METHOD FOR MONITORING A STEERING SYSTEM

Description

State of the art

[0001] The invention is based on a method for monitoring a steering system according to the preamble of claim 1. The invention also relates to a control device with a computing unit for carrying out such a method, a steering system with a computing unit for carrying out such a method and a vehicle with such a steering system.

[0002] A method for monitoring a steering system is known from the prior art, such as DE 10 2008 021 849 A1. A belt jump detection device is used to detect a belt jump and consequently a loss of traction and / or torque in the steering system. This device detects a belt jump by evaluating a manual torque applied to the steering wheel, a manual angle applied to the steering wheel, a steering angle of the vehicle wheels, or an operating signal from a steering actuator. However, detecting a belt jump based on a detected manual torque leads to problems, for example, in autonomous vehicles or steer-by-wire steering systems. Furthermore, in this case, the detection is influenced by system stiffness and may be distorted.

[0003] The object of the invention is, in particular, to provide a method for monitoring a steering system with improved efficiency characteristics. This object is achieved by the features of claims 1, 10, 11, and 12, while advantageous embodiments and further developments of the invention can be found in the subclaims. Disclosure of the invention

[0004] The invention is based on a method for monitoring a steering system, in particular during operation in a vehicle, wherein the steering system comprises at least one steering actuator, and wherein at least one operating signal of the steering actuator is determined and evaluated in order to determine a frictional connection and / or torque break in the steering system.

[0005] It is proposed that, in order to determine the loss of adhesion and / or torque in the steering system, a jerk signal is determined from the operating signal and monitored for changes. Advantageously, a temporal profile of the jerk signal, in particular over an entire monitoring time interval, is determined and evaluated. The evaluation is advantageously carried out in the time domain. In principle, however, the jerk signal could also be evaluated in the frequency domain. This embodiment can, in particular, improve efficiency, in particular detection efficiency, computing efficiency and / or cost efficiency. In addition, advantageously robust detection and / or evaluation of a loss of adhesion and / or torque in the steering system can be achieved and operational reliability can be increased. Furthermore, particularly high flexibility and / or variability can be achieved.

[0006] The vehicle is preferably designed as a motor vehicle and, in particular, comprises the steering system and a detection sensor system designed to detect at least one operating signal from the steering actuator. Furthermore, the steering system can be designed as a conventional steering system, in particular as an electric power steering system, and include a mechanical interlock. Alternatively, however, the steering system can also be designed as a steer-by-wire steering system, in which a steering command is transmitted purely electrically to the vehicle wheels. Furthermore, a "steering actuator" is understood to mean an at least partially electrically and / or electronically configured actuator unit designed to provide a steering torque and thereby advantageously influence the direction of travel of the vehicle.The steering actuator is preferably designed to provide a steering torque to assist a manual torque applied to a steering handle and / or a steering torque for automatic and / or autonomous control of a direction of travel of the vehicle. For this purpose, the steering actuator can comprise at least one electric motor.

[0007] Furthermore, the vehicle comprises a computing unit designed to carry out the method for monitoring the steering system. A "computing unit" is understood to mean, in particular, an electrical and / or electronic unit having an information input, an information processing unit, and an information output. Advantageously, the computing unit further comprises at least one processor, at least one operating memory, at least one input and / or output means, at least one operating program, at least one control routine, at least one calculation routine, at least one determination routine, at least one evaluation routine, and / or at least one monitoring routine. In particular, the computing unit is designed to determine the operating signal, in particular to retrieve and / or receive it from the detection sensor system, and to evaluate it.In addition, the computing unit is designed to determine a jerk signal from the operating signal to determine the loss of traction and / or torque in the steering system and to monitor it for changes. The computing unit is preferably integrated into a control unit of the vehicle, for example, a central vehicle control unit, or a control unit of the steering system, in particular in the form of a steering control unit. In this context, a "loss of traction and / or torque" is understood to mean, in particular, a sudden and / or abrupt relative movement and / or an at least brief interruption and / or a release of a traction connection between two components of the steering system that are connected to one another by a force-locking and / or positive locking. The loss of traction and / or torque leads, in particular, to an at least brief loss of steering assistance.In addition, the loss of traction and / or torque can also fundamentally lead to an offset in the steering system, particularly in a sensor and / or servo system of the steering system, and thus, for example, cause an offset between a measured steering angle and an actual steering angle. Furthermore, a "jerk signal" is understood to mean, in particular, a signal that correlates with a jerk occurring in the steering system, i.e., a temporal change in acceleration. "Intended" is understood to mean, in particular, specially programmed, designed, and / or equipped. The fact that an object is intended for a specific function is understood to mean, in particular, that the object fulfills and / or executes this specific function in at least one application and / or operating state.

