Means of transport, steer-by-wire steering system and method for establishing a geometric zero position of a steering wheel

Abstract

A means of transport, a steer-by-wire steering system (10), and a method for establishing a geometric zero position of a steering wheel (7) with an imbalance in a steer-by-wire steering system (10) are proposed. The method comprises the following steps: automatically rotating the steering wheel (7) by a motor through a first angular range (a) in a first direction, automatically determining a first force acting on the steering wheel (7) during rotation through the first angular range (a), automatically determining a first relationship between the first force acting over the first angular range (a), and automatically establishing the geometric zero position depending on the first relationship.

Description

[0001] The present invention relates to a means of locomotion, a steer-by-wire steering system, and a method for producing a geometric zero position of a steering wheel with an imbalance. In particular, the present invention relates to a simple, efficient, and gentle method for producing and determining a geometric zero position of a steering wheel in a single production or maintenance step.

[0002] Vehicles, especially road vehicles, are typically steered laterally via steering wheels. The steering wheel usually has a visually and / or haptically identifiable neutral position (corresponding to straight-ahead driving), which correlates with or coincides with the straight-ahead position of the steerable wheels. During production and maintenance, the correct position of the steering wheel must be checked on the wheel alignment test stand, in addition to verifying the straight-ahead driving of the wheels on the steered axle. This ensures that the vehicle travels straight ahead when the steering wheel is in the center position. The steering wheel's center position must currently be set using an external measuring device (called a steering wheel scale). This measuring device is clamped into the steering wheel and is typically aligned with geometric (symmetrical) structures into which it is fitted.Attaching the steering wheel measuring scale not only requires additional time but also introduces a potential for error if handled incorrectly. Furthermore, damage to the steering wheel can occur during the installation or removal of the measuring scale. The process known in the prior art is dictated by the mechanical connection between the steering wheel and the steered wheels.

[0003] It is an object of the present invention to be able to perform the adjustment of a straight-line running of a means of transport in a time-efficient, error-free and gentle manner.

[0004] The aforementioned problem is solved according to the invention by a method with the features of claim 1, a steer-by-wire steering system with the features of claim 11, and a means of propulsion with the features of claim 12. The dependent claims describe preferred embodiments of the invention.

[0005] A classic steering wheel is axially symmetrical with respect to weight distribution around the vertical center axis through the contact point between the steering wheel and the steering column. This is necessary to ensure a symmetrical steering feel for the driver when changing direction. The integrated steer-by-wire system decouples the steering wheel from the steered axle (at least when de-energized). Furthermore, an electric motor (hand wheel actuator, HWA) is installed at the human-machine interface (i.e., the connection between the driver and the steering wheel). This motor simulates the steering torque and road feedback, and can therefore rotate the steering wheel independently of the front axle. A rotor position sensor is integrated into the HWA to detect this rotation. A predefined movement of the steering wheel (e.g., sine wave, quarter turn, half turn, etc.) is used to control the steering.The required torques can be determined from the phase currents of the electric motor in the steering wheel control unit (HWA) in both directions (relative to the center axis). In other words, an imbalance in the steering wheel leads to an uneven current draw across the rotational position, from which the center position can be determined (usually the position with the lowest current draw). By comparing the phase currents and the resulting torques, and superimposing the position sensor data, a steering wheel misalignment can be detected. If the steering wheel is correctly installed, a symmetrical current-rotor angle curve results, with a current minimum at the center of the rotor angle. If the steering wheel is rotated relative to the steering axis, a corresponding shift (phase shift) in the current curve or the current amplitude occurs.A phase deviation due to steering wheel misalignment can subsequently be stored as an offset in the HWA control unit and used for a correction function. In other words, the steering wheel (with the steerable wheels pointing straight ahead) can be adjusted using the correction function to the position in which the HWA's current draw is lowest. After the correction is complete, the desired steering wheel position is saved. If, for technical reasons (interior design, instrument panel, etc.), a steering wheel offset from the neutral position is desired or necessary, this offset value can also be specifically adjusted. In other words, the correction function is used to establish the desired neutral position (possibly slightly rotated according to the offset value).

