Method for improving the accuracy of speed determination of a vehicle driven by at least one electric machine

Abstract

A method for improving the accuracy of a speed determination of a vehicle driven by at least one electric machine is described, comprising the steps: - Determining at least one speed of the at least one electrical machine of the vehicle; - Comparing the determined speed with a predefined speed threshold; - Determine the vehicle speed depending on the comparison. Furthermore, a corresponding electronic control unit, a corresponding computer program and a corresponding machine-readable storage medium with the computer program are described.

Description

[0001] The present invention is based on a method for improving the accuracy of a speed determination of a vehicle driven by at least one electric machine. State of the art

[0002] With regard to highly autonomous or fully autonomous driving (HAD), numerous questions exist regarding the functional validation of the systems required for HAD. A key element is driving state detection. This represents a central element in the architecture of an autonomous vehicle. It is used in traditional systems of the automotive industry, such as ESP, EPS, ABS, and the powertrain, but also in the systems required for autonomous driving, such as behavior, planning, sensor fusion, localization, and perception.

[0003] The state of the art regarding a known state estimation is described in patent DE 10 2009026994. This patent describes how a driving state estimation can be formed using a strapdown algorithm, inertial measurement technology in the x, y, and z directions, a Kalman filter, and a Vx signal formed from speed sensors for support.

[0004] The procedure described in the aforementioned patent is also used for HAD systems, but there are increased requirements for signal accuracy, especially in the lower speed range, for example, below 10 km / h. Furthermore, a so-called fail-operational system is required in fully autonomous vehicles.

[0005] The document US2015343874 AA describes a device for vehicle state estimation in which rotor position sensors are used.

[0006] Document US4106094 A describes a device for vehicle condition estimation.

[0007] The document EP 2 581 258 A1 describes a method for changing a driving situation of a motor vehicle as a function of a detected operating variable, in particular the speed of a rotor of a drive motor of the motor vehicle. Disclosure of the inventionAdvantages of the invention

[0008] A method for improving the accuracy of speed determination of a vehicle driven by at least one electric machine is disclosed, having the features of the independent patent claim.

[0009] For this purpose, the speed of at least one of the vehicle's electric motors is determined. The resulting speed is then compared with a predefined speed threshold, and the vehicle speed is then determined based on the comparison.

[0010] This is advantageous because the most accurate method of speed determination is selected depending on the speed of the electric machine, which improves the accuracy of the determined speed.

[0011] Further advantageous embodiments of the present invention are the subject of the subclaims.

[0012] Determining the vehicle speed expediently includes determining the vehicle speed as a function of the determined engine speed and / or determining the vehicle speed as a function of a determined vehicle acceleration. This is advantageous because it allows the most suitable method for determining the speed to be selected depending on the application. When determining the vehicle speed using the determined vehicle acceleration, for example determined using an inertial measuring unit, there is the problem that the calculation of the vehicle speed drifts during long standstill phases because noise is also integrated. This problem has so far been solved using movement thresholds for the acceleration signals and wheel sensors. Due to the measuring principle, the wheel sensors in particular have a delay when starting off and when stopping compared to the actual movement of the vehicle.This is advantageously improved or remedied by determining the vehicle speed depending on the determined speed.

[0013] For practical purposes, the vehicle speed is determined based on a mathematical drivetrain model of the vehicle. This is advantageous because it increases the accuracy of the vehicle speed determination by taking into account, for example, drivetrain dynamics.

[0014] When the speed threshold is exceeded, the vehicle speed is additionally determined based on a wheel sensor signal. This is advantageous because, above a certain speed, the wheel sensors provide accurate speed values. This improves speed determination.

[0015] Conveniently, the at least one rotational speed of the at least one electric machine is determined using a rotor position sensor. This is advantageous because this sensor outputs a very accurate rotor position signal, allowing the rotational speed to be precisely determined from the highly accurate rotor position signal. The rotor position sensor is a so-called resolver sensor. This sensor delivers a continuous signal whose quality is only degraded by the quantization of the AD conversion. Conventional speed sensors, on the other hand, deliver a signal based on their teeth on the rotor wheel and are already limited by this measuring principle.

[0016] Furthermore, the invention relates to an electronic control unit configured to execute all steps of a method according to the invention. Thus, the aforementioned advantages can be achieved.

