Control device and method for controlling electrically operated apparatuses of a commercial vehicle

Abstract

The invention relates to a control device (30) and method for controlling electrically operated apparatuses of a commercial vehicle (1), the control device (30) comprising an electric motor (5), a hydraulic steering pump (8) for supplying hydraulic flow to an electrically powered hydraulic steering system, a compressor (10) for supplying compressed air to a pneumatic system, a pump clutch (18) provided between said electric motor (5) and said hydraulic steering pump (8), and a compressor clutch (20) provided between said motor (5) and said compressor (10), said pump clutch (18), said motor (5) and said compressor clutch (20) being controllable by a central control unit (16), wherein said pump clutch (18) is provided for engaging and disengaging said hydraulic steering pump (8) with and from said electric motor (5), and said compressor clutch (29) is provided for engaging and disengaging said compressor (10) with and from said motor (5).

Description

[0001] Hannover, 15.01.2025

[0002] IP, Copi, Bremer / sw 304641 -WO-PCT ID 304641 CONTROL DEVICE AND METHOD FOR CONTROLLING ELECTRICALLY OPERATED APPARATUSES OF A COMMERCIAL VEHICLE

[0003] The invention relates to a control device and method for controlling electrically operated apparatuses of a commercial vehicle. Furthermore, a control system comprising the control device and a commercial vehicle are provided. In particular, the invention can be applied in a commercial vehicle which does not comprise an internal combustion engine, but has an non-combustion engine, in particular an electric engine.

[0004] Conventional commercial vehicles typically comprise an internal combustion engine to drive the vehicle and power a compressor of a pneumatic system. In addition, many commercial vehicles comprise an electrically powered hydraulic steering system EPHS to assist the driver in steering the vehicle. A combustion engine can therefore drive the vehicle, power the compressor of the pneumatic system and charge the battery for electric consumer circuits such as an EPHS. However, as vehicles become more electrified and more fuel efficient, the motor-driven components are often converted to electrically driven components. The consumer circuits therefore require motorised devices for their respective actions and for the fluid supply. A fully electric commercial vehicle therefore typically comprises an electrically driven compressor and an electrically powered hydraulic steering system EPHS. The increasing number of such electrical consumer circuits therefore increases the total cost and number of devices, resulting in complex hardware systems with increased weight and cost.

[0005] It is therefore an object of the invention to provide a method and a control device for controlling electrically operated apparatuses of a commercial vehicle, wherein said method and control device reduce the costs, the hardware equipment and the electrical energy consumption.

[0006] This object is realised by a method and a control device according to the independent claims. Furthermore, a commercial vehicle with the control device is provided. The subclaims describe preferred embodiments. The control device is in particular provided for carrying out the method. The method can be carried out by the inventive control device.Thus, a control device is provided comprising an electric motor, a compressor and a hydraulic steering pump, the electric motor driving both the compressor and the hydraulic steering pump. The connections between the common electric motor and the two driven devices, i.e. the compressor and the hydraulic steering pump, are realised by respective clutch mechanisms; thus the hydraulic steering pump is connected to the electric motor by a pump clutch mechanism and the compressor is connected to the common motor by a compressor clutch mechanism.

[0007] The inventive control device offers several advantages: Only a single common electric motor is used to drive two apparatuses of different fluid systems or fluid circuits, in particular the most relevant consumer circuits of the commercial vehicle, which are the compressor of the pneumatic system and the hydraulic steering pump of the EPHS. This provides a space-saving and cost-effective solution. The invention is based on the idea that it is possible to operate these two apparatuses, i.e. the compressor and the hydraulic steering pump, with only one electric motor, since these two devices do not interfere with each other and can be operated in separate time intervals or time slots. In particular, the compressor does not require continuous operation, but can be operated during active compressor periods, in particular by means of closed control loops; moreover, the hydraulic steering pump can be activated depending on relevant condition signals.

