Method for operating the steering system

Abstract

The present invention begins with a method for operating a steering system (10) of a vehicle (12), the steering system (10) including a steering mechanism (14) and at least one electric motor (16) cooperating with the steering mechanism (14), in which a stiffness of at least one steering assembly (18, 20, 22) of the steering mechanism (14) and / or a play within the steering mechanism (14) is determined. In the method, it is proposed that in order to determine the stiffness of the at least one steering assembly (18, 20, 22) and / or the play in the steering mechanism (14), the steering mechanism (14) is moved to a defined test position and / or stopped in the test position, the electric motor (16) is driven and controlled using an excitation signal, and the stiffness of the at least one steering assembly (18, 20, 22) and / or the play in the steering mechanism (14) are determined by monitoring a motor torque of the electric motor (16) and a rotor position angle of the electric motor (16) during the period of driving and controlling the electric motor (16) using the excitation signal, and evaluating the change in the motor torque depending on the rotor position angle.

Description

[Technical Field]

[0001] Conventional technology The present invention begins with a method for operating a steering system, based on the broader concept of claim 1. Furthermore, the present invention relates to a computing unit for carrying out such a method, a steering system equipped with such a computing unit, and a vehicle equipped with such a steering system. [Background technology]

[0002] Currently, only a small fraction of the mechanical anomalies that can occur during the operation of a vehicle or steering system are detected automatically. Therefore, the vast majority of such anomalies must be detected by the driver themselves. However, with the increasing trend towards automated and / or autonomous driving, this type of manual error identification is becoming impossible. Furthermore, vehicles equipped with steer-by-wire steering systems are known, but these systems operate without a direct mechanical connection between the steering wheel and the wheels being steered. Based on this mechanical separation, in this case, for example, mechanical anomalies that may occur in the steering gear are not directly fed back to the steering wheel, making manual detection equally difficult.

[0003] For this reason, German Patent Application Publication No. 102019212618 proposes a method for automatically determining the stiffness of at least one steering assembly and / or the play within the steering mechanism. For this purpose, a monitoring device is used to determine the wheel position using a wheel position sensor and associate it with an input variable pre-set by an electric motor. In this case, the steering mechanism is not moved to a predetermined inspection position and / or stopped at the inspection position. Furthermore, in this type of procedure, it is necessary to determine the wheel state or wheel position, which may lead to undesirable results in certain circumstances.

[0004] Furthermore, German Patent Application Publication No. 102018112812 discloses a method for automatically determining the play in a steering mechanism by performing excitation via motor torques having different frequencies. However, even in this case, the steering mechanism cannot be moved to a specified inspection position and / or stopped at the inspection position. This results in the fact that excitation can only be performed for small torques, because otherwise the entire steering system would be moved. Accordingly, the play in this case can only be determined in the low load range. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] German Patent Application Publication No. 102019212618 [Patent Document 2] German Patent Application Publication No. 102018112812 [Overview of the project] [Problems that the invention aims to solve]

[0006] The object of the present invention is to provide a method for operating a steering system having improved characteristics with respect to efficiency. This object is resolved by the features of claims 1, 17, 18 and 19, and preferred embodiments and variations of the present invention can be seen from the dependent claims. [Means for solving the problem]

[0007] Disclosure of the invention The present invention relates to a method for operating a steering system of a vehicle, particularly a computer-implemented method, wherein the steering system comprises a steering mechanism and at least one electric motor cooperating with the steering mechanism, and particularly to a method that automatically and / or automates the stiffness of at least one steering assembly of the steering mechanism and / or the play within the steering mechanism.

[0008] In this method, in order to determine the stiffness of at least one steering assembly and / or the play within the steering mechanism, the steering mechanism is moved to a specified inspection position and / or stopped at the inspection position, and an electric motor is driven and controlled using an excitation signal. The stiffness of at least one steering assembly and / or the play within the steering mechanism is determined by monitoring the motor torque and rotor position angle of the electric motor during the period of drive control of the electric motor using the excitation signal, and evaluating the change in motor torque depending on the rotor position angle. Thus, in this embodiment, in the first method step, the steering mechanism is positioned and / or stopped at the inspection position; in the second method step, the steering system is excited by drive control of the electric motor using an excitation signal, more specifically while the steering mechanism is in the inspection position; and in the third method step, the system response of the steering system to the excitation signal is determined and evaluated using motor torque and rotor position angle. The positioning of the steering mechanism at the inspection location can, in this context, be performed, for example, manually by the vehicle occupants and / or driver, or automatically and / or automated by the drive control of the corresponding electric motor. Furthermore, the three method steps described above for determining the stiffness and / or play humidity characteristic variables within the steering mechanism of at least one steering assembly can be repeated in a fourth method step for at least one further inspection location different from the said inspection location. This repetition can, in particular, apply to the same steering assembly or to further steering assemblies different from the said steering assembly. This embodiment allows for improvements in efficiency, in particular inspection efficiency, performance efficiency, component efficiency, energy efficiency, and / or cost efficiency. Furthermore, it can particularly enhance the operational safety of the steering system. Moreover, the stiffness and / or play within the steering mechanism of at least one steering assembly can be determined advantageously in both low and high load ranges.

[0009] In this embodiment, the steering system may be configured as a conventional steering system, particularly an electric power steering system, and may include mechanical interventions. Alternatively, the steering system may be configured as a steer-by-wire steering system in which steering presets are preferably transmitted to the wheels purely electrically. The steering mechanism further includes at least one steering assembly, preferably a plurality, particularly various types of steering assemblies. The steering mechanism may include, for example, a first steering assembly configured as a servo train, a second steering assembly configured as a sensor train, and / or a third steering assembly configured as an axle and / or as part of an axle. In this context, the servo train corresponds in particular to the steering gear of the steering system, while the sensor train corresponds to the steering shaft and / or steering column of the steering system. Furthermore, the steering system preferably includes an electrically and / or electronically configured steering actuator system, particularly having an electric motor. In this context, “steering actuator system” should be understood to mean, particularly preferably, an actuator unit coupled to a servo train and configured to transmit steering torque to the steering mechanism, particularly the servo train, using an electric motor to influence the direction of travel of the vehicle. Preferably, the steering actuator system is configured to use an electric motor to provide steering torque to assist the manual torque applied to the steering wheel of the steering system, and / or steering torque to automatically and / or autonomously control the direction of travel of the vehicle. Furthermore, the steering system may preferably include a mechanical locking mechanism, which is configured to stop the steering mechanism in an inspection position, particularly to fix and / or lock it. For this purpose, the locking mechanism may include, in particular, at least one electrical and / or mechanical lock, for example, a steering lock in the area of ​​the steering wheel, a locking unit in the area of ​​the steering shaft, particularly the input shaft of the steering shaft, and / or a wheel lock in the area of ​​the vehicle's wheels.

