DE102006018978A1 - Motor vehicle roll angle determining method, involves determining yaw rate or correlated size, and vehicle speed, and determining roll angle of motor vehicle using yaw rate or correlated size and specific vehicle roll spring rigidity - Google Patents

Abstract

The method involves determining a yaw rate or a correlated size by a determining device (1), and determining vehicle speed by a determining device (2). A roll angle of a motor vehicle is determined using the yaw rate or the correlated size and specific vehicle roll spring rigidity. A centripetal force is computed from the yaw rate or the correlated size. The yaw rate measurement is calibrated in the standstill position of the vehicle and when driving the vehicle. The vehicle is assumed as a mass (m) with specific height (h). An independent claim is also included for a sensor for environment detection in a motor vehicle.

Description

The The invention relates to a method for determining the roll angle in a motor vehicle and a camera system with such Method.

A Determination of the roll angle is especially for the assessment and control the dynamic characteristics of motor vehicles. In addition, driver assistance systems, e.g. the lane of a Predict vehicle and Objects on or next to the lane identify ever greater spread. Such motor vehicles are equipped with at least one sensor for environmental monitoring fitted. I. d. R. is this camera and / or Lidar or radar systems. The sensors are shipped before delivery of the vehicle adjusted and take a certain, predetermined line of sight one. Now, if the roll angle of the vehicle is e.g. during non-zero cornering, so also corresponds the line of sight of the sensor system to the vehicle environment not the original anymore set viewing direction. The lane will be faulty in this case predicted and a detected environment object is particularly in the far field (Distance to the vehicle> 70 m) assigned a faulty position. For vehicles with an air spring is an estimate of the roll angle based on the air spring sensors, including the Vehicle width possible. For vehicles with steel spring, however, this is not readily possible.

It is therefore the object of the present invention, the roll angle in a motor vehicle.

These The object is achieved by Method with the features described in claim 1. advantageous Further developments can be found in the dependent claims.

It is a method for determining the roll angle for a motor vehicle specified. The motor vehicle comprises at least one device for Determination of the yaw rate or a correlated quantity, a Device for determining the vehicle speed and possibly a forward directed camera system. The roll angle is using the yaw rate or a correlated size and the specific roll stiffness of the vehicle determined. The specific one Stiff spring stiffness is a characteristic of the vehicle that is suitable for every vehicle type determined, which is equipped with steel springs. alternative can of course also an average for several vehicle types are specified.

In a particular embodiment of the invention is one of the yaw rate correlated magnitude of the lateral acceleration or the steering angle. These data are e.g. provided by an ESP control unit.

In In a particular embodiment of the invention, the vehicle is modeled is assumed to be a mass point (m) having a height (h), the assumed Earth point by an angle (φ) directly proportional to is deflected attacking force.

In An advantageous embodiment of the invention is called attacking Force assumed the centripetal force when cornering acts. The centripetal force is the yaw rate or a correlated one Size calculated.

wobei ϕ der Wankwinkel, m die Aufbaumasse des Fahrzeugs, h der Abstand zwischen Aufbauschwerpunkt und Drehpunkt, ν_x die Geschwindigkeit in Längsrichtung, ω_z die Gierrate des Fahrzeugs und C proportional oder gleich der Wankfedersteifigkeit des Fahrzeugs ist. Eine weitere Relation zur Bestimmung des Wankwinkels wird mit

angegeben. Dabei ist ϕ der Wankwinkel, m die Aufbaumasse des Fahrzeugs, h der Abstand zwischen Aufbauschwerpunkt und Drehpunkt, α_y die Querbeschleunigung des Fahrzeugs und C proportional oder gleich der Wankfedersteifigkeit des Fahrzeugs ist.In an advantageous embodiment of the invention applies

where φ is the roll angle, m is the body weight of the vehicle, h is the distance between the center of articulation and the center of rotation, ν _{x is} the speed in the longitudinal direction, ω _{z is} the yaw rate of the vehicle, and C is proportional to or equal to the roll stiffness of the vehicle. Another relation for determining the roll angle is with

specified. Where φ is the roll angle, m is the body weight of the vehicle, h is the distance between the center of articulation and the fulcrum, α _{y is} the lateral acceleration of the vehicle, and C is proportional to or equal to the roll stiffness of the vehicle.

