DE102012213754A1 - Method for adjusting sensor signal of sensor in vehicle, involves comparing waveform of sensor signal with reference value of sensor signal at position of vehicle to obtain difference, where signal waveform is recorded on trip to position - Google Patents

Abstract

The method involves comparing a waveform of a sensor signal (102) with a reference value (112) of the sensor signal at a position of a vehicle to obtain a difference. The signal waveform is recorded on a trip to the position. A matched sensor signal (122) is provided using the sensor signal and a differential (118). An integral of the sensor signal is represented during the trip while comparing the sensor signal. The reference value is determined using a stored site model at the position. An orientation of the vehicle in a space at the position is represented by the sensor signal. An independent claim is included for a computer program product with a program code for performing the signal adjustment method.

Description

State of the art

The present invention relates to a method for matching a sensor signal of a sensor in a vehicle, to a corresponding information system and to a corresponding computer program product.

The DE 44 15 993 A1 describes a correction method for a map-based navigation system, in which the position of a motor vehicle found by coupling location is checked and corrected. To correct the coupled position, an error range is set up whose size is determined by the tolerances of the vehicle sensors.

Sensors in vehicles are conventionally calibrated during manufacture. For this purpose, a sensor is exposed to defined measured variables and the resulting measurement signal is analyzed. From this, a correction quantity is calculated, which is written directly into the sensor. Thus, the sensor forms the measured value correctly at least in the delivery condition. After the sensor is installed in the vehicle, the sensor is subject to an aging process and its measurement signal loses accuracy.

Disclosure of the invention

Against this background, the present invention provides a method for matching a sensor signal of a sensor in a vehicle, a corresponding information system using this method, and finally a corresponding computer program product according to the main claims. Advantageous embodiments emerge from the respective subclaims and the following description.

The invention is based on the recognition that a sensor signal can be secured by assumptions, and thus systematic errors in the sensor signal, such as drift and / or offset can be detected and compensated. The assumptions may be based on a positioning that may provide framework conditions for a benchmark. For example, at a certain position due to a known terrain inclination at the position, a certain vehicle tilt may be expected. If the sensor signal indicates a different vehicle tilt, it is likely that either the sensor signal is faulty or the assumption is incorrect. Likewise, on the basis of the position determination, an assumption can be made that a vehicle longitudinal axis points in a certain direction. If a gyroscope sensor outputs a different signal, it is likely that either the signal is faulty or the assumption is incorrect. By a high probability of the correctness of the assumption a deviation of the signal can be determined. If the deviation is known, the signal can be changed to re-map the measured quantity correctly.

The present invention provides a method for matching a sensor signal of a sensor in a vehicle, the method comprising the following steps:
Comparing a waveform of the sensor signal with a reference value of the sensor signal at a position of the vehicle to obtain a difference, wherein the waveform was recorded on a drive to the position;
Providing a balanced sensor signal using the sensor signal and the difference.

A sensor can be understood as meaning a position sensor, for example a tilt angle sensor or a rotation rate sensor. The sensor provides a sensor signal representing, analogously or digitally, a value of a magnitude measured by the sensor. The sensor signal may have interfering influences or measurement errors, for example noise, offset or drift. The vehicle may include a positioning device, such as a GPS receiver. The vehicle may also include a navigation device. The position of the vehicle can be read in by the receiver or the navigation device in a preceding step of the reading. The position can be read in as coordinate value. The sensor signal can be processed directly. The sensor signal can also be processed with a time delay. For this purpose, the sensor signal can be stored. A position-related reference value may represent a probable and / or expected attitude of the vehicle at the position. A calibrated sensor signal can represent the sensor signal freed from the measurement error or the interfering influences. For example, the control deviation can be subtracted from the sensor signal in order to obtain the calibrated sensor signal.

The waveform may represent an integral of the sensor signal during travel. The waveform can be recorded between leaving a starting point and reaching the position. The sensor signal can be integrated. For example, positive values can increase the integral and negative values can reduce the integral. For example, in the case of a direction signal, the integral may be a multiple of a full circle angle when the vehicle is again at the (home) position. Assuming that the vehicle at the same position again the same position and / or orientation a change in the sensor signal can be detected to compensate for this. This allows the sensor signal to be used with greater safety for safety-relevant applications.

The reference value can be determined using a stored terrain model at the location. The reference value can be determined based on a database. For example, a terrain orientation and / or a terrain altitude and / or a terrain condition may be deposited. For example, based on the terrain orientation, a terrain slope and exposure can be determined, and from this, an anticipated banking angle of the vehicle can be determined. The difference may represent a difference between the terrain model and the sensor signal.

