Method and control device for operating steering device of vehicle

Abstract

To provide a method for operating a steering device (100) of a vehicle.SOLUTION: According to the present invention, in a method for operating a steering device (100) of a vehicle, in response to identifying (106) a squealing situation (108), at least two steerable wheels (102) of the vehicle are steered according to an Ackerman manner.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention relates to a method for operating a steering system of a vehicle, a corresponding control device and a corresponding computer program product. [Background technology]

[0002] Conventional technology A vehicle may have a steering dynamics that allows a compromise between different driving situations. This steering dynamics may deviate from the Ackermann steering angle to improve the vehicle's driving dynamics. This may cause large slippage that may result in squealing, especially on smooth floors and at large steering angles. Summary of the Invention [Problem to be solved by the invention]

[0003] Disclosure of the Invention Against this background, the approach presented herein provides a method for operating a steering device of a vehicle, a corresponding control device and a corresponding computer program product as set forth in the independent claims. Advantageous developments and improvements of the approach presented herein become apparent from the description and are set forth in the dependent claims. [Means for solving the problem]

[0004] Advantages of the invention In the approach presented herein, in situations where squealing may occur, the steered wheels are steered at an Ackermann steering angle, which causes the vehicle wheels to roll around the vehicle's turning center, ideally without slip. Since no or little slip occurs, squealing is prevented. If a squealing situation is not identified, or if a non-squealing situation is identified, the wheels are preferably steered at a different steering angle than the Ackermann steering angle.

[0005] The approach presented herein can, for example, block or at least reduce the squeal of vehicle wheels in an indoor parking garage, thereby allowing better perception of other noises, such as the engine noise of a vehicle moving straight ahead, which might otherwise be drowned out.

[0006] A method is presented for operating a steering system of a vehicle, wherein in response to identifying a squeal condition, at least two steerable wheels of the vehicle are steered in an Ackermann manner.

[0007] The conception of the embodiments of the present invention can be considered to be based in particular on the ideas and knowledge set forth below.

[0008] A squeal situation can occur due to a combination of different factors. Particularly characteristic of a squeal situation would be a floor surface with poor grip or a ground surface with a low coefficient of friction. Furthermore, a squeal situation can be caused by the acoustics around the vehicle. In particular, in an interior space, tire noise can be reflected back into the vehicle and perceived more strongly by vehicle occupants than in an outdoor environment without sound-reflecting walls. Moreover, squeal can also be caused by a low coefficient of friction of the tires.

[0009] When a tire squeals, it has a large amount of slip. When a tire squeals, the tread blocks of the tire slide on the ground, which causes the squeal, facilitated by the stick-slip phenomenon.

[0010] During normal driving, a vehicle may have a steering motion theory in which a steering angle or a steering turn angle is set that deviates from the Ackermann function. In particular, when the steering angle or the steering turn angle is large, a large slip may occur in at least one wheel of an axle.

[0011] The vehicle may have means for changing the steering dynamics, so that if there is a high potential for tire squeal when steering, the steering dynamics can be converted to an Ackermann steering angle, thus allowing the vehicle wheels to roll about a common turning center and minimizing slip on all wheels.

[0012] One means for changing the steering dynamics may be, for example, an individual wheel steering adjuster provided on at least one axle of the vehicle. The individual wheel steering adjuster can set the steering angle of each steered wheel independently of one another. In the individual wheel steering adjuster, the steering angle steered at the wheel is set using a steering angle characteristic curve and a steering wheel angle. In this case, the steering angle characteristic curve describes the relationship between the steering wheel angle and the steering angle or the gear ratio. To set the steering dynamics according to the Ackermann method, the steering angle characteristic curve can be changed or replaced.

[0013] When the vehicle is in a potential squeal situation, the steering angle can be Ackermann steered at more than two wheels of the vehicle.

[0014] At least one of the wheels can be steered away from the Ackermann principle at the maximum steering angle. At the maximum steering wheel angle, the smallest possible radius of curvature can be required. For example, by setting the steered wheels parallel to each other, the radius of curvature can be reduced compared to Ackermann driving. At the maximum steering angle, improving vehicle maneuverability may be more important than minimizing squeal. Alternatively or additionally, at the maximum steering angle, one of the wheels can abut against a mechanical stop and thus prevent further rotation. This also prevents the steering angle from being set according to the Ackermann principle.

