Method for Monitoring a Steering System

Abstract

A method is for monitoring a steering system during operation in a vehicle. The steering system includes at least one steering actuator. In order to determine a force-closure detachment and/or torque detachment in the steering system, at least one operating signal of the at least one steering actuator is determined and evaluated, and a jerk signal is determined from the at least one operating signal and is monitored for changes.

Claims

1. A method monitors a steering system during operation in a vehicle, the steering system comprises at least one steering actuator, the method comprising: determining at least one operating signal of the at least one steering actuator; evaluating the determined at least one operating signal to determine a force-closure detachment and/or torque detachment in the steering system; determining a jerk signal from the at least one operating signal; and monitoring the determined jerk signal for changes to determine the force-closure detachment and torque detachment in the steering system.

2. The method according to claim 1, further comprising: determining the force-closure detachment and torque detachment in the steering system based on at least one signal peak in the jerk signal, and/or determining the force-closure detachment and torque detachment in the steering system when the jerk signal exceeds a threshold value.

3. The method according to claim 1, wherein a position signal, a speed signal, or an acceleration signal of the at least one steering actuator is used as the at least one operating signal.

4. The method according to claim 1, further comprising: determining the jerk signal based on a time rate of change of the at least one operating signal and/or based on a time derivation of the at least one operating signal.

5. The method according to claim 1, wherein the force-closure detachment and torque detachment in the steering system corresponds to a force-closure detachment and torque detachment in a sensor train and/or a force-closure detachment and torque detachment in a servo train.

6. The method according to claim 1, wherein: the steering system comprises at least one traction device and/or at least one tolerance ring, and the force-closure detachment and torque detachment is caused by a slippage, sliding, and/or a jump of the at least one traction device and/or the at least one tolerance ring.

7. The method according to claim 1, further comprising: using an event counter to determine the force-closure detachment and torque detachment in the steering system; and initiating a system response when a counter value of the event counter exceeds a limit value.

8. The method according to claim 1, wherein: when determining the force-closure detachment and/or torque detachment in the steering system at least one plausibility variable is considered, and the plausibility variable is a sensor train-side operating and/or detection signal, a servo train-side operating and/or detection signal, and/or an operating and/or detection signal correlated with a driving state of the vehicle.

9. The method according to claim 1, wherein: the steering system comprises at least one traction device including a tooth belt with a plurality of teeth, and the force-closure detachment and/or torque detachment in the steering system is determined based on a signal peak in the jerk signal, and a number of signal peaks in the jerk signal is used to determine a number of jumped teeth of the plurality of teeth.

10. A control unit comprising: a computing unit configured to carry out the method according to claim 1.

11. A steering system comprising: at least one steering actuator; and a computing unit configured to perform the method according to claim 1.

12. The steering system according to claim 11, wherein a motor vehicle includes the steering system.

Description

DRAWINGS

[0018] Further advantages will become apparent from the description of the drawings hereinafter. The drawings illustrate an exemplary embodiment of the invention.

[0019] The drawings show:

[0020] FIG. 1a-b an example of a vehicle comprising a steering system in a simplified illustration,

[0021] FIG. 2 a diagram of various signals for monitoring the steering system, and

[0022] FIG. 3 an exemplary flowchart showing the main method steps of a method for monitoring the steering system.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

[0023] FIGS. 1a and 1b show a simplified illustration of a vehicle 12, which, as an example, is configured as a passenger vehicle comprising a plurality of vehicle wheels 40 and comprising a steering system 10. The steering system 10 is operatively connected to the vehicle wheels 40, which in the present case are in particular configured as front wheels, and is provided for influencing a direction of travel of the vehicle 12. The steering system 10 is moreover configured as an electrically assisted steering system and accordingly comprises electric power assistance in the form of a servo steering system. In principle, however, it is also conceivable to configure a steering system as a hydraulically assisted steering system, in particular comprising hydraulic power assistance. A steering system could furthermore in principle also be configured as a steer-by-wire steering system.

[0024] The steering system 10 comprises a steering handle 42, configured for example in the present case as a steering wheel, for applying a manual torque, a steering gearbox 44, which is configured for example as a rack-and-pinion steering gear, comprises a steering actuating element 46 and is provided for converting a steering input at the steering handle 42 into a steering movement of the vehicle wheels 40, and a steering shaft 48 for, in particular mechanically, connecting the steering handle 42 to the steering gear 44. The steering shaft 48 defines a sensor train 28 of the steering system 10. The steering gear 44 defines a servo train 30 of the steering system 10. A steering handle could alternatively also be configured as a steering lever or a steering ball or the like. It is also conceivable to forgo a steering handle. A steering shaft could moreover also connect a steering handle to a steering gear only intermittently and/or have a mechanical separation, such as in a steer-by-wire steering system.