[0008] It is further proposed that the traction and / or torque break in the steering system is determined on the basis of at least one signal peak, in particular on the basis of a peak, in the jerk signal, whereby in particular a particularly simple detection of a short-term traction and / or torque break in the steering system, such as a slip and / or a jump, can be achieved.

[0009] Alternatively or additionally, it is proposed that the loss of traction and / or torque in the steering system is determined if the jerk signal exceeds a, in particular defined and / or definable, threshold value. In this case, a period of time during which the jerk signal exceeds the threshold value can also be monitored and / or determined, whereby a type of traction and / or torque loss can advantageously be inferred. If the jerk signal only exceeds the threshold value briefly, for example for a few milliseconds, a temporary loss of traction and / or torque in the steering system, such as slipping and / or a jump, can be inferred. If, on the other hand, the jerk signal exceeds the threshold value for a longer period or permanently, damage to the steering system, such as deformation or breakage, can be inferred.

[0010] Furthermore, it is proposed that a position signal, a speed signal, or an acceleration signal of the steering actuator be used as the operating signal, whereby the jerk signal can advantageously be determined easily. The position signal can advantageously be a rotor position signal of the steering actuator, in particular of the electric motor of the steering actuator. The speed signal can advantageously be a rotor speed signal of the steering actuator, in particular of the electric motor of the steering actuator. Furthermore, the acceleration signal can advantageously be a rotor acceleration signal of the steering actuator, in particular of the electric motor of the steering actuator.

[0011] The jerk signal is preferably determined based on a temporal rate of change of the operating signal and / or by means of a temporal derivative of the operating signal. Advantageously, a position signal of the steering actuator can be used as the operating signal, and the jerk signal can be determined, for example, based on a third temporal derivative of the position signal. Alternatively, however, a speed signal of the steering actuator could also be used as the operating signal, and the jerk signal could be determined, for example, based on a second temporal derivative of the speed signal. In addition, an acceleration signal of the steering actuator could also be used as the operating signal, and the jerk signal could be determined, for example, based on a first temporal derivative of the acceleration signal. This makes it possible to provide an advantageously cost-effective solution, in particular by using signals that are already present or can be retrieved.

[0012] Furthermore, the loss of traction and / or torque in the steering system corresponds to a loss of traction and / or torque in the sensor train and / or a loss of traction and / or torque in the servo train, which in particular allows for variable and / or comprehensive monitoring of the steering system. The sensor train can, for example, correspond to a steering shaft and / or a steering column of the steering system, while the servo train can, in particular, correspond to a steering gear of the steering system.

[0013] The loss of traction and / or torque could also be caused by slipping, a slip, and / or a jump of any mechanical interface in the steering system. According to one embodiment, however, it is proposed that the steering system comprise at least one traction means, in particular acting in a force-locking and / or positive manner, and / or at least one tolerance ring, in particular acting in a force-locking and / or positive manner, and that the loss of traction and / or torque is caused by slipping, a slip, and / or a jump of the traction means and / or the tolerance ring. The traction means can in particular be part of a coupling gear, for example for connecting the steering actuator to the steering gear, and in particular be designed as a belt, preferably as a toothed belt. The tolerance ring can, for example, be part of a slip clutch and / or a helical gear.This can, in particular, increase the efficiency of the process and monitor the main causes of traction and / or torque loss in the steering system.