[0008] Moreover, the invention offers the following functions and benefits:

[0009] - Providing hydraulic flow to a steering gear based on feedback from a driver input and a vehicle condition,

[0010] - Delivering compressed air to an air reservoir for pneumatic applications, in particular braking and auxiliary applications,

[0011] - Operating one control device, in particular as a single unit, with intelligence control logic, wherein a control algorithm can optimize the performance and power consumption, in particular with a demand driven operation

[0012] - Actuating clutches to engage or disengage the compressor and pump based on an input demand,

[0013] - Reducing hardware, in particular eliminating separate controllers, inverters and motors.The terms “clutch”, “pump clutch” and “compressor clutch” correspond to a suitable clutch mechanisms which are preferably known per se in the art. According to a preferred embodiment, the clutches comprise an engaged basic state, resulting in a high reliability and safety, since a failure to control the clutches does not result in a failure of the apparatuses. According to preferred embodiments, the clutches can each be controlled by pneumatic signals. In such an embodiment, the control device preferably comprises one or two solenoid valves for pneumatically controlling the clutches, said solenoid valves being electrically controlled by a central control unit. In an alternative embodiment, the pump clutch and / or the compressor clutch are directly electrically controlled by said central control unit.

[0014] According to a preferred embodiment, the electric motor is controlled by the same central control unit as the clutches. According to a preferred embodiment, the electric motor is switched between different motor states comprising a motor on state and motor off state and preferably a reduced motor state. The motor off state can be realized by an idle state or by completely switching off the motor. Thus, an effective control of the states and conditions is realised.

[0015] The control device can be realised as a single part or one-piece part, for example with a common housing. This control device can then be mounted in the vehicle, preferably on a vehicle structure, and connected to the vehicle battery. The fluid circuits can be connected to this control device; one fluid circuit is the hydraulic steering circuit of the EPHS, for supporting the steering activity of the driver; the other fluid circuit is the pneumatic system of the vehicle. The control device preferably comprises fluid ports for connecting the fluid circuits, in particular hydraulic ports for a steering gear and a hydraulic tank, as well as a pneumatic intake port for an intake line and a pneumatic outlet port for delivering compressed air to at least one air reservoir. In particular, the pneumatic outlet port can be connected to several air reservoirs, in particular by means of a multi-circuit protection valve. In addition, the control device preferably comprises an electric connector for connecting it to the central control unit. Thus, a compact and space-saving design is realised, preferably with only one control device for these fluid circuits.According to a preferred embodiment, the control device is controlled on the basis of one or more signals of the group consisting of:

[0016] a steering angle rate signal, an engine speed signal, a vehicle speed signal, an air pressure signal provided by a pressure sensor connected to said air reservoir, a compressor state signal, a driver warning signal, an ignition signal from an ignition switch, and a battery charge condition signal.

[0017] According to a preferred embodiment, the electric motor is realised as a permanent magnetic synchronous motor (PMSM motor); such a design allows a high efficiency, a high torque and compact design compared to other motor types; thus, the PMSM motor is able to drive two loads such as the pump and the compressor simultaneously.

[0018] According to a preferred embodiment, the inventive commercial vehicle comprises an engine, in particular a non-combustion engine, the control device and / or the control system, the EPHS, and the pneumatic system.

[0019] The pneumatic consumer circuits of the vehicle can comprise a pneumatic brake system and / or a pneumatic suspension system and / or a pneumatic auxiliary system. Each of these pneumatic systems can comprise an own air reservoir. A pressure sensor is preferably connected to the at least one air reservoir for measuring the air pressure and outputting an air pressure signal to the central control unit.

[0020] The central control unit can receive or input several state signals or condition signals, in particular one or more of the group consisting of:

[0021] steering angle rate signal, engine speed signal, vehicle speed signal, air pressure signal, EPHS state signal, compressor state signal, driver warning signal, ignition signal. On the basis of these signals, the central control unit can carry out the method of operating or controlling the electrical systems of the vehicle.

[0022] Moreover, according to a preferred embodiment, the method comprises multiple control loops for different pump clutch states, different compressor clutch states and / or different motor states. In some of these control loops, one or both clutches are disengaged, thereby allowing reduced motor power. According to a preferred embodiment, the motor can be powered in a full power mode to drive both consumers, i.e. the hydraulic pump and the compressor, in a reduced power mode for powering onlyone of said loads (consumers), and in an idle state or switched-off state without powering a load (consumer).

[0023] According to a preferred embodiment, the method comprising the steps:

[0024] Starting with ignition on and initializing the software, and realising a fault diagnosis for warning the driver in case of any problems or failures. If a system is available, the next step for checking the air pressure and the engine speed can be realised, thereby receiving the most relevant data for the subsequent control loops. Afterwards, a decision step for checking the engine speed is preferably provided. If the engine speed is below an engine speed threshold, steering activities are not necessary and the pump clutch can be activated thereby disengaging the hydraulic pump. In this case, a control loop for controlling and regulating the air pressure can be performed; if the pre-determined air pressure threshold is reached, no consumer, neither the hydraulic pump nor the compressor, are to be driven, and the motor can be switched off (switch completely off or switch into an idle mode), thereby redirecting the method. If the engine speed is above the engine speed threshold, then the steering rate and vehicle speed are checked and the EPHS is switched into its assist mode, in which the steering rate and vehicle speed are compared with respective thresholds. If the steering rate and vehicle speed is sufficient, then air pressure must be regulated in a control loop; if the air pressure is below a pressure threshold, the compressor is to be driven, thereby switching the motor into its full power mode, since it drives both consumers. If the pressure threshold is reached, the compressor clutch can be activated thereby disengaging the compressor and switching the motor back into a reduced power, thereby redirecting the method.

