Methods for determining the inclination of a motor vehicle

Abstract

Method for determining the inclination (n) of a motor vehicle (10), wherein the inclination (n) of the motor vehicle (10) is determined on the basis of a measurement signal (S) provided by a longitudinal acceleration sensor (12) of the motor vehicle (10), characterized in that during a stopping process of the motor vehicle (10) the inclination (n) of the motor vehicle (10) is determined from a vibration behavior of the vibrational measurement signal (S) of the longitudinal acceleration sensor (12).

Description

[0001] The invention relates to a method for determining the inclination of a motor vehicle. Furthermore, the invention relates to a control device for a motor vehicle.

[0002] In practice, numerous control functions of motor vehicles are known to rely on the vehicle's tilt angle. For example, it is already known that motor vehicles are equipped with tilt sensors to measure and determine the tilt angle. The use of such sensors in a motor vehicle requires additional hardware and therefore incurs additional costs.

[0003] There is therefore a need to determine the inclination of a motor vehicle, as proposed in principle in DE 10 2004 019 928 A1, without the need for an inclination sensor, although this is not yet possible with sufficient reliability or accuracy.

[0004] DE 102 54 296 A1, DE 10 2008 027 087 A1, DE 10 2009 050 209 A1 and JP 4 361 332 B2 reveal further state of the art.

[0005] Based on this, the present invention aims to create a method for determining the inclination of a motor vehicle and a control device with which the inclination can be determined computationally, simply, reliably and accurately without an inclination sensor.

[0006] This problem is solved by a method according to claim 1. According to the invention, the inclination of the motor vehicle is determined based on a measurement signal provided by a longitudinal acceleration sensor of the motor vehicle, such that during a stopping process, the inclination of the motor vehicle is determined from the oscillation behavior of the oscillating measurement signal of the longitudinal acceleration sensor. The present invention proposes for the first time a method for determining the inclination of a motor vehicle, during a stopping process, from the oscillation behavior of the oscillating measurement signal of a longitudinal acceleration sensor of the motor vehicle. This makes it possible to dispense with an inclination sensor and still determine the inclination simply by calculation with sufficient reliability and accuracy.

[0007] According to an advantageous further development, when the speed of the motor vehicle falls below a defined limit value, a transient value to which the measurement signal of the longitudinal acceleration sensor settles is calculated predictively over several periods of the oscillating measurement signal of the longitudinal acceleration sensor from recorded minimum values ​​of the measurement signal and a maximum value of the measurement signal recorded immediately afterwards or immediately beforehand, and the inclination of the motor vehicle is determined from this predictively calculated transient value.

[0008] To predict the transient response value, a minimum-maximum value is calculated over several periods of the vibration-laden measurement signal of the longitudinal acceleration sensor from the respective minimum value of the measurement signal and the respective immediately following or immediately preceding maximum value of the measurement signal, whereby the respective minimum-maximum value is multiplied by a factor, and the transient response value is determined from the differences between the respective maximum value of the measurement signal and the respective minimum-maximum value multiplied by the factor.

[0009] This evaluation of the vibration-laden measurement signal of the longitudinal acceleration sensor is particularly preferred because it is simple on the one hand and enables a reliable and accurate determination of the inclination value on the other.

[0010] Preferred embodiments of the invention are described in the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the drawing, without being limited thereto. The drawing shows: Fig. 1 a schematic representation of a motor vehicle; Fig. 2 a diagram to illustrate a first variant of the method according to the invention; Fig. 3 a diagram to illustrate a second variant of the method according to the invention; and Fig. 4 a diagram to illustrate a third variant of the method according to the invention.

[0011] The invention presented here relates to a method for determining the inclination of a motor vehicle. Fig. Figure 1 shows a highly schematic representation of a motor vehicle 10 being operated on a roadway 11 inclined to the horizontal.

[0012] One FR direction of travel is in Fig. 1 visualized by an arrow. The invention now relates to a method for determining the inclination of the motor vehicle 10 in which it is operated.

[0013] The motor vehicle 10 is equipped with a longitudinal acceleration sensor 12. The longitudinal acceleration sensor 12 provides a measurement signal to the control unit 13 of the motor vehicle via an interface (not shown).

