DE102016202953A1 - Method for a speed controller and speed controller - Google Patents

Abstract

The invention relates to a method for a speed controller for a motor vehicle, wherein a speed setting (vvor) is set by the driver and wherein an automatic control of the speed of the motor vehicle to a control speed (vfin) and wherein a steering angle (SWA) is monitored, wherein a reduction specification (vred) is specified according to the steering angle and the control speed (vfin) is adjusted, the adjusted control speed (vfin) corresponding to the difference between the speed specification (vvor) and the reduction specification (vred). The invention also relates to a speed controller.

Description

The invention relates to a method for a speed controller for a motor vehicle, wherein a speed setting is set by the driver and wherein an automatic control of the speed of the motor vehicle is at a control speed and wherein a steering angle is monitored. The invention also relates to a speed controller.

In the automatic cruise control of automobiles, the situation often occurs that the set speed is not adequate when driving through bends, so that the safety and comfort of the driver are limited. In the manual operation of a motor vehicle, the driver can continuously adapt the speed to the driving situation, for example by reducing the speed in tight bends. During an automatic cruise control, this is not possible or would miss the purpose of such a control.

From the DE 11 2013 005 524 T5 A method of maintaining the vehicle speed at a target speed is known, wherein the target speed is limited to a fixed, steering angle dependent maximum speed when a steering wheel angle is measured which is above a limit and the road lenght is within predetermined limits. In this way, blocking of the rear axle and subsequent abrupt release of the blockage ("crow-hop") is avoided.

Such a method has the disadvantage that the control is little adapted to the situation. Although the occurrence of crow-hop is reduced, but the process does not intervene at target speeds below the specified maximum speed, so that there is no comfort gain. If a limitation occurs, then the target speed is no longer dependent on the speed set by the driver, so that the regulation does not take into account the driver's request.

It is therefore an object of the present invention to provide a method which allows a comfortable and situation-adapted speed control.

This object is achieved by a method according to claim 1 and a speed controller according to claim 10.

Advantageous embodiments of the invention are the subject of the dependent claims.

The invention is based on the consideration that a speed reduction specification for the speed is specified for the situation-appropriate adjustment of the speed and that the steering angle is a suitable size, according to which such a reduction specification is determined. The control speed is adjusted, with the adjusted control speed corresponding to the difference between the speed default and the reduction target.

Under steering angle can be understood both a steering wheel angle and an adjustment angle of the steered wheels. Usually, the two variables differ only by a vehicle-specific factor.

The evaluation of the steering wheel angle has the advantage that the driver's request is determined directly. The absolute value of the steering angle is a measure of the curve radius. Compared with the use of other driving dynamics variables such as, for example, the lateral acceleration, the use of the steering angle has the advantage that incorrect regulations, caused for example by a transversely inclined roadway, are avoided.

In a preferred embodiment, the reduction specification is determined as an absolute velocity variable. In an alternative preferred embodiment, the reduction specification is determined as a proportion of the speed specification, wherein the proportion factor is predetermined in accordance with the steering angle.

Advantageously, a characteristic of the reduction specification is predefined as a function of the steering angle, and the reduction specification is determined on the basis of this characteristic. Preferably, the characteristic is determined vehicle-dependent, for example by means of driving tests and deposited in a storage medium, so that it can be accessed by the speed controller.

Preferably, during the automatic control of the speed, the speed setting always corresponds to a value set by the driver, while the reduction setting is continuously redetermined by the speed controller. This has the advantage that the driver's request is stored at all times and taken into account, and at the same time there is a dynamic adaptation to the present driving situation.

In a vehicle that makes a turn, in general, the wheels on the inside of the curve travel a smaller distance than the wheels on the outside of the curve. Therefore, there exists a deviation between the wheel speeds of the wheels of the inner and outer sides, or one Deviation between the respective wheel speeds and the vehicle reference speed (speed deviation). When driving through a curve, there is therefore a causal relationship between the set steering angle and the speed deviation. Due to this, the speed deviation between the respective wheel speeds and the vehicle reference speed can be used to make it plausible whether the curve expected after adjustment of the steering angle is actually traversed. The vehicle reference speed is determined by means of methods known per se.

Advantageously, at least one wheel speed is measured, wherein a first speed deviation between the wheel speed and a vehicle reference speed is calculated. Based on the steering angle, a second speed deviation is determined. The second speed deviation is determined in particular by means of a model or by means of a stored characteristic which indicates a relationship between the set steering angle and the second speed deviation. The control speed is adjusted only when the first speed deviation and the second speed deviation differ by less than a predetermined threshold, thereby making the turn of the vehicle plausible.

