can be moved from the valve block 97 to the pressure accumulator 120. When the compressed air stored in the pressure accumulator 120 is used, in particular for filling the spring bellows 91.1, 91.2, 91.3, 91.4, the pressure accumulator air mass flow MS changes direction. In the calculation, the pressure accumulator 120 processes as the bladder volumes 91.1V, 91.2V, 91.3V, 91.4V, but the pressure accumulator volume VD is not changed in the pressure accumulator 120.

Finally, the likewise simplified air dryer 61 is coupled to the valve block 97 via a throttle D7. In this way, the feed section mass flow MZ can be moved through the throttle D7. The air dryer 61 is in turn connected to the compressor arrangement 21, so that a compressor air mass flow MV can flow into the air dryer 61. Furthermore, the air dryer 61 can be connected to the surroundings via an air bleed connection 3, which is not shown here. This connection is modeled in a pneumatic equivalent module PEM by means of a throttle D6. Bleed portion air mass flow ME may move through orifice D6.

All mass flows through the restrictors D1 to D7 can be described by the orifice plate equation (blendegehung) BG. The respective orifice plate equation BG describes the mass flow through the respective throttle element as a function of the fluid properties, the flow diameter and the pressure ratio on both sides of the respective throttle element. Here, a supercritical flow rate and a subcritical flow rate are distinguished.

In the case of a supercritical flow rate (shown in a simplified manner), those counter pressures which are present at the throttle are ignored, since they are below a critical value.

In this case, the mass flow rate is described as follows:

however, in the case of subcritical flows, the back pressure should be taken into account when calculating the mass flow, more precisely in the form:

herein, p is_iDescribes the input pressure of the throttle, and p_aDescribing the output pressure or back pressure, respectively, p_iAnd ρ_aInput and output densities are described, κ describes the isentropic index, and A_{Is effective}The reduction of the individual lines through the restrictors D1 to D7 is carried out by means of these equations and the respective pressure, so that, in particular, the missing variables, in particular the mass flows, through the respective restrictors D1 to D7 can be determined, in particular, the mass flows into and out of the valve block 97 can be determined in this way, in order to determine the total air mass MG, and in particular the individual air masses M L1, M L2, M L3, M L4, M L S, M LL can be determined further on the basis of the mass flow balancing BI L.

The pressures PF1, PF2, PF3, PF4 of the spring bellows 91.1 to 91.4 depend in particular on the offset 92.1A, 92.2A, 92.3A, 92.4A of the respectively associated air spring 92.1, 92.2, 92.3, 92.4 and the instantaneous loading state and can be determined, for example, approximately by measuring the current height d, i.e. the offset of the respective air spring. The offset is determined in particular via height sensors H.1, h.2, H.3, H.4 on the respective spring bellows 91.1, 91.2, 91.3, 91.4 and/or on the respective axle. If necessary, further parameters, in particular the temperature measured in or near the respective volume, can be taken into account in the calculation for correction purposes in this approximate determination.

Furthermore, the volume flow delivered by the compressor arrangement 21 can be determined as a function of the pressure in conjunction with the displacement characteristic 24. In this way, the compressor air mass flow MV can be determined at least approximately.

The displacement characteristic 24 of the compressor depends on an external factor, namely the ambient parameter UP. These external factors may be partly taken into account by sensors already present in the vehicle, for example ambient pressure sensors of the air conditioning installation. Tolerances of the supercharger, which are caused, for example, by mechanical manufacturing tolerances or wear, can be corrected by self-calibration when a known volume is filled (for example, when the pressure accumulator 120 or the air dryer 61 is filled). Thus, the accuracy of pressure calculation can be obviously improved.

Furthermore, the balance volume VBI L of all components considered in the pneumatic equivalent model can be described, in the present case, the balance volume VBI L is formed by the volume of the valve block 97 by forming the mass flow balance BI L, all air mass flows MB1, MB2, MB3, MB4, MS, MZ into the balance volume VBI L and out of the balance volume VBI L can be determined.

