Device and method for setting the angular position of the optical axis of a motor vehicle headlamp

Abstract

The invention proposes a device for setting the angular position of the optical axis of a headlamp of a motor vehicle, wherein the pitch angle is determined from the signals of at least one MEMS acceleration sensor. The device is characterized in that the MEMS acceleration sensor is an integral part of the control device of the headlamp, which has a pitch angle adjustment motor arranged for adjusting the angular position of the optical axis. The device is arranged to determine the longitudinal acceleration of the motor vehicle using the MEMS acceleration sensor and to use this longitudinal acceleration together with a calculation model for driving the pitch angle adjustment motor. One independent claim relates to a corresponding method.

Description

Technical Field

[0001] This invention relates to an apparatus for setting the angular position of the optical axis of a motor vehicle's headlights, as described in the preamble of claim 1. The angular position depends on the vehicle's static pitch angle, which is generated when the vehicle is stationary on a road or moving linearly at a constant speed on a road. The static pitch angle is determined from a signal from at least one MEMS accelerometer sensor, and this static pitch angle depends on load distribution and road gradient.

[0002] The present invention also relates to a method for setting the angular position of the optical axis of a motor vehicle headlight, wherein the angular position depends on a static pitch angle generated when the motor vehicle is stopped on a road or moving in a straight line at a constant speed on a road, and wherein the static pitch angle is determined from a signal from at least one MEMS accelerometer sensor. Background Technology

[0003] This device and method are known from US8838343B2. The position of a motor vehicle in space is described using variables namely pitch angle, roll angle, and yaw angle. These variables are defined in DIN ISO 8855:2013-11, Straßenfahrzeuge, Fahrzeugdynamik und Fahrverhalten, Begriffe, (ISO 8855:2011), Berlin: Beuth, 2013. The pitch angle describes the rotational deflection of the vehicle's longitudinal axis about its lateral axis. The roll angle describes the rotational deflection of the vehicle's lateral axis about its longitudinal axis. The yaw angle describes the rotational deflection of the vehicle's longitudinal axis about its vertical axis.

[0004] Since 1998, vehicle registration authorities have required compensation for the effects of load variations on the position of the optical axis of motor vehicle headlights. This aims to avoid glare to oncoming road users while providing the widest possible range of the low beam headlights. The device that performs this task is also known as a Vertical Aiming Control (VAC) device. Manual VAC devices are known, where the driver manually sets the position of the optical axis from the dashboard. Automatic VAC devices (AVAC) are also known, which compensate for static position changes of the optical axis that occur as a result of load variations. The aforementioned US8838343B2 uses a MEMS accelerometer sensor but is limited to compensating for static position changes.

[0005] Furthermore, dynamic AVAC devices are known to compensate for dynamic changes in the position of the optical axis that occur while a motor vehicle is in motion. These devices use deflection sensors to detect the position of the optical axis. This solution is already disadvantageous due to the associated cost of cabling for typically four deflection sensors. Summary of the Invention

[0006] In this context, the object of the present invention is to provide a device of the type mentioned at the beginning that allows for compensation of dynamic changes in the position of the optical axis without having to consider the cable laying costs associated with the use of a deflection sensor.

[0007] This objective is achieved using the features of the independent claim. The device according to the invention differs from the prior art mentioned at the beginning in that the MEMS accelerometer is a component of the control device for a motor vehicle's headlight, wherein the headlight has at least one optical module with an optical axis of the motor vehicle's headlight and a pitch angle adjustment motor configured to adjust the angular position of the optical axis, and wherein the control device is configured to determine the longitudinal acceleration of the motor vehicle from the acceleration detected by the MEMS accelerometer, multiply the longitudinal acceleration by a predetermined coefficient to obtain a product, add the product to a static pitch angle to obtain a total pitch angle, and set an angular position dependent on the total pitch angle by driving the pitch angle adjustment motor. In principle, the invention is applicable to all types of headlights for which a vertical setting device is specified. In the case of such headlights, the emission direction of the optical module is typically set.