[0010] Furthermore, the vehicle includes at least one computing unit provided to implement a method for operating the steering system. “Computing unit” should be understood to mean, in particular, an electrical and / or electronic unit having an information input terminal, an information processing terminal, and an information output terminal. Preferably, the computing unit further includes at least one processor, at least one operating memory, at least one input means and / or output means, at least one operating program, at least one control routine, at least one adjustment routine, at least one calculation routine, and / or at least one evaluation routine. In particular, the computing unit is provided to determine the stiffness of at least one steering assembly and / or the play in the steering mechanism. Furthermore, the computing unit is provided to drive and control an electric motor. Moreover, the computing unit may be provided to drive and control a locking mechanism. In this embodiment, the computing unit is provided to at least drive and control an electric motor using an excitation signal, monitor the motor torque and rotor position angle of the electric motor during the period of drive and control of the electric motor using the excitation signal, and evaluate the change in motor torque depending on the rotor position angle. Furthermore, the calculation unit may be configured to move the steering mechanism to a specified inspection position by drive control of an electric motor, and / or to stop it at the inspection position by drive control of a locking mechanism. Preferably, the calculation unit is integrated here in the vehicle's control system and / or in the steering system's control system, particularly in the form of a steering control unit. "Configured" should be understood to mean, in particular, specially programmed, designed, and / or equipped. Where an object is configured for a particular function, it should be understood to mean, in particular, that the object fulfills and / or performs this particular function in at least one use and / or operating state.

[0011] Preferably, the stiffness of at least one steering assembly and / or the play in the steering mechanism is further proposed to be determined using the rotor position angle, or the derivative of the motor torque according to the difference quotient between the motor torque and the rotor position angle, i.e., based on the rate of change of the motor torque dependent on the rotor position angle, thereby making it particularly easy to monitor the change in motor torque dependent on the rotor position angle.

[0012] In a further embodiment, it is proposed that, in order to determine the stiffness of at least one steering assembly and / or the play within the steering mechanism, the change in motor torque is compared to a reference value depending on the rotor position angle. This provides a particularly suitable and simple evaluation algorithm.

[0013] Furthermore, it is proposed that linearization may be preferably used for various load levels when determining the stiffness of at least one steering assembly and / or the play within the steering mechanism. In this regard, it is necessary to consider that the stiffness and / or play to be determined usually have a nonlinear relationship. However, in this embodiment, it has been found that even when using the corresponding linearization, relatively accurate and rigorous predictions regarding stiffness and / or play are possible while significantly reducing computational effort.

[0014] If the current temperature is taken into consideration when determining the stiffness of at least one steering assembly and / or the play within the steering mechanism, the evaluation results can be made more accurate. Preferably, the temperature is captured in the area of ​​the steering mechanism, for example, via an additional temperature sensor, or preferably directly within the area of ​​the electric motor. In the latter case, preferably, a temperature sensor system integrated into the steering actuator system can be used to determine the current temperature, thereby preferably minimizing additional costs.

[0015] According to a particularly preferred embodiment, the electric motor is driven and controlled using an excitation signal such that quasi-static excitation is achieved, wherein it is proposed that the motor torque increases continuously, in particular up to a defined and / or definable maximum motor torque, for example +5 Nm. This makes it possible, in particular, to achieve excitation of the steering system that is particularly simple from a control engineering point of view. Preferably, the electric motor is in this case driven and controlled using a ramp-shaped signal, whereby the excitation signal increases continuously and / or in a ramp-like manner. In the present exemplary embodiment, the increase in the motor torque can take place here directly by means of control of the motor torque. However, the increase in the motor torque preferably takes place by means of control of the rotor position angle, as a result of which undesired accelerations and / or load peaks in the measurement can preferably be prevented. Furthermore, it is preferably proposed in this connection that the motor torque is increased continuously up to the maximum motor torque in both steering directions if the steering mechanism is brought to a complete standstill in the test position, i.e. is fixed and / or locked, for example by means of a locking mechanism, and is increased continuously up to the maximum motor torque in only one steering direction if the steering mechanism is not brought to a complete standstill in the test position.

[0016] Alternatively or additionally, the electric motor is driven and controlled using an excitation signal such that dynamic excitation is achieved, wherein it is proposed that the drive control of the electric motor is carried out at a plurality of constant amplitudes using a plurality of different frequencies. This enables a particularly precise evaluation. A frequency sweep is preferably used here for the drive control of the electric motor, which frequency sweep is carried out for at least two different amplitudes of the motor torque. Particularly preferably, the frequency sweep is performed starting from a high frequency in the direction of lower frequencies. Further preferably, the maximum amplitude of the motor torque during the frequency sweep is also below the maximum possible motor torque, i.e. for example at a maximum of 75% or a maximum of 50% of the maximum possible motor torque.

[0017] Particularly high operational safety can be achieved especially when at least one control parameter of the steering control device of the steering system, in particular for drive control of the electric motor, is adjusted on the basis of the determined rigidity of the at least one steering assembly and / or the determined play in the steering mechanism. In particular, this allows the rigidity-sensitive and / or play-sensitive control parameter to be adaptively adjusted on the basis of the determined rigidity and / or the determined play. Preferably, the steering control device, in this case, has an electrical connection to a calculation unit, and particularly preferably is integrated into the control device of the vehicle and / or the control device of the steering system.