[0014] It is further proposed that an event counter be used to determine the loss of traction and / or torque in the steering system. In particular, in this case, by evaluating the jerk signal and in particular based on a signal peak and / or anomaly in the jerk signal, a counter value of the event counter is first incremented and, if the counter value of the event counter exceeds a limit value, for example three or four, a conclusion is drawn that there has been a loss of traction and / or torque in the steering system. As a result, a system response, preferably in the form of a safety measure, can then be initiated and / or executed. The system response can, for example, comprise generating an alert and / or degrading the steering system or the vehicle.Particularly preferably, the counter value of the event counter is also reset, in particular zeroed, if no signal peak and / or abnormality occurs in the jerk signal within a defined and / or definable time. This can further increase robustness and / or operational reliability.

[0015] It is preferably further proposed that at least one plausibility check variable be taken into account when determining the adhesion and / or torque break in the steering system, and in particular to increase robustness and / or ensure plausibility. The plausibility check variable is preferably an operating and / or detection signal from the sensor train side, such as a manual torque and / or a deflection of the steering handle, a servo train side operating and / or detection signal, such as a torque, a rotation angle, a speed, preferably an average value of a rotor speed, and / or an acceleration of the steering actuator, and / or an operating and / or detection signal correlated with a driving state of the vehicle, such as a vehicle speed and / or a yaw moment.Particularly advantageously, when determining the adhesion and / or torque loss in the steering system, several plausibility parameters, for example, at least two or at least three plausibility parameters, can be taken into account and / or linked together. This can, in particular, further increase robustness.

[0016] A particularly efficient method can furthermore be achieved in particular if the steering system comprises at least one traction means in the form of a toothed belt with a plurality of teeth and the frictional connection and / or torque break in the steering system is determined on the basis of a signal peak in the jerk signal, wherein a number of skipped teeth is inferred and / or a number of skipped teeth is determined on the basis of the number of signal peaks in the jerk signal.

[0017] The method for monitoring the steering system is not intended to be limited to the application and embodiment described above. In particular, the method for monitoring the steering system may have a number of individual elements, components, and units that differs from the number stated herein to fulfill a functionality described herein. Drawings

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

[0019] They show: Fig. 1a-b shows an exemplary vehicle with a steering system in a simplified representation, Fig. 2 a diagram of various signals for monitoring the steering system, and Fig. 3 an exemplary flow chart with main method steps of a method for monitoring the steering system. Description of the embodiment

[0020] TheFigures 1a and 1b show a simplified representation of a vehicle 12, embodied as a passenger vehicle, with a plurality of vehicle wheels 40 and with a steering system 10. The steering system 10 has an operative connection with the vehicle wheels 40, which in the present case are embodied in particular as front wheels, and is provided for influencing a direction of travel of the vehicle 12. Furthermore, the steering system 10 is embodied as an electrically assisted steering system and accordingly has an electrical auxiliary power assistance in the form of a power steering system. In principle, however, it is also conceivable to embody a steering system as a hydraulically assisted steering system, in particular with a hydraulic auxiliary power assistance. In addition, a steering system could also, in principle, be embodied as a steer-by-wire steering system.

[0021] The steering system 10 comprises a steering handle 42, in the present case embodied as a steering wheel, for applying a manual torque, a steering gear 44, embodied as a rack and pinion steering gear, which comprises a steering actuator 46 and is provided to convert a steering input to the steering handle 42 into a steering movement of the vehicle wheels 40, and a steering shaft 48 for the, in particular mechanical, connection of the steering handle 42 to the steering gear 44. The steering shaft 48 defines a sensor line 28 of the steering system 10. The steering gear 44 defines a servo line 30 of the steering system 10. Alternatively, a steering handle could also be embodied as a steering lever or steering ball or the like. It is also conceivable to dispense with a steering handle.In addition, a steering shaft could also only temporarily connect a steering handle to a steering gear and / or have a mechanical separation, such as in a steer-by-wire steering system.