[0008] The method according to the invention is characterized by using a MEMS accelerometer to detect the longitudinal acceleration of a motor vehicle and multiplying it by a predetermined coefficient to obtain a product, adding the product to a static pitch angle to obtain a total pitch angle, and setting an angular position dependent on the total pitch angle.

[0009] Regarding the device, it is preferable that the pitch angle adjustment motor is mechanically coupled to the optical module and configured to adjust the pitch angle position of the optical axis.

[0010] Preferably, the angular position depends on the static roll angle, which is generated when the vehicle is stopped on the road or moving linearly at a constant speed on the road, and wherein the static roll angle is determined from a signal from at least one MEMS accelerometer, and wherein the headlight has a roll angle adjustment motor configured to adjust the optical axis of the light module, and wherein the control device is configured to determine the lateral acceleration of the vehicle from the acceleration of the vehicle detected by the MEMS accelerometer, wherein the lateral acceleration of the vehicle is multiplied by a predetermined coefficient to obtain a product, wherein the product is added to the static roll angle to obtain a total roll angle, and wherein the angular position is set depending on the total roll angle.

[0011] Preferably, the roll angle adjustment motor is mechanically coupled to the optical module and configured to adjust the roll angle position of the optical axis.

[0012] Additionally, preferably, the device has a bus connection to another headlight, and the MEMS accelerometer is connected to the control device of the other headlight via the bus connection. The control device of the other headlight is configured to multiply the longitudinal acceleration of the motor vehicle detected by the MEMS accelerometer by a predetermined coefficient to obtain a product, add the product to the static pitch angle to obtain a total pitch angle, and set an angular position dependent on the total pitch angle by driving another pitch angle adjustment motor. Furthermore, the control device is configured to multiply the lateral acceleration of the motor vehicle detected by the MEMS accelerometer by a predetermined coefficient to obtain a product, add the product to the static roll angle to obtain a total roll angle, and set an angular position dependent on the total roll angle by driving another roll angle adjustment motor.

[0013] Another preferred design specifies that the accelerometer is an accelerometer that detects acceleration about two mutually perpendicular axes.

[0014] Preferably, the control device is configured to convert the acceleration detected by the accelerometer around two mutually perpendicular spatial directions into longitudinal acceleration and lateral acceleration.

[0015] In addition, preferably, the accelerometer is an accelerometer that detects acceleration along three mutually perpendicular spatial directions.

[0016] Regarding the design scheme of this method, it is preferred that the angular position also depends on the static roll angle, which is generated when the motor vehicle is stopped on the road or moving in a straight line at a constant speed on the road. The static roll angle is determined from the signal of at least one MEMS accelerometer. The lateral acceleration of the motor vehicle is detected using the MEMS accelerometer and multiplied by a predetermined coefficient to obtain a product. The product is added to the static roll angle to obtain the total roll angle, and the angular position is set depending on the total roll angle.

[0017] Further advantages arise from the following description, drawings, and dependent claims. It should be understood that, without departing from the scope of the invention, the features mentioned above, as well as those still described below, can be used not only in the correspondingly given combinations, but also in other combinations or individually.

[0018] Embodiments of the present invention are shown in the accompanying drawings and described in more detail in the following description. Attached Figure Description

[0019] Here, the accompanying diagrams are shown in schematic form:

[0020] Figure 1 The headlights of the motor vehicle are shown;

[0021] Figure 2 The relationship between the pitch angle and longitudinal acceleration for a low-pass filter with a fixed load distribution is shown.