[0018] Furthermore, it is proposed that the rigidity of the at least one steering assembly and / or the play in the steering mechanism is compared with a threshold value, wherein a safety measure is initiated if the rigidity of the at least one steering assembly and / or the play in the steering mechanism falls below or exceeds the threshold value. This safety measure may in particular include at least generating an instruction message in the vehicle, and / or generating an instruction message on an external electronic device, for example in the form of a smartphone, and / or reducing the level of the driving mode, for example in the form of a maximum vehicle speed reduction. As a result, a warning effect can be achieved in particular, and operational safety can be further enhanced.

[0019] According to a further embodiment, it is proposed that the rigidity of the at least one steering assembly and / or the play in the steering mechanism is used for determining a humidity characteristic variable. The "humidity characteristic variable" is to be understood in particular as meaning a characteristic variable on the basis of which the humidity in the steering system can be inferred, or a characteristic variable with which the humidity in the steering system can be identified. In this connection, it is utilized in particular that the rigidity of the at least one steering assembly and / or the play in the steering mechanism changes depending on the humidity in the steering system. As a result, additional information relating to the humidity in the steering system can be obtained in particular, and / or a correlated change in the determined rigidity and / or the determined play associated therewith can be identified accordingly.

[0020] The stiffness of at least one steering assembly and / or the play in the steering mechanism can be determined, for example, during a period of driving mode for the vehicle. However, it is preferably proposed that the stiffness of at least one steering assembly and / or the play in the steering mechanism be determined when the vehicle is stationary and / or when the vehicle's engine is off, for example, when the vehicle is stopped, for example, before a traffic light, or when the vehicle is parked. This can suitably reduce frustration for the driver and / or passengers while driving.

[0021] Furthermore, it is proposed that the stiffness of at least one steering assembly and / or the play within the steering mechanism be determined at regular time intervals, for example, when each system is started up, when each system is shut down, or annually or biennially, for example, especially during regular vehicle inspections and / or after-sales service, in order to monitor changes in the stiffness of said at least one steering assembly and / or the play within the steering mechanism. This allows for the preferably rapid identification of changes in the stiffness of at least one steering assembly and / or the play within the steering mechanism, thereby further enhancing the operational safety of the vehicle.

[0022] According to one embodiment, the steering mechanism includes at least one steering assembly in the form of a servotrain, where, in order to determine the stiffness of the servotrain and / or the play within the steering mechanism, a steering adjustment element of the servotrain, for example, in the form of a rack, is positioned in the region of a mechanical end stopper of the steering system, and an electric motor is driven and controlled using an excitation signal such that the motor torque continuously increases in the direction of the mechanical end stopper up to the maximum motor torque. In this case, the position of the steering adjustment element in the region of the mechanical end stopper corresponds to the inspection position. However, alternatively, the drive control of the electric motor can be performed in multiple constant amplitudes using multiple different frequencies. Furthermore, the above method step can be repeated in a further method step for at least one further inspection position different from the said inspection position. In this context, for example, in a further method step, in order to determine the stiffness of the servotrain in particular, it is assumed that the steering adjustment element is positioned in the region of a further mechanical end stopper of the steering system, in particular the region opposite to the mechanical end stopper, and the electric motor is driven and controlled using a further excitation signal, in particular a further excitation signal equivalent to said excitation signal, so that the motor torque increases continuously to the maximum motor torque in the direction of the further mechanical end stopper. However, alternatively, the iteration in the further method step may also apply to a further steering assembly different from the steering assembly, in particular to determine the play in the steering mechanism. This allows the stiffness of the servotrain and / or the play in the steering mechanism to be determined in particular, especially in the region of the servotrain, by a particularly preferred method.

[0023] In a further embodiment, the steering mechanism includes at least one steering assembly in the form of a sensor train, where, in order to determine the stiffness of the sensor train and / or the play in the steering mechanism, the sensor train is stopped in a straight position, particularly mechanically, for example by drive control of a locking mechanism, and an electric motor is driven and controlled using an excitation signal such that the motor torque increases continuously to the maximum motor torque in both steering directions. In this case, the position of the sensor train in the straight position corresponds to the inspection position. However, alternatively, the drive control of the electric motor can be performed at multiple constant amplitudes using multiple different frequencies. Furthermore, the above method step can be basically repeated in a further method step for at least one further inspection position different from the inspection position. However, preferably, in this case, the repetition of the method can be omitted in order to determine the stiffness of the sensor train. On the other hand, in order to determine the play in the steering mechanism, the repetition in the further method step may also apply to a further steering assembly different from the steering assembly. This allows for the determination of the rigidity of the sensor train and / or the play in the steering mechanism, particularly in the area of ​​the sensor train, using a particularly preferred method.

[0024] Furthermore, according to a further embodiment, the steering mechanism includes at least one steering assembly in the form of an axle or part of an axle, wherein at least one wheel is stopped, in particular mechanically, for example by drive control of a locking mechanism, in order to determine the stiffness of the axle or part of an axle, and / or the play in the steering mechanism, and an electric motor is driven and controlled using an excitation signal such that the motor torque increases continuously to the maximum motor torque in both steering directions. In this case, the position of the wheel in the stopped state corresponds to the inspection position. However, alternatively, the drive control of the electric motor can also be performed in multiple constant amplitudes using multiple different frequencies. Furthermore, the above method steps can also be repeated in a further method step for at least one further inspection position different from the said inspection position. In this context, for example, in a further method step for determining the stiffness of an axle or part of an axle, it is assumed that at least one additional wheel, in particular the additional wheel opposite to that wheel, is stopped, in particular mechanically, for example by drive control of a locking mechanism, and an electric motor is driven and controlled, using an additional excitation signal, in particular an equivalent excitation signal, so that the motor torque increases continuously to the maximum motor torque in both steering directions. However, alternatively, the iteration in the further method step may also apply to a further steering assembly different from the steering assembly, in particular to determine the play in the steering mechanism. This allows for the determination of the stiffness of an axle or part of an axle, and / or the play in the steering mechanism, in particular in a region of the axle or part of an axle, by a particularly preferred method.