[0022] Furthermore, the steering system 10 comprises a steering actuator 14. The steering actuator 14 is at least partially electrical and / or electronic. The steering actuator 14 has an operative connection to the steering gear 44. The steering actuator 14 is intended to provide a steering torque to support a manual torque applied 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). In the present case, the electric motor is designed in particular as a permanently excited synchronous motor and is intended to generate the steering torque. In principle, a steering actuator could also comprise several electric motors.

[0023] To connect the steering actuator 14 to the steering gear 44, the steering system 10 further comprises a coupling gear 50. In the present case, the coupling gear 50 is designed as a traction drive and comprises at least one traction means 32. The coupling gear 50 is designed as a belt drive and consequently comprises a traction means 32 designed as a belt, in the present case in particular as a toothed belt. The coupling gear 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, a coupling gear designed as a traction drive could also be designed as a chain drive or the like and / or comprise a traction means designed as a flat belt, a round belt, a V-belt and / or a V-ribbed belt. Furthermore, it is conceivable to design a coupling gear as a helical gear drive and / or worm gear drive.In addition, a coupling gear and / or a steering system could also include a tolerance ring.

[0024] In addition, the steering system 10 includes a steering sensor system 52 arranged on the steering shaft 48 and known per se. The steering sensor system 52 is embodied here 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 torsion bar signal. Alternatively, a steering sensor system could also be embodied as a sensor other than a torque sensor, such as a rotation angle sensor and / or a combined torque and rotation angle sensor.

[0025] Furthermore, the steering system 10 includes 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 intended to detect at least one operating signal 16 of the steering actuator 14, in this case, in particular a rotor position signal of the electric motor. Alternatively or additionally, however, a detection sensor system could also be configured as a sensor other than a rotor position sensor, such as a speed sensor and / or an acceleration sensor.

[0026] Furthermore, the vehicle 12 has a control unit 36. The control unit 36 ​​is embodied, for example, as a steering control unit and is therefore part of the steering system 10. The control unit 36 ​​has an electrical connection to the steering actuator 14. In addition, the control unit 36 ​​has an electrical connection to the steering sensor system 52 and the detection sensor system 56. The control unit 36 ​​is provided to receive the sensor signal 54 from the steering sensor system 52 and the operating signal 16 from the detection sensor system 56. In addition, the control unit 36 ​​is provided to control the steering actuator 14.

[0027] For this purpose, the control unit 36 ​​comprises a computing unit 38. The computing unit 38 comprises at least one processor, for example in the form of a microprocessor, and at least one operating memory. Furthermore, the computing unit 38 comprises at least one operating program stored in the operating memory, comprising at least one control routine, at least one calculation routine, at least one determination routine, at least one evaluation routine, and at least one monitoring routine. In principle, however, it is also conceivable to design a control unit separately from a steering system. In this case, a vehicle could, for example, have a single central control unit with a central computing unit.

[0028] To maintain correct functioning of the steering system 10, a permanent power connection in the steering system 10 is generally required. However, certain driving and / or operating situations can lead to a power connection and / or torque break in the steering system 10. However, without sufficiently accurate detection, such a power connection and / or torque break can lead to safety-critical driving situations.

[0029] For this reason, a method for monitoring the steering system 10 during operation in the vehicle 12 is described below. In particular, the computing unit 38 is provided to execute the method and, for this purpose, has a computer program with corresponding program code means.

[0030] According to the invention, to determine a loss of traction and / or torque in the steering system 10, 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. For this purpose, a jerk signal 18 is generated from the operating signal 16 and monitored for changes. The loss of traction and / or torque in the steering system 10 can be determined based on at least one signal peak 20, 22, 24 in the jerk signal 18 or based on an exceeding of a threshold value 26 (cf. in particular Figure 2). In this case, the fact that a loss of traction and / or torque in the steering system 10 generates a very large rotor acceleration is exploited, which can be determined by appropriate evaluation of the jerk signal 18. In principle, however, the jerk signal could also be evaluated in the frequency domain. It is also conceivable to monitor and evaluate a gradient of the jerk signal.