[0017] Furthermore, the invention relates to a computer program configured to execute all steps of a method according to the invention. Thus, the aforementioned advantages can be achieved.

[0018] Furthermore, the invention relates to a machine-readable storage medium on which the computer program according to the invention is stored. Thus, the aforementioned advantages can be achieved. Short description of the drawings

[0019] Advantageous embodiments of the invention are illustrated in the figures and explained in more detail in the following description.

[0020] They show: Fig. 1 a flowchart of a method according to the invention according to a first embodiment; Fig. 2 shows a schematic representation of a speed determination which is improved by a method according to the invention; Fig. 3 a schematic representation of an electronic control unit according to the invention according to an embodiment. Embodiments of the invention

[0021] The same reference numerals designate the same device components or the same process steps in all figures.

[0022] Fig. 1 shows a flowchart of a method according to the invention for improving the accuracy of a speed determination of a vehicle driven by at least one electric machine according to a first embodiment.

[0023] In a first step S11, at least one rotational speed of the at least one electric motor of the vehicle is determined. This can be done, for example, using a rotor position sensor.

[0024] In a second step S12, the determined speed is compared with a predefined speed threshold. This determines, for example, whether the engine rotates quickly or slowly, for example, to drive the vehicle.

[0025] In a third step S13, the vehicle speed is then determined based on the comparison. For this purpose, for example, the vehicle speed can be determined based on the determined speed alone if the threshold value is undershot. A mathematical drivetrain model of the vehicle can be used for this purpose to increase the determination accuracy, for example, a model based on differential equations with damping terms of the drivetrain components. Furthermore, the vehicle speed can also be determined based on a determined vehicle acceleration. For this purpose, both values ​​can be merged, for example. If the speed threshold value is exceeded, the vehicle speed can also be determined based on a determined vehicle acceleration and / or a wheel sensor signal.

[0026] Fig. 2 shows a schematic representation of a speed determination which is improved by a method according to the invention. Fig. Figure 2 shows three schematic diagrams. The top diagram shows the vehicle speed 23 determined by fusion, which is made available in the vehicle for further use, for example in a navigation system or for parking. For this purpose, it is output in a block 26. The vertical axis Vx thus represents a vehicle speed and the right-hand axis represents time. During a standstill phase 21, no speed is determined, but only in a subsequent starting phase 22. The phases can vary depending on the sensor type. Block 24 supplies a signal from the wheel sensor. This does not detect low speeds, as can be seen from the middle diagram, but only above a certain threshold.

[0027] Block 25 supplies a speed signal from an electric motor. From this, the vehicle speed can be accurately determined, especially in the low speed range. Thus, it is used to determine the vehicle speed below a predefined speed threshold.

[0028] Thus, the method according to the invention contributes to improving vehicle speed determination.

[0029] Fig. Figure 3 shows a schematic representation of an electronic control unit 32 according to the invention according to one embodiment. The control unit 32 is configured to execute a method according to the invention. The speed of an electric machine is determined here by means of a rotor position sensor 31 and is determined by the control unit from the rotor position sensor 31. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This 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

[0000] DE 10 2009026994

[0003] US 2015343874

[0005] US 4106094 A

[0006] EP 2 581 258 A1

[0007]

Claims

[1] Method for improving the accuracy of a speed determination of a vehicle driven by at least one electric machine, comprising the steps: - Determining at least one speed of the at least one electrical machine of the vehicle; - Comparing the determined speed with a predefined speed threshold; - Determine the vehicle speed depending on the comparison. [2] Method according to the preceding claim, wherein determining the vehicle speed comprises: - Determining the vehicle speed depending on the determined speed; and / or - Determining the vehicle speed depending on a determined vehicle acceleration. [3] Method according to the preceding claim, wherein the determination of the vehicle speed is carried out as a function of the determined rotational speed as a function of a mathematical drive train model of the vehicle. [4] Method according to one of the preceding claims, wherein when the speed threshold value is exceeded, the vehicle speed is additionally determined as a function of a wheel sensor signal. [5] Method according to one of the preceding claims, wherein the at least one rotational speed of the at least one electrical machine is determined by means of a rotor position sensor. [6] Electronic control unit (30) arranged to carry out all the steps of the method according to any one of the preceding claims. [7] Computer program which is arranged to carry out all the steps of the method according to one of claims 1 to 5. [8] A machine-readable storage medium on which the computer program according to the preceding claim is stored.

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