DE102017213327A1 - Method and device for determining wheel slip information of a wheel of an axle of a motor vehicle - Google Patents

Abstract

The invention relates to a method and a device for determining a wheel slip information of a wheel (12, 14) of an axle of a motor vehicle, wherein the wheels (12, 14) of the axle are each deflectable about a steering axis and have a positive or negative steering roll radius (r ₀ ). have, so that at the wheel contact point of the wheels (12, 14) acting force (F _{wheel, R} , F _{wheel, L} ) generates a steering torque (M _sturgeon ) about the steering axis of the wheels (12, 14), wherein the method according to the Lenkachse of the wheels (12, 14) acting steering disturbances (M _{sturgeon, L} , M _{sturgeon, R} ) are used to determine the wheel slip information.

Description

The invention relates to a method for determining a wheel slip information of a wheel of an axle of a motor vehicle, in particular after a failure of the wheel associated wheel speed sensor, according to the type specified in claim 1 and an apparatus for performing the method according to the patent claim. 9

In order to ensure the vehicle stability or steerability of the motor vehicle on slippery surfaces, information regarding the slip on the wheel is necessary. Today's ABS / ESC systems use wheel speed information to determine which wheel is in slippage.

If one or more wheel speed sensors fail, this is indicated to the driver today (warning by ABS / ESC lamp) and the driver is given the responsibility to drive or park the vehicle safely. In particular with regard to the function of a piloted or (partly) autonomous driving, this would mean that the function of the piloted or (partially) autonomous driving would have to be deactivated in the short term, because due to the lack of information about the wheel slip the vehicle into a safety-critical driving situation, which could no longer be mastered by the system.

The invention is based on the object of specifying a method by means of which, in the event of a failure of a wheel speed sensor, replacement information about the liability situation (slip) on the wheel affected by the wheel speed sensor failure can be generated.

This object is solved by the features of claim 1.

The dependent claims 2 to 8 form advantageous developments of the erfindungsmäßen method.

According to the method for determining a wheel slip information of a wheel of an axle of a motor vehicle, the wheels of the axle are each deflectable about a steering axis and have a positive or negative steering roller radius r ₀ , ie steering roller radius r ₀ ≠ 0, so that directed in the vehicle longitudinal direction, on Radaufstandspunkt the wheels attacking wheel force, z. B. caused by an acceleration or deceleration, generates a steering torque about the steering axis of the wheels. According to the invention, the steering disturbance torques resulting from an acceleration or deceleration acting around the steering axis of the wheels are used to determine the wheel slip information.

By means of the method according to the invention, it is now advantageously ensured that replacement slip information can also be generated in the event of a failure of a wheel speed sensor. Ie. a redundant wheel slip information is provided. This has the positive effect that - since now a replacement slip information is available - in the case of a piloted or (partially) autonomous driving a deactivation is not mandatory.

In order to determine or generate the replacement wheel slip information, according to a particularly preferred embodiment, the forces introduced into the tie rods and / or toe levers and thus into the steering gear due to the steering disturbances are measured.

For this purpose, the forces introduced into the tie rod and / or toe lever are preferably determined by means of a strain gauge. The determination of the forces by means of strain gauges proves to be particularly advantageous because they require less space and are simple in terms of their handling and installation.

The method according to the invention provides that a comparison of the forces introduced into the tie rod and / or toe lever of the left side of the vehicle with the forces introduced into the tie rod and / or toe lever of the right side of the vehicle is performed. If the comparison shows that the forces introduced into the track rod and / or the track lever of the left and the right side of the vehicle are different in magnitude, it is determined as wheel slip information that the wheel on which the smaller absolute force was measured is in slippage ( ie there is an uncontrolled spinning of the wheel). If, on the other hand, the comparison shows that the forces introduced into the tie rod and / or the track lever of the left and the right side of the vehicle are substantially equal in magnitude, an adjustment with a stored reference value is carried out. The reference value is chosen so that there is no slip for this value. If the comparison now shows that the reference value is undershot, then wheel slip information determines that both wheels of the axle are in slip (ie there is an uncontrolled spin on both wheels).

Since, in addition to the steering roller radius, other effects, in particular the vehicle speed, influence the steering torque and thus the forces introduced into the tie rod and / or toggle lever, the reference value is read from a characteristic map taking into account the vehicle speed.