ausgedrückt werden, wobei ϕ der Wankwinkel, m die Aufbaumasse des Fahrzeugs, h der Abstand zwischen Aufbauschwerpunkt und Drehpunkt, ν_x die Geschwindigkeit in x-Richtung, α_LW der Lenkwinkel des Fahrzeugs und C proportional oder gleich der Wankfedersteifigkeit des Fahrzeugs ist. In einer weiteren vorteilhaften Ausgestaltung der Erfindung ist vorgesehen, dass der Wankwinkel nach zwei verschiedenen Ansätzen bestimmt wird, und die Resultate miteinander verglichen werden. Erweist sich eine der Methoden als besonders geeignet für eine Fahrsituation, so werden die Resultate dieser Methode verwendet, wenn eben diese Fahrsituation auftritt.Alternatively, the roll angle through

where φ is the roll angle, m is the body weight of the vehicle, h is the distance between the center of articulation and the fulcrum, ν _{x is} the speed in the x direction, α _{LW is} the steering angle of the vehicle, and C is proportional to or equal to the roll spring rigidity of the vehicle. In a further advantageous embodiment of the invention, it is provided that the roll angle is determined according to two different approaches, and the results are compared with each other. If one of the methods proves to be particularly suitable for a driving situation, then the results of this method are used, if precisely this driving situation occurs.

Since the accuracy of the determined roll angle of the accuracy of approaching for the purpose drawn yaw rate of the vehicle is dependent, a method for calibrating a yaw rate measurement in a motor vehicle is also presented. The method is executed during vehicle operation. The motor vehicle has at least one device for determining the yaw rate, a steering angle sensor and a forward-looking camera system which detects the vehicle surroundings in the direction of travel. For detecting the yaw rate with a high accuracy, at least a first calibration of the measured yaw rate at standstill and at least a second calibration while driving is performed.

The Standstill detection of the vehicle may e.g. done using a speed measurement. Alternatively you can also the position of the handbrake (activated or not), the position the shift lever (gear engaged or not), the wheel speed u.s.w. serve as an indicator. The indicators can also be arbitrary with each other connected become. For example, a standstill of the vehicle is assumed if no gear is engaged and the handbrake is activated. Changes the yaw rate is strong within a given time interval, it is assumed that the vehicle is moving. In a preferred Embodiment of the invention are at a calibration during the Ride the image data used at least one image recorder, wherein the image sensor detects the environment in front of the motor vehicle and predicted a lane. From the course of the lane is a straight-ahead or cornering of the vehicle estimated and derived from it the yaw rate of the vehicle.

In A particular embodiment of the invention is for a calibration while the travel of the steering angle used. This is especially the case if an estimate the yaw rate from a camera image is unsuccessful.

In A preferred embodiment of the invention is at standstill the vehicle an average of yaw rate over a period of time is made, and the averaged value as a correction value in the future Measurements are included. at the averaging will be the first and last values and the values a big Deviation from the adjacent measured values have not been considered.

In a preferred embodiment of the invention, the output value of Yaw rate is compensated in several steps. A connection the correction value in small increments within a given Time interval is particularly useful if the correction value exceeds a predetermined value.

As well instead is a continuous correction of the output values possible in a given time interval to a temperature-dependent drift to compensate for the yaw rate signal.

According to the invention is a Sensor for environmental detection in a motor vehicle with an in an evaluation unit deposited method for determining the Wank angles as described previously. In the evaluation the sensor data, the determined roll angle is taken into account. If the roll angle of the vehicle is e.g. uneven during a turn Zero, the direction of the sensor system also corresponds to the vehicle environment is no longer the originally set viewing direction. The lane would incorrectly predicated in this case and a detected environment object would be particularly in the far field (Distance to the vehicle> 70 m) assigned a faulty position. With the knowledge of Wankwinkels can the sensor data will be corrected. In a preferred embodiment According to the invention, the sensor is a camera system.

The Invention will be described below with reference to embodiments and figures explained in more detail.

1 : Model of a motor vehicle in cornering

2 : Schematic representation of a method for calibrating the yaw rate sensor.

In 1 is a model of a motor vehicle shown in cornering. The body of the vehicle is modeled as a mass m shown. The mass m is rigid with a device 1 connected. The device 1 is over two springs 3 . 4 with a device 2 connected representing the axles and wheels of the vehicle. If no external forces act, the mass m is at rest and the roll angle φ is equal to zero. Now attacks the mass m a horizontally acting force F, as is the case for example when cornering, the mass m and thus the device 1 deflected. contraption 2 remains stationary, or the wheels of a motor vehicle retain the grip. The feathers 3 . 4 are stretched and create a restoring moment M _F on the mass m. The restoring moment M _F is proportional to the roll angle φ. The proportionality factor is referred to as roll stiffness C. The sum of the torques acting on the mass m gives zero in the equilibrium case. The torque of the applied force is M _Z = F * h. H is the distance between the center of articulation and the center of rotation of the vehicle. The torques acting on the mass m are thus represented by the relation F _Z h -M _F = 0.

