Method for calibrating inertial measurement sensor system of vehicle

Abstract

The invention relates to a method for calibrating an inertial measurement sensor system (2) of a vehicle (1), in which a calibration is carried out during the travel of the vehicle (2), and the calibration is carried out on the basis of a determination of an orientation error of a sensor coordinate system of the inertial measurement sensor system (2) relative to a vehicle coordinate system. According to the invention, the determination of the orientation error is interrupted in the event that a level deviation from a reference level is detected by at least one vehicle-own level sensor that exceeds a predetermined threshold value. The invention also relates to a method for adjusting the light illumination range of at least one headlamp of a vehicle (1).

Description

Technical Field

[0001] The invention relates to a method for calibrating an inertial measurement sensor system of a vehicle according to the preamble of claim 1 .

[0002] The invention also relates to a method for adjusting the light coverage of at least one headlight of a vehicle. Background Art

[0003] As is known, inertial measurement sensor systems based on MEMS (MEMS = Micro Electro Mechanical Systems) are installed in vehicles as speed sensors (Drehratensensor) to measure the speed and as accelerometers or acceleration sensors to measure the acceleration of the vehicle in up to three spatial directions. Inertial measurement sensor systems are used in various vehicle systems, such as vehicle dynamic control systems, modern applications of augmented reality technology, and assisted or automated driving.

[0004] However, such inertial measurement sensor systems may have errors in their detection, which may limit the usability or achievable system accuracy in many applications where these detection results are used. Such sensor errors include, for example, incorrect orientation of each inertial measurement sensor system relative to the vehicle and offset errors of each measurement axis. The offset error is an inherent error of the inertial measurement sensor system, which is reflected not only in the output of the current acceleration or speed, but also in the following formula:

[0005] x 测量 = x 实际 +x 偏移 (t) (1),

[0006] Measured value x 测量 Relative to the actual value x 实际 With a constant, slowly varying offset x 偏移 (t).

[0007] As is known, this offset error is determined inside the vehicle by comparing the measured values ​​over a long period of time. It is assumed that over a relatively long period of time, the sum of the accelerations (because the vehicle starts at 0 km / h and stops at 0 km / h) and the sum of the rotational speeds (because the vehicle does not turn upside down or roll over) is equal to zero. Therefore, the deviation of the measured values ​​must mainly come from the offset component x of the inertial measurement sensor system. 偏移估计 , so the offset component can also be estimated and according to the following formula:

[0008] x 测量 = x 实际 +x 偏移 (t)-x 偏移估计 ≈x实际 (2)

[0009] This offset component is subtracted from future measurements.

[0010] However, external influences (e.g. changes in the vehicle attitude due to changes in the pitch or roll angle) may result in these assumptions no longer being valid. Furthermore, since the vehicle can theoretically be in static, infinite circular motion, it is also not possible to reliably determine the offset of the yaw rate in the manner mentioned. Therefore, information from other sensors (e.g. wheel speed sensors) must be consulted to obtain a reference value for the existing yaw situation.

[0011] Since the orientation error (Fehlausrichtung, position offset / misalignment) of the inertial measurement sensor system relative to the vehicle coordinate system leads to the influence of the gravity offset, attempts have been made to compensate for the influence of the sensor installation position by means of offset error estimation. Since the gravity is known from the vehicle's position on the earth, the excess acceleration component at rest is related to the offset. However, since the offset can vary greatly for each sensor axis, it is not possible to completely correctly compensate for the gravity and thus determine the offset.

[0012] For a more precise and comprehensive calibration of the individual IMS systems, special measurement setups are required that apply predefined accelerations and rotational speeds to the IMS systems for offset calibration and provide a tared horizontal surface where both the gravity acceleration direction and the vehicle acceleration direction are defined in the vehicle coordinate system for orientation calibration. The IMS systems can thus be virtually rotated accordingly, but this is very time-consuming and costly.

[0013] DE 10 2005 033 237 A1 discloses a method for determining an orientation error of a sensor in a sensor cluster of a vehicle. The sensor cluster has three linear acceleration sensors or three rotational speed sensors. The desired installation orientation of the sensors with respect to the coordinate axes of a Cartesian coordinate system fixed to the vehicle is predetermined, wherein the actual installation orientation of the sensors may deviate from the desired installation orientation due to the orientation error. The actual installation orientation of the sensors is determined by comparing the values ​​measured by the sensors under different conditions with the values ​​known for these different conditions in the Cartesian coordinate system fixed to the vehicle.

