DE102021115662B3 - Method for supporting a driver of a motor vehicle during braking and/or skidding on a loose surface and motor vehicle - Google Patents

Abstract

The invention relates to a method for supporting a driver of a motor vehicle (10) during braking (B) and/or skidding on loose ground (U). When braking (B) and/or skidding on loose ground (U), at least one drivable wheel (20) of the motor vehicle (10) is driven in the opposite direction (R) in order to shorten the braking distance and/or to compensate for the skidding movement , wherein the relevant wheel (20) is first braked and then driven in the opposite direction (R). The invention also relates to a motor vehicle (10) which has a control device suitable for carrying out the method.

Description

The invention relates to a method for supporting a driver of a motor vehicle during braking and/or skidding on loose ground. In addition to the method, the present invention also relates to a motor vehicle.

Various driver assistance systems for motor vehicles are known from the prior art, which support the driver during a braking process or during a skidding process through automatic or self-acting intervention. These include, for example, the anti-lock braking system (ABS) and the driving dynamics control (ESC or ESP).

The closest EP 2 279 923 A2 describes a method for supporting a driver of a motor vehicle during a skidding process and a motor vehicle designed to carry out the method.

the US 2010/0094521 A1 describes an anti-slip device for the drive wheels of a motor vehicle and a method for its use. A terrain with low adhesion is also described, e.g. B. with sand, gravel or snow. The method provides, inter alia, during a start-up phase, to leave at least one driving wheel, which participates in the traction, unbraked in order to eject foreign objects that reduce the grip of the wheel and to use the speed of this wheel to dig into the ground and the Liability and thus restore the driving force.

the JP H07 - 165 030 A describes a vehicle with a so-called auxiliary wheel which is designed to be able to be raised and lowered towards the road surface. In a starting operation, the auxiliary wheel is driven and rotated to the normal rotation side, and is lowered and brought into contact with the road surface. In a braking operation, the sub-wheel is lowered and brought into contact with the road surface, and braking force is generated by driving and rotating the sub-wheel in the opposite direction to the forward rotation of the front and rear wheels of the vehicle.

The prior art is also still on the DE 10 2018 112 884 A1 , U.S. 2015/0 217 766 A1 and JP 2000 - 142 552 A pointed out.

The aim of the invention is to improve the support provided to a driver of a motor vehicle during braking and/or skidding on a loose surface.

This is achieved with the method according to the invention of patent claim 1. With the subordinate patent claim, the invention also extends to a motor vehicle designed to carry out the method according to the invention. Additional features of the invention result analogously for both subjects of the invention from the dependent patent claims, the following description of the invention (which expressly also includes features that are described as "example", "preferred", "in particular" etc.) and the drawing.

The method according to the invention provides that when the motor vehicle is braking and/or skidding on a loose surface, at least one drivable wheel of the motor vehicle is driven in the opposite direction in order to shorten the braking distance of the motor vehicle and/or to compensate for or reduce the skidding movement of the motor vehicle. to compensate, whereby the wheel in question is first braked and then driven in the opposite direction.

It is therefore proposed that during a braking and/or skidding process of the motor vehicle driving on loose ground, the direction of rotation or rotation of at least one drivable wheel of the motor vehicle is changed, i. That is, the wheel in question is driven in the opposite direction to the actual rolling direction, that is to say backwards, so to speak, in order to shorten the braking distance and/or to compensate for the skidding movement. This takes place in particular automatically or automatically, d. H. without any action on the part of the driver, so that the method according to the invention supports or assists the driver when braking and/or maintaining a desired direction of travel of the motor vehicle.

Depending on the situation and the technical equipment of the motor vehicle, only one wheel, several wheels, in particular on the axle or on the side, or all wheels can be driven in the opposite direction. If several or all wheels are driven in the opposite direction, this can be done synchronously or asynchronously. The latter means that the wheels in question are driven in the opposite direction at different times and/or at different wheel speeds.

A braking process occurs in particular when the driver actuates the vehicle brake, usually by pressing the brake pedal, or releases the accelerator pedal (one-pedal driving). A skidding process occurs in particular when the motor vehicle executes a yaw movement when driving forwards, possibly also when braking. In the EP 2 279 923 A2 describes how a spin process or state can be detected.

The invention is based on the theoretical consideration that on loose ground (see below) by actively or motorically driving at least one wheel in the opposite direction, a very high slip ratio (slip ratio) of over 100% to several hundred percent is achieved and thus opposite a forward-rolling or blocked wheel, a higher effective friction value (friction coefficient) can be generated between the wheel or tire and the roadway or subsoil. This higher coefficient of friction can then be used extremely effectively for braking and/or for compensating for a skidding movement or for stabilizing the desired direction of travel.