Der Kurvenradius r kann durch die Gierrate ω_z und die Fahrzeuggeschwindigkeit v_x ersetzt werden r = v/ω, so dass der Wankwinkel nunmehr mit der Kenntnis der Fahrzeugeigenschaften der Geschwindigkeit in Längsrichtung v_x und der Gierrate ω_z berechnet werden kann

Eine Berechnung des Wankwinkels

in Abhängig von der Querbeschleunigung a_y des Fahrzeugs ist mit der Relation a_y=vω_z gegeben Die Genauigkeit der Bestimmung des Wankwinkels hängt in einem hohen Maß von der Genauigkeit der Gierrate bzw. der Querbeschleunigung ab. Es wird ein weiteres Ausführungsbeispiel gegeben, das ein Verfahren zur Kalibrierung des Gierratensensors während der Fahrt vorstellt. In 2 ist das Verfahren schematisch dargestellt. Nach dem Start des Verfahrens wird zunächst der Bewegungszustand des Fahrzeugs geprüft. Befindet es sich im Stillstand, so wird die dafür vorgesehene Stillstandskalibrierung durchgeführt. Ergibt sich dabei ein Korrekturwert, so wird der Ausgabewert der Gierrate in der Kompensationsstufe entsprechend angepasst. Befindet sich das Fahrzeug nicht im Stillstand wird eine Onlinekalibrierung durchgeführt. Dazu werden die Bilddaten zumindest eines Bildaufnehmers verwendet. Der Bildaufnehmer erfasst die Umgebung vor dem Kraftfahrzeug und aus dem Verlauf der Fahrspur wird eine Geradeausfahrt oder Kurvenfahrt des Fahrzeugs und damit die Gierrate abgeschätzt. Z.B. wird eine Geradeausfahrt erkannt, wenn das Fahrzeug eine vorgegebene Geschwindigkeit überschreitet. Diese Geschwindigkeit liegt in diesem Beispiel zwischen 80 und 100 km/h. Ein weiterer Indikator für eine Geradeausfahrt ist, wenn die Krümmung der prädizierte Fahrspur einen vorgegebenen Radius überschreitet. Ein solcher vorgegebener Radius beträgt in diesem Beispiel 2000 m. Anhand der genannten Indikatoren Fahrzeuggeschwindigkeit, Krümmungsradius der Fahrspur wird abgeleitet, ob das Fahrzeug aktuell eine Geradeausfahrt ausführt. Es ist für den Fachmann ersichtlich, dass in weiteren Ausführungsbeispielen andere Indikatoren, wie z.B. die Querbeschleunigung und/oder Lenkwinkel, und andere vorgegebene Grenzwerte angegeben werden können. Eine Kalibrierung wird durchgeführt, wenn eine Geradeausfahrt festgestellt wurde. Dazu wird innerhalb eines vorgegebenen Zeitintervalls, das i. d. R. eine oder wenige Minuten beträgt, die Gierrate aufgenommen, gemittelt und es wird ein Korrekturwert bestimmt. Ist der Krümmungsradius der Fahrspur z.B. aufgrund schlechter Witterungsverhältnisse oder schlechter Fahrbahnmarkierungen nicht möglich wird nur die Stillstandkalibrierung verwendet. In einem weiteren Ausführungsbeispiel der Erfindung wird in diesem Fall der Lenkwinkel und/oder die Querbeschleunigung zur Onlinekalibrierung verwendet. Der Ausgabewert der Gierrate wird in mehreren Schritten kompensiert, so dass erst nach einem vorgegebenen Zeitintervall von wenigen Sekunden bis Minuten der Ausgabewert vollständig korrigiert ist.In the case of cornering, the attacking force can be described with the relation F _Z = mv ² / r, where v is the speed of the vehicle and r is the radius of the curve. This results in the roll angle φ the relation

The curvature radius r can be obtained by the yaw rate _z ω and the vehicle speed v _x be replaced r = v / ω, so that the roll angle _z can now be calculated with knowledge of the properties of the vehicle to the longitudinal speed v _x and the yaw rate ω