[0014] DE 10 2015 115 282 A1 discloses a method for determining the orientation of an inertial measurement sensor system of a vehicle with respect to a vehicle coordinate system, wherein a first sensor signal of the inertial measurement sensor system is detected in a state of no acceleration of the vehicle, wherein a second sensor signal of the inertial measurement sensor system is detected in a state of linear acceleration of the vehicle, and wherein the orientation is determined based on the first sensor signal and the second sensor signal, wherein the first sensor signal is used to find the vertical orientation of the inertial measurement sensor system as a function of the gravitational acceleration, and the second sensor signal is used to determine a rotation of the inertial measurement sensor system about a vertical axis of the vehicle.

[0015] DE 10 2004 045 890 A1 discloses a method for calibrating an inertial measurement sensor system of a vehicle, wherein the inertial measurement sensor system is designed as a single acceleration sensor for measuring the vertical acceleration of the vehicle. It is proposed that the yaw state of the vehicle is determined when the vehicle is stationary and stored as a reference value. The yaw state of the vehicle is determined continuously while the vehicle is moving and the stationary value of the single acceleration sensor is adjusted to a predetermined value as soon as the measured yaw state corresponds to the yaw state stored as a reference value.

[0016] A method for adjusting a vehicle low beam is known from CN 1 08 819 831 A, wherein a light adjustment unit is provided, which receives acceleration data and angular velocity data from an inertial measurement sensor system and receives vehicle information via a data bus. The light adjustment unit determines the pitch angle of the vehicle based on the received information and adjusts the illumination distance of the low beam based on the pitch angle.

[0017] A method for determining an inclination state of a vehicle relative to a road surface is known from WO 2017 / 129 199 A1, wherein the determination is carried out using an inclination model based on measured values ​​and wherein the measured values ​​are determined using an inertial measurement sensor system.

[0018] US 2013 / 0 166 099 A1 discloses a method for monitoring a vehicle condition, wherein an inertial measurement sensor system is used to detect measured values ​​during travel of the vehicle and sample them over a period of time, and wherein a rotation matrix is ​​determined from the measured values, which represents the offset between the orientation of the inertial measurement sensor system and the actual vehicle orientation.

[0019] EP 3 171 134 A1 discloses a method for calibrating an inertial measurement sensor system of a vehicle, wherein sensor data of the inertial measurement sensor system are detected at two stationary positions of the vehicle in different vehicle orientations, and wherein sensor data of the inertial measurement sensor system are also detected when driving straight ahead at a constant speed, when turning right and when turning left, and wherein orientation errors and offsets with respect to a vehicle coordinate system are determined based on the detected sensor data. Summary of the invention

[0020] The object of the present invention is to provide a novel method for calibrating an inertial measurement sensor system of a vehicle and a novel method for adjusting the light coverage of at least one headlamp of a vehicle.

[0021] According to the invention, this object is achieved by a method for calibrating an inertial measurement sensor system of a vehicle having the features specified in claim 1 and a method for adjusting the light coverage of at least one headlight of a vehicle having the features specified in claim 10 .

[0022] Advantageous embodiments of the invention are the subject matter of the dependent claims.

[0023] In the method for calibrating an inertial measurement sensor system of a vehicle according to the invention, calibration is performed during driving of the vehicle, wherein the calibration is performed based on the determination of an orientation error of a sensor coordinate system of the inertial measurement sensor system relative to a vehicle coordinate system, wherein the determination of the orientation error is interrupted when a horizontal deviation relative to a reference level exceeding a predetermined threshold is detected by at least one vehicle-specific horizontal sensor.