[0022] Figure 3 An embodiment of a headlight with a roll angle adjustment motor for setting the angular position of the headlight's optical axis is shown;

[0023] Figure 4 The design of a device with a bus connection to another headlight is shown;

[0024] Figure 5 A flowchart illustrating an embodiment of a method according to the present invention for setting the pitch angle position of the optical axis of a motor vehicle headlight; and

[0025] Figure 6 A flowchart illustrating an embodiment of a method according to the present invention for setting the roll angle position of the optical axis of a motor vehicle headlight is shown. Detailed Implementation

[0026] In detail, Figure 1 A headlight 10 of a motor vehicle is shown, having a housing 12 whose light-emitting opening is covered by a transparent cover 14. The x-direction corresponds to the longitudinal direction of the motor vehicle, the y-direction corresponds to the lateral direction of the motor vehicle, and the z-direction corresponds to the vertical direction of the motor vehicle. This convention applies to all embodiments.

[0027] The headlight 10 has a light module 16, the optical axis 18 of which is the optical axis of the headlight 10. The light module 16, and therefore its optical axis 18, can pivot about the lateral direction y. This pivoting motion, for example, changes the height of the light and dark boundary of the low beam distribution generated by the light module 16. This height changes, for example, with the pitch angle Phi of the motor vehicle. The pitch angle Phi can change when the load of the motor vehicle changes (statically), for example, when the rear is lowered and the front is raised. The static pitch angle Phi_0 of the motor vehicle is generated when the motor vehicle is stationary on the road or moving in a straight line at a constant speed on the road.

[0028] The dynamic change in pitch angle Phi occurs during driving due to the dynamic axle load offset during braking and acceleration in the longitudinal direction.

[0029] The resulting angular position change of the optical axis 18 can be compensated by the reverse pivoting of the optical module 16 around the lateral direction y.

[0030] The headlight 10 has a device 20 for setting the angular position of the optical axis 18. The device 20 includes a MEMS accelerometer 22, which is known per se, arranged in the control device 28 of the headlight 10 along with a processor 24 and an output stage 26 according to the invention. The control device 28 specifically controls a pitch adjustment motor 30, which is coupled to the optical module 16 via a coupling rod and a joint such that the adjusting movement of the pitch adjustment motor 30 causes the optical module 16 to pivot about the y-direction. The pitch adjustment motor 30 is another component of the device 20 and is mechanically coupled to the optical module 16 and configured to adjust the pitch angle position of the optical axis 18.

[0031] The control device 28 is configured to determine the static pitch angle Phi_0 from the signal of at least one MEMS accelerometer 22. The MEMS accelerometer, for example, has an inert mass that is elastically suspended and provided with one or more electrodes. Depending on the deflection of this mass, the distance between one or more electrodes and one or more counter-electrodes changes, which allows for capacitive measurements. Thus, the static change in the angular position of the optical axis 18 can be measured. Such measurements are not considered part of the present invention.

[0032] According to the present invention, the control device 28 is configured to determine the longitudinal acceleration ax of the motor vehicle from the acceleration of the motor vehicle detected by the MEMS accelerometer 22, multiply the longitudinal acceleration ax by a predetermined coefficient Phi_1 to obtain a product, add the product to the static pitch angle Phi_0 to obtain the total pitch angle Phi, and set the angular position of the optical axis 18 dependent on the total pitch angle Phi by driving the pitch angle adjustment motor 30.

[0033] For the present invention, theoretically sufficient is that the MEMS accelerometer 22 is an accelerometer that detects acceleration about two mutually perpendicular axes. However, in practice, it is preferable to use a MEMS accelerometer 22 that detects acceleration along three mutually perpendicular spatial directions. Such a MEMS accelerometer 22 can be mounted in the control device 28 in any orientation, and the longitudinal acceleration detected using the MEMS accelerometer 22, and if necessary, the lateral acceleration, can be calculated from the measurements using a 3D rotation matrix.

[0034] Figure 2 The diagram shows the relationship between the low-pass filtered pitch angle plotted on the ordinate and the longitudinal acceleration plotted on the abscissa. This relationship was recorded during test drives. Clearly, this relationship can be modeled using a low-order polynomial, where a linear relationship is shown here. Performing test drives with alternating lateral acceleration provides a similar relationship between the lateral acceleration and the roll angle occurring at that time.