Preferably, according to a particularly preferred embodiment, provision is made for determining whether the forces (F _L ) introduced into the tie rod and / or toggle lever of the left side of the vehicle and the forces (F _R ) introduced into the tie rod and / or toggle lever of the right side of the vehicle. amount equal in size or amount are different sizes, tolerance limits are defined.

und
die Kräfte werden bevorzugt als betragsmäßig unterschiedlich groß definiert, wenn $$\left|F_L\right|\le \frac{89}{100}\left|F_R\right|oder\left|F_L\right|\ge \frac{111}{100}\left|F_R\right|.$$

Thus, the forces are preferably defined as equal in magnitude, if $$\frac{90}{100}\left|F_R\right|\le \left|F_L\right|\le \frac{110}{100}\left|F_R\right|$$

and
the forces are preferably defined as different in magnitude, if $$\left|F_L\right|\le \frac{89}{100}\left|F_R\right|Oder\left|F_L\right|\ge \frac{111}{100}\left|F_R\right|,$$

A further preferred embodiment of the method according to the invention provides that a gradient of the yawing moment of the motor vehicle and / or the engine torque of the steering motor and / or the steering angle occurring due to the steering torque is detected and taken into account in the determination of the wheel slip information. As a result, a more accurate statement about the replacement wheel slip information is advantageously possible.

In particular, it is provided according to the method that the detected gradient of the yawing moment and / or the engine torque and / or the steering angle is compared with stored reference gradients, and that exceeding the reference gradient (s) is regarded as an indication of an incoming slip.

The invention is further based on the object of specifying a device for carrying out the method for determining a wheel slip information of a wheel of an axle of a motor vehicle.

This object is solved by the patent claim 9.

The dependent claim 10 represents an advantageous development of the device.

The device according to the invention for determining a wheel slip information of a wheel of an axle of a motor vehicle comprises a control / control unit and a wheel speed sensor assigned to each wheel of the axle whose output signals are made available to the control / control unit as input signals, which are assigned to the wheels of the axle Tie rods and / or toggle lever have a force measuring sensor, the output signals of the control / control unit are provided as additional input variables available.

Due to the now the control unit as a further input variable made available information on the forces acting on the tie rods and / or toggle forces, now the determination of a redundant Radschlupfinformation is now possible.

To ensure a particularly space-saving design while the force measuring sensors are preferably designed as strain gauges.

Further advantages and possible applications of the present invention will become apparent from the following description in conjunction with the embodiment shown in the drawing.

• 1 eine Draufsicht von oben auf eine schematisch dargestellte Vorderachse eines Kraftfahrzeugs, und
• 2 eine schematische Darstellung der Vorrichtung zur Bestimmung einer Radschlupfinformation eines Rades einer Achse eines Kraftfahrzeugs

In the drawing:

• 1 a top view of a schematically illustrated front axle of a motor vehicle, and
• 2 a schematic representation of the device for determining a wheel slip information of a wheel of an axle of a motor vehicle

1 shows a total with the reference numeral 10 designated suspension of a front axle of a motor vehicle. In a known manner are the wheels 12 . 14 Body side via a Radführungslenker 16 . 18 guided and stand over a tie rod 20 . 22 , a toe lever 24 . 26 as well as a central steering lever 28 with a steering gear 30 in active connection. A turn of the steering lever 28 around the steering angle δ thus causes a pivotal movement of the wheels 12 . 14 around whose steering or spreading axis.

Here are the wheels 12 . 14 a positive or negative steering roll radius r ₀ on (=> r ₀ ≠ 0), ie the distance between the wheel contact point of the wheels 12 . 14 to the imaginary puncture point of the extended steering axle of the wheels 12 . 14 through the roadway is ≠ 0.

The positive or negative steering roller radius r ₀ has the effect that a directed in the vehicle longitudinal direction, at the wheel contact point of the wheels 12 . 14 engaging _wheel force F _{wheel, R} or F _wheel , _L , z. B. caused by a deceleration or acceleration, a steering torque M _{Stör, R} or M _{Stör, L} about the steering axis of the wheels 12 . 14 generated.

According to the invention, the steering fault torque M _{Sturgeon, R} or M _{Sturgeon, L} is now used to generate replacement slip information in the event of a failure of a wheel speed sensor.