[0025] If in the steering rate and vehicle speed checking mode the thresholds are not reached, the EPHS can be switched into a sleep mode, in which the compressor pressure is closed to be regulated until it reaches its pressure threshold, wherein after the compressor clutch can be activated thereby disengaging the compressor, and the motor can be switched on to reduce power.

[0026] This method therefore enables an operation of both consumers in several routines and control loops, without drawbacks in operating the system.The invention is hereinafter described in more detail with reference to the appended drawings, in which:

[0027] Fig. 1 is a schematic configuration diagram illustrating a commercial vehicle according to an embodiment of the invention, with a control device according to an embodiment of the invention;

[0028] Fig. 2 is a block diagram illustrating a control device according to an embodiment of the invention;

[0029] Fig. 3 is a flowchart illustrating a method of controlling electrically operated apparatuses of a commercial vehicle according to an embodiment of the invention.

[0030] Fig. 1 shows a commercial vehicle 1 comprising an engine 2, an electrically powered hydraulic steering system EPHS 3, a pneumatic system 4 and a control device 30, comprising an electric motor 5. The engine 2 can be an electric engine, an internal combustion engine, a hybrid engine combining combustion and electric motor functions, a fuel cell engine, or any other type of engine. Furthermore, more than one engine can be provided. The engine 2 is used to drive the commercial vehicle 1 ; in particular, the engine 2 can be realised as an electric regenerative engine for converting kinetic energy back into electric energy during braking. The electric motor 5 is thus different from the engine 2; the electric motor 5 is preferably a PMSM (permanent magnetic synchronous motor); however, according to other embodiments, the motor 5 can be an asynchronous motor or another type of electric motor.

[0031] The EPHS 3 comprises an electric hydraulic pump 8 and constitutes a servo-steering system for the driver. The pneumatic system 4 comprises a compressor 10 driven by the motor 5; further, the pneumatic system 4 comprises an air reservoir 15 for storing compressed air, a pneumatic brake system and / or a pneumatic suspension system and / or pneumatic auxiliary systems.

[0032] Fig. 2 shows the control device 30, which comprises the electric motor 5, a hydraulic steering pump 8 and a compressor 10. The electric motor 5 is provided for driving thehydraulic steering pump 8 as well as the compressor 10. The pump 8 is therefore connected to the motor 5 via a pump clutch 18, and the compressor 10 is connected to the motor 5 via a compressor clutch 20, wherein the clutches 18, 20 are controllable independently of one other, lin the depicted embodiment, the pump clutch 18 is controlled by a first solenoid valve 19, and the compressor clutch 20 is controlled by a second solenoid valve 21, the solenoid valves 19 and 21 being electrically controlled by a central control unit 16 by electric control signals S10, S11, respectively, wherein the central control unit 16 also controls the motor 5, as explained hereinafter.

[0033] The central control unit 16 receives signals and data from several sources; according to fig. 2, the central control unit 16 receives: a steering angle rate signal SR, an engine speed signal S2, a vehicle speed signal S3, an air pressure signal S4 from a pressure sensor 23 connected to the at least one air reservoir, an EPHS state signal S5 from the EPHS 3, an ecomp state signal S6 from the compressor 10, a battery charge condition signal S8, and an ignition signal S9 from an ignition switch 38. Furthermore, the central control unit 16 outputs a driver warning signal S7 and the electric control signals S10 and S11.

[0034] The motor 5, the steering pump 8, the compressor 10, the clutches 18, 20 and the solenoid valve 19, 21 are preferably integrated into the control device 30, in particular with a common housing and / or as a single part or one-piece part; the control device 30 can be mounted on the vehicle structure of the vehicle. The control device 30 is then connected to the relevant electrical lines and fluid conduits. The control device 30 comprises preferably at least the following fluid connections for the compressor 10 and the pump 8:

[0035] a first hydraulic port 30a for a hydraulic tank 11 ,

[0036] a second hydraulic port 30b for a hydraulic steering gear 34,

[0037] a pneumatic inlet 30c for an air intake line 32, and

[0038] a pneumatic outlet 30d for an air reservoir 15 and / or a multi-circuit protection valve connected to more than one air reservoir 15.