In the case of a single volume, an unchangeable volume (in particular the pressure reservoir volume VD and the air dryer volume V L) and a variable volume (in particular the bellows volumes 91.1V, 91.2V, 91.3V, 91.4V) are distinguished, the volumes 91.1V, 91.2V, 91.3V, 91.4V of the spring bellows 91.1, 91.2, 91.3, 91.4 substantially being dependent on the offset 92.1A, 92.2A, 92.3A, 92.4A of the respectively associated air springs 92.1, 92.2, 92.3, 92.4.

The pressure in the spring bellows depends primarily on the static wheel load (vehicle dead weight + variable vehicle load) and the contour of the spring bellows, since the offset 92.1A, 92.2A, 92.3A, 92.4A can be measured by means of sensors, in particular height sensors, which are usually already present in the vehicle, and therefore provide the necessary information for calculating the mass flow balance BI L.

The pressure prevailing in the compensation volume can now be calculated on the basis of the total air mass MG by means of a gas equation (GG), in particular an ideal gas equation (IGG), using the compensation volume VBI L the pressure prevailing in the compensation volume can be calculated analogously for the individual volumes 91.1V, 91.2V, 91.3V, 91.4V, VD, V L on the basis of the individual air masses M L1, M L2, M L3, M L4, M L S, M LL assigned to the individual volumes, the pressures prevailing in the individual volumes being generally applicable:

here, V describes the volume, M describes the air mass, T describes the temperature measured or assumed in the volume V, and R describes the gas constant.

Fig. 3 schematically depicts a possible procedure with the aid of a pneumatic equivalent model according to the inventive concept, in particular for pressure determination.

In step S0, it is first checked continuously whether a change in state ZA of the pneumatic system 100 has occurred, the change in state ZA may in particular be a change in the vehicle altitude, i.e. a change in at least one offset 92A, 92.1A, 92.2A, 92.3A, 92.4A or a change in another switching process SV, for example opening the purge valve 250, if a change in state ZA has occurred, it is proceeded via branch V1 to implement step S1 in order to determine a new pressure value P, P L, PV, PS, PE, PF1, PF2, PF3, PF 4.

In step S1, it is checked whether the state change ZA is a switching process SV in which the pressure PMESS is measured (in particular within the scope of an adjustment process). This can be the case, for example, when the vehicle is lifted by the compressor 21, in particular a supercharger, or when the pressure accumulator 120 is filled by the compressor 21.

If this is not the case, the program flow leads via branch V2 to step S2 for the computationally determined pressure P (in the application cycle Z in which the pneumatic equivalent model PEM according to the concept of the invention is applied).

In step S2, a first confirmation of the initial pressure PI is performed. This can be done in particular via the value P calculated in a previous run of the method or in the application of the pneumatic equivalent model PEM or via the value PMESS measured by the pressure sensor 94.

In the following steps S3-S7, a mass flow balance BI L around the balance volume VBI L is established, in step S3 the balance volume VBI L is determined, in the present case, the balance volume is formed by the valve block volume VV of the valve block 97, in particular because all pressure-determination-relevant mass flows, in particular mass flows MB, MB1, MB2, MB3, MB4, MS, MZ, pass through the valve block 97.

In step S4, at least one airbag air mass flow MB, MB1, MB2, MB3, MB4 is determined using the perforated plate equation BG, taking into account the at least one spring airbag pressure PF, PF1, PF2, PF3, PF4 and the at least one effective spring airbag flow cross section AF, AF1, AF2, AF3, AF 4. In this case, when the current height, in particular the offset of the air spring, is measured with the respective air spring lowered, the pressures PF1, PF2, PF3, PF4 of the spring bellows 91.1 to 91.4 are dependent on the offset 92.1A, 92.2A, 92.3A, 92.4A of the respectively associated air spring 92.1, 92.2, 92.3, 92.4 and the momentary loading state and can be determined approximately.