[0025] The steering system 10 also comprises a steering actuator 14. The steering actuator 14 is at least partially configured electrically and/or electronically. The steering actuator 14 is operatively connected to the steering gear 44. The steering actuator 14 is designed to provide a steering torque to support an applied manual torque to the steering handle 42 and to transmit it to the steering actuating element 46. For this purpose, the steering actuator 14 comprises an electric motor (not explicitly shown). The electric motor in the present case is in particular configured as a permanently excited synchronous motor and is provided for producing the steering torque. In principle, however, a steering actuator could also comprise a plurality of electric motors.

[0026] To connect the steering actuator 14 to the steering gear 44, the steering system 10 further comprises a coupling gear box 50. In the present case, the coupling gear box 50 is configured as a traction means drive and comprises at least one traction means 32. The coupling gear box 50 is configured as a belt drive and consequently comprises a pulling means 32 configured as a belt, in the present case in particular as a tooth belt. The coupling gear box 50 is provided to transmit the steering torque of the steering actuator 14 to the steering gear 44 by means of the traction means 32. Alternatively, however, a coupling gear configured as a traction means drive could also be configured as a chain drive or the like and/or comprise a traction means configured as a flat belt, as a round belt, as a V-belt, and/or as a V-ribbed belt. Furthermore, it is conceivable to configure a coupling gear box as a screw gear box and/or a worm gear box. In addition, a coupling gear box and/or steering system could also comprise a tolerance ring.

[0027] In addition, the steering system 10 comprises one steering sensor system 52 which is arranged on the steering shaft 48 and is known per se. In the present case, the steering sensor system 52 is configured as a torque sensor. The steering sensor system 52 is provided to detect a sensor signal 54 correlated with an actuation of the steering handle 42, in particular a manual torque and/or torque applied to the steering handle 42. In the present case, the sensor signal 54 corresponds to a rotational rod signal. A steering sensor system could alternatively also be configured as a sensor other than a torque sensor, for example as a rotation angle sensor and/or as a combined torque and rotation angle sensor.

[0028] Furthermore, the steering system 10 comprises a detection sensor system 56 associated with the steering actuator 14. The detection sensor system 56 is configured as a rotor position sensor and is provided to acquire at least one operating signal 16 of the steering actuator 14, in the present case in particular a rotor position signal of the electric motor. However, alternatively or additionally, a detection sensor system could also be configured as a sensor deviating from a rotor position sensor, for example as a speed sensor and/or as an accelerometer.

[0029] The vehicle 12 also comprises a control unit 36. As an example, the control unit 36 is configured as a steering control unit and is therefore part of steering system 10. The control unit 36 has an electrical connection to the steering actuator 14. The control unit 36 also comprises an electrical connection to the steering sensor 52 and the detection sensor system 56. The control unit 36 is provided to receive the sensor signal 54 from steering sensor system 52 and the operating signal 16 from the detection sensor system 56. The control unit 36 is also provided for controlling the steering actuator 14.

[0030] The control unit 36 comprises a computing unit 38 for this purpose. The computing unit 38 comprises at least one processor, for example in the form of a microprocessor, and at least one operating memory. The computing unit 38 also comprises at least one operating program which is stored in the operating memory and includes at least one control routine, at least one calculation routine, at least one detection routine, at least one evaluation routine, and at least one monitoring routine. In principle, however, it is also conceivable to configure a control unit separately from a steering system. In this case, a vehicle could, for instance, have a single central control unit with a central computing unit.

[0031] In order to maintain correct operation of the steering system 10, a permanent force-closure in the steering system 10 is generally required. However, certain travel and/or operating situations may result in a force-closure detachment and/or torque detachment in the steering system 10. However, such a force-closure detachment and torque detachment may lead to safety-critical travel situations without sufficiently accurate detection.

[0032] For this reason, a method for monitoring the steering system 10 during operation in the vehicle 12 will now be described. In particular, the computing unit 38 is provided in order to carry out the method and has a computer program with corresponding program code means for this purpose.

[0033] According to the invention, at least one operating signal of the steering actuator 14, in the present case in particular the operating signal 16 detected by the detection sensor system 56, is determined and evaluated to determine a force-closure detachment and/or torque detachment in the steering system 10. For this purpose, a jerk signal 18 is generated from the operating signal 16 and monitored for changes. The force-closure detachment and torque detachment in the steering system 10 can be determined by means of at least one signal peak 20, 22, 24 in the jerk signal 18 or by means of exceeding a threshold value 26 (cf. in particular FIG. 2). In the present case, it is exploited that a very large rotor acceleration is generated in the steering system 10 in the event of a force-closure detachment and/or torque detachment, which can be determined by corresponding evaluation of the jerk signal 18. In principle, however, the jerk signal could also be evaluated in the frequency range. It is also conceivable to monitor and evaluate a gradient of the jerk signal.

[0034] The force-closure detachment and/or torque detachment further corresponds by way of example to a force-closure detachment and/or torque detachment in the servo train 30 and can be caused by a slippage, sliding, and/or a jump of the traction means 32. In principle, however, a force-closure detachment and torque detachment can also be effected by any other mechanical interfaces in the steering system 10, for example a tolerance ring, and occur in the sensor train 28, or in the sensor train 28 and in the servo train 30.