The wheel speed provided when driving a wheel in question in the opposite direction (strictly speaking, it is a negative wheel speed) can be significantly higher, e.g. by up to 3 times, possibly even by up to 20 times, than that resulting from the (positive) wheel speed resulting from the current vehicle speed. Due to this comparatively high (negative) wheel speed, even at low vehicle speeds (see below), parts of the loose ground in the tire profile can become detached, which also improves the power transmission between the tire and the loose ground. Furthermore, an additional thrust vector control effect can be achieved by thrown away components of the loose ground.

The method according to the invention can be applied to driver assistance systems (eg ABS and/or ESC or ESP) already present in the motor vehicle and/or use the information already recorded for such systems. “Added on” means that the method according to the invention can be carried out additionally, more or less as an add-on.

A loose surface is understood to mean, in particular, an unpaved roadway without a solid top layer, on which the wheels of the motor vehicle roll. Such loose ground preferably has components that can be picked up and/or thrown away by the wheels or tires of the motor vehicle. A loose surface is, for example, a sandy, scree, gravel or gravel road. Driving on loose ground can also be driving in open terrain (off-road), driving in snow, especially on an uncompacted snow cover, or driving on ground, especially muddy or muddy ground.

The condition of the ground can be automatically detected by the motor vehicle or a device provided for this purpose in the motor vehicle, for example by means of permanent slip monitoring (high slip on the drive wheels indicates loose ground) and/or by means of sensors. That is, loose ground can be detected automatically. It is also conceivable for the driver to set the condition of the ground of the motor vehicle on a user interface of the motor vehicle. That is, the driver can set a loose ground when the motor vehicle is to be driven on a loose ground. In addition, automatic detection or monitoring of the condition of the subsoil can also be provided.

The wheel in question can first be braked to a standstill with the associated wheel brake, in particular a friction brake, and only then driven in the opposite direction. The targeted braking of the wheel protects the drive components and reduces the response time, i. H. the time it takes for the wheel in question to rotate in the opposite direction. Provision can also be made for the anti-lock braking system to be temporarily or temporarily deactivated for the wheel in question, as a result of which the response time can also be reduced. If necessary, the wheel can also be braked with an electromotive brake, in particular a recuperation brake.

For the wheel in question, which is driven in the opposite direction, the wheel speed is preferably increased successively or gradually, in particular after prior braking (see above). The effect achieved can be recorded continuously and a decision can then be made as to whether a higher wheel speed is possible and sensible or whether the wheel speed may have to be reduced again. Driving dynamic overreactions can be prevented in this way.

The method according to the invention is preferably only carried out at vehicle speeds of no more than 50 km/h, preferably no more than 30 km/h and in particular no more than 15 km/h. Even at such comparatively low vehicle speeds, vehicle damage and personal injury often occur, which ideally can be prevented with the invention.

A control unit of the motor vehicle, e.g. the ABS or ESP control unit, preferably calculates, in particular using a mathematical model, which wheel or wheels of the motor vehicle that can be driven during a braking process and/or skidding process (on loose ground) to which Time or in which period of time with which wheel speed is driven in the opposite direction / to shorten the braking distance of the motor vehicle and/or to compensate for the skidding movement of the motor vehicle, the wheel in question being braked first and then driven in the opposite direction.

In addition to the method, the invention also relates to a motor vehicle with a control unit which is designed to cause at least one drivable wheel of the motor vehicle to be driven in the opposite direction during braking and/or skidding (of the motor vehicle) on a loose surface to shorten the braking distance and/or to compensate for skidding, whereby the wheel in question is first braked and then driven in the opposite direction. The control unit is in particular the ESC or ESP control unit.

The motor vehicle is preferably a passenger car, in particular an SUV or off-road vehicle, or a light commercial vehicle.

The motor vehicle can have an internal combustion engine and/or at least one electric motor for the traction drive. Depending on the technical equipment of the motor vehicle, only one wheel, several wheels, in particular axle by axle, or all wheels can be driven in the opposite direction, for which purpose clutches, in particular separating clutches, and/or gears, in particular direction change gears, are provided. The motor vehicle preferably has a driving, i. H. electric motor provided for its drive, which can also be used to brake the wheel in question (electric motor brake; see above). This enables a simple implementation of the method according to the invention and, in particular, also a comparatively easily realizable asynchronous drive of the wheels (see above) by appropriate activation of the electric motors.

• 1 veranschaulicht die Erfindung bei einem Bremsvorgang.
• 2 veranschaulicht die Erfindung bei einem Schleudervorgang.