[0024] In order to be able to provide an inertial measurement sensor system based on an acceleration sensor with the correct angle between the vehicle and the driving surface (e.g. the road surface), information about the installed inertial measurement sensor system is required. Depending on the sensor package, the mounting position on the circuit board and the orientation of the corresponding control unit in the vehicle, different accelerations (e.g. rotational acceleration) are measured. These measurements must be rotated back to the vehicle body direction, i.e. the vehicle coordinate system, internally using information from previous calibration. Since the method can distinguish between the vehicle pitch angle and the sensor installation rotation angle (both have the same influence on the measurement), the inertial measurement sensor system can be calibrated automatically and spontaneously by means of the method. This eliminates the need for cost-intensive and time-consuming calibration under controlled conditions, in which the vehicle pitch angle or the sensor installation rotation angle must be known and the calibration cannot be performed on site. This is particularly advantageous when manufacturing vehicles in the factory or replacing sensors, because such cost-intensive and time-consuming calibration under controlled conditions can be omitted.

[0025] By means of the method, the calibration process can be greatly simplified by using the vehicle's own level sensor (e.g. mounted on the rear axle of the vehicle) to control the calibration. Thus, after vehicle manufacture or sensor replacement, a self-calibration procedure can be started which attempts to identify the installation position of the inertial measurement sensor system relative to the vehicle body plane (i.e. relative to the vehicle coordinate system) in the following driving situation. The static rotation between the vehicle coordinate system (in particular the plane defined by the transverse and longitudinal axes of the vehicle) and the sensor coordinate system (in particular the plane defined by the transverse and longitudinal axes of the sensor) can now be calculated iteratively.

[0026] The method thus makes it possible to control the automatic online calibration of an inertial measurement sensor system in a vehicle according to clear and understandable criteria and prevent undefined scenarios from influencing the calibration result (e.g., static pitch and / or roll angle changes). Depending on the expansion stage of the respective inertial measurement sensor system, for example characterized by the number of measuring axes of the acceleration sensors and the rotational speed sensors of the inertial measurement sensor system, various error components, i.e., orientation errors and offsets of the sensor coordinate system, can be calibrated. No additional hardware components are required for this purpose, which reduces material and cost expenditures and reduces the installation space requirements.

[0027] In one possible embodiment of the method, the calibration is performed within a predetermined time period while the vehicle is traveling.

[0028] In one possible embodiment of the method, a static pitch angle is determined as a function of the orientation of the longitudinal axis of the sensor coordinate system relative to the longitudinal axis of the vehicle coordinate system, based on which an orientation error of the sensor coordinate system relative to the vehicle coordinate system is determined. Based on the static pitch angle, vehicle situations that have a significant influence on error sources in the calibration can be determined in a simple and reliable manner and can therefore be reliably excluded in the calibration.

[0029] In another possible embodiment of the method, the vehicle coordinate system is defined in such a way that a plane defined by the transverse axis and the longitudinal axis of the vehicle extends parallel to the driving surface plane under predetermined normal conditions.

[0030] In another possible embodiment of the method, the acting gravitational acceleration is estimated based on the determined orientation of the sensor coordinate system using map data of a digital road map, in particular the geographic height and the road inclination, and using the inclination of the vehicle relative to the driving surface. During the driving of the vehicle, the acceleration measured by the inertial measurement sensor system is compared with the estimated gravitational acceleration in a time period without further acceleration, and an offset of the inertial measurement sensor system with respect to the acceleration measurement value is determined based on the comparison result. In this way, the offset of the inertial measurement sensor system with respect to the acceleration measurement value can be determined particularly reliably and accurately.

[0031] In another possible embodiment of the method, a check is made based on map data of a digital road map to see whether the inclination of the driving surface has changed in the predetermined section, and an optical environment detection sensor system is used to check whether the contour of the driving surface has changed in the predetermined section by no more than a predetermined threshold value. The rotation of the vehicle in space is determined by an inertial measurement sensor system, and the relative rotation of the vehicle with respect to the driving surface is determined by a level sensor. If the inclination of the driving surface has not changed and the contour of the driving surface has not changed by more than a predetermined threshold value, the offset of the rotation speed sensor of the inertial measurement sensor system is determined by comparing the rotation determined by the inertial measurement sensor system with the relative rotation determined by the level sensor. In this way, the offset of the rotation speed sensor of the inertial measurement sensor system can be determined particularly reliably and accurately.