The sensor signal may represent an orientation of the vehicle in space at the location. For example, the sensor signal may represent an angle of the vehicle relative to a main axis system of the vehicle. For example, the vehicle may have a longitudinally directed and a transverse acceleration sensor and a yaw rate sensor directed about a vertical axis of the vehicle. The stored value may represent values of the sensors that have been recorded at the position in the past.

Data of the terrain model may be compared at the position with the orientation of the vehicle at the position and / or a position signal at the position to obtain a terrain deviation value. The terrain deviation value can be stored in the navigation system for the position. For example, if the difference is greater than a tolerance range, there may be an error in the terrain model. Then the determination of the control deviation can be interrupted so as not to cause a wrong adjustment of the sensor signal. By determining a terrain deviation value, the terrain model can be improved. For example, if a weak signal strength of the GNSS complicates the position determination, the position can be determined with insufficient accuracy. An area where the signal strength is low may also be deposited in the terrain deviation value.

The method may include a step of determining a control deviation for the sensor signal, wherein in the step of providing the adjusted sensor signal is further provided using the control deviation. A control deviation can be an offset or a drift compensation. The control deviation can be determined using a processing rule from the difference or from a plurality of differences. The control deviation can represent, for example, an average of several differences.

The control deviation can be determined using an expected tolerance range for the control deviation. The control deviation can be greater than a minimum value of the control deviation and less than a maximum value of the control deviation. The minimum value can also be negative. Similarly, a tolerance range can be applied to the difference. If a control deviation is detected that would be outside the tolerance range, an error may exist. For example, a control deviation outside the tolerance range for the provision of the adjusted sensor signal can be disregarded.

The differences can be averaged over a predetermined period / distance to obtain the control deviation. By averaging extreme values of the differences can be filtered. For example, an average value of the differences can be determined. The adjustment can be made more robust by the means.

The sensor signal may represent a measured direction of gravitational acceleration. In the comparison step, the reference value to be determined is an expected slope between the position and another position. The measured direction of gravitational acceleration can be compared with the expected slope. Another position may be a future position of the vehicle. Likewise, the further position may be a previous position of the vehicle. The position may, for example, have a first height value and the further position may have a second height value. There may be a distance between the position and the further position. Over the distance and the height values an expected terrain slope can be determined. The expected terrain slope can be compared with an average of a vehicle tilt in the vehicle longitudinal direction to match the sensor.

The present invention further provides an information system adapted to perform the steps of the method according to the invention in corresponding devices. Also by this embodiment of the invention in the form of an information system, the object underlying the invention can be solved quickly and efficiently.

In the present case, an information system can be understood as an electrical device which processes sensor signals and as a function thereof thereof outputs control and / or data signals. The information system may have an interface, which may be formed in hardware and / or software. In the case of a hardware-based embodiment, the interfaces can be part of a so-called system ASIC, for example, which contains various functions of the information system. However, it is also possible that the interfaces are their own integrated circuits or at least partially consist of discrete components. In a software training, the interfaces may be software modules that are present, for example, on a microcontroller in addition to other software modules.

A computer program product with program code which can be stored on a machine-readable carrier such as a semiconductor memory, a hard disk memory or an optical memory and is used to carry out the method according to one of the embodiments described above if the program product is installed on a computer or a device is also of advantage is performed.

The invention will now be described by way of example with reference to the accompanying drawings. Show it:

1 a block diagram of an information system for adjusting a sensor signal of a sensor in a vehicle according to an embodiment of the present invention;

2 a flowchart of a method for adjusting a sensor signal of a sensor in a vehicle according to an embodiment of the present invention;

3 a representation of a vehicle with an information system according to an embodiment of the present invention when reaching a previously reached position; and

4 a representation of a vehicle with an information system according to another embodiment of the present invention, in which a value of a terrain model is used as a reference value.

In the following description of preferred embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and similarly acting, wherein a repeated description of these elements is omitted.

