Steering system and method for operating a steering system for a 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), wherein the control unit (9, 11, 13, 14) is configured to compare the data of the at least one acceleration sensor (25, 29) with expected data for acceleration or comparative values ​​calculated from the acceleration and, in case of deviation, to conclude that there is a defect or wear condition of at least one component of the steering system and to generate an error message, as well as a method for operating such a steering system.

Description

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

[0002] In electromechanical steering systems, where there is a mechanical connection between the steering wheel and the steering gear, the driver receives haptic feedback from both the road and the steering mechanism, particularly the steering gear, for example, when mechanical parts become stiff. The driver can then, for instance, visit a workshop to diagnose the problem. This haptic feedback is eliminated in modern steer-by-wire systems. However, even in conventional steering systems, this haptic feedback disappears when vehicles become automated, meaning the driver no longer needs to keep their hands on the steering wheel.

[0003] From JP 2015 229 380 A, an electromechanical steering system is known which has at least one acceleration sensor to detect vibrations transmitted back from the road. It is proposed to arrange the acceleration sensor on a circuit board of a control unit within a servo motor housing.

[0004] From JP 2005 212 689 A, a steer-by-wire steering system is known which includes a lateral acceleration sensor. In this system, an expected value of the lateral acceleration is compared with the measured lateral acceleration at a given moment at the steering gear, and the steering angle is corrected if there is a deviation.

[0005] A steering system of this type is known from DE 10 2015 122 253 A1.

[0006] The invention is based on the technical problem of improving the diagnostic capability of a steering system for a motor vehicle and providing a suitable method for operating a steering system.

[0007] The solution to the technical problem is achieved by a steering system for a motor vehicle with the features of claim 1 and a method with the features of claim 8. Further advantageous embodiments of the invention are set forth in the dependent claims.

[0008] The steering system for a motor vehicle comprises at least one control unit and at least one acceleration sensor. The control unit is configured to compare the data from the at least one acceleration sensor with expected acceleration data or comparative values ​​calculated from the acceleration, and to infer a defect or wear condition of at least one component of the steering system in the event of a deviation. This allows for the early detection of changing behavior of the at least one component and enables timely countermeasures to be taken before the component fails. The expected acceleration can also be zero. The expected acceleration can also be a previous acceleration behavior of the acceleration sensor.If, for example, the accelerometer normally detects accelerations of a certain magnitude in the X and Y directions, a deviation might occur, for instance, that accelerations are suddenly also detected in the Z direction. Another deviation could be the absence of acceleration values ​​in the X or Y direction, or a deviation in the magnitude of the reading (up or down). The accelerometer's readings are thus compared with its own historical data as expected values.

[0009] Furthermore, the control unit, in particular the steering control unit, is designed to generate predefined control signals for at least one component of the steering system during a test cycle and to evaluate the resulting data from at least one acceleration sensor. An advantage is that the test cycle can be performed in situations where no or few external forces are acting (e.g., vehicle stationary), thus simplifying the evaluation. The test cycle can also be performed multiple times before any information is output, in order to achieve increased reliability of the results.

[0010] The component is a rack and pinion or pushrod, wherein the steering control unit is designed to move the rack and pinion or pushrod into an end stop and / or to accelerate the rack and pinion or pushrod in a predefined manner (e.g. with a small periodic movement, which is, for example, sinusoidal).

[0011] In one embodiment, the at least one acceleration sensor is arranged on a circuit board of the control unit, particularly the steering control unit. An advantage is that this saves on wiring. The component to be monitored can also be the circuit board itself. The acceleration sensor can be designed to detect acceleration in the direction of a mounting point on the circuit board. If the acceleration sensor detects a changing acceleration in this direction, this indicates a loose mounting point. An error message can then inform the user, allowing them to tighten the mounting point before the circuit board falls off and is potentially damaged. Alternatively, another form of repair or replacement of the entire steering system can be requested.