[0035] These observations allow us to formulate the calculation models for pitch and roll angles as a system of linear equations:

[0036] Pitch angle: Phi = Phi_0 + Phi_1 * ax

[0037] Roll angle: Theta = Theta_0 + Theta_1 * ay

[0038] The inventors have recognized that the accuracy of this simple calculation model is sufficient for the purpose of dynamic headlight adjustment (vertical, pitch angle Phi) and, if necessary, supplemental horizontal adjustment (roll angle Theta), and can be directly used in existing setting algorithms for supplying the angular position adjustment of the optical axis 18 of the headlight 10.

[0039] The calculation model is based on four coefficients: Theta_0 and Theta_1 represent the pitch angle Theta, and Phi_0 and Phi_1 represent the roll angle. The coefficients Phi_0 and Theta_0 represent the static pitch angle and roll angle, respectively.

[0040] The coefficients Phi_1 and Theta_1 represent the pitch and roll angle changes that occur during driving as a result of longitudinal acceleration ax and lateral acceleration ay. These accelerations can be generated by a combination of gravity and changes in the longitudinal and / or lateral slope of the road, or by the driving effects of the motor vehicle.

[0041] These coefficients depend on the design of the vehicle's chassis and can be defined as parameters characteristic of a specific chassis (specific vehicle suspension). These two parameters can also be determined from information detected during driving and are repeatedly updated throughout the vehicle's lifespan to monitor aging and allow for timely maintenance or repair of the suspension system.

[0042] It is understandable that the accuracy of the computational model can be improved by considering higher orders of the mapped square and cubic components.

[0043] Another possibility for improving accuracy is to use a six-axis sensor, which includes a three-axis gyroscope and a three-axis accelerometer. The gyroscope measures angular velocity. The accelerometer measures linear acceleration along one or more axes. For example, the determination of the total pitch and total roll angles can be improved by fusing the data with the gyroscope output variables. The data fusion process is preferably performed using a complementary filter, wherein precise high-frequency information provided by the gyroscope is combined with precise components from the lower-frequency components of the total pitch and total roll angles, as further described above.

[0044] The integral of the gyroscope output allows for the determination of the sensor's orientation change. However, due to sensor bias error, this determined orientation carries an error that increases infinitely over time. More precisely, the accelerometer only achieves a noisy determination of the sensor orientation. This is particularly suitable for dynamic driving situations. But the orientation error is still finite and does not increase infinitely over time. The idea based on complementary filters is to combine the slowly changing signal from the accelerometer with the rapidly changing signal from the gyroscope.

[0045] An accelerometer determines orientation under static conditions. A gyroscope determines orientation under dynamic conditions. Advantageously, the accelerometer signal is low-pass filtered, while the gyroscope signal is high-pass filtered. The filtered signals are then combined. The frequency responses of the high-pass and low-pass filters add up to 1 at all frequencies, ensuring that the combined signal is either high-pass filtered or low-pass filtered at any given time. In a preferred design, complementary filters are used to combine information from the suspension model. This allows for better angle determination.

[0046] Figure 3 As shown Figure 1 The illustrated headlight embodiment has an additional roll angle adjustment motor for compensating for changes in the roll angle position of the optical axis of the headlight 10.

[0047] As already explained, the angular position of the optical axis 18 depends on the static roll angle Theta_0, which is generated when the vehicle is stationary on the road or moving linearly at a constant speed on the road. The static roll angle Theta_0 is determined from a signal from at least one MEMS accelerometer sensor 22. The headlight 10 has a roll angle adjustment motor 32 configured to adjust the optical axis 18 of the light module 16. The control device 28 is configured to determine the lateral acceleration ay of the vehicle from the acceleration of the vehicle detected by the MEMS accelerometer sensor 22. The lateral acceleration of the vehicle is multiplied by a predetermined coefficient Theta_1 to obtain a product. This product is added to the static roll angle Theta_0 to obtain the total roll angle Theta. The angular position of the optical axis 18 is then set depending on the total roll angle Theta thus formed.