Similarly, in step S5, at least one storage air mass flow rate MS is determined by means of the orifice plate equation, taking into account at least one storage pressure PS and at least one effective storage flow cross section AS.

Furthermore, in step S6, the delivery air mass flow MZ. is determined using the perforated plate equation BG, taking into account at least one air dryer pressure P L and at least one effective delivery flow cross section AZ, the air dryer pressure P L also being, as already shown in fig. 2, dependent on the compressor air mass flow MV and the bleed air mass flow ME, the air dryer having a constant air dryer volume V L, the compressor air mass flow MV being derived in this case in particular from the displacement characteristic curve of the compressor, the bleed air mass flow ME likewise being determined using the perforated plate equation, taking into account a throttle D6 with an effective bleed flow cross section AE and the bleed air pressure PE, a further mass flow balance BI L' being formed around the air dryer volume V L of the air dryer 61, in particular, in order to determine the delivery air mass flow MZ.

It should be noted in connection with steps S4, S5, and S6 that it is not always necessary to determine all air mass flows, or that one or more air mass flows may be made zero when determined. In particular, it is even expedient and preferred to determine only a single air mass flow, to be precise at the respective point in time, when the respective valve is actuated for triggering that, in particular, the single air mass flow.

After the determination of the air mass flow or air mass flows, in a subsequent step S6, a balance of the air mass flows, in particular of the air mass flows MB, MB1, MB2, MB3, MB4, MS, MZ, is calculated for calculating the total air mass MG.

After reaching the equilibrium in step S7, the information is provided in order to recalculate the pressures P, P L, PV, PS, PE, PF1, PF2, PF3, pf4 in a second determination in step S8 for this purpose, the pressure P is calculated, for example on the basis of the gas equation (GG), in particular the ideal gas equation (IGG), taking into account the total air mass MG of the equilibrium volume VBI L, in particular the measured temperature T.

It is also possible to calculate individual pressure values P L, PV, PS, PE, PF1, PF2, PF3, pf4 according to the inventive concept, in order to determine individual pressure values P L0, PV, PS, PE, PF1, PF2, PF3, PF4 of individual volumes 91V, 91.1V, 91.2V, 91.3V, 91.4V, VD, V L, also on the basis of mass flow balances BI L1, based on the calculated air mass flows MB, MB1, MB2, MB3, MS, MZ assigned to individual volumes 91V, 91.1V, 91.2V, 91.3V, 91.4V, VD, V L3 by means of mass flow balances BI L2, it is possible to calculate the respective air mass flows resulting from individual air mass flows MB, MB 72, MB3, MS 3, MZ 3, PF 72V.

For example, the pressure reservoir volume VD in the pressure reservoir 120 and the pressure reservoir pressure PS. can be determined for the reservoir volume VD by means of the reservoir air mass flow MS determined by the mass flow balancing BI L (and thus the pressure reservoir individual air mass M L S present in the pressure reservoir 120) for variable bladder volumes 91.1V, 91.2V, 91.3V, 91.4V, with additional information about the offsets 92A, 92.1A, 92.2A, 92.3A, 92.4A) and the associated spring bladder pressures PF1, PF2, PF3, PF4 can likewise be calculated with the respective bladder mass flows MB1, MB2, MB3, MB4 (and the resulting bladder individual air masses M L1, M L2, M L3, M L4).