As 2 shows, this is every wheel 12 . 14 the axle is a wheel speed sensor 12 - 1 respectively. 14 - 1 assigned. The wheels 12 . 14 are shown in dashed lines. In addition, they are the wheel 12 associated components tie rod 20 and track levers 24 with a force measuring sensor 20 - 1 respectively. 24 - 1 Mistake. The same are true of the wheel 14 associated components, namely tie rod 22 and track levers 26 with a force measuring sensor 22 - 1 . 26 - 1 Mistake. In the present case, the force measuring sensors are designed as strain gauges.

The output signals of the wheel speed sensors 12 - 1 and 14 - 1 and the output signals of the force measuring sensors 20 - 1 . 24 - 1 and 22 - 1 . 26 - 1 become a control unit 32 provided as input signals, which in turn with an actuator 34 is operatively connected to influence the braking force.

For the following explanation of the method, it is assumed that the left wheel 14 assigned wheel speed sensor 14 - 1 failed. The left wheel 14 is below with the index L and the right wheel 12 denoted by the index R.

For the determination of the replacement slip information is now by the control unit 32 the over the force measuring sensors 20 - 1 . 24 - 1 and 22 - 1 . 26 - 1 evaluated forces were evaluated.

In the present case, the comparison has shown that the over the tie rods 20 . 22 and the track levers 24 . 26 steering forces F _Lenk apply: $$\left|F_{Lenk.R}\right|>>\left|F_{Lenk.L}\right|$$

Consequently, the same applies to the steering disturbances M _Stör and thus also to the wheel contact points of the wheels 12 . 14 attacking wheel forces F _Rad : $$\left|M_{Stör.R}\right|>>\left|M_{Stör.L}\right|=>\left|F_{Rad.R}\right|>>\left|F_{Rad.L}\right|$$

Since those at the wheels 12 . 14 acting in the vehicle longitudinal direction wheel forces F _{wheel, R} , F _{wheel, L} depending on the friction between the road surface and the wheels friction force F is _friction , applies accordingly for the frictional forces: $$\left|F_{\text{re}ib.R}\right|>>\left|F_{\text{re}ib.L}\right|$$

From this it can be inferred that the following applies to the friction coefficients: $${\mu }_R>>{\mu }_L$$

Therefore, according to the method, replacement slip information is determined to be the left wheel 14 in the slip.

According to a second scenario, the comparison has revealed that over the tie rods 20 . 22 and the track levers 24 . 26 introduced into the steering forces F _{steering are} about the same size. Ie. it applies: $$\left|F_{Lenk.R}\right|\approx \left|F_{Lenk.L}\right|\approx \left|F_{Lenk}\right|$$

Thus, the steering disturbances M _sturgeon , the wheel forces F _Rad and the friction forces F _friction are approximately the same in magnitude, so that the following applies to the friction coefficients: $${\mu }_R\approx {\mu }_L$$

In a further method step, therefore, a reference force F _{Lenk, Ref is} read from a speed-dependent map.

The amount of the reference force F _Lenk , _Ref is chosen so that for generating the introduced into the steering reference force F _Lenk , _Ref a large Lenkstörmoment M _sturgeon must act, which in turn requires that at Radaufstandspunkt a magnitude large _wheel force F _{wheel, ref} attack must, which in turn necessarily a large friction force F _{friction, Ref} between the road and the wheels and thus has a large coefficient of friction μ _Ref result.

In a further process step now a comparison of F _steering with F _steering , _Ref :

und somit ist $${\mu }_R\approx {\mu }_L<{\mu }_{\text{Re }f}.$$

In the present case, the comparison has shown that $$\left|F_{Lenk.R}\right|\approx \left|F_{Lenk.L}\right|=\left|F_{Lenk}\right|\approx \left|F_{Lenk.\text{re}f}\right|$$

and thus is $${\mu }_R\approx {\mu }_L<{\mu }_{\text{re}f},$$

Since the friction coefficient of the right and left wheels is smaller than the reference friction value, it is determined as replacement slip information that both the right wheel 12 as well as the left wheel 14 are in the slip.

As explained above, it is made possible by the method according to the invention that substitute slip information can be generated even after the failure of a wheel speed sensor.