[0039] In the control device 30, the compressor 10 is connected to the pneumatic inlet 30c and the pneumatic outlet 30d, and the pump 8 is connected to the first hydraulic port 30a and the second hydraulic port 30b.The central control unit 16 can be separate from the control device 30 or integrated with the control device 30. The control device 30 further comprises an electric connector 35 connected to the central control unit 30, wherein the electric connector 35 comprises data connections for various signals. The central control unit 16 is further connected to a vehicle battery 7 for its power supply and for receiving the battery charge condition signal S8, and to the ignition switch 38 for receiving the ignition signal S9.

[0040] The flowchart of Fig. 3 shows a preferred embodiment of the inventive method 100 of controlling electrically operated apparatuses of the commercial vehicle 1. In step 101, the ignition is switched on; the signal “ignition on” corresponds to the active state of the commercial vehicle 1. In step 102, the software in the central control unit 16 is initialised. In step 103, a fault diagnosis is carried out, as it is usual in vehicle electronic systems. If the fault diagnosis is positive, i.e. fault diagnosis YES, a driver warning signal S7 is output in step 104. If the fault diagnosis is negative, according to the branch NO, the next step 105 of the method is carried out. In step 105, relevant state signals are received by the central control unit 16, in particular the air pressure signal S4 and the engine speed signal S2. In the following decision step 106, the engine speed Nengine is compared with an engine speed threshold N_THD, in order to decide whether there is a relevant demand for the EPHS 3. If YES, in step 107 the pump clutch 18 is activated, thereby disengaging the hydraulic pump 8. As a result, the electric motor 5 is used only for the pneumatic system 4, thereby allowing efficient compressor use and rapidly increasing the air pressure Pa.

[0041] In steps 108 to 110 a first pressure control loop is carried out in order to supply the air tank 15 with enough pressure. In step 108, the air pressure Pa of the air tank 15 is compared with a pressure threshold P_THD; if the air pressure Pa is below the pressure threshold P_THD, i.e. NO, in step 109 the electric motor 5 is switched on and the method is redirected to step 108. Otherwise, if the air pressure Pa is above the pressure threshold Pa_THD, the motor 5 is switched off in step 110, and the method is redirected to step 105.If in the decision step 106 the engine speed Nengine is lower than the threshold N_THD, the branch NO directs to a routine or sub method in which the pump clutch 18 is still engaged and the EPHS 3 is in assist mode. In the next step 111 , the steering angle rate signal SR and the vehicle speed signal S3 are checked. In the following decision step 112, the steering angle rate signal SR and the vehicle speed signal S3 are compared with thresholds THD; the decision step 112 serves to check the demand for active steering assist. If the output of the decision step 112 is NO, which means no relevant hydraulic EPHS assist is necessary, then in step 118 the EPHS is switched into sleep mode; however, the pump clutch 20 is still engaged.

[0042] Steps 119 to 122 form a second pressure control loop in the EPHs sleep mode. In step 119, the air pressure Pa is compared with the pressure threshold P_THD, in order to check the demand for pressure delivery. If the air pressure Pa is not above the pressure threshold P_THD, which means the result is NO, then in step 120 the remaining pressure is not sufficient and the method is redirected to step 119. If in step 119 the air pressure Pa is above the pressure threshold P_THD, the branch YES directs to step 121 , in which the compressor clutch 20 is activated, thereby disengaging the compressor 10. In this situation, both motor driven apparatuses, the pump 8 and the compressor 10, are passive, wherein the EPHS is in sleep mode but engaged, and the compressor 10 is disengaged. In the next step 122, the motor 5 is switched into reduced power, and the method is redirected to step 106. Thus, the full control loop starting from step 106 with new data of the engine speed Nengine is repeated.

[0043] If in the decision step 112 the decision is YES, the steering angle rate SR and the vehicle speed S3 are above their thresholds THD, which corresponds to a relevant steering activity of the vehicle 1. In this situation, both consumers, the pump 8 and the compressor 10, must be powered, since the driving vehicle 1 needs available pneumatic brakes and available steering assist. Therefore, the third control loop of steps 113 to 116 is carried out. In step 113, the air pressure Pa is compared with the pressure threshold P_THD. If enough pressure is detected, which corresponds to the decision YES, in step 114 the compressor clutch 20 is activated thereby disengaging the compressor 10, and in the next step 115 the motor 5 is switched on into a motor state of reduced power. This situation corresponds to a normal driving situation ornormal steering map with disengaged compressor 10. The method is then redirected to step 111.