[0025] The method for operating the steering system is not limited to the uses and embodiments described herein. In particular, the method for operating the steering system may have a different number of individual elements, parts, and units than those listed herein in order to satisfy the functional forms described herein.

[0026] Further advantages will become apparent from the description of the drawings below. These drawings illustrate one embodiment of the present invention. [Brief explanation of the drawing]

[0027] [Figure 1a] This is a schematic diagram showing an exemplary vehicle equipped with a steering system. [Figure 1b] This is a schematic diagram showing an exemplary vehicle equipped with a steering system. [Figure 2a] This is an illustrative diagram showing various signals for determining the stiffness and / or play within the steering mechanism of at least one steering assembly of a steering system's steering mechanism. [Figure 2b] This is an illustrative diagram showing various signals for determining the stiffness and / or play within the steering mechanism of at least one steering assembly of a steering system's steering mechanism. [Figure 3] This is an illustrative flowchart showing the main method steps for operating the steering system. [Modes for carrying out the invention]

[0028] Description of the Examples Figures 1a and 1b schematically show a vehicle 12 configured as an exemplary passenger car, comprising a plurality of wheels 34, 36 and a steering system 10. This vehicle 12 is suitable for automated and / or autonomous driving. The steering system 10 has operational connections with the wheels 34, 36 and is provided to influence the direction of travel of the vehicle 12. Furthermore, the steering system 10 is configured purely exemplary as an electric assist steering system, having electric assist force assistance in the form of power steering. However, alternatively, the steering system may be configured as a steer-by-wire steering system, which is known in itself.

[0029] The steering system 10 includes a steering mechanism 14 known on its own, and a steering actuator system 40 known on its own that interacts with the steering mechanism 14.

[0030] In this embodiment, the steering mechanism 14 includes a steering handle 42, which is exemplary configured as a steering wheel for applying manual torque, and a plurality of steering assemblies 18, 20, 22 that are operationally connected to the steering handle 42. In this embodiment, the steering mechanism 14 includes a first steering assembly 18 configured as a servo train, a second steering assembly 20 configured as a sensor train, and a third steering assembly 22 configured as an axle and / or as part of an axle. The first steering assembly 18 corresponds to a steering gear, which is exemplary configured as a rack and pinion steering gear, and in this embodiment includes at least one steering adjustment element 28, which is particularly configured as a rack. The first steering assembly 18 is provided to convert steering presets in the steering handle 42 into steering motion of wheels 34, 36, which are particularly configured as front wheels. The second steering assembly 20 corresponds to a steering shaft in this embodiment and is used to mechanically connect the steering handle 42 to the first steering assembly 18. The third steering assembly 22 may include at least a portion of the tie rods assigned to the wheels 34, 36, and / or a portion of the rims of the wheels 34, 36. Alternatively, the steering handle may be configured as a steering lever and / or steering ball, etc. Furthermore, it is conceivable that the steering shaft and / or steering handle may be omitted, as in the case of a steer-by-wire steering system.

[0031] The steering actuator system 40 includes an electric motor 16 and has an operational connection to a first steering assembly 18, particularly a steering adjustment element 28. The steering actuator system 40 is configured to provide steering torque using the electric motor 16. In this embodiment, the steering actuator system 40 is configured to provide steering torque, at least in the form of assist torque, and to transmit it to the steering adjustment element 28.

[0032] Furthermore, the steering system 10 has a rotor position sensor system 44 located in the area of ​​the steering actuator system 40. This rotor position sensor system 44 is provided to non-contact capture at least one operating signal of the electric motor 16, in this embodiment in particular a rotor position signal or rotor position angle.

[0033] Furthermore, the steering system 10 has a locking mechanism 46, which is provided to stop the steering mechanism 14, in particular to fix and / or lock it. For this purpose, the locking mechanism 46 in this embodiment includes a plurality of electrically and / or mechanically configured locks, in particular a steering lock 48 in the area of ​​the steering handle 42, a first wheel lock 50 in the area of ​​the first wheel 34 of the wheels 34,36, and a second wheel lock 52 in the area of ​​the second wheel 36 of the wheels 34,36. However, it is also conceivable that this type of locking mechanism may be omitted.

[0034] Furthermore, the vehicle 12 has a control device 54. This control device 54 is configured as a steering control device and is therefore part of the steering system 10. The control device 54 has an electrical connection to the steering actuator system 40, in particular to the electric motor 16. Furthermore, the control device 54 has an electrical connection to the rotor position sensor system 44. Furthermore, the control device 54 has an electrical connection to the locking mechanism 46. The control device 54 is provided to control the operation of the steering system 10. In this embodiment, the control device 54 is provided to drive and control at least the electric motor 16. Alternatively, the control device may be different from the steering control device, for example, it may be configured directly as a centralized vehicle control device.

[0035] The control device 54 includes a computing unit 38. This computing unit 38 includes, for example, at least one processor (not shown) in the form of a microprocessor, and at least one operating memory (not shown). Furthermore, the computing unit 38 includes at least one operating program stored in the operating memory.

[0036] Furthermore, the control device 54 includes a steering control device 26 known in itself for driving and controlling the electric motor 16. This steering control device 26 has an electrical connection to the computing unit 38. Furthermore, the steering control device 26 is electrically connected to the electric motor 16. In this embodiment, the steering control device 26 is provided to control the position of the steering adjustment element 28, and therefore in particular the direction of travel of the vehicle 12, at least in the driving modes of the vehicle 12.

[0037] Normally, only a small fraction of the mechanical anomalies that may occur during the operation of the vehicle 12 or the steering system 10 are detected automatically, while the vast majority of such anomalies must be detected by the driver themselves. However, this fact may become increasingly problematic in the future, especially in automated vehicles and / or autonomous vehicles and / or steering systems in the form of steer-by-wire steering systems. In this context, determining the rigidity of the steering assemblies 18, 20, 22 of the steering mechanism 14, and / or the play within the steering mechanism 14, plays a particularly important role, because signs of wear and / or the effects of aging can have a particularly critical impact here.