[0048] The roll angle adjustment motor 32 is mechanically coupled to the optical module 16 and configured to adjust the roll angle position of the optical axis 18. For this purpose, the roll angle adjustment motor 32 is specifically configured such that it causes the optical module 16 to rotate about the optical axis 18 of the optical module 16.

[0049] Figure 4A design of device 20 is shown, characterized in that it has a bus connection 34 to another headlight 34, and the MEMS acceleration sensor 22 is connected via the bus connection 34 to another control device 38, which is a component of another headlight 36.

[0050] The additional control device 38 of the additional headlight 36 is configured to process the longitudinal acceleration ax of the vehicle detected by the MEMS accelerometer 22 as if these longitudinal angular velocities had already been detected by its own MEMS accelerometer arranged in the additional headlight 36. In other words, the additional control device 38 is configured to multiply the detected longitudinal acceleration by a coefficient to obtain a product, add the product to the static pitch angle to obtain the total pitch angle, and set the angular position dependent on the total pitch angle by driving the additional pitch angle adjustment motor 40. Regarding the roll angle, the additional control device 38 is further configured to multiply the lateral acceleration ay of the vehicle detected by the MEMS accelerometer 22 by a predetermined coefficient Theta_1 to obtain a product, add the product to the static roll angle Theta_0 to obtain the total roll angle Theta, and set the angular position of the optical axis 18 dependent on the total roll angle by driving the additional roll angle adjustment motor 42, which is a component of the additional headlight 36.

[0051] In a preferred alternative, the total pitch and total roll angles are calculated by control unit 28 and transmitted to another control unit 38. Technically, this is better than transmitting the raw data to the control unit, as the more advantageous method requires less information to be transmitted and the other control unit 38 must perform less complex operations.

[0052] Figure 5 An embodiment of a method for setting the angular position of the optical axis of a motor vehicle headlight according to the present invention is shown, wherein the angular position depends on the static pitch angle. In a first step 100, the static pitch angle is determined from a signal from at least one MEMS accelerometer 22. In a second step 102, the longitudinal acceleration ax of the motor vehicle is detected using the MEMS accelerometer 22, and in a third step 104, this longitudinal acceleration ax is multiplied by a predetermined coefficient Phi_1, which is a characteristic of the chassis, to obtain a product. In a fourth step 106, this product is added to the static pitch angle Phi_0 to obtain the total pitch angle. In a fifth step 108, the angular position of the optical axis 18, which depends on the total pitch angle Phi, is set by driving the pitch angle adjustment motor 30 in a correspondingly compensated manner.

[0053] Figure 6A flowchart illustrating an embodiment of the method according to the present invention is shown, which also compensates for the dependence of the angular position of the optical axis on the roll angle. In a first step 200, a static roll angle Theta_0 is determined from a signal from at least one MEMS accelerometer 22. In a second step 202, the lateral acceleration ay of the motor vehicle is detected using the MEMS accelerometer 22. In a third step 204, the detected lateral acceleration ay is multiplied by a predetermined coefficient Theta_1 to obtain a product. In a fourth step 206, this product is added to the static roll angle Theta_0 to obtain the total roll angle Theta. In a fifth step 208, the angular position of the optical axis 18, which depends on the total roll angle Theta, is set by a corresponding drive roll angle adjustment motor 32.