[0014] In accordance with the present invention, the inclination of the motor vehicle 10 is determined on the basis of the measurement signal provided by the longitudinal acceleration sensor 12 in such a way that, during a stopping process of the motor vehicle, the inclination of the motor vehicle 10 is determined from a vibration behavior of the vibrational measurement signal of the longitudinal acceleration sensor 12.

[0015] The method according to the invention therefore does not require an inclination sensor; rather, the measurement signal provided by the longitudinal acceleration sensor 12 is used to determine the inclination of the motor vehicle 10. This is done by evaluating or analyzing the vibration behavior of the vibrational measurement signal from the longitudinal acceleration sensor 12.

[0016] The method according to the invention is started when the vehicle's speed falls below a defined, applicable limit value. When the speed falls below this limit value, a transient value, at which the longitudinal acceleration sensor 12's measurement signal settles, is calculated predictively over several periods of the oscillating measurement signal from the longitudinal acceleration sensor 12. This transient value is derived from the minimum values ​​of the measurement signal and the maximum values ​​of the measurement signal that are immediately preceding or following each period. The vehicle's inclination is then determined from this predictively calculated transient value.

[0017] To predict the transient response value to which the measurement signal of the longitudinal acceleration sensor settles, a minimum-maximum value is calculated over several periods of the oscillating measurement signal from the respective minimum value and the respective immediately following or immediately preceding maximum value, whereby the respective minimum-maximum value is multiplied by a factor, and the transient response value is calculated from the differences between the respective maximum value of the measurement signal and the respective minimum-maximum value multiplied by the factor.

[0018] The factor by which the respective minimum-maximum value is multiplied is a constant that is identical for all periods to be evaluated, whereby this constant is empirically or experimentally determined and applicable.

[0019] Fig. Figure 2 shows the course of a measurement signal S=a(t) of the longitudinal acceleration sensor 12 over time t, where Fig. 2 can be seen to show that the longitudinal acceleration a of the motor vehicle 10 provided by the measurement signal S over time t is subject to oscillation.

[0020] According to Fig. 2. Over several periods of this oscillation, a difference is determined between a minimum value a,min of the respective period and an immediately following maximum value a,max of the respective period, wherein Fig. Figure 2 shows this for three consecutive periods. For the first period, defined by the minimum value a,min-1 and the immediately following maximum value a,max-1, the difference Δa1 is determined. For the subsequent, second period, defined by the minimum value a,min-2 and the immediately following maximum value a,max-2, the difference Δa2 is determined. The difference Δa3 is determined from the minimum value a,min-3 and the immediately following maximum value a,max-3 of the subsequent, third period.

[0021] For each of these periods, the respective difference between the minimum value and the maximum value, which is a minimum-maximum value Δa, is multiplied by a factor k, where, as already mentioned, this factor is a constant that is determined empirically and can be applied in the control device 13.

[0022] For the first period, the minimum-maximum value Δa1 is multiplied by the constant k, for the second period the minimum-maximum value Δa2 is multiplied by the constant k, and for the subsequent third period the minimum-maximum value Δa3 is multiplied by the constant k.

[0023] The transient response c of the oscillating signal S of the longitudinal acceleration sensor 12 is determined from the differences a,max - k*Δa between the maximum value of the measurement signal of the respective period and the minimum-maximum value Δa of the respective period multiplied by the factor or constant k. In the first period, the difference a,max-1 - Δa1*k is used as the transient response c. In the second period, the difference a,max-2 - Δa2*k is used as the transient response c. In the third period, the difference a,max-3 - Δa3*k is determined as the transient response c. With an increasing number of periods, the accuracy of the transient response c increases.

[0024] The transient value c is in Fig. 3 is shown by a dotted line. An average value can be calculated from the transient values ​​determined over the individual periods.

[0025] From the transient value c of the oscillating measurement signal S of the longitudinal acceleration sensor 12 determined in the above manner and on the basis of the acceleration due to gravity g, the inclination n of the motor vehicle 10 is determined using the following equation: n=tan(arcsin(c / g))*100% wherein the tangent function tan and arcsine function arcsin of the above equation are preferably mapped via a common characteristic map in order to reduce the computational effort in the control device 13.

