DE102013001590B4 - METHOD FOR DETECTING A OPERATING STATE OF A STEERING WHEEL IN A STEERING SYSTEM OF A MOTOR VEHICLE - Google Patents

Abstract

A method for detecting an operating state (hands_off; hands_on) of a steering wheel (10) in a steering system (1) of a motor vehicle, wherein the operating state (hands_off; hands_on) describes whether a driver operates the steering wheel (10), an actual torque ( M) on a torsion bar (9) of the steering system (1) and a steering position (Pos) of the steering system (1) are determined, characterized in that the operating state (hands_off), in which the driver does not operate the steering wheel (10), then is detected when the actual torque (M) on the torsion bar (9) of the steering system (1) above the steering position (Pos) of the steering system (1) has a characteristic curve (26; 29).

Description

The invention relates to a method for detecting an operating state of a steering wheel according to the preamble of claim 1, a computer program that is designed to perform such a method, a control device with a digital computing device on which such a computer program is executable and a storage medium for a Such control device for storing such a computer program.

The operating state describes whether a driver is operating the steering wheel and, in particular, whether the driver has at least one hand on the steering wheel or has both hands removed from the steering wheel.

In mechatronic steering systems, in particular in electrically assisted steering systems, the so-called driver torque applied by the driver to the transverse guidance of the vehicle is influenced as a function of the situation by means of a so-called assist torque in a plurality of operating areas. As part of a tracking, the driver is assisted, for example, by the driver being provided with haptic feedback via a track course recognized by means of a camera or another sensor system. This feedback is realized by a suitable manual torque, wherein the corresponding haptic perceptible information is transmitted to the driver via the manual torque. This guidance assistance allows increased driving safety, especially on highways and highways.

Driver assistance systems are regularly designed so that the driver is included in the control loop. This means that the driver always has to keep his hands on the steering wheel in order to be able to react to the haptic information. The level of the assist torque is limited such that overshooting of the resultant torque by the driver is possible at any time by the driver generating a counter torque on the steering wheel.

However, for legal reasons, a fully automatic tracking by the driver assistance system must not take place, since the driver must always have full control of the vehicle. The assistance system must therefore be able to be switched off when the driver takes his hands off the steering wheel. In addition, a warning can be issued to alert the driver that the driver assistance system is switched off and that hands should be put back to the steering wheel.

For this purpose, from the prior art, the generic EP 2 591 942 A1 in which it is proposed to determine the operating condition in which the driver does not operate the steering wheel by a "hand-off" metric based on a relationship between the actual steering torque and the determined steering position.

Furthermore, the DE 10 2007 039 332 A1 a method in which a "contact state" of a hand on the steering wheel is detected, wherein the steering movement is detected by a torque sensor and an angle sensor and a free steering movement is modeled using measurement data and the driver steering torque is estimated by a state observer.

In the DE 10 2009 028 647 A1 the operating state is detected, in which a high-resolution steering wheel angle and a current steering torque is detected and from a currently applied by the driver driver's manual torque is determined and closed depending on the operation of the driver's manual torque on the operating state.

In previously known systems, a warning message is often output incorrectly and / or the driver assistance system is switched off. This is especially often the case when the driver touches the steering wheel relatively lightly.

It is therefore an object of the invention to provide a method for detecting the operating state of the steering wheel, which works much more reliably compared to the known methods and in particular avoids or at least reduces erroneous outputs of warning messages and / or an erroneous shutdown of a driver assistance system.

The object is achieved by a method for detecting an operating state of a steering wheel with the features of claim 1, by a computer program having the features of claim 12, by a control device having the features of claim 13 and by a storage medium having the features of claim 14 Advantageous further developments are specified in the subclaims. Claimed features are explained in more detail in the following description and in the drawings, wherein the features both in isolation and in different combinations for the invention may be important, without being explicitly referred to again.

An operating state in which the driver does not operate the steering wheel is advantageously detected when a determined actual torque on a torsion bar of the steering system has a characteristic course over a steering position of the steering system. This advantageously provides a reliable and robust method for detecting the operating state of the steering wheel, which improves the use of lane departure warning systems, for example. In addition, for example, no corresponding sensors on the steering wheel must be provided to detect the operating state of the steering wheel.

In an advantageous embodiment of the method, the characteristic curve is present when a plurality of temporally successive types of sections are detected. By dividing the characteristic course into sections, a simple representation of the characteristic profile is achieved, which simplifies machine recognition.

In an advantageous development, the characteristic curve has an essentially trapezoidal, in particular substantially hysteresis-like, arrangement of the sections. Again, a simple representation of the characteristic course and a correspondingly simple detection are possible.

In an advantageous embodiment of the method, the operating state in which the driver does not operate the steering wheel is recognized when the characteristic course is present for more than a predetermined period of time, in particular longer than 25 seconds. Due to the predetermined period of time is advantageously excluded that a "steering" of the driver without actually influencing the torque on the torsion bar to an immediate mis-detection of the operating state in which the driver does not operate the steering wheel leads.

The advantageous embodiments for recognizing a type of span provide simple and robust detection methods.

In an advantageous embodiment of the method, the operating state in which the driver does not operate the steering wheel is recognized when the steering angle in one direction passes over a certain range of values. This prevents, for example, that the driver does not operate the steering wheel during a slight cornering with the lane assistant switched on.