Claims (10)

A method for determining a wheel slip information of a wheel (12, 14) of an axle of a motor vehicle, wherein the wheels (12, 14) of the axle are each deflectable about a steering axis and have a positive or negative steering roll radius (r ₀ ), so that one at the wheel contact point the wheels (12, 14) acting force (F _{wheel, R} , F _{wheel, L} ) generates a steering disturbance torque (M _sturgeon ) about the steering axis of the wheels (12, 14), wherein according to the procedure around the steering axis of the wheels (12, 14 ) acting steering disturbances (M _{sturgeon, L} , M _{sturgeon, R} ) are used to determine the wheel slip information. Method according to Claim 1 , characterized in that due to the steering disturbances (M _{sturgeon, L} , M _{sturgeon, R} ) in the tie rods (20, 22) and / or toggle lever (24, 26) introduced forces (F _{steering, L} , F _{steering, R} ) be measured. Method according to Claim 2 , characterized in that in the tie rod (20, 22) and / or toggle lever (24, 26) introduced forces (F _{steering, L} , F _{steering, R} ) by means of a strain gauge (20-1, 22-1, 24- 1, 26-1) are determined. Method according to Claim 2 or 3 , characterized in that a comparison of the in the tie rod (22) and / or in the track lever (26) of the left vehicle side introduced forces (F _{steering, L} ) with the in the tie rod (20) and / or in the track lever (24 ) of the right side of the vehicle the forces introduced F _{steering, R)} is performed, wherein in the case that the forces (F _{steering, L,} F _{steering, R)} of magnitude are different in size, is determined as Radschlupfinformation that the wheel with the smaller absolute force in the event that the forces (F _{steering, L} , F _{steering, R} ) are the same in magnitude, a comparison with a reference value (F _{steering, Ref} ) is performed and that _{falls below} the reference value ( F _{steering, Ref} ) is determined as Radschlupfinformation that both wheels (12, 14) of the axis are in slip. Method according to Claim 4 , characterized in that the reference value (F _{steering, Ref} ) is read out of a map taking into account the vehicle speed. Method according to Claim 4 or 5 , characterized in that the forces (F _{steering, L} , F _{steering, R} ) are regarded as equal in magnitude, if for the amounts of forces (F _{steering, L} , F _{steering, R} ) applies: $$\left|F_{Lenk.L}\right|=\left|F_{Lenk.R}\right|:\frac{90}{100}\left|F_{Lenk.R}\right|\le \left|F_{Lenk.L}\right|\le \frac{110}{100}\left|F_{Lenk.R}\right|$$

and that the forces (F _L , F _R ) are regarded as different in magnitude, if the amounts of the forces (F _L , F _R ) are: $$\left|F_{Lenk.L}\right|\ne \left|F_{Lenk.R}\right|:\left|F_{Lenk.L}\right|\le \frac{89}{100}\left|F_{Lenk.R}\right|Oder\left|F_{Lenk.L}\right|\ge \frac{111}{100}\left|F_{Lenk.R}\right|,$$

Method according to one of the preceding claims, characterized in that a gradient of the yawing moment of the motor vehicle and / or the engine torque of the steering motor and / or the steering angle occurring due to the steering disturbances (M _{Stör, L} , M _{Stör, R} ) is detected and during the determination the wheel slip information is taken into account. Method according to one of the preceding claims, characterized in that the detected gradient of the yawing moment and / or the engine torque and / or the steering angle is compared with stored reference gradients, and that exceeding the / the reference gradients is regarded as an indication of an incoming slip. Device for determining wheel slip information of a wheel (12, 14) of an axle of a motor vehicle, comprising a control / control unit (32) and a wheel speed sensor (12-1, 14-1) associated with each wheel (12, 14) of the axle, whose output signals are made available to the control unit (32) as input signals, wherein the tie rods (20, 24) and / or track levers (22, 26) assigned to the wheels (12, 14) of the axle comprise a force measuring sensor (20-1, 22). 1, 24-1, 26-1) whose output signals are provided to the control / control unit (32) as additional input variables. Device after Claim 9 , characterized in that the tie rods (20, 22) and / or track levers (24, 26) associated force measuring sensors as strain gauges (20-1, 22-1, 24-1, 26-1) are formed.

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