[0035] Furthermore, a position signal, in particular a rotor position signal, of the steering actuator 14 is used as an example as the operating signal 16, wherein the jerk signal 18 can be determined by means of a time derivation of the operating signal 16, in the present case in particular by means of a third time derivation of the operating signal 16. Alternatively, however, a speed signal or an acceleration signal of a steering actuator could be used as the operating signal.

[0036] Moreover, an event counter may be used to determine the force-closure detachment and/or torque detachment in the steering system 10. For example, the event counter may be integrated into the computing unit 38. In this case, by evaluating the jerk signal 18, and in particular based on a signal peak 20, 22, 24 and/or abnormality in the jerk signal 18, a counter value of the event counter is initially incremented and, in the event that the counter value of the event counter exceeds a threshold value, for example three or four, a force-closure detachment and/or torque detachment in the steering system 10 is concluded. As a result, a system response may then be initiated and/or performed. For example, the system response may comprise generating an information message and/or a degradation of the steering system 10 or vehicle 12. However, such an event counter could in principle also be omitted. In this case, a corresponding system response could already occur at a single signal peak and/or based on a time span during which the jerk signal 18 exceeds the threshold value 26.

[0037] In order to further increase a robustness of the method, at least one plausibility variable 34 can also be taken into account when determining the force-closure detachment and/or torque detachment in the steering system 10 (cf. in particular FIG. 2). In the present case, the plausibility variable 34 is a servo-side operating and/or detection signal, in particular a torque of the steering actuator 14. Alternatively or additionally, however, an operating and/or detection signal on the sensor train side, such as sensor signal 54 and/or an operating and/or detection signal correlated with a driving state of the vehicle 12, such as a vehicle speed and/or a yaw moment, could also be used as a plausibility variable. In addition, it is conceivable to use an operating and/or detection signal on the servo train side that deviates from a torque of the steering actuator 14, such as a rotation angle and/or a rotational speed, preferably an average value of a rotor speed, of the steering actuator 14, as a plausibility variable. In addition, it is generally also conceivable to completely dispense with a plausibility check.

[0038] FIG. 2 shows an exemplary diagram of various signals for monitoring the steering system 10.

[0039] A first ordinate axis 58 is configured as a size axis and shows a jerk in [1/s.sup.3]. A time is shown in [s] on a first abscissa axis 60. A first curve 62 shows a time curve of the jerk signal 18. A second ordinate axis 64 is configured as a further size axis and shows a torque in [Nm]. A time is also shown in [s] on a second abscissa axis 66. A second curve 68 shows a time curve of the plausibility variable 34 or in the present case of the torque of the steering actuator 14.

[0040] Curve 62 indicates that after approximately 8.5 s, multiple signal peaks 20, 22, 24 appear in the jerk signal 18 which are characteristic of a force-closure detachment and/or torque detachment in the steering system 10. When using a traction means 32 in the form of a tooth belt with a plurality of teeth, the number of signal peaks 20, 22, 24 in the jerk signal 18 may also be used to conclude a number of jumped teeth. In the present case, this means that three teeth of the traction means 32 have been jumped.

[0041] Curve 68 may further be utilized to increase robustness and/or for the plausibility check of the force-closure detachment and/or torque detachment in the steering system 10. It can be seen from the curve of the plausibility variable 32 that shortly before the first signal peak 20 in the jerk signal 18, a drop in the torque of the steering actuator 14 occurs. This drop in torque of the steering actuator 14 in connection with the temporally subsequent signal peaks 20, 22, 24 in the jerk signal 18, are used as an indication of a force-closure detachment and torque detachment in the steering system 10.

[0042] Finally, FIG. 3 shows an exemplary flowchart with the main method steps of the method for monitoring the steering system 10.

[0043] In a method step 70, the operating signal 16 of the steering actuator 14 is determined.

[0044] In a method step 72, the jerk signal 18 is determined from the operating signal 16. In the present case, this is done by a time derivation of the operating signal 16, in the present case in particular by a third time derivation of the operating signal 16.

[0045] In a method step 74, the jerk signal 18 is monitored and evaluated. In the present case, it is in particular monitored whether a signal peak 20, 22, 24 is present in the jerk signal 18 and/or whether the jerk signal 18 exceeds the threshold value 26. If this is the case, a force-closure detachment and/or torque detachment in the steering system 10 is concluded and a method step 76 follows.

[0046] In method step 76, a system response is initiated and/or performed. For example, the system response may comprise generating an information message and/or a degradation of the steering system 10 or vehicle 12.

[0047] The exemplary flowchart in FIG. 3 is only intended to describe a method for monitoring the steering system 10 by way of example. In particular, individual method steps can also vary, or additional method steps can be added. For example, an event counter may be used to determine the force-closure detachment and/or torque detachment in the steering system 10. Furthermore, when determining the force-closure detachment and torque detachment in the steering system 10, the plausibility variable 34 may be considered.