1 shows a block diagram of an information system 100 for adjusting a sensor signal 102 a sensor 104 in a vehicle according to an embodiment of the present invention. The information system 100 has a facility 106 for comparison, a facility 108 for identifying and a facility 110 to deploy. The sensor 104 represents the sensor signal 102 ready. The sensor signal 102 represents a position of the vehicle, not shown, in space. This is indicated by the sensor signal 102 a component of an acceleration in the vehicle longitudinal direction x, a component of an acceleration in the vehicle transverse direction y, a component of an acceleration in the vehicle vertical direction z, and a yaw rate about the vehicle vertical axis ω. When the vehicle is at rest, only the gravitational acceleration acts on the vehicle. The sensor signal 102 then has proportional to the acceleration of gravity in the x, y and z components. The sensor 104 may have a signal drift and / or a signal offset, whereby the sensor signal 102 would be corrupted. The device 106 for comparison compares the sensor signal 102 with a reference value 112 by a means for providing the reference value 112 in response to a position signal 116 of the vehicle is provided. The reference value 112 is position-related and represents a comparison value to the sensor signal 102 at the position. The device 106 to compare represents a difference 118 the values ready. The difference 118 will be in the facility 108 used to determine a control deviation 120 provide. The deviation 120 is calculated from the difference using a processing rule 118 determined. The device 110 for providing receives the sensor signal 102 and the deviation 120 and gives a balanced sensor signal 122 which has less or no signal drift and / or signal offset.

The block diagram in 1 shows calibration possibilities of sensors by means of navigation according to an embodiment of the present invention.

For a variety of systems on board a vehicle are precisely calibrated sensors 104 important, z. B. for the slope determination (including HillHold, ESP, ...) an acceleration sensor in the vehicle longitudinal direction x, for ESP the tire diameter and a gyroscope ω. By using a navigation device, calibration can be faster compared to traditional methods.

In addition to information from the map can be determined by a navigation that a vehicle is back to a position it was once. If this is the case, then there are none between these two times Differences in position, allowing a very accurate calibration.

2 shows a flowchart of a method 200 for adjusting a sensor signal 102 a sensor in a vehicle according to an embodiment of the present invention. The method has one step 202 of comparing, one step 204 determining and a step 206 of providing. In step 202 the comparing becomes the sensor signal recorded at a position of the vehicle 102 with a position-related reference value 112 the sensor signal 102 compared to the position at a difference 118 to obtain. In step 204 the determination becomes a control deviation 120 for the sensor signal using the difference 118 determined. In the providing step, a calibrated sensor signal is generated 122 using the control deviation 120 and the sensor signal 102 provided.

3 shows a representation of a vehicle 300 with an information system 100 according to an embodiment of the present invention when reaching a previously reached position 302 , The vehicle 300 has a sensor 104 and an unillustrated unit for determining position. The sensor 104 provides a sensor signal representing a location of the vehicle 300 at the position 302 represents. The position 302 is a position where the vehicle is 300 at least for the second time. The position determination unit represents the coordinates of the current vehicle position 302 ready. For example, the position 302 a rented parking space for the vehicle 300 be. To the position 302 can the vehicle 300 keep coming back after the vehicle 300 changeable routes 304 has covered. Because the vehicle 300 back to the position 302 has returned, the vehicle points 300 there a reproducible location. The sensor signal should be almost the same again. Assuming that the sensor signal at the position 302 should be equal, the sensor signal may be one of the last times when the vehicle 300 at the position 302 was to be compared with the current sensor signal. In this case, a difference can be obtained which represents, for example, a signal drift of the sensor signal. By a further processing of the difference, a control deviation of the sensor signal can be determined. By means of the control deviation, the original sensor signal can be adjusted, so that the adjusted sensor signal at the position 302 always within a tolerance range. This allows safety-relevant systems of the vehicle 300 Use the adjusted sensor signal with high reliability.

In vehicles 300 There are various safety systems and comfort functions available. z. ESP, HillHold, Airbag, ... These require well-calibrated sensors for proper operation 104 , Only then can the systems make a correct image of the outside world and function properly. Are the sensors 104 poorly calibrated, the associated functions are reduced or completely shut down.

A good calibration is therefore essential. Various methods of calibration are presented below.

sensors 104 are exposed during production to the most diverse, well-defined situations and it becomes the output of the sensors 104 directly in the sensor 104 stored with the respective associated situation. It is so directly during the production of the sensor 104 learned. (The sensors 104 be z. B. pushed through heat ovens o. Ä.)

Heuristics can be used to control the sensors 104 to calibrate during operation. This is how a vehicle becomes 300 on average (over a lot of miles) straight and horizontal drive. Such a heuristic is of the order of magnitude for very long distances 100 and more kilometers.

sensors 104 can on the hand of other sensors 104 be calibrated. Thus, the calibration of gyroscopes and tire diameters by means of GNSS (Global Navigation Satellite System) measurements is possible.

In the approach presented here are further calibration options of sensors 104 shown, resulting from the use of a navigation system.

