Method and device for detecting a steering wheel state on a steering wheel of a steering system

Abstract

The invention relates to a method for detecting a steering wheel state on a steering wheel (52) of a steering system (51), wherein a movement of a toothed or connecting rod (53) of the steering system (51) is detected or determined, wherein a movement of the steering wheel (52) is detected and / or determined, wherein a hands-on state (21) is determined based on a phase position between the movement of the toothed or connecting rod (53) and the movement of the steering wheel (52).Furthermore, the invention relates to a device (1) for detecting a steering wheel state on a steering wheel (52) of a steering system (51), comprising a steering sensor (2) configured to detect or determine a movement of a rack or pushrod (53) of the steering system (51), a steering wheel sensor (3) configured to detect and / or determine a movement of the steering wheel (52), and a control device (4), wherein the control device (4) is configured to detect a hands-on state (21) based on a phase position between the movement of the rack or pushrod (53) and the movement of the steering wheel (52).

Description

The invention relates to a method and a device for detecting a steering wheel state on a steering wheel of a steering system. Both mechanically coupled and mechanically decoupled steering systems face the challenge of detecting driver intervention (hands-on / off). This is necessary, for example, for the operation of driver assistance systems where the human driver must be available as a safe fallback. It must be ensured that the driver holds the steering wheel firmly in predefined situations or even continuously, and that the driver assistance system merely provides recommendations and support. Currently, the hands-on / off state is typically detected by integrating a capacitive sensor into the steering wheel, which entails additional wiring, a further control unit, and increased production costs. Overall, this is a robust but complex and expensive solution for detecting the steering wheel's state. Another method for detecting the steering wheel's state involves observing the driver using one or more cameras. Triangulation with two cameras can determine the driver's hand position. However, this requires an unobstructed view of both hands, which cannot always be guaranteed. Alternatively, 3D cameras (e.g., based on LiDAR) can be used. These also allow for the three-dimensional localization of the driver's hands.Camera-based approaches require a comparatively high computing power, which, in addition to the costs for the camera(s) and their installation, also necessitates a correspondingly powerful control unit. DE 10 2017 128 554 A1 describes a method for controlling a steer-by-wire steering system for motor vehicles with the following steps for calculating a resulting restoring torque of a feedback actuator depending on an operating state (hands-on / hands-off): Determining a base restoring torque for a first operating state in which the driver's hand is touching the steering wheel; Determining a hands-off restoring torque for a second operating state in which the driver's hand is not touching the steering wheel; Determining a return speed of the steering wheel for the first operating state and for the second operating state; Determining the resulting restoring torque based on the base restoring torque or the hands-off restoring torque, whereby the steering wheel rotates into the defined position at the determined return speed. The invention is based on the objective of improving a method and a device for detecting a steering wheel state on a steering wheel of a steering system. The problem is solved according to the invention by a method with the features of claim 1 and a device with the features of claim 8. Advantageous embodiments of the invention are set forth in the dependent claims. In particular, a method for detecting a steering wheel state on a steering wheel of a steering system is provided, wherein a movement of a rack or pushrod of the steering system is detected or determined, wherein a movement of the steering wheel is detected and / or determined, wherein a hands-on state is determined based on a phase position between the movement of the rack or pushrod and the movement of the steering wheel. Furthermore, in particular a device for detecting a steering wheel state on a steering wheel of a steering system is provided, comprising a steering sensor system configured to detect or determine a movement of a rack or pushrod of the steering system, a steering wheel sensor system configured to detect and / or determine a movement of the steering wheel, and a control device, wherein the control device is configured to determine a hands-on state based on a phase relationship between the movement of the rack or pushrod and the movement of the steering wheel. The method and device enable the detection of a steering wheel's state. This is based on the principle that the phase relationship between the movements of the rack or linkage and the steering wheel allows for the identification of whether the steering system is being stimulated by the road surface (e.g., unevenness, etc.) or by driver input at the steering wheel. When stimulated by the road surface, the