[0012] In one embodiment, the accelerometer is designed as a multi-axis accelerometer. This has several advantages. For example, a component can oscillate in multiple directions. Furthermore, this increases the degree of freedom in the arrangement of the accelerometer, since the combination of the three translational accelerations allows any acceleration in any spatial direction to be determined.

[0013] In another embodiment, the at least one acceleration sensor is arranged on a wear- and / or corrosion-sensitive component of the steering system. This wear- and / or corrosion-sensitive component may also have no function related to the steering or may have a subordinate function. For example, the component is a tab located in a part of the steering system that is heavily exposed to moisture. If the tab then changes its acceleration behavior due to corrosion (in extreme cases, the tab falls off), this can also indicate corrosion of other components, and maintenance or replacement of the steering system may be recommended.

[0014] In a further embodiment, the control unit, in particular the steering control unit, is designed to determine the expected data from the at least one acceleration sensor using a vehicle model, preferably a single-track model. This allows accelerations due to driving dynamics to be factored out.

[0015] In a further embodiment, the steering control unit is designed to use the data from at least one acceleration sensor to determine a vehicle dynamics or steering-specific parameter. For example, a rack force based on vehicle dynamics influences can be determined from the data of a lateral acceleration sensor and an axle model.

[0016] In another embodiment, the steering system is designed as a steer-by-wire steering system.

[0017] The method for operating a steering system for a motor vehicle, wherein the steering system has at least one control unit and at least one acceleration sensor, comprises the process steps of the control unit comparing the data of the at least one acceleration sensor with expected data for acceleration and, in the event of a deviation of the data from the expected data, concluding that at least one component of the steering system is defective and generating an error message.

[0018] Regarding further details, reference can be made to the preceding explanations concerning the steering system.

[0019] The invention is explained in more detail below with reference to a preferred embodiment. The single figure shows a schematic block diagram of a steer-by-wire steering system.

[0020] In the Fig.Figure 1 shows a steer-by-wire steering system 1 comprising a steering column module 2 and a steering gear module 3. The steering column module 2 includes a steering handle 4, a steering column 5, a torque sensor 6, a first force feedback actuator 7, and a second force feedback actuator 8. Furthermore, the steering column module 2 includes a first control unit 9 with a first power electronics unit 10 for the first force feedback actuator 7. Correspondingly, a second control unit 11 with a second power electronics unit 12 is provided for the second force feedback actuator 8. The torque sensor 6 can also be redundant. The first control unit 9, the first power electronics unit 10, and the first force feedback actuator 7 are supplied by a first power supply U1, and the second control unit 11, the second power electronics unit 12, and the second force feedback actuator 8 are supplied by a second power supply U2.

[0021] The steering gear module 3 comprises a first steering control unit 13 and a second steering control unit 14. Furthermore, the steering gear module 3 comprises a first power electronics unit 15 and a second power electronics unit 16. The steering gear module 3 also comprises a first half-motor 17 and a second half-motor 18, both of which operate on a common rotor 19 with a rotor shaft 20. The two half-motors 17, 18 are configured, for example, as independent stator windings on a common core. The first half-motor 17 and the rotor 19 form a first servomotor 21, and the second half-motor 18 and the rotor 19 form a second servomotor 22, with the two servomotors 21, 22 being arranged in a common housing. The rotor shaft 20 is connected to a rack 23 via a gearbox (not shown).The first steering control unit 13, the second steering control unit 14, the first power electronics unit 15, and the second power electronics unit 16 are rigidly connected to the housing of the first servomotor 21 and the second servomotor 22. The first steering control unit 13 and the second steering control unit 14 each have at least one circuit board 24. An acceleration sensor 25 and an axle model 26 are arranged on at least one circuit board 24 of a steering control unit 13, 14.

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

[0023] Using the data from the accelerometer 25, the mounting of the circuit board 24 can now be monitored, for example. Due to increasing corrosion of the corrosion-sensitive component 28, its acceleration behavior also changes. From these changes, conclusions can then be drawn about the corrosion stress on other components in this area, and a corresponding warning can be generated. It should be noted that components of the steering column module 2 can also be assigned to acceleration sensors.