[0038] Therefore, in order to improve efficiency and / or operational safety, appropriate methods for operating the steering system 10 are proposed below. In this embodiment, a computing unit 38 is provided to carry out this method and has a computer program having appropriate program code means for this purpose.

[0039] In this embodiment, in order to determine the stiffness of at least one steering assembly 18, 20, 22 and / or the play within the steering mechanism 14, the steering mechanism 14 is first moved to a defined inspection position and / or stopped in the inspection position. Preferably, the stiffness of at least one steering assembly 18, 20, 22 and / or the play within the steering mechanism 14 are determined here with the vehicle 12 stationary and / or with the engine of the vehicle 12 stopped. Furthermore, the positioning of the steering mechanism 14 to the inspection position can be done manually, for example, by the occupants and / or driver of the vehicle 12, or preferably automatically and / or automated by the corresponding drive control of the electric motor 16. Furthermore, stopping the steering mechanism 14 in the inspection position can be done by the automated drive control of the locking mechanism 46.

[0040] Next, the electric motor 16 is driven and controlled using an excitation signal. The drive control of the electric motor 16 using the excitation signal can be performed in basically two different ways.

[0041] On the one hand, the electric motor 16 can be driven and controlled using an excitation signal to achieve quasi-static excitation, where the motor torque of the electric motor 16 is continuously increased up to the maximum motor torque, for example, +5 Nm. In this case, the electric motor 16 is driven and controlled using a ramp-like signal, thereby the excitation signal is continuously and / or ramp-like increased. Furthermore, the increase in motor torque is preferably achieved by controlling the rotor position angle of the electric motor 16, thereby preventing unwanted acceleration and / or load peaks in the measurement. Moreover, the motor torque is continuously increased up to the maximum motor torque in both steering directions when the steering mechanism 14 is completely stopped at the inspection position, and continuously increased up to the maximum motor torque in only one steering direction when the steering mechanism 14 cannot be completely stopped at the inspection position.

[0042] Alternatively or additionally, for example in further applications, the electric motor is driven and controlled using an excitation signal to achieve dynamic excitation, where the drive control of the electric motor is performed at multiple constant amplitudes using multiple different frequencies. In this case, a frequency sweep or frequency sweep is used for the drive control of the electric motor 16, and this frequency sweep or frequency sweep is performed for at least two different amplitudes of motor torque. Preferably, the frequency sweep or frequency sweep is performed here from a high frequency toward a low frequency, for example, from a frequency of 100 Hz toward 0 Hz, or from a frequency of 40 Hz toward 0 Hz. Furthermore, the maximum amplitude of the motor torque during the frequency sweep or frequency sweep is also preferably below the maximum possible motor torque, i.e., for example, at a maximum of 75% or a maximum of 50% of the maximum possible motor torque. In this regard, for example, amplitudes of 0.2 Nm to 0.5 Nm have been found to be appropriate. By positioning and / or stopping at least one steering assembly 18, 20, 22 in the inspection position, it is possible to determine the stiffness of at least one steering assembly 18, 20, 22 and / or the play within the steering mechanism 14, both in the low-load and high-load ranges.

[0043] Next, the stiffness of at least one steering assembly 18, 20, 22 and / or the play in the steering mechanism 14 is determined by monitoring the motor torque and rotor position angle of the electric motor 16 during the drive control period of the electric motor 16 using an excitation signal, and evaluating the change in motor torque depending on the rotor position angle. The motor torque of the electric motor 16 can, for example, be read directly from the control device 54 or captured using an additional capture sensor system, while the rotor position angle of the electric motor 16 can preferably be determined from the rotor position signal of the rotor position sensor system 44. In this embodiment, in this case, the derivative of the motor torque according to the rotor position angle, or the difference quotient from the motor torque and the rotor position angle, is formed and compared with a reference value 24 to determine the stiffness of at least one steering assembly 18, 20, 22 and / or the play in the steering mechanism 14 (see also Figure 2b).

[0044] Preferably, linearization can be used when determining the stiffness of at least one steering assembly 18, 20, 22 and / or the play in the steering mechanism 14. In this regard, it is necessary to consider that the stiffness and / or play to be determined usually have a nonlinear relationship. However, in this embodiment, it has been found that even when using the corresponding linearization, relatively accurate and precise predictions regarding the stiffness of at least one steering assembly 18, 20, 22 and / or the play in the steering mechanism 14 can be made while significantly reducing computational effort.

[0045] To improve the accuracy of the measurement, the current temperature can be further considered when determining the stiffness of at least one steering assembly 18, 20, 22 and / or the play in the steering mechanism 14. In this regard, it is particularly useful that the stiffness of at least one steering assembly 18, 20, 22 and / or the play in the steering mechanism 14 changes depending on the current temperature. Preferably, the temperature is captured directly in the area of ​​the electric motor 16, and more specifically, using a temperature sensor system integrated within the steering actuator system 40. However, alternatively, an additional temperature sensor can be used in the area of ​​the electric motor 16 or in the area of ​​the steering mechanism 14. Furthermore, existing temperature sensors in the vehicle 12, such as a temperature sensor for displaying ambient temperature, can also be used to determine the temperature. Moreover, it is conceivable that the additional determination of temperature may be omitted entirely.

[0046] Next, after the stiffness of at least one steering assembly 18, 20, 22 and / or the play in the steering mechanism 14 have been determined, various actions can be performed and / or initiated depending on the determined values.

[0047] For example, at least one control parameter of the steering control device 26 can be adjusted based on the required stiffness of at least one steering assembly 18, 20, 22 and / or play within the steering mechanism 14, thereby preferably allowing the stiffness-sensitive and / or play-sensitive control parameters to be adaptively adjusted based on the required stiffness and / or play.

[0048] Furthermore, the stiffness of at least one steering assembly 18, 20, 22 and / or the play within the steering mechanism 14 can be compared to a threshold, where if the stiffness and / or play is below or above the threshold, safety measures are initiated. These safety measures may include, at a minimum, the generation of an instruction message within the vehicle and / or the generation of an instruction message on an external electronic device, for example, an instruction to bring the vehicle into a service center, and / or a reduction in the driving mode, for example, in the form of a reduction in maximum vehicle speed.

