DE102018220259A1 - Method and control device for operating a vehicle - Google Patents

Abstract

The present invention relates to a method for operating a vehicle (100), in which road condition information (106) representing a coefficient of friction of a road in the area of the vehicle (100) is read in by an ultrasonic sensor system (104) of the vehicle (100) and one Adhesion limit (112) of at least one wheel of the vehicle (100) is determined using the road condition information (106), a response behavior of the vehicle (100) being influenced using the adhesion limit (112).

Description

Field of the Invention

The invention relates to a method and a control device for operating a vehicle

State of the art

If a wheel of a vehicle loses grip and slips, torque on the wheel can be reduced to restore grip. A speed of the wheel can be monitored via sensors. A corresponding system can be referred to as an anti-lock system or anti-slip control.

Disclosure of the invention

Against this background, the approach presented here presents a method for operating a vehicle, a corresponding control device, and finally a corresponding computer program product and a machine-readable storage medium in accordance with the independent claims. Advantageous further developments and improvements of the approach presented here result from the description and are described in the dependent claims.

Advantages of the invention

Embodiments of the present invention can advantageously make it possible to influence driving behavior of a vehicle in a preventive manner in such a way that the wheels of the vehicle are prevented from slipping even in poor weather-related road conditions. This can improve driving stability of the vehicle and the safety of vehicle occupants

A method for operating a vehicle is proposed in which road condition information representing a coefficient of friction of a road in the area of the vehicle is read in by an ultrasound sensor system of the vehicle and an adhesion limit of at least one wheel of the vehicle is determined using the road condition information, a response behavior of the vehicle is influenced using the adhesive limit.

Ideas for embodiments of the present invention can be viewed, inter alia, as based on the thoughts and knowledge described below.

A road's coefficient of friction is essentially determined by the surface condition of the road due to wetness, mud, leaves or snow or the like. influenced. Wetness in particular can be detected by an ultrasonic sensor system. The coefficient of friction can be determined or estimated depending on how much water is recognized on the road. The amount of water can be recognized, for example, by evaluating a noise level. The noise level represents a volume or intensity of background noise, which is detected by an ultrasonic sensor. A rolling noise of tires is already significantly increased, for example, when the road is only slightly moistened, and thus also increases the volume of the background noise. The noise level generally gets higher the wetter the road is.

An adhesion limit can be a maximum transferable frictional force between a wheel and a surface. The adhesion limits of the wheels of a vehicle can differ from wheel to wheel. When determining the respective detention limit, individual factors can be taken into account. The response behavior can also be influenced individually for each wheel. The response behavior can be influenced so that a friction force required on the wheel is less than the maximum transferable friction force.

The maximum transferable frictional force or adhesion limit can depend on the direction. For example, the grip limit may be higher in a rolling direction of the wheel than in a transverse direction.

The grip limit can also be determined using a wheel contact force of the wheel. A wheel contact force can depend on a load on the vehicle. The wheel contact force can be measured by a sensor. The wheel contact force can also be dependent on an acceleration acting on the vehicle. For example, the wheel contact force on wheels on the outside of the curve can be greater than on wheels on the inside of the curve.

The grip limit can also be determined using tire condition information of a tire of the wheel. The adhesion limit can depend on the type and condition of the tire. For example, a winter tire can have a higher grip limit in the cold than a summer tire. Tire depth can also affect the grip limit. An air pressure prevailing in the tire can also influence the grip limit. A tire can age and lose grip. Tire condition information may include information about the tire. For example, the tire condition information can depict the type of tire, its age and / or the tread depth. One in the Tire prevailing air pressure can be detected using a sensor.

A drag torque on the wheel can be limited to keep a resulting frictional force below the stick limit. A drag torque brakes the vehicle. For example, an electric machine can be operated as a generator by the drag torque. An internal combustion engine can also generate the drag torque, for example, through frictional forces. If the drag torque is too high, a wheel can slip. The drag torque can be reduced by burning more fuel efficiently. The driving stability of the vehicle can be increased by limiting the drag torque.

A drive torque on the wheel can be limited to keep the resulting frictional force below the stick limit. A drive torque accelerates the vehicle or counteracts driving resistance. If the drive torque is too high, a wheel can spin. The driving stability of the vehicle can be increased by limiting the drive torque.