The invention is explained in more detail below with reference to the drawing.

• 1 illustrates the invention during a braking operation.
• 2 illustrates the invention in a spinning operation.

This in 1a Motor vehicle 10 shown is traveling at a speed V in the indicated direction. The wheels 20 roll on loose ground U. 1b shows a braking process B. During the braking process B, i.e. while the motor vehicle 10 is still moving forward in the indicated direction, the wheels 20, in particular all wheels 20, if necessary only the wheels 20 of the front axle or rear axle, are moved in the opposite direction R, i.e. driven in the opposite or reverse direction, so to speak, in order to shorten the braking distance. The opposite drive of the wheels 20 is preferably carried out only at lower vehicle speeds V, ie possibly only at the end of a braking process B when a specific speed threshold (see above) is reached and undershot.

The (negative) wheel speeds provided when driving the wheels 20 in opposite directions can be many times higher than the (positive) wheel speeds resulting from the current vehicle speed, which is 1b illustrated by the longer rotation arrows (R).

As in 1b shown, the wheels 20 rotating in the opposite direction R can throw loose components of the loose subsoil U forward in the direction of movement of the motor vehicle 10 . This may favor or even enhance the effect intended by counter-rotating the wheels 20 through a thrust vectoring effect.

2 shows a motor vehicle 10 in a plan view, which drives forward at the speed V in the indicated direction. Motor vehicle 10 is in a skidding process or state S, which results in a yaw movement in the clockwise direction, for example. In order to compensate for this yaw movement (as illustrated by the curved arrows K) or to stabilize the desired direction of travel, the wheels 20 on the left-hand side of the vehicle are driven in the opposite direction R or in the opposite direction. The wheels 20 on the right-hand side of the vehicle are meanwhile driven forward or in the forward direction or decoupled so that they can roll freely.

• - Erfassen des Untergrunds, auf dem das Kraftfahrzeug 10 fährt, bzw. Erfassen der Untergrundbeschaffenheit;
• - Erfassen eines Bremsvorgangs B und/oder eines Schleudervorgangs S;
• - falls ein Bremsvorgang B und/oder ein Schleudervorgang S auf losem Untergrund U erfasst wird, dann Ändern der Dreh- bzw. Rotationsrichtung wenigstens eines antreibbaren Rads 20 des Kraftfahrzeugs 10 bzw.

The method according to the invention can have the following steps in order to shorten the braking distance B in a motor vehicle 10 driving on loose ground U and/or to compensate for a skidding movement S:

• - detecting the ground on which the motor vehicle 10 is driving, or detecting the condition of the ground;
• - detecting a braking process B and/or a skidding process S;
• - if a braking process B and/or a skidding process S on a loose surface U is detected, then changing the direction of rotation or rotation of at least one drivable wheel 20 of the motor vehicle 10 or

Driving the relevant wheel 20 in the opposite direction R (reverse direction).

Claims (10)

Method for supporting a driver of a motor vehicle (10) during a braking process (B) and/or skidding process (S) on loose ground (U), characterized in that during a braking process (B) and/or skidding process (S) on loose ground (U) at least one drivable wheel (20) of the motor vehicle (10) is driven in the opposite direction (R) in order to shorten the braking distance and/or to compensate for the skidding movement, with the relevant wheel (20) first being braked and then in the opposite direction (R) is driven. procedure after claim 1 , characterized in that the condition of the subsoil is automatically detected. procedure after claim 1 , characterized in that the condition of the ground is set by the driver. Method according to one of the preceding claims, characterized in that the anti-lock braking system for the relevant wheel (20) is temporarily deactivated. Method according to one of the preceding claims, characterized in that the wheel speed of the wheel (20) driven in the opposite direction (R) is increased successively. Method according to any of the preceding Claims 1 until 5 , characterized in that this method is only carried out at a vehicle speed (V) of not more than 30 km/h. Method according to any of the preceding Claims 1 until 5 , characterized in that this method is only carried out at a vehicle speed (V) of not more than 15 km/h. Method according to one of the preceding claims, characterized in that a control unit calculates which drivable wheel (20) of the motor vehicle (10) during a braking process (B) and/or skidding process (S) at which point in time with which wheel speed in the opposite Direction (R) is driven. Motor vehicle (10) with a control unit which is designed to cause at least one drivable wheel (20) of the motor vehicle (10) to move into the is driven in the opposite direction (R) in order to shorten the braking distance and/or to compensate for the skidding movement, the wheel in question (20) being braked first and then being driven in the opposite direction (R). Motor vehicle (10) after claim 9 , characterized in that it has a driving electric motor for each wheel (20).

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