[0049] Furthermore, the stiffness of at least one steering assembly 18, 20, 22 and / or the play within the steering mechanism 14 can be used to determine a humidity characteristic variable, where the humidity within the steering system 10 can be inferred or identified based on the humidity characteristic variable. This allows for obtaining additional information regarding the humidity within the steering system 10 and / or, consequently, identifying correlated changes in the determined stiffness and / or the determined play.

[0050] Furthermore, in this embodiment, the stiffness of at least one steering assembly 18, 20, 22 and / or the play within the steering mechanism 14 are determined at regular time intervals, for example, when each system is started or shut down, in order to monitor changes in the stiffness of the at least one steering assembly 18, 20, 22 and / or changes in the play within the steering mechanism 14. This makes it possible to preferably quickly recognize changes in the stiffness of at least one steering assembly 18, 20, 22 and / or changes in the play within the steering mechanism 14, further enhancing the operational safety of the vehicle 12. However, alternatively, it is also conceivable to set relatively long monitoring intervals, for example, daily, monthly, or yearly.

[0051] Hereinafter, we will describe some specific application examples of the general facts described above with respect to a first steering assembly 18 configured as a servo train, a second steering assembly 20 configured as a sensor train, and a third steering assembly 22 configured as an axle and / or part of an axle.

[0052] According to the first embodiment, in order to determine the rigidity of the first steering assembly 18 or servo train, the steering adjustment element 28 is positioned in the region of the mechanical end stopper 30 of the steering system 10, and the electric motor 16 is driven and controlled using an excitation signal so that the motor torque continuously increases to the maximum motor torque in the direction of the mechanical end stopper 30. In this case, the position of the steering adjustment element 28 in the region of the mechanical end stopper 30 corresponds to the inspection position. To position the steering adjustment element 28 to the inspection position, the steering adjustment element 28 can be directly positioned in the region of the mechanical end stopper 30 using appropriately learned software functions, for example, by drive control of the electric motor 16, or it can be moved in the direction of the mechanical end stopper 30 at a constant motion speed (approximately 10 mm / s to 40 mm / s) until it reaches the inspection position or until the inspection position is recognized based on the decreasing motion speed. Next, based on the motor torque of the electric motor 16 and the rotor position angle of the electric motor 16, the total stiffness from the servo train and the mechanical end stopper 30 can be determined for the corresponding load direction, that is, in the direction of the mechanical end stopper 30. Here, the following equation is used: 1 / c1=(1 / c Servo ) + (1 / c A ) (1) This applies.

[0053] Here, c1 describes the total stiffness from the servo train and the mechanical end stopper 30 for the corresponding load direction, and c Servo This describes the stiffness of the first steering assembly 18 or servo train, and c AThis describes the stiffness of the mechanical end stopper 30. Once the stiffness of the mechanical end stopper 30 is known, the stiffness of the first steering assembly 18 or servo train can be inferred accordingly based on equation (1). In particular, if an end stopper damper is used here, the stiffness of the mechanical end stopper 30 is governed by the proportion of this end stopper damper. However, alternatively, the drive control of the electric motor can also be performed at multiple constant amplitudes using multiple different frequencies.

[0054] Next, the above method steps can be repeated for the opposite side. Here, the steering adjustment element 28 is positioned in the region of a further mechanical end stopper 32 of the steering system, particularly in the region opposite to the mechanical end stopper 30, and the electric motor 16 is driven and controlled using a further excitation signal, particularly an equivalent excitation signal, so that the motor torque continuously increases to the maximum motor torque in the direction of the further mechanical end stopper 32. Thus, in this case, the position of the steering adjustment element 28 in the region of the further mechanical end stopper 32 corresponds to a further inspection position. The positioning of the steering adjustment element 28 at the further inspection position and the evaluation of its rigidity can be performed here using the methodology described above.

[0055] According to the second embodiment, in order to determine the stiffness of the second steering assembly 20 or sensor train, the sensor train is stopped in the straight-ahead position, particularly by the drive control of the locking mechanism 46, or more precisely, the drive control of the steering lock 48, and the electric motor 16 is driven using an excitation signal so that the motor torque continuously increases to the maximum motor torque in both steering directions. In this case, the position of the sensor train in the straight-ahead position corresponds to the inspection position. Positioning of the sensor train in the straight-ahead position can be done manually, or preferably by corresponding drive control of the electric motor 16 and the locking mechanism 46. Subsequently, the total stiffness from the sensor train and the servo train can be determined based on the motor torque of the electric motor 16 and the rotor position angle of the electric motor 16. Herein, the following formula: 1 / c² = (1 / c Sensor ) + (1 / c Servo ) (2) This applies.

[0056] Here, c2 describes the total stiffness from the sensor train and the servo train, and c Sensor This describes the stiffness of the second steering assembly 20 or sensor train, and c Servo This describes the stiffness of the first steering assembly 18 or servo train. Once the stiffness of the first steering assembly 18 or servo train is determined as described above and is thus known, the stiffness of the second steering assembly 20 or sensor train can be inferred accordingly based on equation (2). However, alternatively, the drive control of the electric motor can also be performed in this case using multiple different frequencies at multiple constant amplitudes. The repetition of the method step can be omitted in this case because excitation is performed in both steering directions as described above.

[0057] According to the third aspect, in order to determine the rigidity of the third steering assembly 22 or the axle or a part of the axle, one of the wheels 34, 36 is stopped, in particular by drive control of the locking mechanism 46, or more precisely by drive control of the wheel lock 50 or the wheel lock 52, and the electric motor 16 is driven and controlled using an excitation signal such that the motor torque continuously increases up to the maximum motor torque in both steering directions. The other of the wheels 34, 36 is in a state of free rotation in this case, for example on a lifting platform. Therefore, in this case, the position of the wheels 34, 36 in the stopped state corresponds to the inspection position. Subsequently, the total rigidity from the axle and the servo train can be determined based on the motor torque of the electric motor 16 and the rotor position angle of the electric motor 16. Here, the following formula: 1 / c3=(1 / c FZ )+(1 / c Servo ) (3) is applied.

