Method and device for compensating a steering wheel angle signal, which is subject to an offset, in a vehicle

Abstract

A method for compensating a steering wheel angle signal, which is subject to an offset, in a vehicle, includes: a filtering step; and a use step. In the filtering step, the steering wheel angle signal is filtered while the vehicle is traveling, using a filtering rule, in order to obtain a mean value of the steering wheel angle signal. The steering wheel angle signal is filtered if a lane and/or a roadway of the vehicle meets predetermined criteria. In the use step, the mean value is used to compensate the offset.

Claims

1. A method for compensating a steering wheel angle signal, which is subject to an offset, in a vehicle, the method comprising: determining whether or not at least one of (i) a lane along which the vehicle is to travel, and (ii) a roadway along which the vehicle is to travel, meets at least one predetermined criteria; filtering the steering wheel angle signal while the vehicle is traveling, using a filtering rule, in order to determine a mean value of the steering wheel angle signal, wherein the steering wheel angle signal is filtered and included in the determination of the mean value based on a result of the determining step; and using the mean value to compensate the offset of the steering wheel angle signal.

2. The method as recited in claim 1, wherein, in the filtering step, the steering wheel angle signal is filtered and included in the determination of the mean value if the roadway is detected as being curved to a lesser extent than a predefined curvature limiting value.

3. The method as recited in claim 2, wherein, in the filtering step, the roadway is detected as being curved to a lesser extent than the predefined curvature limiting value if a right-hand curvature of a right-hand roadway boundary and a left-hand curvature of a left-hand roadway boundary are smaller than the predefined curvature limiting value.

4. The method as recited in claim 1, wherein, in the filtering step, the steering wheel angle signal is filtered and included in the determination of the mean value if a yaw angle between the lane and the roadway is detected as being smaller than a predefined yaw angle limiting value.

5. The method as recited in claim 4, wherein, in the filtering step, the yaw angle is detected as being smaller than the predefined yaw angle limiting value if (i) a right-hand yaw angle difference between the lane and the right-hand roadway boundary and (ii) a left-hand yaw angle difference between the lane and the left-hand roadway boundary are smaller than the predefined yaw angle limiting value.

6. The method as recited in claim 4, wherein, in the filtering step, the steering wheel angle signal is filtered using a low-pass filter in order to obtain the mean value.

7. The method as recited in claim 4, wherein, in the use step, the mean value is used after the steering wheel angle signal has been filtered over more than a minimum driving distance of the vehicle.

8. The method as recited in claim 1, further comprising: detecting surroundings of the vehicle using a video-based surroundings monitoring device; and detecting the curve of the roadway by analyzing images from a video camera of the surroundings monitoring device; wherein, in the filtering step, the steering angle signal is filtered and included in the determination of the mean value of the steering wheel angle signal when the detected curve of the roadway is detected as being curved to a lesser extent than a predefined curvature limiting value.

9. The method as recited in claim 1, wherein, in the filtering step, the steering wheel angle signal is filtered out from determining the mean value of the steering wheel angle signal when a drive through a tight turn is detected.

10. The method as recited in claim 1, wherein, in the filtering step, the steering wheel angle signal is filtered out from determining the mean value of the steering wheel angle signal when a lane change is detected.

11. A control device for compensating a steering wheel angle signal, which is subject to an offset, in a vehicle, the control device comprising: a controller including a processor configured to: filter the steering wheel angle signal while the vehicle is traveling, using a filtering rule, in order to determine a mean value of the steering wheel angle signal, wherein the steering wheel angle signal is filtered and included in the determination of the mean value only if at least one of (i) a lane along which the vehicle is to travel, and (ii) a roadway along which the vehicle is to travel, meets at least one predetermined criterion; and use the mean value to compensate the offset of the steering wheel angle signal.

12. A non-transitory, computer-readable data storage medium storing a computer program having program codes which, when executed on a computer, perform a method for compensating a steering wheel angle signal, which is subject to an offset, in a vehicle, the method comprising: filtering the steering wheel angle signal while the vehicle is traveling, using a filtering rule, in order to determine a mean value of the steering wheel angle signal, wherein the steering wheel angle signal is filtered and included in the determination of the mean value only if at least one of (i) a lane along which the vehicle is to travel, and (ii) a roadway along which the vehicle is to travel, meets at least one predetermined criterion; and using the mean value to compensate the offset of the steering wheel angle signal.

13. The control device as recited in claim 12, wherein the curve of the roadway is detected by analyzing images from a video camera of a video-based surroundings monitoring device of the vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a representation of a vehicle including a device for compensating a steering wheel angle signal, which is subject to an offset, according to one exemplary embodiment of the present invention.

(2) FIG. 2 shows a flow chart of a method for compensating a steering wheel angle signal, which is subject to an offset, according to one exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(3) In the following description of advantageous exemplary embodiments of the present invention, identical or similar reference numerals will be used for the similarly acting elements shown in the various figures, a repeated description of these elements being omitted.

(4) FIG. 1 shows a representation of a vehicle 100 including a device 102 for compensating a steering wheel angle signal 104, which is subject to an offset, according to one exemplary embodiment of the present invention. Vehicle 100 has a steering wheel angle sensor 106. Steering wheel angle sensor 106 portrays an angle position of a steering wheel of the vehicle in an electrical signal, steering wheel angle signal 104. The steering wheel angle signal may be subject to an offset. The offset feigns a non-existent turning of the steering wheel. Although the steering wheel is in a middle position, for example, steering wheel angle signal 104 with the offset has a value which represents an angle position relative to the middle position.