movement of the rack or linkage precedes any movement of the steering wheel. Conversely, when the driver is initiating steering, the movement of the steering wheel precedes any movement of the rack or linkage. This phase relationship allows for the detection of a hands-on state. This is achieved by detecting or determining the movement of a rack or linkage within the steering system. Furthermore, the movement of the steering wheel is detected and / or determined.A hands-on state is determined by a phase difference between the movement of the rack or pushrod and the movement of the steering wheel. The hands-on state is particularly evident when the movement of the steering wheel precedes the movement of the rack or pushrod. Based on a detection result, a steering wheel status signal is generated and provided. This steering wheel status signal can be generated and provided, and in particular output, as an analog or digital signal, for example, in the form of a data packet. Based on this steering wheel status signal, a driver assistance system can be controlled, and / or a warning message and / or a request to take over steering can be issued. One advantage of the method and the device is that they can operate using sensors already integrated into a steering system. Therefore, an additional capacitive sensor on the steering wheel is unnecessary. A hands-off state is, in particular, a state in which the driver does not touch the steering wheel. Specifically, none of the driver's fingers are in contact with the steering wheel. A hands-on state is, in particular, a state in which the driver does touch the steering wheel. Parts of the device, in particular the control unit, can be configured individually or collectively as a combination of hardware and software, for example, as program code executed on a computing unit, in particular a microcontroller or microprocessor. However, it can also be provided that parts are configured individually or collectively as an application-specific integrated circuit (ASIC) and / or a field-programmable gate array (FPGA) and / or a graphics processing unit (GPU) and / or a digital signal processor (DSP). The control unit can, in particular, comprise at least one computing unit and at least one memory. In one embodiment, the movement of the rack or pushrod in a steer-by-wire steering system is detected or determined as a rod acceleration, while the movement of the steering wheel is detected or determined as a steering wheel acceleration. A hands-on state is detected when the steering wheel acceleration leads the rack acceleration. This allows for the simple detection of a hands-on state in a steer-by-wire steering system. The rod acceleration is detected, in particular, by means of suitable sensors, including, for example, a torque sensor directly or indirectly coupled to the rack or pushrod, and / or an acceleration sensor directly or indirectly coupled to the rack or pushrod. An angle sensor on a rotor of the electric machine that drives the rack or pushrod can also be used. The steering wheel acceleration is, in particular, an angular acceleration.The steering wheel acceleration is detected in particular by means of suitable sensors, including, for example, a torque sensor that is directly or indirectly coupled to the steering wheel, and / or an angle sensor and / or an acceleration sensor that is directly or indirectly coupled to the steering wheel. The steer-by-wire steering system otherwise works in a way that is familiar in itself. In one embodiment, the movement of the rack or pushrod in an electromechanical steering system is detected or determined as a rod acceleration, while the movement of the steering wheel is detected or determined as a torque. The phase relationship is determined by comparing the signs of the torque gradient and the rod acceleration, with a hands-on state being detected when the signs are the same. This allows for a simple way to detect a hands-on state in a steering system. The rod acceleration is detected, in particular, by means of suitable sensors, comprising, for example, a torque sensor that is directly or indirectly coupled to the rack or pushrod, and / or an angle sensor and / or an acceleration sensor that is directly or indirectly coupled to the rack or pushrod.The torque at the steering wheel is detected in particular by means of suitable sensors, including, for example, a torque sensor that is directly or indirectly coupled to the steering wheel. If the signs of the gradient ṀDME of the torque at the steering wheel (or the torque measured by a torque measuring unit, DME) and the rod acceleration are the same, then the driver is actively steering. It can then be assumed that a hands-on state exists, in which the driver has their hands on the steering wheel. If the signs are opposite, the rack or pushrod is moved (by road excitation or by a driver assistance system): In one embodiment, the system detects steering wheel acceleration caused by excitation of the rack or pushrod of the steering system. This detected steering wheel acceleration is then compared to a predetermined acceleration threshold based on the excitation. This predetermined acceleration threshold is determined, or is determined, taking into account the moment of inertia of the untouched steering wheel. A hands-off