In a preferred embodiment, the first speed deviation is calculated as the difference between the wheel speed of a wheel on the inside of the curve, in particular a non-driven wheel, and the vehicle reference speed. In a further preferred embodiment, the first speed deviation is calculated as the difference between the wheel speed of a wheel on the outer side of the curve, in particular a non-driven wheel, and the vehicle reference speed.

In a further preferred embodiment, the first speed deviation is calculated as the difference between the wheel speed of a wheel on the inside of the curve, in particular a non-driven wheel, and the vehicle reference speed and a third speed deviation as the difference between the wheel speed of a wheel on the outside of the curve, in particular a non-driven wheel , and the vehicle reference speed calculated. A fourth speed error is determined based on a model or other stored characteristic that indicates a relationship between the adjusted steering angle and the fourth speed deviation, where both the first speed deviation must differ from the second speed deviation by less than a predetermined limit and the third speed deviation must differ by less than a predetermined limit from the fourth speed deviation in order to plausibilize the cornering.

In other embodiments of the invention, a sum, a difference or an average of several measured wheel speeds of different wheels is used as the first speed deviation.

In a preferred embodiment, the control speed is adjusted only when the vehicle speed is above a predetermined speed limit. In a very low speed range, adjustment of the control speed is not required and not conducive to comfort.

In a further preferred embodiment, the control speed is adjusted only when the steering angle is above a predetermined steering angle limit. This has the advantage that false excitations are avoided with small steering wheel movements. For very gentle curves, an adjustment of the control speed is not necessary.

Advantageously, a maximum reduction specification is determined as a function of the speed specification, wherein the reduction specification is selected such that it does not exceed the maximum reduction specification. In order to avoid an excessive reduction of the speed, a maximum reduction specification is defined depending on the speed specification. The reduction specification determined in accordance with the steering angle is then compared with the maximum reduction specification. If the reduction specification is below the maximum reduction specification, the reduction specification is used. On the other hand, if it is above the maximum reduction specification, then the maximum reduction specification is used instead as a reduction specification.

Preferably, the reduction specification is determined depending on a background condition. The background condition is particularly preferably determined either via an environment identifier, or specified by the driver via an input.

In a preferred embodiment, the steering angle change is used as a measure of the Einlenkintensität. Advantageously, at low Changes the speed slowly adjusted (low delay), with high changes, the adjustment is faster.

The speed controller is preferably a controller for a low speed range, in particular for off-road operation. Below a low speed range are preferably understood speeds below about 30km / h.

An embodiment of the invention will be explained in more detail with reference to five drawings. In it show in a highly schematic representation:

1 a highly schematic flowchart of the method,

2 exemplary characteristics of the second speed deviation,

3 an exemplary characteristic of the reduction specification as a function of the steering angle,

4 an exemplary course of maximum reduction specifications as a function of the speed specification,

5 an example of a course of a speed specification and a Reduzierungsvorgabe while driving through a curve.

1 shows a highly schematic flowchart of the exemplary method. The procedure is always carried out when a speed controller is active. It starts with the determination of the steering angle SWA in step 1 , By way of example, the steering angle SWA is determined by means of a steering wheel angle sensor.

In step 10 For example, the wheel speeds of the left and right wheels of the non-driven axle are measured, and a first speed deviation Δ _vi between a wheel speed and a vehicle reference speed is calculated.

In step 2 Based on a speed difference characteristic curve from the measured steering angle SWA a second, theoretical, speed deviation Δ _{Ref is} determined. In step 3 the first and second speed deviations are compared with each other. If the first and second speed deviations differ by less than a predefined limit value, then step 4 continued. Otherwise, with step 5 continued.

In step 4 the measured steering angle SWA is compared with a steering angle limit value SWA _Min . If the steering angle SWA is greater than the steering angle limit value SWA _Min , then step 6 otherwise, continue with step 5 continued.

In step 6 For example, the speed preset v _{before is} compared with a speed limit v _min . If the speed preset v _{before is} greater than the speed limit v _Min , then step 7 otherwise, continue with step 5 continued.

In step 5 it is determined that no adjustment of the control speed takes place. The process is run again from the beginning.

In step 7 For example, based on a vehicle-specific reduction characteristic, a reduction specification v _{red is determined} as a function of the measured steering angle SWA.

Subsequently, in step 8th For example, as a function of the speed specification v _before a maximum reduction specification v _{red, lim} determined. The in step 7 in accordance with the steering angle SWA certain reduction requirement v _red is then compared with the maximum reduction specification v _{red, lim} . If the reduction specification v _red lies below the maximum reduction specification v _{red, lim} , then the reduction specification v _{red is transferred} to step 9 more given. If, on the other hand, it lies above the maximum reduction specification v _{red, lim} , then the maximum reduction specification v _{red, lim is} instead referred to step 9 passed.

In step 9 the final reduction target v _{red, fin is passed} to the velocity controller.