A speed change limit of the wheel can be adjusted using the grip limit to keep the resulting frictional force below the grip limit. A speed change limit defines how fast a wheel can become faster or slower. If the wheel becomes faster or slower too quickly, it can slip or spin. The driving stability of the vehicle can be increased by setting the speed change limit.

A jerk limit can be set using the grip limit to keep the resulting frictional force below the grip limit. The jerk is a change in acceleration. If the jerk is too great, a wheel may slip or spin. The driving stability of the vehicle can be increased by setting the jerk limit.

A slip angle of the wheel can be limited to keep the resulting frictional force below the stick limit. If the slip angle is too large, the vehicle can understeer and slide over the front axle. Limiting the slip angle can improve the cornering stability of the vehicle.

Gear change speed thresholds can be adjusted using the stuck limit to keep the resulting frictional force below the stuck limit. A gear change speed threshold may be a threshold at which one changes from one gear to the next. The gear change speed threshold values can be reduced at a low grip limit in order to change to a higher gear at a lower speed, as a result of which the torque on driven wheels can be limited.

The method can be implemented, for example, in software or hardware or in a mixed form of software and hardware, for example in a control unit.

The approach presented here also creates a control device which is designed to carry out, control or implement the steps of a variant of the method presented here in corresponding devices.

The control device can be an electrical device with at least one computing unit for processing signals or data, at least one storage unit for storing signals or data, and at least one interface and / or a communication interface for reading or outputting data which are embedded in a communication protocol, be. The computing unit can be, for example, a signal processor, a so-called system ASIC or a microcontroller for processing sensor signals and outputting data signals as a function of the sensor signals. The storage unit can be, for example, a flash memory, an EPROM or a magnetic storage unit. The interface can be designed as a sensor interface for reading in the sensor signals from a sensor and / or as an actuator interface for outputting the data signals and / or control signals to an actuator. The communication interface can be designed to read in or output the data wirelessly and / or via line. The interfaces can also be software modules that are present, for example, on a microcontroller alongside other software modules.

Also advantageous is a computer program product or computer program with program code, which can be stored on a machine-readable carrier or storage medium such as a semiconductor memory, a hard disk memory or an optical memory and for carrying out, implementing and / or controlling the steps of the method according to one of the embodiments described above is used, in particular if the program product or program is executed on a computer or a device.

It is noted that some of the possible features and advantages of the invention are described herein with respect to different embodiments. A specialist realizes that the features of the control device and the method can be combined, adapted or exchanged in a suitable manner in order to arrive at further embodiments of the invention.

Figure list

• 1 zeigt eine Darstellung eines Fahrzeugs mit einem Steuergerät gemäß einem Ausführungsbeispiel.

Embodiments of the invention are described below with reference to the accompanying drawing, wherein neither the drawing nor the description are to be interpreted as limiting the invention.

• 1 shows a representation of a vehicle with a control device according to an embodiment.

The figure is only schematic and not to scale. The same reference numerals in the figure denote the same or equivalent features.

Embodiments of the invention

1 shows a representation of a vehicle 100 with a control unit 102 according to an embodiment. The control unit 102 is with an ultrasonic sensor system 104 of the vehicle 100 connected. The ultrasonic sensor system 104 provides road condition information 106 ready. The road condition information 106 is evaluated by evaluating at least one on the vehicle 100 detected noise level 108 certainly. The road condition information 106 maps whether the road is in the area of the vehicle 100 is damp, wet or flooded.

If the road is damp, wet or flooded, it has a lower coefficient of friction than the same road when it is dry. Therefore, a wheel can transfer less friction to the road when the road is damp, wet, or flooded. It is irrelevant whether longitudinal forces for acceleration or deceleration or lateral forces for steering or keeping in lane are considered.

The transferable longitudinal forces are generally somewhat larger than the lateral forces, even on dry roads.

In the control unit 102 is in a determination facility 110 the road condition information 106 evaluated and a detention limit for each bike 112 per wheel of the vehicle 100 certainly. An influencing device 114 uses the stick limits 112 to a vehicle response 100 to influence. The influencing device can 114 into the driving dynamics of the vehicle 100 intervene to keep the frictional forces on the wheels smaller than the adhesion limit 112 to keep.

In the approach presented here, vehicle behavior is influenced as a function of a water level on the roadway measured using ultrasound.

A measurement of the road condition using a noise level 108 is possible. The higher the vehicle's own speed, the greater the measured noise level 108 your own vehicle 100 is emitted and measured by the ultrasonic sensors (USS).