[0032] In a further possible embodiment of the method, the calibration is carried out on the basis of the detection and evaluation of a plurality of values ​​of the longitudinal acceleration and the transverse acceleration of the vehicle over a predetermined period of time, whereby the calibration can be carried out particularly easily and reliably.

[0033] In another possible embodiment of the method, long-term average values ​​are formed from the detected values ​​of the longitudinal acceleration and the transverse acceleration of the vehicle, and the calibration is performed based on these long-term average values. This further simplifies the method.

[0034] In a further possible embodiment of the method, the calibration is carried out on the basis of at least one learning algorithm, so that it is automatically possible to adapt to different situations of the vehicle, so that the calibration is optimized.

[0035] In the method according to the invention for adjusting the light illumination range of at least one headlamp of a vehicle, the inertial measurement sensor system is calibrated according to the above method, the orientation of the vehicle relative to the driving surface is determined by the calibrated inertial measurement sensor system, and the light illumination range of the headlamp is adjusted according to the determined orientation. The method of calibrating the inertial measurement sensor system and using it for adjusting the light illumination range can compensate for changes in the light illumination range caused by vehicle acceleration. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Embodiments of the present invention are explained in more detail below with reference to the accompanying drawings.

[0037] in:

[0038] Figure 1 A vehicle, a vehicle coordinate system, a sensor coordinate system and a driving surface with a ground coordinate system are schematically shown, and

[0039] Figure 2 The learning curve for the sensor mounting angle is schematically shown.

[0040] In all the figures, parts which correspond to one another are provided with the same reference numerals. DETAILED DESCRIPTION

[0041] Figure 1 A vehicle 1 , in particular a land vehicle, a Cartesian vehicle coordinate system, a Cartesian sensor coordinate system and a driving surface, in particular a driving surface plane E, with a Cartesian ground coordinate system are shown.

[0042] The vehicle coordinate system is fixed on the body of the vehicle 1 and has a horizontal axis y v , vertical axis x v and the vertical axis z v The origin of the vehicle coordinate system is located in particular at the center of gravity of the vehicle 1. The vertical axis z v The normal vectors parallel to the floor and roof of the car point upward, and the longitudinal axis x v parallel to the longitudinal axis of the vehicle and perpendicular to the aforementioned normal vector, and the horizontal axis y v Parallel to the vehicle's transverse axis and also perpendicular to the above normal vector.

[0043] The ground coordinate system also has a horizontal axis y E , vertical axis x E and the vertical axis z E .

[0044] The sensor coordinate system is assigned to inertial measurement sensor system 2 of vehicle 1 and likewise has a transverse axis y, a longitudinal axis x and a vertical axis z.

[0045] An orientation error of an inertial measurement sensor system 2, which is used, for example, for operating an anti-lock braking system, a vehicle dynamics control system and / or other applications, is caused by a rotation of the sensor coordinate system relative to the vehicle coordinate system. Causes thereof are, for example, orientation errors of the sensor axes in the sensor package of the inertial measurement sensor system 2 by the sensor manufacturer, orientation errors on the circuit board of the control unit of the inertial measurement sensor system 2, assembly distortions in the housing of the control unit or distortions in the connection of the housing of the inertial measurement sensor system 2 to the vehicle body. In practice, all components simultaneously cause an orientation error of the inertial measurement sensor system 2 relative to the vehicle coordinate system.

[0046] The rotation of the inertial measurement sensor system 2 describing the orientation error can be described by a sequence of three rotations Θ, Φ, Ψ, which can be regarded as the roll angle, pitch angle and yaw angle. However, various dynamic control and tasks of the vehicle (e.g., vehicle dynamic control systems) require accelerations in the vehicle coordinate system in order to be able to perform correct calculations.

[0047] In order to operate the inertial measurement sensor system 2 reliably and accurately, calibration is required, wherein the error sources of the inertial measurement sensor system 2 to be detected in the calibration are mainly: the orientation error of the sensor coordinate system relative to the vehicle coordinate system due to packaging, installation and assembly, the offset of the acceleration sensor of the inertial measurement sensor system 2, and the offset of the rotation speed sensor of the inertial measurement sensor system 2. Through calibration, the inertial measurement sensor system 2 can be rotated back to the orientation of the vehicle 1, that is, the orientation of the vehicle coordinate system.