[0031] The traction and / or torque loss further corresponds, for example, to a traction and / or torque loss in the servo train 30 and can be caused by slipping, a slip, and / or a jump in the traction mechanism 32. In principle, however, a traction and / or torque loss can also be caused by any other mechanical interfaces in the steering system 10, such as a tolerance ring, and can occur, for example, in the sensor train 28 or in the sensor train 28 and the servo train 30.

[0032] Furthermore, a position signal, in particular a rotor position signal, of the steering actuator 14 is used as the operating signal 16, for example, wherein the jerk signal 18 can be determined by means of a time derivative of the operating signal 16, in this case in particular based on a third time derivative of the operating signal 16. Alternatively, however, a speed signal or an acceleration signal of a steering actuator could also be used as the operating signal.

[0033] In addition, an event counter can be used to determine the loss of traction and / or torque in the steering system 10. The event counter can, for example, 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 an abnormality in the jerk signal 18, a counter value of the event counter is first incremented. If the counter value of the event counter exceeds a limit value, for example three or four, a conclusion is drawn that there has been a loss of traction and / or torque in the steering system 10. As a result, a system response can then be initiated and / or executed. The system response can, for example, include generating an alert and / or degrading the steering system 10 or the vehicle 12. In principle, however, such an event counter could also be dispensed with.In this case, a corresponding system reaction could already occur in the case of a single signal peak and / or based on a period of time during which the jerk signal 18 exceeds the threshold value 26.

[0034] In order to further increase the robustness of the method, at least one plausibility value 34 can be taken into account when determining the adhesion and / or torque break in the steering system 10 (cf. in particular Figure 2). In the present case, a servo-train-side operating and / or detection signal, in particular a torque of the steering actuator 14, serves as the plausibility check variable 34. Alternatively or additionally, however, an operating and / or detection signal from the sensor train, such as the 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 the plausibility check variable. It is also conceivable to use an operating and / or detection signal from the servo train that differs from a torque of the steering actuator 14, such as an angle of rotation and / or a speed, preferably an average value of a rotor speed, of the steering actuator 14, as the plausibility check variable. Furthermore, it is also conceivable in principle to dispense with a plausibility check variable entirely.

[0035] Figure 2shows an example diagram of various signals for monitoring the steering system 10.

[0036] A first ordinate axis 58 is configured as a magnitude axis and shows a jerk in [1 / s 3< ]. A first abscissa axis 60 represents a time in [s]. A first curve 62 shows a temporal progression of the jerk signal 18. A second ordinate axis 64 is configured as a further magnitude axis and shows a torque in [Nm]. A second abscissa axis 66 also represents a time in [s]. A second curve 68 shows a temporal progression of the plausibility variable 34, or in this case, the torque of the steering actuator 14.

[0037] Curve 62 shows that after approximately 8.5 s, several signal peaks 20, 22, 24 appear in the jerk signal 18, which are characteristic of a loss of traction and / or torque in the steering system 10. When using a traction device 32 in the form of a toothed belt with multiple teeth, the number of signal peaks 20, 22, 24 in the jerk signal 18 can also be used to determine the number of skipped teeth. In the present case, this means that three teeth of the traction device 32 were skipped.

[0038] Curve 68 can also be used to increase robustness and / or to verify the plausibility of the traction and / or torque loss in the steering system 10. Based on the curve of the plausibility variable 32, it can be seen that a drop in the torque of the steering actuator 14 occurs shortly before the first signal peak 20 in the jerk signal 18. This drop in the torque of the steering actuator 14, in conjunction with the temporally subsequent signal peaks 20, 22, 24 in the jerk signal 18, serves as an indication of a traction and / or torque loss in the steering system 10.

[0039] Figure 3 Finally, an exemplary flow chart with main process steps of the method for monitoring the steering system 10 is shown.

[0040] In a method step 70, the operating signal 16 of the steering actuator 14 is determined.