[0058] Here, c3 describes the total rigidity from the axle and the servo train, c FZ describes the rigidity of the third steering assembly 22 or the axle or a part of the axle, and c Servo describes the rigidity of the first steering assembly 18 or the servo train. If the rigidity of the first steering assembly 18 or the servo train is determined as described above, whereby this becomes known, the rigidity of the third steering assembly 22 or the axle or a part of the axle can be inferred according to formula (3) accordingly. However, alternatively, the drive control of the electric motor can also be carried out here at a plurality of constant amplitudes using a plurality of different frequencies.

[0059] Subsequently, the above method steps can be repeated for the opposite side. At that time, the other of the wheels 34, 36 is stopped, and the electric motor 16 is driven and controlled using a further excitation signal, in particular a further excitation signal equivalent to the said excitation signal, such that the motor torque continuously increases up to the maximum motor torque in both steering directions. The evaluation of the rigidity can again be carried out using the above-described methodology.

[0060] In order to determine the play within the steering mechanism 14, according to the fourth embodiment, at least two of the above-described methodologies for determining rigidity can be combined with each other.

[0061] In one modified form, to determine the play within the steering mechanism 14, particularly the play between the first steering assembly 18 and the second steering assembly 20, the stiffness of the first steering assembly 18 or the servo train is determined using the first methodology described above, and the stiffness of the second steering assembly 20 or the sensor train is determined using the second methodology described above. Subsequently, the total play from the servo train and the sensor train can be determined based on the motor torque of the electric motor 16 and the rotor position angle of the electric motor 16. Herein, the following equation is used: Δφ1 = Δφ Servo +Δφ Sensor (4) This applies.

[0062] Here, Δφ1 describes the total play from the servo train and sensor train, and Δφ Servo This describes the play in the region of the first steering assembly 18 or servo train, and Δφ Sensor This describes the play in the region of the second steering assembly 20 or sensor train. In this case, Δφ Servo and Δφ Sensor There is no need to distinguish between them, because if the corresponding threshold is exceeded, they will be brought to the factory anyway. Similarly, repeating the method steps is unnecessary in this case as well.

[0063] In a further modified form, to determine the play within the steering mechanism 14, particularly the play between the first steering assembly 18 and the third steering assembly 22, the stiffness of the first steering assembly 18 or the servo train is determined using the first methodology described above, and the stiffness of the third steering assembly 22 or the axle or a part of the axle is determined using the third methodology described above. Subsequently, the total play from the servo train and the axle can be determined based on the motor torque of the electric motor 16 and the rotor position angle of the electric motor 16. Herein, the following equation: Δφ² = Δφ Servo +Δφ FZ (5) This applies.

[0064] Here, Δφ2 describes the total play from the servo train and the axle, and Δφ Servo This describes the play in the region of the first steering assembly 18 or servo train, and Δφ FZ This describes the play in the third steering assembly 22 or in a region of the axle or part of the axle. In this case, Δφ Servo and Δφ FZ There is no need to distinguish between the two, because if the corresponding threshold is exceeded, it will be brought to the factory anyway. Therefore, the cause can be finally narrowed down there. Repeating the method steps is also unnecessary in this case.

[0065] Furthermore, the total play from the servo train, axles, and sensor train can also be basically determined by a combination of all the methodologies described above.

[0066] Figures 2a and 2b illustrate various signals for determining the stiffness and / or play within the steering mechanism 14 of at least one steering assembly 18, 20, 22. The examples shown in Figures 2a and 2b are, hereby limited, to the first steering assembly 18 and the third steering assembly 22.

[0067] In Figure 2a, the motor torque of the electric motor 16 is plotted on the vertical axis 56. The rotor position angle of the electric motor 16 is shown on the horizontal axis 58. Curve 60 shows the motor torque over time, particularly the linearized version, depending on the rotor position angle.

[0068] The first region 62 schematically illustrates an exemplary process of the rotor position angle-dependent motor torque for determining the stiffness in the region of the first steering assembly 18 or servo train.

[0069] The second region 64 schematically illustrates an exemplary process of motor torque dependent on rotor position angle for determining the stiffness of the third steering assembly 22 or a region of the axle or part of the axle.

[0070] In Figure 2b, stiffness is plotted on a further vertical axis 66. The rotor position angle of the electric motor 16 is again shown on a further horizontal axis 68. Curve 70 shows the progression of stiffness depending on the rotor position angle. To obtain curve 70, the derivative of the motor torque according to the rotor position angle, or the difference quotient from the motor torque and the rotor position angle, is formed.

[0071] The first region 72 schematically illustrates the exemplary course of the total stiffness from the servo train and the mechanical end stopper 30 in the corresponding load direction, i.e., the direction of the mechanical end stopper 30.

[0072] The second region 74 schematically illustrates the exemplary progression of total stiffness from Bohr friction between the contact surfaces of the axle, servo train, and tires and the road surface.

[0073] The third area 76 further characterizes the play within the steering mechanism 14, in particular the play between the first steering assembly 18 and the third steering assembly 22.

[0074] Finally, Figure 3 shows an exemplary flowchart illustrating the main method steps for operating the steering system 10.

[0075] In step 80 of the method, the steering mechanism 14 is positioned and / or stopped at the corresponding inspection position. Positioning of the steering mechanism 14 to the inspection position can be done manually, for example, by the occupants and / or driver of the vehicle 12, or preferably automatically and / or automated by the corresponding drive control of the electric motor 16.

[0076] In the subsequent step 82, the steering system 10 is excited by drive control of the electric motor 16 using an excitation signal, and more specifically, the steering mechanism 14 is in the inspection position. At this time, the electric motor 16 can be driven and controlled using the excitation signal so that quasi-static excitation and / or dynamic excitation are achieved.

