Steering system and method for operating steering system of motor vehicle

Abstract

The invention relates to a steering system for a motor vehicle, comprising at least one control unit (9, 11, 13, 14) and at least one acceleration sensor (25, 29), the control unit (9, 11, 13, 14) being designed to compare data of the at least one acceleration sensor (25, 29) with expected data of an acceleration or a comparison quantity calculated from the acceleration, and if there is a deviation, the control unit (9, 11, 13, 14) being designed to control the acceleration sensor (25, 29). If so, it is determined that at least one component of the steering system is defective or worn and an error message is generated. The invention also relates to a method for operating such a steering system.

Description

TECHNICAL FIELD

[0001] The invention relates to a steering system for a motor vehicle and to a method for operating such a steering system. BACKGROUND

[0002] In electromechanical steering systems in which there is a mechanical connection between the steering wheel and the steering gear, the motor vehicle driver receives haptic feedback from the road and from the steering device, in particular the steering gear, for example when mechanical components are difficult to move. The motor vehicle driver can then, for example, go to the workshop, which can then look for the error. Modern steer-by-wire steering systems eliminate this haptic feedback. But even in conventional steering systems, this haptic feedback is not needed if the motor vehicle is driving autonomously, i.e. the motor vehicle driver no longer needs to have his hands on the steering handle.

[0003] From JP 2015 229 380 A1 an electromechanical steering system is known which has at least one acceleration sensor in order to detect vibrations which are fed back from the road. It is suggested therein to arrange the acceleration sensor on a circuit board of a controller in a housing of a servo motor.

[0004] From JP 2005 212 689 A a steer-by-wire steering system is known which has a lateral acceleration sensor. At certain times on the steering device, the expected value of the lateral acceleration is compared with the measured lateral acceleration and if a deviation occurs, the steering angle is corrected. SUMMARY

[0005] The technical problem addressed by the invention is to improve the diagnostic capability of a motor vehicle steering system and to provide a suitable method for operating a steering system.

[0006] The solution to the technical problem is derived from a steering system for a motor vehicle having the features of claim 1 and from a method having the features of claim 10. Further advantageous embodiments of the invention result from the dependent claims.

[0007] A steering system for a motor vehicle comprises at least one controller and at least one acceleration sensor, the controller being designed to compare data from the at least one acceleration sensor with expected data for the acceleration or a comparison quantity calculated from the acceleration, and if there is a deviation, to determine that at least one component of the steering system is defective or in a state of wear. This allows a change in the behavior of at least one component to be detected early, before the component fails, and countermeasures can be taken early, before the component fails. The expected acceleration can also be zero. The expected acceleration can also be the previous acceleration behavior of the acceleration sensor. If the acceleration sensor detects, for example, an acceleration in the X and Y directions of a certain variable under normal circumstances, a deviation can be, for example, the sudden detection of an acceleration in the Z direction. Another deviation can be, for example, the disappearance of the acceleration value or a deviation in the value (down or up) in the X or Y direction. The value of the acceleration sensor is therefore compared with its own historical data as expected value.

[0008] In one embodiment, the at least one acceleration sensor is arranged on a circuit board of the controller, in particular a steering controller. One advantage is that this saves wiring. The element to be monitored can also be the circuit board itself. The acceleration sensor can be designed such that it detects the acceleration in the direction in which the circuit board is attached. If the acceleration sensor subsequently detects a change in acceleration in this direction, it indicates that the fastening is loose. An error message can then be used to inform the user and tighten the attachment before the circuit board falls and can be damaged. It can also be necessary to carry out another form of repair or replacement of the entire steering system.

[0009] In one embodiment, the acceleration sensor is designed as a multi-axis acceleration sensor. This has several advantages. On the one hand, for example, one component can oscillate in several directions. On the other hand, this increases the degree of freedom of the acceleration sensor arrangement, since every acceleration in any spatial direction can be determined from a combination of three translational accelerations.

[0010] In another embodiment, the at least one acceleration sensor is arranged on a component of the steering system that is sensitive to wear and / or corrosion. The component that is sensitive to wear and / or corrosion can also not have a steering function or have a secondary function. For example, the component is a connecting tab that is located in a position in the steering system that is highly exposed to moisture. If the connecting tab changes its acceleration behavior due to corrosion (in the extreme case the connecting tab falls off), it can also be concluded that other components are corroding and maintenance or replacement of the steering system is recommended.