[0044] If the decision in the decision step 113 is NO, both consumers 8 and 10 must be powered. In step 116, the motor 5 is switched into a full power state or full power level, and the method is redirected to step 113.

[0045] Thus, the method 100 of fig. 3 constitutes an efficient control strategy for supporting sufficient compressed air and sufficient hydraulic flow, by switching the clutches 18 and 20 and the motor 5.

[0046] -IQ-List of reference numerals

[0047] 1 commercial vehicle

[0048] 2 engine

[0049] 3 electrically powered hydraulic steering system EPHS

[0050] 4 pneumatic system

[0051] 5 electric motor

[0052] 6 vehicle ecomp state

[0053] 7 vehicle battery

[0054] 8 electric hydraulic steering pump

[0055] 10 compressor

[0056] 11 hydraulic tank

[0057] 15 air reservoir, air tank

[0058] 16 central control unit

[0059] 18 pump clutch

[0060] 19 solenoid valve

[0061] 20 compressor clutch

[0062] 21 solenoid valve

[0063] 23 pressure sensor

[0064] 30 control device

[0065] 30a, 30b hydraulic port

[0066] 30c pneumatic inlet port

[0067] 30d pneumatic outlet port

[0068] 32 air intake line

[0069] 34 steering gear

[0070] 35 electric connector

[0071] 38 ignition switch

[0072] 40 control system comprising the control device 30 and the central control unit 16

[0073] 100 method

[0074] 101 to steps of the method 100

[0075] Pa air pressure, pneumatic pressure in said air reservoir 15Nengine engine speed

[0076] N_THD engine speed threshold

[0077] P_THD pressure threshold

[0078] THD thresholds

[0079] Pa_THD pressure threshold

[0080] SR steering angle rate signal

[0081] S2 engine speed signal

[0082] S3 vehicle speed signal

[0083] S4 air pressure signal

[0084] S5 EPHS state signal

[0085] S6 ecomp state signal

[0086] S7 driver warning signal

[0087] S8 battery charge condition signal

[0088] S10 electric control signal from the central control unit 16 S11 electric control signal from the central control unit 16

Claims

Claims1. A control device (30) for controlling electrically operated apparatuses of a commercial vehicle (1), said control device (30) comprisingan electric motor (5),a hydraulic steering pump (8) for supplying hydraulic flow to an electrically powered hydraulic steering system (3),a compressor (10) for supplying compressed air to a pneumatic system (4), a pump clutch (18) provided between said electric motor (5) and said hydraulic steering pump (8), and a compressor clutch (20) provided between said motor (5) and said compressor (10),said pump clutch (18), said motor (5) and said compressor clutch (20) being controllable by a central control unit (16),wherein said pump clutch (18) is provided for engaging and disengaging said hydraulic steering pump (8) with and from said electric motor (5), and said compressor clutch (29) is provided for engaging and disengaging said compressor (10) with and from said motor (5).

2. The control device (30) according to claim 1 , wherein said pump clutch (18) and / or said compressor clutch (20) comprise an engaged basic state and are switched into a disengaged state.

3. The control device (30) according to claim 2, wherein said pump clutch (18) and / or said compressor clutch (20) are controllable- by an electric control signal (S10, S11) from said central control unit (16), and / or - by a pneumatic control pressure signal (P10, P11), said pneumatic control pressure signal (P10, P11 ) being supplied by a respective solenoid valve (19, 21 ), said solenoid valve (19, 21) being electrically controllable by said electric control signal (S10, S11), respectively.

4. The control device (30) according to one of the previous claims, wherein said control device (30) is designed or realised in one piece, e. g. with a single housing.

5. The control device (30) according to one of the previous claims,wherein said control device (30) comprises one or more of the following connections: a first hydraulic port (30a) for a hydraulic tank (11 ) of the electrically powered hydraulic steering system (3),a second hydraulic port (30b) for a steering gear (34) of the electrically powered hydraulic steering system (3), said first and second hydraulic port (30a, 30b) being connected to said hydraulic steering pump (8),a pneumatic inlet port (30c) to be connected to an air intake line (32), a pneumatic outlet port (30d) to be connected to an air reservoir (15), said first and second pneumatic port (30c, 30d) being connected to said compressor (10) of said control device (30),an electric connector (35) for receiving electrical signals () from said central control unit (16), for switching said clutches (18, 20) and / or said motor (5).