[0024] Furthermore, a lateral acceleration a can be calculated using the data from the acceleration sensor 25. y can be determined at the rack 23. By means of the lateral acceleration a y and of axle model 26, the rack force F acting on the rack 23 can be determined. Z1 are determined based on driving dynamics influences. The other components of the rack force F Z2can be determined, for example, from the motor currents of the half-motors 17, 18 or by means of a wheel load model and / or friction model, so that a total rack force F can be calculated. Z,ges This total rack force F can be calculated. Z,ges can then be supplied to the control units 9, 11, which then control the force feedback actuators 7, 8 to generate a desired counter-torque at the steering handle 4, taking into account other signals such as the vehicle speed if necessary. Reference symbol list 1 Steer-by-wire steering system 2 Steering column module 3 Steering gear module 4 Steering handle 5 Steering column 6 Torque sensor 7 first force feedback actuator 8 second force feedback actuator 9 first control unit 10 first power electronics 11 second control unit 12 second power electronics 13 first steering control unit 14 second steering control unit 15 first power electronics 16 second power electronics 17 first half-engine 18 second half-engine 19 Rotor 20 Rotor shaft 21 first servo motor 22 second servo motor 23 Rack and pinion 24 circuit boards 25 Lateral acceleration sensor 26-axle model 27 Rotor position sensor 28 corrosion-sensitive components 29 Accelerometer

Claims

[1] Steering system for a motor vehicle, comprising at least one control unit (9, 11, 13, 14) and at least one acceleration sensor (25, 29), wherein the control unit (9, 11, 13, 14) is configured to compare the data of the at least one acceleration sensor (25, 29) with expected data for acceleration or comparative values ​​calculated from the acceleration and, in case of deviation, to conclude that there is a defect or wear condition of at least one component (28) of the steering system and to generate an error message, characterized by, that the control unit (9, 11, 13, 14) is configured to generate predefined control signals for the at least one component (28) of the steering system in a test cycle and to evaluate the resulting data from the at least one acceleration sensor (25, 29), wherein the at least one component (28) is a rack (23) or pushrod, wherein the steering control unit (13, 14) is configured to move the rack or pushrod into an end stop and / or to accelerate the rack or pushrod in a predefined manner. [2] Steering system according to claim 1, characterized by , that the at least one acceleration sensor (25) is arranged on a circuit board (24) of the control unit (9, 11, 13, 14). [3] Steering system according to claim 1 or 2, characterized by , that the at least one acceleration sensor (25, 29) is designed as a multi-axis acceleration sensor. [4] Steering system according to any of the preceding claims, characterized by, that the at least one acceleration sensor (29) is arranged on a wear- and / or corrosion-sensitive component (28) of the steering system. [5] Steering system according to any of the preceding claims, characterized by , that the control unit (9, 11, 13, 14) is designed to determine the expected data of the at least one acceleration sensor (25, 29) using a vehicle model. [6] Steering system according to any of the preceding claims, characterized by , that the steering control unit (13, 14) is designed to use the data from the at least one acceleration sensor (25) to determine a vehicle dynamics parameter. [7] Steering system according to any of the preceding claims, characterized by , that the steering system is designed as a steer-by-wire steering system (1). [8] Method for operating a steering system for a motor vehicle, using at least one control unit (9, 11, 13, 14) and at least one acceleration sensor (25, 29), wherein the control unit (9, 11, 13, 14) compares the data of the at least one acceleration sensor (25, 29) with expected data for acceleration or comparative values ​​calculated from the acceleration and, if the data deviates from the expected data, concludes that there is a defect or wear condition of at least one component (28) of the steering system and generates an error message, wherein the control unit (9, 11, 13, 14) generates predefined control signals for the at least one component (28) of the steering system in a test cycle and evaluates the resulting data of the at least one acceleration sensor (25, 29), wherein the at least one component (28) is a rack (23) or pushrod, wherein the steering control unit (13,14) the rack or pushrod is moved into an end stop and / or the rack or pushrod is accelerated in a predefined manner.

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