A calculation of the roll angle

in Depending on the lateral acceleration a _y of the vehicle is connected to the relation a = _{y z} vω Given the precision of the determination of the roll angle depends to a large extent on the accuracy of the yaw rate or the lateral acceleration. A further embodiment is presented, which presents a method for calibrating the yaw rate sensor while driving. In 2 the method is shown schematically. After the start of the method, first the state of motion of the vehicle is checked. If it is at a standstill, the dedicated standstill calibration is performed. If a correction value results, the output value of the yaw rate in the compensation stage is adjusted accordingly. If the vehicle is not at a standstill, an online calibration is performed. For this purpose, the image data of at least one image recorder are used. The image sensor detects the environment in front of the motor vehicle and from the course of the lane a straight-ahead or cornering of the vehicle and thus the yaw rate is estimated. For example, a straight-ahead driving is recognized when the vehicle exceeds a predetermined speed. This speed is in this example between 80 and 100 km / h. Another indicator of straight-ahead driving is when the curvature of the predicated lane exceeds a given radius. Such a given radius is 2000 m in this example. Based on the above-mentioned indicators vehicle speed, radius of curvature of the lane is derived whether the vehicle is currently running a straight ahead. It will be apparent to those skilled in the art that other indicators, such as lateral acceleration and / or steering angle, and other predetermined limits may be provided in other embodiments. Calibration is performed when a straight-ahead travel has been detected. For this purpose, within a predetermined time interval, which is generally one or a few minutes, the yaw rate is recorded, averaged and a correction value is determined. If the radius of curvature of the lane is not possible due to bad weather conditions or poor road markings, for example, only standstill calibration is used. In a further embodiment of the invention, the steering angle and / or the lateral acceleration is used for online calibration in this case. The output value of the yaw rate is compensated in several steps, so that the output value is completely corrected only after a predetermined time interval of a few seconds to minutes.

Claims (14)

Method for determining the roll angle for a motor vehicle having at least one device for determining the yaw rate or a variable correlated therewith, a device for determining the vehicle speed, characterized in that the roll angle is determined using the yaw rate or a variable correlated therewith and the specific roll stiffness of the vehicle becomes. Method according to claim 1, characterized in that that one of the yaw rate correlated magnitude is either the lateral acceleration or the steering angle is. Method according to one of the preceding claims, characterized characterized in that the vehicle is modeled as a mass point (m) with a height (h) over the vehicle axles is assumed and the assumed mass point (m) by an angle (φ) directly proportional to the attacking Power is deflected. Method according to one of the preceding claims, characterized characterized in that as an attacking force the centripetal force when cornering acts, the centripetal force from the Yaw rate or a correlated size is calculated. Method according to one of the preceding claims, characterized in that

where φ is the roll angle, m is the mass of the vehicle, h is the height of the mass point, ν _{x is} the velocity in the x direction, ω _{z is} the yaw rate of the vehicle, and C is the roll stiffness of the vehicle. Method according to one of the preceding claims, characterized in that

where ν is the roll angle, m is the mass of the vehicle, h is the height of the mass point, α _{y is} the lateral acceleration of the vehicle, and C is the roll stiffness of the vehicle. Method according to one of the preceding claims, characterized in that

where φ is the roll angle, m is the mass of the vehicle, h is the height of the mass point, ν _{x is} the speed in the x direction, α _{LW is} the steering angle of the vehicle, and C is the roll stiffness of the vehicle. Method according to one of the preceding claims, characterized in that a method for calibrating the yaw rate measurement is provided, with a first calibration at a standstill and a second calibration during the ride is done, Method according to claim 8, characterized in that that the motor vehicle comprises a forward facing camera system and when calibrating the yaw rate while driving, the image data of the Camera system used, the camera system surrounding recorded in front of the vehicle and from the course of the lane (straight ahead, Cornering) the yaw rate is estimated. Method according to one of the preceding claims 8 or 9, characterized in that for a calibration of the yaw rate while the ride the steering angle is used, especially if a appraisal the yaw rate from a camera image is unsuccessful. Method according to one of the preceding claims 8 or 9, characterized in that at standstill of the vehicle a Averaging the yaw rate values over a certain period of time, and the averaged value is taken into account as a correction value of the yaw rate. Method according to one of the preceding claims 8-11, characterized in that the output value of the yaw rate in several Steps is compensated when a correction value has been determined. Sensor for environmental detection in a motor vehicle with a method of determination stored in an evaluation unit of the roll angle according to one of the preceding claims, wherein in the evaluation taken into account the recorded image data of the determined roll angle becomes. Sensor according to claim 13, characterized that the sensor is a camera system.