[0011] In another embodiment, the controller, in particular the steering controller, is designed to determine the expected data for the at least one acceleration sensor using a vehicle model, preferably a single-track model. This means that accelerations due to driving dynamics can be eliminated.

[0012] In another embodiment, the controller, in particular the steering controller, is designed to generate predefined control signals for at least one component of the steering system and to evaluate the resulting data from the at least one acceleration sensor in a test cycle. One of the advantages is that the test cycle can be carried out without or with little external force action (e.g. the vehicle is stationary), thus simplifying the evaluation. The test cycle can also be carried out several times before the output information, in order to increase the reliability of the results.

[0013] In another embodiment, the component is a rack or a push rod, wherein the steering controller is designed to move the rack or the push rod to an end stop and / or to accelerate the rack or the push rod in a predetermined manner (e.g. in small periodic movements, which are for example sinusoidal).

[0014] In another embodiment, the steering controller is designed to determine driving dynamics or steering-specific variables using the data from the at least one acceleration sensor. For example, the rack force due to driving dynamic influences can be determined from the data from the lateral acceleration sensor and the axle model.

[0015] In another embodiment, the steering system is designed as a steer-by-wire system.

[0016] A method for operating a steering system of a motor vehicle, wherein the steering system has at least one controller and at least one acceleration sensor, the method comprising the following method steps: the controller compares the data from the at least one acceleration sensor with expected data for the acceleration, if there is a deviation of the data from the expected data, a conclusion is drawn that there is a defect in at least one component of the steering system, and an error message is generated.

[0017] With regard to further refinements, reference is made to the previous statements regarding the steering system. BRIEF DESCRIPTION OF DRAWINGS

[0018] The application is explained in more detail below using preferred exemplary embodiments.

[0019] Figure 1 A schematic block diagram of a steer-by-wire system is shown. DETAILED DESCRIPTION

[0020] Figure 1A steer-by-wire system 1 is shown, which has a steering column module 2 and a steering gear module 3. The steering column module 2 has a steering handle 4, a steering column 5, a torque sensor 6 and a first and a second force feedback actuator 7, 8. Furthermore, the steering column module 2 has a first controller 9, which has a first power electronics 10 for the first force feedback actuator 7. Accordingly, the second force feedback actuator 8 is provided with a second controller 11 having a second power electronics 12. The torque sensor 6 can also be designed redundantly. The first controller 9, the first power electronics 10 and the first force feedback actuator 7 are supplied with power by a first voltage source Ul, and the second controller 11, the second power electronics 12 and the second force feedback actuator 8 are supplied with power by a second voltage source U2.

[0021] The steering gear module 3 has a first and a second steering controller 13, 14. The steering gear module 3 also has a first and a second power electronics 15, 16. The steering gear module 3 also has a first and a second half electric machine 17, 18, which both work on a common rotor 19 having a rotor shaft 20. The two half electric machines 17, 18 are designed, for example, as separate stator windings on a common core. The first half electric machine 17 and the rotor 19 form a first servo motor 21, the second half electric machine 18 and the rotor 19 form a second servo motor 22, both servo motors 21, 22 being arranged in a common housing. The rotor shaft 20 is connected to a rack 23 via a gear not shown. The first and the second steering controller 13, 14, the first and the second power electronics 15, 16 are rigidly connected to the housing of the first and the second servo motor 21, 22. The first and the second steering controller 13, 14 each have at least one circuit board 24. An acceleration sensor 15 is arranged on at least one circuit board 24 of the steering controller 13, 14 and realizes a shaft model 26.

[0022] A rotor position sensor 27 is also shown, which measures the rotor angle of the rotor shaft 20. Finally, a corrosion-sensitive component 28 is shown, which has a further acceleration sensor 29. The corrosion-sensitive component 28 is arranged at a point on the steering gear module 3 that is exposed to strong moisture.

[0023] Using the data from the acceleration sensor 15, for example, it is now possible to monitor the fixation of the circuit board 24. As the corrosion of the corrosion-sensitive component 28 increases, its acceleration behavior also changes. From these changes, conclusions can be drawn about the corrosion of other components in this area and corresponding warnings are generated. It should be noted that the components of the steering column module 2 can also be assigned an acceleration sensor.