[0006] The method according to the invention serves to create a geometric zero position for a steering wheel with an imbalance in a steer-by-wire steering system. For the sake of simplicity, the term "steering system" will be used below. "Imbalance" is understood as a gravitational bias of the steering wheel relative to the angle of rotation in its installed state / position. In other words, the physical axis of rotation is not located at the center of mass of the steering wheel. Such a situation frequently occurs when the steering wheel has spokes (single, double, or multiple spokes) in its lower range (four o'clock to seven o'clock position). In a first step, the steering wheel is automatically rotated by a motor through a first angular range in a first direction. For example, the steering wheel is rotated 45°, 90°, 100°, or even 180° or more to the right from a (roughly set) zero position.Meanwhile, the initial force exerted by the steering wheel during rotation through the first angular range is automatically determined. This can be done, for example, by measuring the current through the steering system's main waveform sensor (HWA). In other words, a signal representing the torque of the HWA is recorded as a function of the steering angle. Particularly after a deflection in the range of 70° to 120°, an extreme value can be highlighted. For example, the highest measured current can be determined along with its corresponding angular position. In a further step, an initial correlation between the initial force exerted over the first angular range is automatically determined. This correlation can exist between the initial force (torque / current, etc.) and the respective angular angle. In other words, the relationship between the initial force and the angular angle is analyzed using data processing.Finally, the geometric zero position is automatically established based on the initial relationship. This can, for example, involve identifying the 90° position of the steering wheel, detectable due to imbalance, by measuring maximum current draw. Subsequently, a correction function can return the steering wheel to the straight-ahead position from this 90° position, counter-clockwise, covering exactly 90°. If an offset for a non-straight-ahead position is desired, this can also be taken into account. In any case, the tracking can now be adjusted, or, knowing the geometric zero position of the steering wheel, the steering system can be initialized. A steering wheel scale is not required in this process, making the proposed method particularly efficient, simple, and gentle on the vehicle's interior.

[0007] Optionally, a second angular range can be traversed during the inventive process. In accordance with the steps described above, the steering wheel is automatically rotated by motor through a second angular range in a second direction, the second direction being oriented in the opposite direction to the first. For example, a rotation of -70°, particularly -120°, preferably -180° or less, can be performed. During this process, a second force acting on the steering wheel is also determined as a function of the steering angle through the second angular range. The HWA (High-Voltage Indicator) can be used again in this context to determine the force or the required torque via its current consumption, thereby revealing a second relationship between the second force and the steering angle over the second angular range.Finally, taking into account the first relationship and the second relationship, the geometric zero position of the steering wheel is automatically (motorically) established (straight-ahead position or with optional offset, as shown).

[0008] Optionally, the force effect can be determined using a direct or indirect measuring device. For example, a torque measuring device in the form of a torsion bar or similar can be used to record the torque between the steering system's control unit (CSU) and the steering wheel. Depending on the CSU's design, its motor can be used to analyze its current draw, or at least its phase current, and to obtain a maximum / minimum value or other parameters in the current waveform as an indicator of the steering wheel's geometric position in the first and second angular ranges. This approach eliminates the need for external measuring devices, particularly torque measuring devices.

[0009] The relationship between the force and the angular range can be determined using a sensor in the steering system and / or an evaluation unit in the steering system. For example, the current sensor can be used to detect an abnormal condition of the steering system. Such a measurement can be used during operation of the vehicle (on the road, in series production, etc.). In any case, this eliminates the need for additional hardware, making the method according to the invention simple and cost-neutral with regard to the tooling.

[0010] Since the steering system is a steer-by-wire system, one of the steering rods can remain stationary during the execution of the method according to the invention. In other words, the wheels remain in a straight-ahead position, which is established and ensured by other tools / measuring devices. In this way, the inventive adjustment of the steering wheel's neutral position can be carried out independently of the steered wheels and their angular position. Once the steering wheel is in the desired neutral position (or offset position) and the steered wheels are oriented in the straight-ahead position, the method according to the invention can be completed by a data-based linking of the two positions (steering wheel and steered wheels).

[0011] The initial offset angle, if determined, between an initial position of the steering wheel and its geometric zero position can be determined using data / sensor technology and ultimately stored as a memory value in a digital memory. This memory can be assigned to the steering system or the means of transport. It can be used, for example, to establish an actual zero position of the steering wheel (again, if necessary). The same applies to a desired / predefined offset angle / value, which is predefined for the alignment of the steering wheel. In particular, the method according to the invention can be carried out again at a later time, and the (possibly updated) offset value can be realized again by rotating the steering wheel by the offset value from the geometric zero position using the steering angle sensor.

[0012] The method according to the invention can be initiated by a diagnostic tool (for example, a diagnostic job on a laptop, other computer, or tablet PC, etc.). In other words, a signal triggers the determination of the geometric zero position of the steering wheel according to the invention solely through wired or wireless communication with the vehicle's electrical system, or at least with the vehicle's control unit. In this way, operating steps at the vehicle's user interface are unnecessary. The diagnostic tool can, for example, be connected to an OBD port, a USB port of the vehicle, or similar.

[0013] According to a second aspect of the present invention, a steer-by-wire steering system is proposed which is configured to perform a method as described in detail above. The steer-by-wire steering system is configured to implement the features, combinations of features, and the resulting advantages of the method according to the invention in such a way that, to avoid repetition, reference is made to the above descriptions.