(5) Vehicle 100 also has a video-based surroundings monitoring device 108. Surroundings monitoring device 108 is connected to a video camera 110 which detects the surroundings of vehicle 100 ahead of vehicle 100. Surroundings monitoring device 108 analyzes images from camera 110 in order to obtain information 112 about the surroundings.

(6) Device 112 has a filter unit 114 for filtering steering wheel angle signal 104 and a compensation unit 116 for compensating steering wheel angle signal 104. In filter unit 114, steering wheel angle signal 104 is filtered using a filtering rule if it is discernible from information 112 provided by surroundings detection device 108 that the road or a roadway 118 along which vehicle 100 is traveling, and alternatively or additionally a lane 120 of vehicle 100, meet(s) certain criteria.

(7) In one exemplary embodiment, steering wheel angle signal 104 is filtered only when roadway 118 has a sufficiently large curve radius. In particular, monitoring is carried out to ascertain whether a right-hand radius of curvature 122 of a right-hand roadway boundary 124 is greater than a minimum radius of curvature. Monitoring is also carried out to ascertain whether a left-hand radius of curvature 126 of a left-hand roadway boundary 128 is greater than the minimum radius of curvature.

(8) Furthermore, in one exemplary embodiment, steering wheel angle signal 104 is filtered only when lane 120 of vehicle 100 forms a small enough angle 130 relative to roadway 118. In particular, an alignment of a vehicle longitudinal axis 132 relative to roadway markings 124, 128 is checked.

(9) In filter unit 114, the steering wheel angle signal is filtered, in one exemplary embodiment, by a low-pass filter while vehicle 100 is traveling, so that brief steering movements are filtered out from steering wheel angle signal 104 on account of their speed. After the filtering, a mean value 134 of steering wheel angle signal 104 remains, which represents the offset by which steering wheel angle sensor 106 falsely measures.

(10) In compensation unit 116, steering wheel angle signal 104 is compensated using mean value 134 in order to obtain a compensated steering angle signal (not shown here), for example for safety-relevant applications in vehicle 100.

(11) Steering wheel angle sensor 106 often delivers a steering wheel angle signal 104 which is subject to an offset. This may be attributed, for example, to an installation tolerance of sensor 106 but also to effects of aging. In other words, sensor 106 often delivers an angle signal 104 which has or is a relatively constant and slightly negative or positive value, even though vehicle 100 is traveling straight ahead.

(12) Since for many functions it is necessary that the steering wheel angle is determined in a manner free of any offset, compensation of this offset is necessary.

(13) The previous compensation, which is used for example in the ESP, filters raw signal 104 over a very long period of time or driving distance, using a low-pass filter. Assuming that vehicle 100 is on average traveling straight ahead, filtered value 134 is thus zero.

(14) Until now, the algorithm requires approximately 30 km in order to achieve a first estimate of the offset.

(15) With the aid of a lane detection algorithm LDA 108, the compensation may be accelerated since the instantaneous vehicle movements relative to lane 118, 120 may be taken into account. In addition, it is possible to filter out directly those driving situations which are not helpful to the compensation but rather disrupt the latter. For example, lane changes or drives through tight turns, where the steering wheel deviates greatly from the middle position, may be filtered out.

(16) FIG. 2 shows a flow chart of a method 200 for compensating a steering wheel angle signal, which is subject to an offset, according to one exemplary embodiment of the present invention. Method 200 may be carried out on a device as shown in FIG. 1. Method 200 includes a filtering step 202 and a use step 204. In filtering step 202, the steering wheel angle signal is filtered while the vehicle is traveling, using a filtering rule, in order to obtain a mean value of the steering wheel angle signal. The steering wheel angle signal is filtered if a lane, and alternatively or additionally a roadway, of the vehicle meet(s) predetermined criteria. In use step 204, the mean value is used to compensate the offset.

(17) In other words, FIG. 2 shows a Steering Wheel Angle Offset Compensation 200 (SWAOC) using Lane Detection Algorithm (LDA).

(18) The Steering Wheel Angle Offset Compensation SWAOC is carried out when these conditions are met:

(19) abs(.sup.LE)<.sub.lim

(20) abs(.sup.RI)<.sub.lim

(21) abs(.sup.LE)<.sub.lim

(22) abs(.sup.RI)<.sub.lim

(23) Here,

(24) .sup.LE is the curvature of the left-hand roadway boundary

(25) .sup.RI is the curvature of the right-hand roadway boundary

(26) .sub.lim is the limiting parameter for the curvature, which results in a compensation only when the lane is relatively straight

(27) .sup.LE is the yaw angle difference of the left-hand roadway boundary

(28) .sup.RI is the yaw angle difference of the right-hand roadway boundary

(29) .sub.lim is the limiting parameter for the yaw angle difference, which results in a compensation only when the alignment of the vehicle is relatively parallel to the lane.

(30) The concept presented here is based purely on optical lane detection.

(31) The exemplary embodiments described herein and shown in the figures are selected only by way of example. Different exemplary embodiments may be combined with one another entirely or with respect to individual features. One exemplary embodiment may also be supplemented by features of another exemplary embodiment.

(32) Furthermore, the method steps presented here may be carried out repeatedly and in an order different from the order described.

(33) If an exemplary embodiment includes an and/or linkage between a first feature and a second feature, this is to be interpreted to mean that the exemplary embodiment according to one specific embodiment has both the first feature and the second feature and according to another specific embodiment has either only the first feature or only the second feature.