[0024] Furthermore, the data from the acceleration sensor 25 can be used to determine the lateral acceleration a y over the rack 23. Using the lateral acceleration ay With shaft model 26, the rack force F acting on rack 23 can be determined based on driving dynamics. Z1 Other components of the rack force F Z2 The total rack force F can be determined, for example, based on the motor current of half-motors 17 and 18 or through a wheel load model and / or friction model. Z,ges It can be calculated. Then, the total rack force F Z,ges It can be fed to controllers 9 and 11, and then controllers 9 and 11 control force feedback actuators 7 and 8 to generate the desired counter torque on steering handle 4, wherein other signals, such as vehicle speed, are also taken into account.

[0025] List of reference numerals

[0026] 1. Steer-by-wire system

[0027] 2 Steering column modules

[0028] 3 Steering module

[0029] 4 steering handles

[0030] 5 steering columns

[0031] 6 torque sensors

[0032] 7 First force feedback actuator

[0033] 8 Second force feedback actuator

[0034] 9 First Controller

[0035] 10 First Power Electronic Equipment

[0036] 11 Second Controller

[0037] 12 Second Power Electronic Equipment

[0038] 13 First Steering Controller

[0039] 14 Second Steering Controller

[0040] 15 First Power Electronic Equipment

[0041] 16 Second Power Electronic Equipment

[0042] 17 First Half Motor

[0043] 18 Second Half Motor

[0044] 19 rotors

[0045] 20 rotor shaft

[0046] 21 First servo motor

[0047] 22 second servo motor

[0048] 23 rack

[0049] 24 circuit board

[0050] 25 lateral acceleration sensor

[0051] 26 shaft model

[0052] 27 rotor position sensor

[0053] 28 corrosion-sensitive components

[0054] 29 acceleration sensor

Claims

1. A steering system for a motor vehicle, comprising at least one controller (9, 11, 13, 14) and at least one acceleration sensor (25, 29), characterized in that the controller (9, 11, 13, 14) is designed to compare data of the at least one acceleration sensor (25, 29) with expected data of the acceleration or a comparison quantity calculated from the acceleration and, if there is a deviation, to determine a defect or a wear state of at least one component of the steering system and to generate an error message.

2. The steering system of claim 1, wherein, The at least one acceleration sensor (25) is arranged on a circuit board (24) of the controller (9, 11, 13, 14).

3. A steering system according to claim 1 or 2, characterised in that, The at least one acceleration sensor (25, 29) is designed as a multi-axis acceleration sensor.

4. A steering system according to any one of the preceding claims, characterised in that, The at least one acceleration sensor (29) is arranged on a wear- and / or corrosion-sensitive component (28) of the steering system.

5. A steering system according to any one of the preceding claims, characterised in that, The controller (9, 11, 13, 14) is designed to determine the expected data of the at least one acceleration sensor (25, 29) by means of a vehicle model.

6. A steering system according to any one of the preceding claims, characterised in that, The controller (9, 11, 13, 14) is designed to generate predefined control signals for at least one component of the steering system in a test cycle and to evaluate the result data of the at least one acceleration sensor (25, 29).

7. The steering system of claim 6, wherein, The at least one component is a rack (23) or a push rod, wherein the steering controller (13, 14) is designed to move the rack or the push rod against an end stop and / or to accelerate the rack or the push rod in a predefined manner.

8. A steering system according to any preceding claim, characterised in that, The steering controller (13, 14) is designed to determine a driving dynamic variable using data from the at least one acceleration sensor (25).

9. A steering system according to any one of the preceding claims, characterised in that, The steering system is designed as a steer-by-wire steering system (1).

10. A method for operating a steering system for a motor vehicle by means of at least one controller (9, 11, 13, 13) and at least one acceleration sensor (25, 29), characterized in that the controller (9, 11, 13, 14) compares data of the at least one acceleration sensor (25, 29) with expected data of the acceleration or a comparison quantity calculated from the acceleration and, if the data deviates from the expected data, determines a defect or a wear state of at least one component of the steering system and generates an error message.

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