[0048] It is assumed that all sensor axes (lateral axis y, longitudinal axis x, vertical axis z) of inertial measurement sensor system 2 are perpendicular to each other and the coordinate system of the rotational speed sensor of inertial measurement sensor system 2 coincides with the coordinate system of the acceleration sensor of inertial measurement sensor system 2 .

[0049] The current calibration concept is, for example, to evaluate the direction of the acceleration occurring on the vehicle 1. For the basic calibration, a basic state of the vehicle 1 is defined for calibration. In particular, this basic state is characterized by the presence of an adult driver in the vehicle 1 and a half-full fuel tank. Other situations of large loads and passengers are now detected by at least one level sensor mounted on the axle A1, A2 of the vehicle 1 and, for example, by seat occupancy mats and are excluded from the calibration.

[0050] This means that in the automatically controlled calibration of the inertial measurement sensor system 2, the rotation state of the vehicle 1 is detected with the aid of at least one level sensor, not shown in detail. Therein, the orientation error and the offset of the sensor coordinate system of the inertial measurement sensor system 2 are determined, and the calibration is performed within a predetermined time period during driving of the vehicle 1. In the calibration, the orientation error of the sensor coordinate system relative to the vehicle coordinate system is determined, wherein during driving, the determination of the orientation error is interrupted if a level deviation from a reference level exceeding a predetermined threshold is detected by means of the vehicle's own level sensor.

[0051] The orientation error of the sensor coordinate system relative to the vehicle coordinate system is determined as a function of the static pitch angle α, which is the angle between the longitudinal axis x of the sensor coordinate system and the longitudinal axis x of the vehicle coordinate system. v For details, see Figure 2 As mentioned above, the vehicle coordinate system is defined as: under normal conditions (ie, when the vehicle is normally loaded, for example), the longitudinal axis x v and the horizontal axis y vThe defined plane extends parallel to the driving plane E. Therefore, the actual static pitch angle α is equal to zero. The pitch angle α is measured in the sensor coordinate system. If the measured static pitch angle α is not equal to zero, there is a rotation of the sensor coordinate system relative to the vehicle coordinate system. In this case, the measured static pitch angle α indicates how many degrees the sensor coordinate system is rotated about the pitch axis relative to the vehicle coordinate system. The pitch angle α therefore corresponds to the longitudinal axis x of the sensor coordinate system relative to the longitudinal axis x of the vehicle coordinate system. v orientation error.

[0052] In addition, the above information can be combined with high-precision map data to obtain an estimate of the gravitational acceleration acting through the current geographical altitude, the inclination of the driving surface, and the inclination of the vehicle relative to the driving surface. Thus, the acceleration measured by the inertial measurement sensor system 2 can be compared with the estimated gravitational acceleration during a period of time without further acceleration, so as to obtain the offset of the acceleration sensor of the inertial measurement sensor system 2 according to the measured acceleration = gravity + vehicle acceleration + inertial force + offset.

[0053] The time period without further acceleration can be detected, for example, by wheel speed sensors and wheel steering angles, it being assumed that there is no vehicle acceleration at constant wheel speeds and that no inertial forces are present if the level sensor detects no wheel steering angle and no rotational change.

[0054] Furthermore, the body rotation measured by the speed sensor and the level sensor can be compared. It must be noted that the two systems measure different rotations. The speed sensor measures the complete rotation of the vehicle 1 in space, while the level sensor only measures the relative rotation relative to the driving ground plane E.

[0055] Therefore, for the purpose of comparison, it must be ensured that the inclination of the driving plane E does not change and that the surface of the driving plane E does not have large contour changes, for example due to bumps and / or potholes. Movements that meet these criteria are pitch and roll movements of the vehicle 1 that are purely caused by acceleration and by braking. It is then possible to check whether the inclination of the driving plane E is constant in a given road section based on the high-precision map data. The flatness of the surface of the driving plane E is checked using data from an optical environment detection sensor system (e.g., a camera and / or a lidar). Only if these conditions are met are the measured values ​​used for the offset calibration of the rotational speed sensor of the inertial measurement sensor system 2.

[0056] Here, the cost can be minimized based on the existing inertial measurement sensor system 2 that is already used in the vehicle 1 for a vehicle dynamics control system and other driver assistance systems, for example, and an appropriate combination can be selected based on the accuracy and redundancy required by the system.