[0026] The number of periods to be evaluated of the oscillating measurement signal S of the longitudinal acceleration sensor 12 is limited by a defined time period Δt, which can be applied in the control unit 13 and which starts to run from the time at which the speed of the motor vehicle falls below the already defined limit value.

[0027] Fig. Figure 3 shows a variation of the procedure of Fig. 2, in which the minimum-maximum values ​​Δa are determined between a minimum value a,min and an immediately preceding maximum value a,max. However, with regard to the remaining procedure, the method of Fig. 3 using the procedure of Fig. 2 agree, so to avoid unnecessary repetition, reference is made to the above statements.

[0028] Another variant of the inventive method shows Fig. 4, wherein in Fig. 4. The maximum value a,max and the minimum values ​​a,min are used multiple times. Thus, in Fig. 4. On the one hand, minimum-maximum values ​​Δa1, Δa3, Δa5 are determined between the respective minimum value a,min and the immediately following maximum value a,max, and on the other hand, minimum-maximum values ​​Δa2, Δa4 are determined between the respective minimum value a,min and the immediately preceding maximum value a,max. This increases the number of determined minimum-maximum values ​​and thus the computational effort, but it improves the accuracy of determining the transient value c and the slope value n.

Claims

[1] Method for determining the inclination (n) of a motor vehicle (10), wherein the inclination (n) of the motor vehicle (10) is determined on the basis of a measurement signal (S) provided by a longitudinal acceleration sensor (12) of the motor vehicle (10), characterized by that during a stopping process of the motor vehicle (10) the inclination (n) of the motor vehicle (10) is determined from an oscillation behavior of the oscillating measurement signal (S) of the longitudinal acceleration sensor (12). [2] Method according to claim 1, characterized bythat when a travel speed of the motor vehicle (10) falls below a defined limit value, a settling value (c), to which the measurement signal (S) of the longitudinal acceleration sensor (12) settles, is predictively calculated over several periods of the oscillating measurement signal (S) of the longitudinal acceleration sensor (12) from detected minimum values ​​(a,min) of the measurement signal (S) and a maximum value (a,max) of the measurement signal (S) detected immediately thereafter or immediately before; wherein the inclination (n) of the motor vehicle (10) is determined from this predictively calculated settling value (c). [3] Method according to claim 2, characterized byin that for the predictive calculation of the transient value (c) over several periods of the oscillating measurement signal (S) of the longitudinal acceleration sensor (12), a minimum-maximum value (Δa) is formed from the respective minimum value (a,min) of the measurement signal (S) and the respective immediately following or immediately preceding maximum value (a,max) of the measurement signal (S), wherein the respective minimum-maximum value (Δa) is multiplied by a factor (k), and wherein the transient value (c) is determined from the differences (a,max - k*Δa) between the respective maximum value (a,max) of the measurement signal (S) and the respective minimum-maximum value (Δa) multiplied by the factor (k). [4] Method according to claim 3, characterized by that the factor (k) by which the respective minimum-maximum value (Δa) is multiplied is constant. [5] Method according to claim 3 or 4, characterized bythat an empirically determined value is used as the factor (k) by which the respective minimum-maximum value (Δa) is multiplied. [6] Method according to one of claims 1 to 5, characterized by that the inclination (n) is determined from the settling value (c) and the gravitational acceleration constant (g) using the following equation: n=tan(arcsin(c / g))*100%. [7] Method according to claim 6, characterized by that the tangent function tan and the arcsine function arcsin are mapped via a common characteristic field. [8] Method according to one of claims 1 to 7, characterized by that the number of evaluated periods of the vibration-affected measuring signal (S) of the longitudinal acceleration sensor (12) is limited by a predetermined time period (Δt). [9] Control device (13) of a motor vehicle (10), which receives and evaluates a measurement signal (S) detected by a longitudinal acceleration sensor (12) via an interface, characterized by Means for carrying out the method according to one of claims 1 to 8.

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