[0015] The steering dynamics of an axle of a vehicle that is steered away from the Ackermann principle can be corrected by the Ackermann principle using a further steered axle of the vehicle, for example, by driving the rear axle steering so that all wheels roll around a common turning center.

[0016] If the vehicle is traveling slower than a predetermined speed value, the wheels can be steered in the Ackermann manner. At low speeds, the wheels can be steered in the Ackermann manner. Above the predetermined speed value, the advantages of driving away from the Ackermann manner can prevail. The speed value can be, for example, 30 km / h, 20 km / h, 10 km / h, or 5 km / h.

[0017] The steering angle difference of the individual wheel steering regulators of at least one axle of the vehicle can be set by the Ackermann method. The use of individual wheel steering regulators allows for a particularly efficient implementation of the approach presented herein.

[0018] The squeal condition can be identified using at least one microphone in the vehicle. The microphone can be, for example, an external microphone and can detect external noise. The microphone can be, for example, located near the wheels. Alternatively or additionally, the microphone can be an internal microphone in the vehicle. The internal microphone can pick up noise that intrudes from the outside to the inside. The microphone can detect tire squeal and identify the squeal condition. Tire squeal can directly result in a change in steering angle according to the Ackermann method.

[0019] A squeal situation can be identified when entering an interior space. In interior spaces such as indoor parking garages and underground parking garages, particularly many sounds are reflected back to the vehicle, and the squeal can be particularly loud and perceptible to vehicle occupants or pedestrians. When entering the interior space, the steering angle can be converted to Ackermann mode to reduce the probability of squeal in the interior space.

[0020] Entry into an interior space can be identified using the time of day and the ambient brightness. If the ambient brightness drops almost suddenly during the day, the vehicle is considered to have just entered the interior space. If the ambient brightness increases almost suddenly during the night, the vehicle is also considered to have just entered the interior space. The time of day and the ambient brightness can identify situations where it should be bright or dark but is not. In such cases, the vehicle is considered to have just entered the interior space.

[0021] Alternatively or additionally, the entry into an interior space can be identified using the vehicle's navigation system, where, for example, the received signal from the navigation satellites deteriorates rapidly. Similarly, the vehicle's position and a digital map can be used to identify whether the vehicle is located on a road or inside a building. The entry into a tunnel can also be identified based on speed, for example, because the vehicle's speed exceeds 30 km / h.

[0022] Intrusions may also be identified using a vehicle's camera. Camera images and / or video may be evaluated to identify intrusions.

[0023] The method is preferably computer-implemented and may for example be implemented in software or hardware or in a mixed form of software and hardware, for example in a driver assistance system.

[0024] The approach presented herein further provides a control device configured to implement, drive or execute each step of one variant of the method presented herein in a corresponding device.

[0025] The control device may be an electrical device comprising at least one computing unit for processing signals or data, at least one memory unit for storing signals or data, and at least one interface and / or communication interface for reading or outputting data embedded in a communication protocol. The computing unit may be, for example, a signal processor, a so-called system ASIC, for processing sensor signals and outputting data signals depending on the sensor signals, or a microcontroller. The memory unit may be, for example, a flash memory, an EPROM, or a magnetic memory unit. The interface may be configured as a sensor interface for reading sensor signals from sensors and / or as an actuator interface for outputting data and / or control signals to actuators. The communication interface may be configured to read or output data wirelessly and / or via a wired connection. The interface may be, for example, a software module located adjacent to other software modules on the microcontroller.

[0026] Also advantageous is a computer program product or computer program with program code that can be stored on a machine-readable carrier or machine-readable memory medium, such as a semiconductor memory, a hard disk or an optical memory, and that is used to implement, execute and / or drive the steps of the method according to one of the above-described embodiments, in particular when the program product or program is run on a computer, control device or device.

[0027] It should be noted that some of the achievable features and advantages of the present invention are described herein in relation to different embodiments, and those skilled in the art will recognize that the features of the control device and method can be combined, adjusted, or substituted in any suitable manner to arrive at further embodiments of the present invention.

[0028] In the following, embodiments of the present invention will be described with reference to the accompanying drawings, in which neither the drawings nor the description should be construed as limiting the present invention. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a flowchart of a method according to an embodiment.