For example, use of an identical position 302 as they are in 3 is shown. On many trips 304 with a vehicle 300 is the vehicle 300 After a fairly short time at one point 302 which it has been before. This is how a vehicle parks 300 z. B. at night mostly in the same garage. For example, during a daily commute 304 between workplace and place of residence, rides 304 for shopping etc. It is stopped again and again at the same intersection to grant the right of way or the like.

A navigation device can now detect when the vehicle 300 again exactly in a place that has ever been. In addition, the navigation provides the time or the distance traveled since then 304 ,

This information can be used to calibrate sensors 104 to be used.

If the inclination is neglected in steep curves, then the sum of all changes of direction since the last visit to this position 302 a multiple of 360 °. This can be the offset of a rotation rate sensor 104 be calibrated very accurately, because the integrated yaw rate will exactly match this multiple. The offset is the critical calibration variable for a gyro.

Has the gyro 104 an offset Z, a scaling factor S and G represents the gyro's readings, and N full circles have been completed, then 2πNS = ∫ (G - Z) dt apply, from which the offset can be determined very accurately, even if the scaling factor is determined only with a low accuracy.

When returning to exactly the same place 302 there can be no height difference. With this information, the offset of an acceleration sensor 104 be calibrated very accurately in the vehicle longitudinal direction, because the integral of all accelerations in the vehicle longitudinal direction over the distance traveled 304 is zero.

Is the number of driven circles since the last stop at this point 302 As is known, the difference between the distances traveled by the wheels is equal to the number of full circles (2π) times the center distance. With this approach, the wheels can be calibrated very accurately relative to each other when the wheels have been moved without slippage.

4 shows a representation of a vehicle 300 with an information system 100 according to another embodiment of the present invention, wherein a value of a terrain model 400 as a reference value 112 is used. As in 3 points the vehicle 300 a sensor 104 on. The sensor 104 provides a sensor signal indicative of the gravitational acceleration g relative to the vehicle 300 represents. The information system 100 can be on a data store 402 access in which the terrain model 400 is deposited. The terrain model 400 maps terrain characteristics, such as terrain slope and exposure. In the information system 100 become data of the terrain model 400 at a current position of the vehicle 300 with the sensor signal of the sensor 104 compared, and determined from the difference, a correction factor or correction value. The correction value or correction factor is used to adjust the sensor signal in order to obtain a calibrated or adjusted sensor signal for further processing. The sensor 104 has a workspace within which the sensor signal would have to be located. If the difference to the terrain model 400 is larger than the work area, then, for example, the terrain model 400 be flawed. Then, a terrain correction value may be generated, for example, a need for correction of the terrain model 400 displays. Similarly, the terrain correction value may inhibit future comparison at the location to incorrectly balance the sensor 104 to prevent.

For example, shows 4 a use of slope data to adjust the sensor 104 , Gradient data is increasingly being added to the maps 400 entered. These are important for ecological driving routes. Accuracy sensors can be used with this information 104 be calibrated. Is the vehicle located 300 z. B. on one of the card 400 known slope, then an acceleration sensor 104 in the longitudinal direction of the vehicle, measure the sine component of the gravitational acceleration g. This allows the acceleration sensor 104 be calibrated. When the vehicle is moving from z. B. the odometer values known tangential acceleration from braking / accelerating be calculated out.

Another example is a use of elevation data 400 , The navigation uses a global navigation satellite system (GNSS) to determine the current altitude or find this information in the map data 400 (eg from a digital terrain model 400 ). Altitudes are usually not very accurate, but can be determined with an accuracy of about 20 to 50 m. Despite this low quality can thus be an accelerometer 104 calibrated very well if there is enough distance between the two measurements. After a distance of, for example, 6 km, the offset of an acceleration sensor can thus be used 104 be calibrated to within 1 °. This is still little distance compared to the more than 100 km needed when using heuristics.

This principle is not limited to one measurement at the beginning and a second measurement at the end of the calibration path. The GNSS and the elevation model 400 continuously provide independent readings for continuous calibration.

The above mentioned applications can be partly security relevant. If the security standards are high, it may be necessary to verify the synchronization. map data 400 for example, can be wrong, a GNSS can provide wrong data through multipath, etc.

The sensors 104 in safety-related applications have well-defined characteristics. So it is known exactly in which interval, for example, an offset can move.

Through this knowledge, obvious erroneous measurements can be discarded. The remaining, plausible measured values are used for calibration. However, the calibration value is never set by a single measurement. Instead, the new measured values are slowly filtered through a filter process into the already known calibration values.