[0077] In the subsequent method step 84, the system response of the steering system 10 to the excitation signal is determined and evaluated using the motor torque of the electric motor 16 and the rotor position angle of the electric motor 16, more specifically using the derivative of the motor torque according to the rotor position angle, or using the difference quotient from the motor torque and the rotor position angle. This system response can then be used to determine the stiffness of at least one steering assembly 18, 20, 22 of the steering mechanism 14, and / or the play within the steering mechanism 14.

[0078] Next, in the subsequent method step 86, various actions can be performed and / or initiated depending on the determined stiffness value and / or play value, such as adjusting at least one control parameter of the steering control device 26 and / or initiating safety measures if the value exceeds or falls below a threshold.

[0079] The illustrative flowchart in Figure 3 merely illustrates the method for operating the steering system 10. In particular, individual method steps can be modified, or additional method steps can be added. For example, these method steps 80, 82, and 84 can be repeated for at least one further inspection position different from the inspection position in a method step that directly follows method step 84. This repetition may, in particular, apply to the same steering assembly 18, 20, 22 or one of other steering assemblies 18, 20, 22.

Claims

1. A method for operating the steering system (10) of a vehicle (12), The steering system (10) includes a steering mechanism (14) and at least one electric motor (16) that cooperates with the steering mechanism (14), In a method for determining the rigidity of at least one steering assembly (18, 20, 22) of the steering mechanism (14), and / or the play within the steering mechanism (14), In order to determine the rigidity of at least one steering assembly (18, 20, 22) and / or the play in the steering mechanism (14), the steering mechanism (14) is moved to a specified inspection position and stopped in the inspection position, and the electric motor (16) is driven and controlled using an excitation signal. The rigidity of at least one steering assembly (18, 20, 22), and / or the play in the steering mechanism (14) is determined by monitoring the motor torque of the electric motor (16) and the rotor position angle of the electric motor (16) during the drive control period of the electric motor (16) using the excitation signal, and evaluating the change in the motor torque depending on the rotor position angle. A method wherein the rigidity of at least one steering assembly (18, 20, 22) is determined using the rotor position angle, or the derivative of the motor torque according to the difference quotient between the motor torque and the rotor position angle, and / or the play in the steering mechanism (14) is determined using the derivative of the motor torque according to the difference quotient between the motor torque and the rotor position angle.

2. The method according to claim 1, wherein the change in motor torque is compared to a reference value (24) depending on the rotor position angle in order to determine the stiffness of the at least one steering assembly (18, 20, 22) and / or the play in the steering mechanism (14).

3. The method according to claim 1, wherein linearization is used when determining the stiffness of the at least one steering assembly (18, 20, 22) and / or the play in the steering mechanism (14).

4. The method according to claim 1, wherein the current temperature is taken into consideration when determining the stiffness of the at least one steering assembly (18, 20, 22) and / or the play in the steering mechanism (14).

5. The electric motor (16) is driven and controlled using the excitation signal to achieve quasi-static excitation, wherein the motor torque is continuously increased up to the maximum motor torque, according to claim 1.

6. The method according to claim 5, wherein the motor torque increases continuously to the maximum motor torque in both steering directions when the steering mechanism (14) is stopped at the inspection position, and increases continuously to the maximum motor torque in one steering direction when the steering mechanism (14) is not stopped at the inspection position.

7. The electric motor (16) is driven and controlled using the excitation signal to achieve dynamic excitation, wherein the drive control of the electric motor (16) is performed at a plurality of constant amplitudes using a plurality of different frequencies, according to claim 1.

8. The method according to claim 1, wherein at least one control parameter of the steering control device (26) of the steering system (10) is adjusted for drive control of the electric motor (16) based on a required stiffness of the at least one steering assembly (18, 20, 22) and / or a required play in the steering mechanism (14).

9. The method according to claim 1, wherein the stiffness of the at least one steering assembly (18, 20, 22) and / or the play in the steering mechanism (14) is compared to a threshold, and if the stiffness of the at least one steering assembly (18, 20, 22) and / or the play in the steering mechanism (14) is below or above the threshold, a safety measure is initiated.

10. The method according to claim 1, wherein the stiffness of the at least one steering assembly (18, 20, 22) and / or the play in the steering mechanism (14) is used to determine a humidity characteristic variable.

11. The method according to claim 1, wherein the rigidity of the at least one steering assembly (18, 20, 22) and / or the play in the steering mechanism (14) is determined when the vehicle (12) is stopped and / or when the engine of the vehicle (12) is stopped.

12. The method according to claim 1, wherein the stiffness of the at least one steering assembly (18, 20, 22) and / or the play in the steering mechanism (14) is determined at regular time intervals to monitor changes in the stiffness of the at least one steering assembly (18, 20, 22) and / or the play in the steering mechanism (14).

13. The method according to claim 1, wherein the steering mechanism (14) includes at least one steering assembly (18) in the form of a servotrain, and a steering adjustment element (28) of the servotrain is positioned in the region of mechanical end stoppers (30, 32) of the steering system (10) to determine the stiffness of the servotrain and / or play within the steering mechanism (14), and the electric motor (16) is driven and controlled using the excitation signal such that the motor torque increases continuously in the direction of the mechanical end stoppers (30, 32) up to the maximum motor torque.

14. The method according to claim 1, wherein the steering mechanism (14) includes at least one steering assembly (20) in the form of a sensor train, the sensor train is stopped in a straight position in order to determine the stiffness of the sensor train and / or the play within the steering mechanism (14), and the electric motor (16) is driven and controlled using the excitation signal such that the motor torque increases continuously to the maximum motor torque in both steering directions.

15. The steering mechanism (14) includes at least one steering assembly (22) in the form of an axle or part of an axle, and at least one wheel (34, 36) is stopped in order to determine the stiffness of the axle or part of the axle and / or play in the steering mechanism (14), and the electric motor (16) is driven controlled using the excitation signal such that the motor torque increases continuously to the maximum motor torque in both steering directions, according to claim 1.

16. A computing unit (38) for carrying out the method described in claim 1.

17. A steering system (10) comprising a steering mechanism (14), at least one electric motor (16) cooperating with the steering mechanism (14), and a calculation unit (38) according to claim 16.

18. A vehicle (12) comprising the steering system (10) described in claim 17.

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