[0030] The drawings are only schematic and are not to scale. Identical reference signs refer to identical features or features with equivalent action. DETAILED DESCRIPTION OF THE INVENTION

[0031] Embodiments of the invention 1 shows a flowchart of a method according to one embodiment. Using this method, a vehicle steering system 100 is adaptively actuated. In this case, once a squeal situation 108 is identified 106, the vehicle's wheels 102 are steered with an Ackermann steering angle 104. Ackermann steering causes each wheel 102 to roll about a common pivot point, resulting in minimal slip between the wheels 102 and the ground. Slip can result in the tread blocks of the wheels 102 squealing on the ground, especially on surfaces with a low coefficient of friction.

[0032] Once the squealing condition 108 has ended, the wheels 102 are again driven with a steering angle 104 according to a characteristic curve specific to each vehicle.

[0033] The squeal condition 108 is identified, in one embodiment, when the vehicle is located within an interior space 110, which may be identified via, for example, a GPS 112, a microphone 114, an ambient sensor 116, and / or a light sensor 118.

[0034] In one embodiment, the vehicle's drivetrain 120 is further activated to reduce power output if a squeal condition 108 is identified.

[0035] In one embodiment, if a squeal condition 108 is identified, the steering angle 104 for each individual wheel is determined and actuated by an Ackermann method due to individual wheel steering adjusters 122 provided on at least one axle of the vehicle. The steering angle 104 can be determined by the Ackermann method, for example, using a characteristic curve.

[0036] In the following, possible embodiments of the present invention will be summarized again or described using slightly different word choices.

[0037] A function for optimized operation of the steering regulator to avoid tire noise is presented.

[0038] Today's vehicles are equipped with electromechanical steering connected to both wheels. Developments in steering systems are increasingly moving toward by-wire systems that are mechanically decoupled from the driver, i.e., the classic mechanical connection between the driver and the wheels is omitted. In these steering systems, the corresponding actions are implemented purely via one or more regulators. Central, but also decentralized, by-wire steering regulators are already part of the prior art for the rear axle. For the front axle, the first prototype vehicles with by-wire individual wheel steering regulators are known.

[0039] Cornering at slow speeds around tight radii, such as in a parking garage or on a smooth surface, often causes tire squeal. This is due to normal tire slip on a smoother surface than typical asphalt. Particularly in enclosed spaces such as underground or parking garages, this sound can reverberate and sound much louder, drowning out other ambient noise.

[0040] In conventional steering systems, an unpleasant high-pitched squeal can occur in the interior area, for example on a floor surface that has been painted with a special paint to reduce adhesion. This is caused by the tire not rolling ideally without slip due to steering kinematics theory, but generating shear forces in the tread, which cause the rubber blocks to slip on such a surface with a low coefficient of friction μ, resulting in an unpleasant squeal.

[0041] Here, in an interior area, such as a car park, the actuation of the (individual wheel) steering adjuster is proposed using a characteristic curve / gear ratio that is as close as possible to the Ackermann gear ratio or a characteristic curve / gear ratio that corresponds to the Ackermann gear ratio. In this case, the proposed function includes selecting the steering gear ratio depending on whether the vehicle is located inside or outside.

[0042] The central aspect is the adjustment of the steering gear ratio by changing the characteristic curve for driving the (individual wheel) steering regulator, so that when changing from the outside to the inside, the steering gear ratio is adjusted in a manner that approximates Ackermann, thereby enabling nearly ideal rolling of the vehicle around the turning center and thus avoiding the occurrence of squealing noise. In other words, it is proposed to select the steering angle difference depending on the location in order to ensure acoustically favorable behavior of the tires.

[0043] The driving situation can be identified, for example, based on GPS signals or based on ambient sensors. It is also possible to add microphones (ideally in the exterior area, e.g., in the wheel arch to detect moisture) or interior space microphones.

[0044] Vehicles are generally equipped with a brightness sensor and a clock, so that entry into an indoor parking garage can be reliably identified.

[0045] In particular, in the case of by-wire steering, the magnitude of the actual steering output is known. Therefore, it is very easy to identify when the vehicle is traveling at low speed on a relatively smooth surface. Here, it is necessary to further distinguish whether this is a case of slow driving in a parking garage or, for example, a case of slow driving around a curve on a smooth road with a similarly small coefficient of friction μ.