If it is ascertained in step S1 that the process of measuring the pressure PMESS is a switching process SV, this measured pressure is known in step S9, for this purpose, in particular, the measured pressure value measured in the region of the regulating process RV is read via a control of a pneumatic system, not shown here, then in step S10, the measured value PMESS is compared with the value P calculated in particular in the previous cycles in steps S2 to S8, and the calculated value P is corrected in particular by the measured value PMESS, in this way, the value PMESS measured in contrast for other purposes, in particular for the regulating process, can advantageously be used to correct the computationally determined value P, and thus the accuracy of the method can be improved, the pressure sensor 94 is switched to a single volume 91V, 91.1V, 91.2V, 91.3V, 91.4V, VD, V L by means of a single pressure correction spring 91V, 91.26V, VD, V L, and thus the pressure of the single pressure sensor 94 is corrected by means of a single pressure correction spring pfess 3693, PF 26, PF2, PF3, PF 93, and thus the pressure of the first spring measured by means of a corresponding correction, PF3, can be switched to a first pressure correction, PF 3.

If in step S0 it is ascertained that no switching process of the pneumatic system 100 has taken place and therefore sufficient free time period TFREI is available for measurement, the program flow is led via branch V1 to carry out step S11. In step S11, it is checked whether the instantaneous operating state of the vehicle allows the compressed air measurement. In particular, if it is particularly anticipated that a compressed air supply for the level regulation of the vehicle must be made available within a sufficiently short period of time, the compressed air measurement is abandoned and the program flow is returned to the starting point by means of the branch V3 and therefore to the step S0. However, if compressed air measurement is possible according to the above criteria, in step S12 compressed air measurement is performed, in particular by means of the compressed air sensor 94. Then in a subsequent step S13, the measured value PMESS is compared (analogously to step S10) with the calculated value P (in particular in the previous cycle) and the calculated value P is corrected, in particular by the measured value PMESS. After step S13, program flow returns to the starting point, and thus to step S0.

During operation, that is to say during operation of the pneumatic system (100), in particular of a vehicle (1000) having the pneumatic system (100), such changes in state (ZA) occur relatively frequently, in particular when loading changes, temperature fluctuations or dynamic forces resulting from operation are small, which have an effect in particular on the vehicle height level, that is to say the offset amounts 92A, 92.1A, 92.2A, 92.3A, 92.4A. The determination of the air pressure can thus be carried out computationally continuously or quasi-continuously, in particular because the time for carrying out the calculation of the pressure P on the basis of the pneumatic equivalent model PEM is relatively short compared to the determination of the passing measurement of the pressure PMESS.

Fig. 4 shows a time course of the switching state of the pneumatic system 100 and the measured pressure PMESS and the calculated pressure P.

The lower part of the diagram shows a pressure profile over time in pascals in the pressure reservoir 120, wherein the measured pressure value PMESS on the one hand and the calculated pressure value P on the other hand are shown.

In this example, initially at time T1, the pressure accumulator valve 250 is actuated together with the valves 93.3, 93.4 of the rear axle 932. Since the pressure level in the pressure reservoir 120 is higher than the pressure in the airbags 91.3, 91.4 (airbag pressure not shown here), air flows from the pressure reservoir 120 into the airbags 91.3, 91.4. Thus, the vehicle rises at the rear axle 932 and the pressure in the pressure reservoir 120 drops.

After the rear axle 932 is lifted, the lifting of the front axle 930 occurs at time T2. Here, the pressure accumulator valve 250 is actuated again with the airbag valves 93.1, 93.2.

Since it is currently not possible to measure the pressure in the pressure accumulator 120 during the lift, a subsequent additional pressure measurement is required at time T3.

At times T4, T5, and T6, the steps at times T1, T2, and T3 are similarly repeated. At time T4, rear axle 932 is raised by actuation of valves 93.3, 93.4. At time T5, front axle 930 is raised by actuating valves 93.1, 93.2. A pressure measurement is then taken at time T6 for determining the measured pressure PMESS.

It should be noted that the measured pressure values PMESS are only updated during the pressure measurements (T3, T6), respectively. And the calculated pressure values will be continuously updated (change of the dotted lines at T1 and T2 and T4 and T5).

The small pressure difference DP between the measurement PMESS and the calculation P after the actual pressure measurement shows that even a subsequent measurement for correction can be completely eliminated with the calculation method according to the inventive concept.