state is detected when the detected steering wheel acceleration is greater than or equal to the predetermined acceleration threshold. This allows for simple detection of a hands-off state. When the rack or pinion of a steering wheel is excited, either by the road surface or by a driver assistance system, a torque MFFA is applied to the steering wheel (by a force feedback actuator, FFA) in a steer-by-wire steering system, based on the excitation detected by a sensor in a steering unit (road wheel actor, RWA). This results in an angular acceleration αFFA. The moment of inertia of the steering wheel (FFA) ΘFFA,Hands-Off in its unaffected state is known or can be determined, for example, at the factory after manufacturing. The following applies: The (angular) acceleration threshold is derived from the applied torque MFFA as αFFA,Hands-Off, according to the preceding equation. A hands-off state is detected when the measured steering wheel acceleration is greater than or equal to the predefined acceleration threshold αFFA,Hands-Off. This allows for simple detection of a hands-off state. The steering wheel acceleration is measured or determined using suitable sensors, such as an angle sensor. In a further developed embodiment, a hands-on state is detected when the detected steering wheel acceleration is less than the predefined acceleration threshold αFFA,Hands-Off. In this case, the actual moment of inertia of the steering wheel no longer corresponds to the moment of inertia ΘFFA,Hands-Off of the untouched steering wheel, since the hand on the steering wheel increases the moment of inertia, which, at the same torque MFFA, reduces the detected steering wheel acceleration. The procedure is essentially the same for an electromechanical steering system. A torque MDME, generated by external input to the steering wheel, is measured at the steering wheel using a torque measuring unit (DME). Taking into account the moment of inertia Θsteering wheel, hands-off of the unaffected steering wheel, the resulting acceleration is calculated. The measured acceleration is then compared to this calculated value. The following then applies accordingly: In one embodiment, if no movement of the rack or pinion and / or steering wheel is detected or determined for a predetermined period, a test signal is generated to excite the steering wheel. This artificially induces movement of the steering wheel, during which, for example, an (angular) acceleration of the steering wheel can be evaluated to determine, by comparing threshold values, whether the steering wheel is being touched (hands-on) or not (hands-off). This allows, in particular, the determination of the steering wheel's moment of inertia, which can then be compared with the moment of inertia of the untouched steering wheel to detect whether or not it is being touched. The test signal can, for example, be a sine wave or a sin² wave. Friction compensation can be performed using a friction estimation to account for friction in the steering system. In one embodiment, the system analyzes the steering wheel's acceleration over time and / or its moment of inertia to detect misuse. This allows, for example, the detection of objects attached to the steering wheel that might suggest someone is using the steering wheel. For instance, a bottle inserted into the steering wheel could be identified by a periodically decaying signal in the steering wheel acceleration, caused by the sloshing of liquid inside the bottle. Furthermore, a constant offset relative to the moment of inertia of the untouched steering wheel could indicate the presence of an additional mass attached to the steering wheel. Further features regarding the design of the device are derived from the description of embodiments of the method. The advantages of the device are the same in each case as in the embodiments of the method. Furthermore, a steering system is also created, comprising a device according to one of the described embodiments. Furthermore, in particular a vehicle is created comprising a device according to one of the described embodiments and / or a steering system according to one of the described embodiments. The invention is explained in more detail below with reference to preferred embodiments and the figures. Figure 1 shows a schematic representation of embodiments of the device for detecting the steering wheel state of a steering system; Figure 2 shows a schematic flowchart of embodiments of the method for detecting the steering wheel state of a steering system. Figure 1 shows a schematic representation of an embodiment of the device 1 for detecting the steering wheel state of a steering wheel 52 of a steering system 51. The device 1 is, for example, part of the steering system 51 in a vehicle 50. The steering system 51 can be, for example, a steer-by-wire steering system or an electromechanical steering system. The method is described below with reference to the device 1. The device 1 comprises a steering sensor 2 configured to detect or determine the movement of a rack or pushrod 53 of the steering system 51. The device 1 further comprises a steering wheel sensor 3 configured to detect and / or determine the movement of the steering wheel 51. The device 1 also comprises a control unit 4, the control unit 4 being configured to detect a hands-on state 