[0046] The approach presented here can be used, for example, in public car parks, factories, underground car parks in private buildings, garages, and possibly also in access roads and outdoor car parks depending on the choice of paving. The approach can also be used in situations such as manual or automatic driving / parking by the driver inside or outside the vehicle, e.g., when parking via a remote control / key.

[0047] The approach presented herein provides improved safety by allowing the perception of other noises, such as vehicles that are not steering or vehicles that generate less powerful tire noise, and also provides improved comfort for vehicle occupants and those within the vehicle's sound range by reducing / avoiding squeal noise in interior space situations.

[0048] In the case of individual wheel adjusters on the rear axle, the left and right steering angle difference can be selected accordingly, likewise in order to achieve as slip-free a roll as possible.

[0049] The approach presented herein can also be used with conventional steering systems when they are installed with rear axle steering, allowing the rear axle steering to operate in a manner that is advantageous with respect to tire noise while coordinating with the front axle steering.

[0050] The rear axle steering improves the performance of the approach presented here. Front axle steering with a central adjuster typically uses a compromise solution, deviating from ideal Ackermann steering, because such Ackermann steering is only a good option in certain situations. The rear axle steering virtually changes the vehicle length. Therefore, the steering angle at the rear axle can be selected so that the front axle moves at an angle that approximates the Ackermann system.

[0051] When using a rear axle steering system with individual wheel adjusters, the ideal solution of the proposed function can be achieved for the entire vehicle. In this case, a multi-stage procedure can be used. At the maximum steering wheel angle, the smallest turning radius is achieved. As soon as the steering wheel angle is reduced somewhat, additional wheel steering angle play is used to set the respective ideal angle distribution for minimizing noise in this turning radius.

[0052] In addition to the steering dynamics, the drivetrain can also cause the noise mentioned above. Side slip at the tires of the steered axle occurs when the vehicle speed due to the drive torque requested by the driver is too high and therefore not suited to the steering angle of the wheels (Ackermann / rolling condition). Therefore, the drivetrain can be taken into account in the proposed function. In this case, a reduction in the drive torque requested by the driver is implemented in the case of small radii of curvature, so that the speed required to comply with the rolling condition is not exceeded. The drivetrain is taken into account only on flat roads or in situations where this does not result in changes in vehicle behavior, such as acceleration.

[0053] Finally, it should be noted that terms such as "comprise" or "include" do not exclude other elements or steps, and terms such as "a" or "an" do not exclude a plurality. Reference signs in the claims are not to be construed as limiting.

Claims

1. A method for operating a steering system (100) of a vehicle, comprising: In response to identifying a squeal condition, at least two steerable wheels of the vehicle are steered in an Ackermann manner.

2. At least one of the wheels (102) is steered so as to deviate from the Ackermann principle at the maximum steering angle. The method of claim 1.

3. the steering motion theory of an axle of the vehicle that is steered so as to deviate from the Ackermann principle is corrected by the Ackermann principle using a further steered axle of the vehicle; 3. The method according to claim 1 or 2.

4. When the vehicle is traveling slower than a predetermined speed value, the wheels (102) are steered by the Ackermann method.

4. The method according to any one of claims 1 to 3.

5. The steering angle difference of the individual wheel steering adjuster (122) of at least one axle of the vehicle is set by the Ackermann method.

5. The method according to any one of claims 1 to 4.

6. The squeal condition (108) is identified using at least one microphone (114) of the vehicle.

6. The method according to any one of claims 1 to 5.

7. The squeal condition (108) is identified upon entry into an interior space (110).

7. The method according to any one of claims 1 to 6.

8. Entry into the interior space (110) is identified using time of day and ambient brightness. The method of claim 7.

9. The entry into the interior space (110) is identified using a navigation system (112) of the vehicle.

9. The method according to claim 7 or 8.

10. A control device configured to implement, execute and / or drive the method according to any one of claims 1 to 9 in a corresponding device.

11. 10. A computer program product configured to cause a processor to implement, perform and / or drive a method according to any one of claims 1 to 9 when the computer program product is executed.

12. 12. A machine-readable memory medium having stored thereon the computer program product of claim 11.

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