At the same time, independent measured values are available (eg once slope data from the map 400 and once slope from GNSS), these can be plausibilized with each other before use.

Due to the multiple combination of scattered but independent and expectation-true measured values results in accordance with the probability theory in total a very reliable reading.

Another embodiment is a use of a protection level of navigation. The navigation can spend a security area for each position, in which they z. B. to 99.999% security. This is called a protection level. For example, the protection level may be used in pure GNSS location for aircraft using SBAS (Satellite Based Augmentation System). Together with this specification of accuracy then also the navigation meets the safety-relevant requirements. Such readings together with the specified error intervals can be used directly for calibration without further averaging.

For further improvement, a return channel to the navigation can be used. During calibration, the controller rates 100 , whether the measured values or the map data 400 the navigation are plausible. If errors are now detected in the navigation component, the control unit can 100 inform the navigation about it. There will be the corresponding map data 400 marked as faulty and / or corrected. Or the area is classified as a bad GNSS area.

Drives the vehicle 300 now at a point with marked as incorrect map data 400 or in a badly marked GNSS area, these values are not even used for calibration. Navigation can thus learn map errors or bad GNSS areas in this way.

This information can be sent to a central server 402 be dubbed. This not only corrects the local data in your own navigation. The knowledge can thus all users of the data server 402 to provide.

Vehicle control equipment 100 can request data from the navigation. These data are sent via a channel, typically a CAN. The CAN messages are exactly specified. Thus, these data can be read easily and thus be detected, which information is exchanged. For example, a message of the type "stop at known position" can be transmitted.

The embodiments described and shown in the figures are chosen only by way of example. Different embodiments may be combined together or in relation to individual features. Also, an embodiment can be supplemented by features of another embodiment.

Furthermore, method steps according to the invention can be repeated as well as carried out in a sequence other than that described.

If an exemplary embodiment comprises a "and / or" link between a first feature and a second feature, then this is to be read so that the embodiment according to one embodiment, both the first feature and the second feature and according to another embodiment either only first feature or only the second feature.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The 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

• DE 4415993 A1 [0002]

Claims (10)

Procedure ( 200 ) for adjusting a sensor signal ( 102 ) of a sensor ( 104 ) in a vehicle ( 300 ), the process ( 200 ) includes the following steps: compare ( 202 ) a signal waveform of the sensor signal ( 102 ) with a reference value ( 112 ) of the sensor signal ( 102 ) at a position ( 302 ) of the vehicle ( 300 ) by a difference ( 118 ), the signal being traversed to the position ( 302 ) was recorded; Provide ( 206 ) of a calibrated sensor signal ( 122 ) using the sensor signal ( 102 ) and the difference ( 118 ). Procedure ( 200 ) according to claim 1, wherein in step ( 202 ) of comparing the waveform an integral of the sensor signal ( 102 ) while driving. Procedure ( 200 ) according to one of the preceding claims, wherein in step ( 202 ) of comparing the reference value ( 112 ) using a stored terrain model ( 400 ) at the position ( 302 ) is determined. Procedure ( 200 ) according to one of the preceding claims, in which the sensor signal ( 102 ) an orientation of the vehicle ( 300 ) in the room at the position ( 302 ). Procedure ( 200 ) according to claim 4, wherein in step ( 202 ) of Comparing Data of the Terrain Model ( 400 ) at the position ( 302 ) with the orientation of the vehicle ( 300 ) at the position ( 302 ) and / or a position signal ( 116 ) at the position ( 302 ) are compared to obtain a terrain deviation value, wherein the terrain deviation value in a navigation system to the position ( 302 ) is deposited. Procedure ( 200 ) according to one of the preceding claims, with a step of determining ( 204 ) of a control deviation ( 120 ) for the sensor signal ( 102 ), wherein in the step of providing ( 206 ) the adjusted sensor signal is further provided using the control deviation. Procedure ( 200 ) according to claim 6, wherein in step ( 204 ) determining the control deviation ( 118 ) using an expected tolerance range for the control deviation ( 118 ) is determined. Procedure ( 200 ) according to one of the preceding claims, in which the sensor signal ( 102 ) represents a measured direction of gravitational acceleration (g), and in step ( 202 ) of comparing the reference value ( 112 ) an expected slope between the position ( 302 ) and another position, wherein the measured direction of gravitational acceleration (g) is compared with the expected slope. Information system ( 100 ), which is adapted to the steps of a method ( 200 ) according to one of claims 1 to 8. Computer program product with program code for carrying out the method ( 200 ) according to one of claims 1 to 8, when the program product is executed on a device.

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