The speed controller calculates, for example, in step 11 a difference value between the set speed preset by the driver v _before and reducing default v _{red, fin} and uses this difference value as the control velocity v _fin.

2 shows exemplary characteristics of the relationship between the steering angle SWA and the second speed deviation Δ _Ref . In this case, the steering angle SWA is plotted on the x-axis and the second speed deviation Δ _Ref on the y-axis as a percentage of the vehicle reference speed. The history 21 represents the curve for the outside wheel, the course 22 the characteristic for the inside wheel. The curves are determined according to the vehicle by means of driving tests, for example, and stored in a memory.

For example, the second speed deviation becomes the current steering angle SWA corresponds, determined by the characteristic for a first vehicle side and compared with the first speed deviation, which corresponds to the deviation Δ _vi between the wheel speed of the first vehicle side and the vehicle reference speed. A fourth speed deviation, which corresponds to the current steering angle SWA, is determined by means of the characteristic curve for the other, second vehicle side and compared with a third speed deviation, which corresponds to the deviation between the wheel speed of the second vehicle side and the vehicle reference speed.

3 shows an exemplary characteristic 31 the reduction specification v _red as a function of the steering angle SWA. In this case, the measured steering angle SWA is plotted on the x-axis and the reduction target v _{red is} plotted on the y-axis. The reduction target v _red is determined by this reduction characteristic 31 certainly.

4 shows an example course 41 the maximum reduction prescriptions v _{red, lim} depending on the speed default v _before . In this case, the velocity preset v _is plotted on the x axis and the corresponding maximum reduction target v _{red, lim is} plotted on the y axis.

5 shows an exemplary course of a speed specification and a reduction specification v _red during the passage through a curve. It is on the x-axis 54 the time is plotted and on the y-axis 56 the speed variables. The speed preset v in _{front of} the driver is in the course 51 is displayed and remains constant over time, as long as the driver does not change his specification. When driving through a curve, the speed controller makes a reduction default due to the set steering angle SWA 53 calculated. The speed controller forms the difference between the speed preset v _before and the reduction preset 53 and calculates a control speed v _fin that over time 52 is shown. The control speed v _fin is lowered in the curve with respect to the speed preset v _before and after completing the cornering again increased to the speed preset v _before .

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 112013005524 T5 [0003]

Claims (10)

Method for a speed controller for a motor vehicle, wherein a speed setting (v _before ) is set by the driver and wherein an automatic regulation of the speed of the motor vehicle to a control speed (v _fin ) takes place and wherein a steering angle (SWA) is monitored, characterized in that a reduction specification (v _red ) is specified in accordance with the steering angle and the regulation speed (v _fin ) is adapted, wherein the adjusted regulation speed (v _fin ) corresponds to the difference between the speed specification (v _before ) and the reduction specification (v _red ). Method according to Claim 1, characterized in that a reduction characteristic ( 31 ) for the reduction specification (v _red ) as a function of the steering angle (SWA) and the reduction specification (v _red ) on the basis of the reduction characteristic ( 31 ) is determined. Method according to one of the preceding claims, characterized in that during the automatic regulation of the speed, the speed specification (v _before ) always corresponds to a value set by the driver and the reduction specification (v _red ) is continuously redetermined by the speed controller. Method according to one of the preceding claims, characterized in that at least one wheel speed is measured, wherein a first speed deviation (Δ _vi ) between the wheel speed and a vehicle reference speed is calculated and based on the steering angle (SWA) a second speed deviation (Δ _Ref ) is determined wherein the control speed (v _fin ) is adjusted only when the first speed deviation (Δ _vi ) and the second speed deviation (Δ _Ref ) differ by less than a predetermined limit. Method according to one of the preceding claims, characterized in that the control speed (v _fin ) is adjusted only when the speed command (v _before ) is above a predetermined speed limit (v _min ). Method according to one of the preceding claims, characterized in that the control speed (v _fin ) is adjusted only when the steering angle (SWA) is above a predetermined steering angle limit (SWA _Min ). Method according to one of the preceding claims, characterized in that a maximum reduction specification (v _{red, lim} ) is determined as a function of the speed specification (v _before ), wherein the reduction specification (v _red ) is selected such that it sets the maximum reduction specification (v _{red , lim} ). Method according to one of the preceding claims, characterized in that the reduction specification (v _red ) is determined as a function of a background condition. Method according to one of the preceding claims, characterized in that the speed controller is a controller for a speed range up to about 30km / h, in particular for off-road operation. Speed controller for a motor vehicle, which performs an automatic control of the speed of the motor vehicle to a control speed (v _fin ) and the signals of a steering angle detection device (SWA) are fed, characterized in that a method according to any one of the preceding claims is performed ,

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