[0057] Figure 2 The learning curve of the sensor installation angle, in particular the pitch angle α, is shown as a function of the driving time t. In addition, regions B1 to Bn are shown in which the value of the level sensor is used to interrupt the calibration as described above, thereby interrupting the learning process of the pitch angle α during the driving of the vehicle 1.

[0058] This means that in the event of a change in the chassis conditions of the vehicle 1 , for example in the event of a heavy load and thus a static, constant pitch angle α, which would otherwise be included in the calibration, the calibration process is suspended.

[0059] Other error sources include, for example, the tension of the vehicle when braking or parking on a steep slope, which can also lead to a static pitch angle α. These situations can also be effectively detected using the information from the level sensor.

Claims

1. A method for calibrating an inertial measurement sensor system (2) of a vehicle (1), wherein the calibration is performed while the vehicle (2) is moving and the calibration is performed based on the determination of an orientation error of a sensor coordinate system of the inertial measurement sensor system (2) relative to a vehicle coordinate system, It is characterized in that In the event that a level deviation from a reference level exceeding a predetermined threshold is detected by at least one vehicle-specific level sensor, the determination of the orientation error is interrupted.

2. The method according to claim 1, It is characterized in that According to the longitudinal axis (x) of the sensor coordinate system relative to the longitudinal axis (x) of the vehicle coordinate system v ) is determined based on the orientation of the sensor coordinate system, and the orientation error of the sensor coordinate system relative to the vehicle coordinate system is determined based on the static pitch angle.

3. The method according to claim 1 or 2, It is characterized in that The vehicle coordinate system is defined as: the horizontal axis (y v ) and the vertical axis (x v ) extends parallel to the driving ground plane (E) under predetermined normal conditions.

4. The method according to any one of the preceding claims, It is characterized in that - based on the determined orientation of the sensor coordinate system, estimating the acting gravitational acceleration from map data of a digital road map, in particular the geographical altitude and the road inclination, and from the inclination of the vehicle (1) relative to the driving plane (E), - during the travel of the vehicle (1), during a period without further acceleration, comparing the acceleration measured by the inertial measurement sensor system (2) with the estimated gravitational acceleration, and - Determining an offset of the inertial measurement sensor system (2) with respect to the acceleration measurement value based on the comparison result.

5. The method according to any one of the preceding claims, It is characterized in that - checking whether the inclination of the driving surface (E) in the predetermined section has changed based on the map data of the digital road map, and checking by means of an optical environment detection sensor system whether the contour change of the driving surface (E) in the predetermined section has not exceeded a predetermined threshold value, - Determine the position of the vehicle (1) in space by means of the inertial measurement sensor system (2) The rotation in - determining the relative rotation of the vehicle (1) with respect to the driving plane (E) by means of the level sensor, and - If the inclination of the driving surface (E) does not change and the contour of the driving surface (E) does not change by more than the predetermined threshold value, the offset of the rotation speed sensor of the inertial measurement sensor system (2) is determined by comparing the rotation determined by the inertial measurement sensor system (2) with the relative rotation determined by the horizontal sensor.

6. The method according to any one of the preceding claims, It is characterized in that The calibration is performed within a predetermined time period during the driving of the vehicle (2).

7. The method according to claim 6, It is characterized in that The calibration is performed based on the detection and evaluation of a plurality of values ​​of the longitudinal acceleration and the lateral acceleration of the vehicle (1) during the predetermined period of time.

8. The method according to claim 7, It is characterized in that A long-term average value is formed from the detected values ​​of the longitudinal acceleration and the lateral acceleration of the vehicle (1), and the calibration is performed based on the long-term average value.

9. The method according to any one of the preceding claims, It is characterized in that The calibration is performed based on at least one learning algorithm.

10. A method for adjusting the light coverage of at least one headlamp of a vehicle (1), wherein - calibrating an inertial measurement sensor system (2) according to the method of any of the preceding claims, - determining the orientation of the vehicle (1) relative to the driving surface (E) by means of the calibrated inertial measurement sensor system (2), and - adjusting the light coverage of the headlight as a function of the determined orientation.

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