[0041] In a method step 72, the jerk signal 18 is determined from the operating signal 16. In the present case, this is done by temporally deriving the operating signal 16, in this case in particular based on a third temporal derivative of the operating signal 16.

[0042] In a method step 74, the jerk signal 18 is monitored and evaluated. In the present case, it is monitored in particular 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 loss of traction and / or torque in the steering system 10 is concluded, and a method step 76 follows.

[0043] In method step 76, a system response is initiated and / or executed. The system response may, for example, include generating an alert message and / or degrading the steering system 10 or the vehicle 12.

[0044] The example flow chart in Figure 3 is intended to describe a method for monitoring the steering system 10 merely by way of example. In particular, individual method steps can also vary or additional method steps can be added. For example, an event counter can be used to determine the adhesion and / or torque loss in the steering system 10. Furthermore, the plausibility variable 34 can be taken into account when determining the adhesion and / or torque loss in the steering system 10.

Claims

1. Method for monitoring a steering system (10), in particular during operation in a vehicle (12), wherein the steering system (10) comprises at least one steering actuator (14), and wherein, in order to determine a sudden reduction in frictional engagement and / or torque in the steering system (10), at least one operating signal (16) of the steering actuator (14) is determined and evaluated, characterized in that, in order to determine the sudden reduction in frictional engagement and / or torque in the steering system (10), a jerk signal (18) is determined from the operating signal (16) and is monitored for changes.

2. Method according to Claim 1, characterized in that the sudden reduction in frictional engagement and / or torque in the steering system (10) is determined on the basis of at least one signal peak (20, 22, 24) in the jerk signal (18), and / or in that the sudden reduction in frictional engagement and / or torque in the steering system (10) is determined if the jerk signal (18) exceeds a threshold value (26).

3. Method according to Claim 1 or 2, characterized in that a position signal, a speed signal or an acceleration signal of the steering actuator (14) is used as the operating signal (16).

4. Method according to one of the preceding claims, characterized in that the jerk signal (18) is determined on the basis of a rate of change over time of the operating signal (16) and / or on the basis of a time derivative of the operating signal (16).

5. Method according to one of the preceding claims, characterized in that the sudden reduction in frictional engagement and / or torque in the steering system (10) corresponds to a sudden reduction in frictional engagement and / or torque in the sensor section (28) and / or a sudden reduction in frictional engagement and / or torque in the servo section (30).

6. Method according to one of the preceding claims, characterized in that the steering system (10) comprises at least one traction means (32) and / or at least one tolerance ring, and the sudden reduction in frictional engagement and / or torque is caused by a slipping, sliding and / or a jump of the traction means (32) and / or of the tolerance ring.

7. Method according to one of the preceding claims, characterized in that an event counter is used for determining the sudden reduction in frictional engagement and / or torque in the steering system (10) and, in the event of a counter value of the event counter exceeding a limit value, a system response is initiated.

8. Method according to one of the preceding claims, characterized in that, when determining the sudden reduction in frictional engagement and / or torque in the steering system (10), at least one plausibility variable (34) is considered, wherein the plausibility variable (34) is a sensor-section-side operating and / or sensing signal, a servo-section-side operating and / or sensing signal and / or an operating and / or sensing signal correlated with a driving state of the vehicle (12).

9. Method according to at least Claim 1, characterized in that the steering system (10) comprises at least one traction means (32) in the form of a toothed belt with multiple teeth and the sudden reduction in frictional engagement and / or torque in the steering system (10) is determined on the basis of a signal peak (20, 22, 24) in the jerk signal (18), wherein on the basis of the number of signal peaks (20, 22, 24) in the jerk signal (18) a number of skipped teeth is inferred.

10. Control device (36) with a computing unit (38) for carrying out a method according to one of the preceding claims.

11. Steering system (10) with at least one steering actuator (14) and with a computing unit (38) for carrying out a method according to one of Claims 1 to 9.

12. Vehicle (12), in particular a motor vehicle, with a steering system (10) according to Claim 11.