21 based on a phase difference between the movement of the rack or pushrod 53 and the movement of the steering wheel 52. For this purpose, the control unit 4 includes, in particular, at least one computing unit 4-1 and at least one memory 4-2. The control unit 4 generates, in particular, a steering wheel status signal 20, which includes the hands-on state 21. The steering wheel status signal 20 can, for example, be an analog or digital signal and be provided to a vehicle control unit 54 or a vehicle assistance system 55. In a steer-by-wire steering system, the movement of the rack or pushrod 53 is detected or determined in the form of a rod acceleration, and the movement of the steering wheel 52 is detected or determined in the form of a steering wheel acceleration. A hands-on state 21 is detected when the steering wheel acceleration leads the rod acceleration. The rod acceleration is detected directly or indirectly by means of the steering sensor 2, and the steering wheel acceleration directly or indirectly by means of the steering wheel sensor 3. The control unit 4 compares, in particular, the values ​​of the accelerations over time and can thereby determine whether the detected or determined steering wheel acceleration leads the detected or determined rod acceleration. If this is the case, the hands-on state 21 is detected. It can be provided that, in an electromechanical steering system, the movement of the rack or pushrod 53 is detected or determined in the form of a rod acceleration, and the movement of the steering wheel 52 is detected or determined in the form of a torque. The phase relationship is determined by comparing the signs of the torque gradient and the rod acceleration, and a hands-on state 21 is detected when the signs are the same. The rod acceleration is detected directly or indirectly by means of the steering sensor 2, and the torque directly or indirectly by means of the steering wheel sensor 3, in particular by means of a torque measuring unit. The control unit 4 compares the signs of the rod acceleration and the torque gradient. If the signs are the same, the hands-on state 21 is detected. It can be provided that a steering wheel acceleration caused by an excitation of the rack or pushrod 53 of the steering system 51 is detected, wherein the detected steering wheel acceleration is compared with an acceleration threshold specified based on the excitation, wherein the specified acceleration threshold is or is determined taking into account a moment of inertia of the untouched steering wheel, and wherein a hands-off state 22 is detected if the detected steering wheel acceleration is greater than or equal to the specified acceleration threshold. The steering wheel acceleration is detected directly or indirectly by means of the steering wheel sensor 3. Furthermore, starting from a torque caused by the excitation (or generated by the steering system 51 for feedback at the steering wheel 52) and the moment of inertia of the steering wheel in the untouched state, an acceleration is determined that defines the acceleration threshold.The control unit 4 then compares the detected steering wheel acceleration with the determined and specified acceleration threshold and, based on a comparison result, establishes the hands-off state 22 if the detected steering wheel acceleration is greater than or equal to the specified acceleration threshold. It may be further specified that a hands-on state 21 is detected if the detected steering wheel acceleration is less than the specified acceleration threshold. The control unit 4 also detects this case based on the comparison result. It can be provided that if no movement of the rack or pushrod 53 and / or the steering wheel 52 is detected or determined for a predetermined period of time, a test signal 30 is generated to excite the steering wheel 52. This is done, for example, by means of an actuator of the steering system 51, either an actuator 5 designed to apply feedback to the steering wheel 52 (force feedback actuator, FFA). This is particularly relevant for a steer-by-wire steering system. Alternatively, an electric motor 6 designed to apply a steering torque to the rack or pushrod 53 can be used. This is particularly relevant for an electromechanical steering system, whereby the torque applied by the electric motor 6 also acts on the steering wheel 52 via the mechanical connection. The control unit 4 specifically checks whether the time period has elapsed if no movement is detected.To detect that no movement is present, the recorded values ​​are compared, in particular, with a predefined minimum movement threshold. It is assumed that no movement is present if the recorded value is below the predefined minimum movement threshold. Based on the applied test signal 30, it can be determined, in particular, whether the steering wheel acceleration 52 caused by this signal is above or below the predefined acceleration threshold described above. Thus, the steering wheel's state can be detected. Furthermore, it may also be possible to evaluate a natural frequency shift of the steering wheel in its unaffected state. It may be possible to evaluate the time history of the steering wheel acceleration of the steering wheel 52 and / or the moment of inertia of the steering wheel 52 in order to detect misuse. The