Claims

1. A device (20) for setting the angular position of the optical axis (18) of a headlight (10) of a motor vehicle, wherein, The angular position depends on the static pitch angle of the motor vehicle, which is generated when the motor vehicle is stationary on the road or moving linearly at a constant speed on the road, and wherein the static pitch angle is determined from a signal from at least one MEMS accelerometer (22), characterized in that the MEMS accelerometer (22) is a component of the control device (28) of the headlight (10), wherein the headlight (10) has at least one optical module (16) having the optical axis (18) of the headlight (10). The control device (28) is configured to determine the longitudinal acceleration of the vehicle from the acceleration of the vehicle detected by the MEMS accelerometer (22), multiply the longitudinal acceleration by a predetermined coefficient to obtain a product, add the product to the static pitch angle to obtain a total pitch angle, and set the angular position of the optical axis (18) dependent on the total pitch angle by driving the pitch angle adjustment motor (30). The angular position depends on the static roll angle, which is generated when the vehicle is stopped on the road or moving linearly at a constant speed on the road. The static roll angle is determined from a signal from at least one MEMS accelerometer (22). The headlight (10) has a roll angle adjustment motor (32) for adjusting the optical axis (18) of the light module (16). The control device (28) is configured to determine the lateral acceleration of the vehicle from the acceleration detected by the MEMS accelerometer (22), multiply the lateral acceleration by a predetermined coefficient to obtain a product, add the product to the static roll angle to obtain a total roll angle, and set the angular position of the optical axis (18) depending on the total roll angle. The device (20) has a bus connection (34) to another headlight (36), and the MEMS accelerometer (22) is connected to the control device (38) of the other headlight (36) via the bus connection (34). The control device (38) of the other headlight (36) is configured to multiply the longitudinal acceleration of the vehicle detected by the MEMS accelerometer (22) by a predetermined coefficient to obtain a product, add the product to the static pitch angle to obtain a total pitch angle, and set the angular position dependent on the total pitch angle by driving another pitch angle adjustment motor (40). The control device (38) is further configured to multiply the lateral acceleration of the vehicle detected by the MEMS accelerometer (22) by a predetermined coefficient to obtain a product, add the product to the static roll angle to obtain a total roll angle, and set the angular position of the optical axis (18) dependent on the total roll angle by driving another roll angle adjustment motor (42).

2. The device (20) according to claim 1, characterized in that, The pitch angle adjustment motor (30) is mechanically coupled to the optical module (16) and configured to adjust the pitch angle position of the optical axis (18).

3. The apparatus (20) according to claim 2, characterized in that, The roll angle adjustment motor (32) is mechanically coupled to the optical module (16) and configured to adjust the roll angle position of the optical axis (18).

4. The apparatus (20) according to any one of claims 1 to 3, characterized in that, The accelerometer is an accelerometer that detects acceleration around two mutually perpendicular axes.

5. The apparatus (20) according to claim 4, characterized in that, The control device is configured to convert the acceleration detected by the acceleration sensor around two mutually perpendicular spatial directions into the lateral acceleration and longitudinal acceleration of the motor vehicle.

6. The apparatus (20) according to any one of claims 1 to 3, characterized in that, The accelerometer is an accelerometer that detects acceleration along three mutually perpendicular spatial directions.

7. A method for setting the angular position of the optical axis of a motor vehicle headlight, wherein, The angular position depends on the static pitch angle, which is generated when the vehicle is stationary on the road or moving linearly at a constant speed on the road. The static pitch angle is determined from signals from at least one MEMS accelerometer. The method is characterized by detecting the longitudinal acceleration of the vehicle using the MEMS accelerometer, multiplying the longitudinal acceleration by a predetermined coefficient to obtain a product, adding the product to the static pitch angle to obtain a total pitch angle, and setting the angular position dependent on the total pitch angle. The angular position further depends on the static roll angle, which is generated when the motor vehicle is stopped on the road or moving in a straight line at a constant speed on the road. The static roll angle is determined from a signal from at least one MEMS accelerometer. The lateral acceleration of the motor vehicle is detected using the MEMS accelerometer and multiplied by a predetermined coefficient to obtain a product. The product is added to the static roll angle to obtain a total roll angle, and the angular position is set based on the total roll angle.

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