6. The control device (30) according to one of the previous claims, wherein the electric motor (5) is realised as a permanent magnetic synchronous motor.

7. A control system (40), said control system (40) comprisingthe control device (30) according to one of the previous claims,a central control unit (16) for outputting control signals (S11 , S12, S13) to said control device (30) and for receiving state signals (SR to S7), in particular one or more signals of the group consisting of:a steering angle rate signal (SR), an engine speed signal (S2), a vehicle speed signal (S3), an air pressure signal (S4) provided by a pressure sensor (23) connected to said air reservoir (15), a compressor state signal (S6), a driver warning signal (S7), and an ignition signal (S9) from ignition switch (38), and a battery charge conditon signal (S8) from a vehicle battery (7).

8. A commercial vehicle (1 ) comprising:the control system (40) according to claim 7, an engine (2) for driving said commercial vehicle (1), in particular a non-combustion engine (2), a battery (7) for providing electrical energy, an electrically powered hydraulic steering system (3), and a pneumatic system (4),wherein said motor (5) is different to said engine (2).

9. A method of controlling electrically operated apparatuses of a commercial vehicle (1), said operated apparatuses comprise an electrically powered hydraulic steering pump (8) of an electrically powered hydraulic steering system (3) and a compressor (10) of a pneumatic system (4) of said commercial vehicle (1),wherein an electric motor (5) is connected to said electrically powered hydraulic steering pump (8) via a pump clutch (18), and said electric motor (5) is connected to said compressor (10) via a compressor clutch (20),said method comprising the steps ofswitching an electric motor (5) between at least an off state or idle state, a full power state and a reduced power state,switching said pump clutch (18) between an engaged state for driving said steering pump (8) and a disengaged state without driving said steering pump (8), switching said compressor clutch (20) between an engaged state for driving said compressor (10) and a disengaged state without driving said compressor (10), wherein said electric motor (5), said pump clutch (18), and said compressor clutch (20) are switched independently of each other depending on state signals (SR, S2, S3, S4, S5, S6, S7. S8, S9).

10. The method according to claim 9, wherein said electric motor (5) is switched into its full power state for driving both said hydraulic pump (8) and said compressor (10), and is switched into its reduced power state for driving either said hydraulic pump (8) or said compressor (10).

11. The method according to claim 9 or 10, wherein said method comprising the following steps:a step (105) of checking an air pressure (Pa) in said air reservoir (15) and an engine speed (Nengine) of said engine (2),a first decision step (106) for comparing said engine speed (Nengine) with an engine threshold (N_THD),wherein dependent on a result of said first decision step (106)either said pump clutch (18) is disengaged (107) and a first air pressure control loop (108, 109, 110) is carried out,or an EPHS assist mode is activated (111), in which a steering angle rate (SR) and avehicle speed (S2) are compared with thresholds (TH) in a second decision step (112), to initiate either a second air pressure control loop (118, 119, 120, 121, 122) with the electrically powered hydraulic steering system (3) in sleep mode or a third air pressure control loop (113, 114, 115, 116) in which the steering pump (8) is driven.

12. The method according to claim 11 , wherein one or more of the following subroutines are provided:- in said first air pressure control loop (108, 109, 110) said electric motor (5) is switched on to drive the compressor (10) and increase the air pressure (Pa), or said motor (5) is switched off to redirect said method before said decision step (106), - in said second air pressure control loop (118, 119, 120, 121, 122) said electric motor (5) is switched on with full power to drive the compressor (10) and increase the air pressure (Pa), or said compressor clutch (20) is activated and the compressor (10) is disengaged(121), to redirect said method before said second decision step (112), - in said third air pressure control loop (113, 114, 115, 116) said electric motor (5) is switched on with full power to drive the compressor (10) and increase the air pressure (Pa), or said compressor clutch (20) is activated and the compressor (10) is disengaged to redirect said method before said first decision step (106).

13. The method according to claim 12, wherein in said second air pressure control loop (118, 119, 120, 121, 122) and said third air pressure control loop (113, 114, 115, 116), if the compressor clutch (20) is activated, said electric motor (5) is switched into a state of reduced power (115, 122).

14. The method according to one of claims 9 to 13, wherein it is used to operate a control device of one of claims 1 to 6.

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