Moisture on the road can be detected with the help of ultrasonic sensors. As an alternative or in addition, wetness information can be provided 116 can be received via radio interface.

With the help of wetness information 116 or the road condition information 112 becomes the driving behavior of the vehicle 100 optimized.

Ultrasound sensors are used to measure whether the road is wet or dry, and the vehicle speed, the nature of the tires and the forces acting on the wheels are used to estimate whether one of the wheels has reached the limit of grip 112 is coming. Depending on the measurement and assessment, the forces acting on the wheels are limited.

In one embodiment, the maximum permissible recuperation torque is reduced to such an extent that there is no fear of a negative influence on vehicle stability. Recuperation is prevented if there is a risk of aquaplaning. This increases the stability of the vehicle 100 elevated.

In one embodiment, the drag torque of the internal combustion engine is reduced on a wet road and completely compensated for when there is a risk of aquaplaning. Noticeable interventions are combined with information to the driver. This increases the stability. In addition, the braking torque on the rear wheels is reduced to a minimum and a gear change is blocked in order to avoid moments on the drive train (positive and negative). This increases the stability of the vehicle 100 also increased.

In one embodiment, the speed change limit prevents the tires from spinning or blocking. For this purpose, the speed change limit is selected so that the speed can only increase as quickly as would be possible with friction locking and dry or wet road surfaces. The speed change limit is therefore chosen higher on dry roads and lower on wet roads. This allows the vehicle 100 be accelerated faster.

In one embodiment, the maximum jerk limit is chosen higher on a dry road than on a wet road. A large jerk or a large change in torque can lead to the vehicle 100 becomes unstable. This will limit the risk of the vehicle 100 unstable on wet roads while optimal response is guaranteed on dry roads.

In one embodiment, the transmission shifts into higher gears earlier when accelerating on wet roads than when on dry roads. Conversely, it later shifts into lower gears when braking. The ratio gear to speed g / v from the selected gear g in relation to the vehicle speed v is chosen higher on a wet road than on a dry road. This increases efficiency and vehicle stability.

In one embodiment, the steering control device limits the maximum slip angle. This means that a counter torque is applied to the steering in order to reduce excessive steering. This enables tighter curve radii and increases stability.

The approach presented here increases energy efficiency and it can be accelerated faster, whether wet or dry. The vehicle continues to behave 100 more stable and safer.

In conclusion, it should be pointed out that terms such as "showing", "comprehensive", etc. do not exclude other elements or steps, and terms such as "one" or "one" do not exclude a large number. Reference signs in the claims are not to be viewed as a restriction.

Claims (12)

Method for operating a vehicle (100), in which road condition information (106) representing a coefficient of friction of a road in the area of the vehicle (100) is read in by an ultrasound sensor system (104) of the vehicle (100) and an adhesion limit (112) of at least one wheel of the vehicle (100) is determined using the road condition information (106), a response behavior of the vehicle (100) being influenced using the grip limit (112). Procedure according to Claim 1 at which the adhesion limit (112) is further determined using a wheel contact force of the wheel. A method according to any preceding claim, wherein the grip limit (112) is further determined using tire condition information of a tire of the wheel. Method according to one of the preceding claims, in which a drag torque on the wheel is limited in order to keep a resulting frictional force below the adhesion limit (112). Method according to one of the preceding claims, in which a drive torque on the wheel is limited in order to keep the resulting frictional force below the adhesion limit (112). Method according to one of the preceding claims, in which a speed change limit of the wheel is set using the adhesion limit (112) in order to keep the resulting frictional force below the adhesion limit (112). Method according to one of the preceding claims, in which a jerk limit is set using the adhesion limit (112) in order to keep the resulting frictional force below the adhesion limit (112). Method according to one of the preceding claims, in which a slip angle of the wheel is limited in order to keep the resulting frictional force below the adhesion limit (112). Method according to one of the preceding claims, in which gear change speed threshold values are set using the adhesion limit (112) in order to keep the resulting frictional force below the adhesion limit (112). Control device (102) which is designed to execute, implement and / or control the method according to one of the preceding claims in corresponding devices. Computer program product which is set up to implement the method according to one of the Claims 1 to 9 execute, implement and / or control. Machine-readable storage medium on which the computer program product according to Claim 11 is saved.

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