time history can reveal, for example, whether the moment of inertia of the steering wheel 52 exhibits a constant offset over time compared to the moment of inertia of the unaffected steering wheel 52, which could be caused, for example, by an additional mass attached to the steering wheel 52. Fig. 2 shows a schematic flowchart of embodiments of the method for detecting a steering wheel state on a steering wheel of a steering system. In process step 100, the movement of a rack or pushrod of the steering system is detected or determined. This movement can be detected, for example, using steering sensors already present in the steering system, comprising, for instance, a torque sensor and / or an angle sensor on the rotor of an electric machine that provides the rack or pushrod. In process step 101, a movement of the steering wheel is detected and / or determined. This movement can be detected, for example, using steering wheel sensors already present in the steering system, including, for instance, a torque sensor and / or an angle sensor on the steering wheel. In process step 102, a hands-on state is determined based on a phase relationship between the movement of the rack or pushrod and the movement of the steering wheel. From this, a steering wheel status signal is generated and provided. Further embodiments of the method have already been described above with reference to the device. Reference symbol list 1 Device 2 Steering sensors 3 Steering wheel sensors 4 Control unit 5 Actuator (FFA) 6 Electric machine 20 Steering wheel status signal 21 Hands-on state 22 Hands-off state 30 Test signal 50 Vehicle 51 Steering system 52 Steering wheel 53 Rack and pinion 54 Vehicle control 55 Vehicle assistance system 100 Procedure steps QUOTES INCLUDED IN THE DESCRIPTION This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature DE 10 2017 128 554 A1

[0004]

Claims

Method for detecting a steering wheel state on a steering wheel (52) of a steering system (51), wherein a movement of a rack or pushrod (53) of the steering system (51) is detected or determined, wherein a movement of the steering wheel (52) is detected and / or determined, wherein a hands-on state (21) is determined based on a phase position between the movement of the rack or pushrod (53) and the movement of the steering wheel (52). Method according to claim 1, characterized in that in a steer-by-wire steering system the movement of the rack or pushrod (53) is detected or determined in the form of a rod acceleration, wherein the movement of the steering wheel (52) is detected or determined in the form of a steering wheel acceleration, wherein a hands-on state (21) is detected when the steering wheel acceleration leads the rod acceleration. Method according to claim 1, characterized in that in an electromechanical steering system the movement of the rack or pushrod (53) is detected or determined in the form of a rod acceleration, wherein the movement of the steering wheel (52) is detected or determined in the form of a torque, wherein the phase position is determined by comparing the signs of a gradient of the torque and the rod acceleration, wherein a hands-on state (21) is detected when the signs are the same. Method according to one of the preceding claims, characterized in that a steering wheel acceleration caused by an excitation of the rack or pushrod (53) of the steering system (51) is detected, wherein the detected steering wheel acceleration is compared with an acceleration threshold value predetermined from the excitation, wherein the predetermined acceleration threshold value is or is determined taking into account a moment of inertia of the untouched steering wheel (52), and wherein a hands-off state (22) is detected if the detected steering wheel acceleration is greater than or equal to the predetermined acceleration threshold value. Method according to claim 4, characterized in that a hands-on state (21) is detected when the detected steering wheel acceleration is less than the predetermined acceleration threshold. Method according to one of the preceding claims, characterized in that if no movement of the rack or pushrod (53) and / or the steering wheel (52) is detected or determined for a predetermined period of time, a test signal (30) is generated to excite the steering wheel (52). Method according to one of the preceding claims, characterized in that, in order to detect misuse, a time course of the steering wheel acceleration of the steering wheel (52) and / or a moment of inertia of the steering wheel (52) is evaluated. Device (1) for detecting a steering wheel state on a steering wheel (52) of a steering system (51), comprising: a steering sensor system (2) configured to detect or determine a movement of a rack or pushrod (53) of the steering system (51), a steering wheel sensor system (3) configured to detect and / or determine a movement of the steering wheel (52), and a control device (4), wherein the control device (4) is configured to detect a hands-on state (21) based on a phase position between the movement of the rack or pushrod (53) and the movement of the steering wheel (52). Steering system (51) comprising a device (1) according to claim 8. Vehicle (50) comprising a device (1) according to claim 8 and / or a steering system (51) according to claim 9 .

Images