Fig. 5 shows a schematic illustration of a vehicle 1000 (in the present form of a passenger vehicle) with a pneumatic system 100 having a compressed air supply system 10 and an air spring system 90. In particular in vehicles in the passenger vehicle sector, it is particularly important to rapidly provide compressed air for level regulation during operation, since in particular pauses for carrying out air pressure measurements can be perceived by the driver of the vehicle. The passenger vehicle 1000 illustrated here by way of example and without limitation to the applicability of a load-carrying vehicle or other commercial vehicle therefore has four wheels 920, two of the front wheels each being illustrated here on the basis of a sectional illustration. The air spring system 90 has four air springs 92.1, 92.2, 92.3, 92.4, similar to the number of wheels, two of the front airbags being shown here on a cross-sectional view, similar to a wheel base. The four air springs 92.1, 92.2, 92.3, 92.4, which are each associated with four wheels 920, are supplied with compressed air by the compressed air supply system 10 as part of the air spring system 90. The compressed air supply 10 is connected in a fluid-conducting manner via a supply line 96, the main port 12 and the passage 95 to the components of the pneumatic system 90, in this case the four air springs 92.1, 92.2, 92.3, 92.4.

List of reference numerals

1 compressed air delivery section

2 compressed air interface

3 air bleeding interface

10 compressed air supply installation

12-way main interface

21 compressor structure, compressor

24 displacement characteristic curve

60 pneumatic main circuit

61 air dryer

62 first throttle member

63 second throttle member

68 air filter

70 air bleed line

82 pressure accumulator supply line

90 air spring facility, pneumatic facility

91. 91.1, 91.2 spring airbag, airbag

91.3、91.4

91V, 91.1V, 91.2V, airbag volume

91.3V、91.4V

92. 92.1, 92.2, air spring

92.3、92.4

92A, 92.1A, 92.2A, offset of air spring

92.3A、92.4A

93. 93.1, 93.2, reversing valve, air bag valve

93.3、93.4

94 pressure sensor

94L sensor circuit

94C pressure determination unit

95 channel

96 supply line

97 valve block

100 pneumatic system

120 pressure accumulator

120V pressure reservoir volume

240 air release valve

241 control valve

250 pressure accumulator valve

300 device for controlling and regulating a pneumatic system

302 control circuit

304 pressure regulator

920 wheel of vehicle

930 front axle

932 rear axle

1000 vehicle

M motor

Effective AE bleed cross section

AF-effective spring balloon flow cross section

AS-efficient memory flow cross section

AV effective compressor flow cross section

AZ effective transport section flow cross section

Equation for BG orifice plate

BI L, BI L' Mass flow Balancing, additional Mass flow Balancing

D1-D7 pneumatic equivalent module throttling element

D L compressed air

DP pressure differential

GG gas equation

Equation for GGI ideal gas

H.1-H.4 height sensor

MB, MB1-MB4 air bag mass flow

Air mass flow of ME bleed part

Total air mass of MG

M L1-4 first through fourth air cell Individual air Mass

M L S pressure accumulator single air mass

M LL air dryer Individual air Mass

MS memory mass air flow

MV compressor air mass flow

MZ conveying section air mass flow

P pressure, calculated pressure

PE deflation pressure

PF, PF1, PF2, spring bladder pressure

PF3、PF4

Equivalent module for PEM pneumatics

P L air dryer pressure

Pressure measured by PMESS

PS reservoir pressure

PV compressor pressure

Ambient pressure of PU

PZ conveying section pressure

RV regulation process

Environment around U

UK compressor supply voltage

UP ambient parameters

SV handoff procedure

T temperature

Time of T1-T6 switching process

TFREI free time period for pressure measurement

VD pressure accumulator volume

V L air dryer volume

VV valve block volume

Application cycle of Z-pneumatic equivalent modules