[0014] According to a third aspect of the present invention, a means of transport (e.g., a car, a van, a truck, a motorcycle, an aircraft and / or watercraft) is proposed which has a steer-by-wire steering system according to the second aspect of the invention. The means of transport can, in particular, be designed as a road vehicle. In this way, the means of transport also realizes the features, combinations of features, and advantages mentioned in connection with the method.

[0015] An exemplary embodiment of a method according to the invention is disclosed below without limiting character, which facilitates the understanding of the present invention: As a first step, a diagnostic job for "steering wheel alignment" is initiated. The steering wheel then automatically moves from its neutral position to an angle of 80° to 120°, specifically approximately 90° to the left, and then returns to its neutral position. Next, the steering wheel automatically moves from its neutral position to an angle of 90° to the right and then returns to its neutral position. The measured current-rotor position profiles for both rotations are compared. In steering systems, the rotor position can always be determined via the existing signal path used to transmit the steering signals to the axle motor. Any common offset in the rotor position is automatically compensated for, and the steering wheel's neutral position is corrected accordingly. The corrected neutral position is then saved as the new neutral position.If the steered wheels are also in the straight-ahead position at this time, a logical connection between the two positions can be achieved through software and / or mechanical means (for example, by a stored data value or by aligning a sensor with a receiver of a resolver).

[0016] Further details, features and advantages of the invention will become apparent from the following description and the figures. These show: Fig. 1 a schematic representation of an embodiment of a steer-by-wire steering system according to the invention; Fig. 2 a schematic representation of steering wheel positions during the execution of an embodiment of a method according to the invention; Fig. 3. A representation of two phase currents illustrating an initial offset of a geometric zero position of a steering system usable according to the invention; and Fig. 4 A flowchart illustrating the steps of an embodiment of a method according to the invention for producing a geometric zero position of a steering wheel with an imbalance in a steering system.

[0017] Fig. Figure 1 schematically shows components of an embodiment of a steer-by-wire steering system 10 according to the invention. A steering wheel 7, which is to be brought into a geometric zero position according to the invention, is monitored by a hand wheel actuator 8 with regard to its angular position and provided with suitable feedback on road conditions and straight-ahead position. For this purpose, a motor 3 with a control unit (not shown) and an angle sensor 4 are provided in the hand wheel actuator 8. The hand wheel actuator 8 is connected via a logic connection 6 to a road wheel actuator 9, which is mechanically linked to the tie rods 2 and ultimately to the steered wheels 1. The road wheel actuator 9 also has a motor 3 with a control unit (not shown) and a sensor in the form of an angle sensor 4. The force generated by the motor 3 is transmitted to the tie rods 2 via a mechanical transmission.Once the steered wheels 1 are in a straight-ahead position, the vehicle according to the invention can be used to establish a logical connection between the angular positions of the motors 3. For this purpose, a geometric zero position of the steering wheel 7 is required and is created as a prerequisite in the manner of the invention.

[0018] Fig. Figure 2 shows angular positions of a steering wheel 7, which, according to the invention, are to be brought into a zero position with respect to a steer-by-wire steering system. The steering wheel has an eccentric center of gravity 11, through which a motor rotating the steering wheel 7 must apply a torque that varies over the angle of rotation. In partial figure a) (initial position), the steering wheel 7 is approximately in a straight-ahead position. According to the invention, in partial figure b), it is rotated to the left by an angle of 90° as the first angular range. Here, the center of gravity 11 of the steering wheel 7 is raised. Its effective lever arm with respect to the axis of rotation is at its maximum in the position shown. This position is characterized by a maximum phase current in the (not shown) HWA. Subsequently, starting from the position of the maximum phase current (exactly geometrically 90°), the steering wheel 7 is rotated to the right, thereby achieving an exact geometric zero position ( Fig. c)) is achieved. Optionally, the aforementioned procedure, as shown in sub-figures b), e), and f), can also be carried out in the opposite direction to reduce friction effects, singularities, and other disturbances. In this case, the steering wheel 7 is rotated approximately 90° to the right from its neutral position, thereby sweeping through a second angular range b). Based on the rotational positions of the steering wheel at which the phase current exhibits its respective maximum, the (presumed) three o'clock and nine o'clock positions can be determined. Purely mathematically, the six o'clock position of the third steering wheel spoke and the twelve o'clock position of the steering wheel can now be determined with considerable certainty and accuracy.

[0019] Fig. Figure 3 shows two currents (phase currents) as examples. 1,I2 of a HWA as a function of the steering wheel angle ϕ. The respective positions of the maximum 12 are offset by an angularly rotated mounting of the steering wheel (offset 13, 14). The phase current I2 thus reveals an initial misalignment of the associated steering wheel or steering system. This misalignment can subsequently be automatically corrected by a motor, resulting in a perfect geometric zero position for the steering wheel.

[0020] Fig.Figure 4 shows steps of an exemplary embodiment of a method according to the invention for establishing a geometric zero position of a steering wheel. In step 100, a predefined signal from a diagnostic tool is first determined to initiate a motorized rotation of the steering wheel. For this purpose, the diagnostic tool can, for example, execute a diagnostic job ("Start steering wheel adjustment"). In step 200, the steering wheel is then automatically rotated by motor through a first angular range in a first direction. For example, it can be assumed that the twelve o'clock position of the steering wheel is initially accurate to at least 2°, in particular to 5°, preferably to 10°, so that a rotation of approximately 110° should in any case be sufficient to detect a current maximum of a phase current of the HWA. Subsequently, in step 300, a first force effect of the steering wheel during the rotation through the first angular range is automatically determined.The phase current of the HWA can be used for this purpose. In step 400, an initial relationship between the current or the initial force effect and the steering wheel position / steering angle is automatically determined. Finally, a geometric zero position is automatically established in step 500, depending on the initial relationship. In this way, the steering wheel is logically and / or mechanically linked to the steering angle / turn of the wheels on the steered axle of the vehicle. Provided that the steered wheels are also in a straight-ahead position at this point, the straight-ahead position of the wheels can subsequently be achieved by establishing the geometric zero position of the steering wheel. In step 600, an offset angle between an initial position of the steering wheel and the geometric zero position of the steering wheel is then determined. For example, such an (advantageous orThe desired steering wheel rotation can result from a gravitational asymmetry of the steering wheel itself or from a design specification for the vehicle's interior. In response, a value representing the offset angle is stored in a digital memory of the steering system or the vehicle in step 700. In other words, the offset value that the steering wheel should have relative to its actual geometric zero position is stored. If the steering wheel's center of gravity is asymmetrical, a geometric or optical zero position can be established by considering the offset value based on an analysis of the phase currents across the steering wheel's rotation angle. Reference symbol list: 1 steered wheels 2 tie rods 3 Engine 4 angle sensor 5 mechanical translation 6 logical connections 7 Steering wheel 8 HWA 9 RWA 10 Steer-by-wire steering system 11 Focus 12 Maximum 13, 14 Offset 100 to 700 process steps a first angle range b second angle range I1, I2 phase currents ϕ Steering wheel angle

Claims

[1] Method for producing a geometric zero position of a steering wheel (7) with an imbalance in a steer-by-wire steering system (10) comprising the steps: • Automatic motorized rotation (200) of the steering wheel (7) about a first angular range (a) in a first direction, • Automatic detection (300) of a first force effect of the steering wheel (7) during rotation through the first angular range (a), • Automatic determination (400) of a first relationship between the first force action over the first angular range (a) and • Automatic creation (500) of the geometric zero position depending on the first relationship. [2] Method according to claim 1 further comprising • Automatic motorized rotation of the steering wheel (7) through a second angular range (b) in a second direction, • Automatic detection of a second force effect of the steering wheel (7) during rotation through the second angular range (b), • Automatic determination of a second relationship between the second force action over the second angular range (b) and • Automatic establishment of the geometric zero position depending on the second relationship. [3] Method according to claim 1 or 2, wherein the first direction and the second direction are oriented in opposite directions. [4] Method according to one of the preceding claims, wherein the motorized rotation of the steering wheel (7) is carried out by means of a motor (3) of the steering system (10). [5] Method according to one of the preceding claims, wherein the determination of the force effect is carried out using a direct or indirect measuring device, in particular - of a phase current and / or - a torque measuring device of the steering system (10). [6] Method according to one of the preceding claims, wherein the relationship between the force effect over the angular range (a) is determined by means of a sensor (4) of the steering system (10). [7] Method according to any one of the preceding claims, wherein - the first angle range (a) is greater than 45°, preferably greater than 80°, most preferably greater than 90° and particularly preferably greater than 100° and / or - the second angle range (b) is less than 45°, preferably less than 80°, most preferably less than 90° and most preferably less than 100°. [8] Method according to one of the preceding claims, wherein a tie rod (2) of the steering system (10) is stationary during the turning of the steering wheel (7). [9] Method according to any of the foregoing claims, further comprising - Determining (600) an offset angle between an initial position of the steering wheel (10) and the geometric zero position and - Storing (700) a value representing the offset angle in a digital memory of the steering system / means of transport. [10] Method according to any of the foregoing claims, further comprising - Determining (100) a predefined signal from a diagnostic tool to initiate motorized rotation of the steering wheel (7). [11] Steer-by-wire steering system (10) which is configured to perform a method according to any of the preceding claims. [12] Means of transport comprising a steer-by-wire steering system (10) according to claim 11.

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