In an advantageous embodiment, the actual torque and / or the steering position is low-pass filtered before the detection of the operating state. Advantageously, this smoothing can contribute to an improved detection of the sections.

In an advantageous embodiment, the actual torque corresponds to a sensor signal of a torque sensor and the steering position corresponds to a rotational angle of the torsion bar or a rack position. Advantageously, the method does not require absolutely calibrated signals, but comes with an offset without further justification, since the method a relative position of the actual torque or the steering position is sufficient.

Other features, applications and advantages of the invention will become apparent from the following description of embodiments of the invention, which is illustrated in the figures of the drawing. All claimed features alone or in any combination form the subject matter of the invention, regardless of their summary in the claims or their dependency and regardless of their formulation or representation in the description or in the drawing. It will be used for functionally equivalent sizes in all figures, even with different embodiments, the same reference numerals.

Embodiments of the invention will now be described by way of example with reference to the drawings. In the drawing show:

1 a schematic representation of a steering system of a motor vehicle;

2 a history of an actual torque on a steering position in an operating state in which a driver operates a steering wheel;

3 a course of the actual torque on the steering position in an operating state in which the driver does not operate the steering wheel;

4 a schematically illustrated characteristic curve of the actual torque on the steering position in the operating state in which the driver does not operate the steering wheel;

5 a schematically represented state transition diagram; and

6 a schematic block diagram.

1 shows a schematic representation of a steering system 1 a vehicle with a steering device 2 and a controller 3 , In the control unit 3 is a microprocessor 4 arranged, which is also referred to in particular as a digital computing device. The microprocessor 4 is via a data line, for example a bus system, with a memory element 5 connected. In the memory element 5 are storage areas 5a trained, in which workable computer programs and / or data are stored. The data can be both predefinable sizes and during execution be determined by the method or specified during the application of the method according to the invention data.

Via a signal line 6 is the control unit 3 with a torque adjuster, for example one as an electric motor 7 trained engine, connected, allowing a control of the electric motor 7 through the control unit 3 is possible. The electric motor 7 acts via a gearbox 8th on a torsion bar 9 , On the torsion bar 9 is a steering wheel 10 arranged. According to another possible embodiment, the electric motor 7 parallel to a rack 12b arranged, wherein the engine torque is transmitted via a belt and a ball screw. In yet another possible embodiment, the electric motor acts 7 over another pinion on the rack.

The steering device 2 also has a steering gear 11 on, according to the in 1 embodiment illustrated as a rack and pinion steering gear is formed. The steering gear 11 is about a pinion 12a and the rack 12b on each side of the vehicle with a steering linkage 13 , each with a wheel 14 cooperates, connected.

The steering system 1 also has a torque sensor 16 on, with a current torque via a corresponding sensor signal can be detected. The current torque is also referred to as actual torque M. The torque sensor 16 is on the torsion bar 9 arranged. The current torque is determined, for example, by measuring the actual torsion of the torsion bar 9 , preferably taking into account a torsional rigidity of the torsion bar 9 , certainly. The torque sensor 16 is via a data line with the control unit 3 connected. At the electric motor 7 an angle sensor is arranged, with which a motor angle can be detected. Furthermore, the steering system points 2 an angle sensor 18 on, the detection of a rotation angle of the torsion bar 9 allows. The angle sensors 17 and 18 are via signal lines to the controller 3 connected.

About further signal lines is the control unit 3 with an angle adjuster, for example a motor designed as a servomotor 15 , connected, giving a control of the engine 15 through the control unit 3 is possible. The motor 15 acts via an angle superposition gear 19 , For example, a planetary gear, on the torsion bar 9 and allows the realization of an angle overlay in an active steering.

This in 1 illustrated steering system 1 is suitable for carrying out the method according to the invention. Of course, the inventive method can also perform on other steering systems. The operation of the steering system 1 will be explained in the following description.

In the in 2 illustrated diagram 20 the actual moment M is plotted over a steering position Pos. The actual torque M can in this case the sensor signal of the torque sensor 16 , ie the current torque, correspond. The steering position Pos can be the current angle of rotation of the torsion bar 9 or a position of the rack 12b correspond. Of course, other comparable measured values can be used for the actual torque M and the steering position Pos.

A first course 22 of the actual torque M above the steering position Pos was in 2 exemplified over a period of about 25 seconds in a first operating state hands_on recorded in which the driver has operated the steering wheel.

3 shows a diagram 24 in which like in 2 perpendicular to the actual torque M and horizontally the steering position Pos are plotted. In contrast to 2 shows the diagram 24 of the 3 a course 26 which has been recorded hands_off for about 25 seconds during a second operating condition, wherein in the second operating condition hands_off the driver has not operated the steering wheel and a movement of the torsion bar 9 and the steering wheel 10 by a support torque, given by the control unit 3 , is moved.

Recognizable excels in the course 26 a substantially trapezoidal, in particular substantially hysteresis-like arrangement of stretchers from. A path is characterized in that, for example, by interpolation of measuring points, which are composed of the actual moment M and the steering position Pos, form essentially straight line pieces. These stretches are lined up in chronological order in such a way that the course 26 results.

The different widths of the path pieces, which extend substantially parallel to the horizontal axis of the steering position Pos, result from the fact that the driver assistance system has performed different steering movements. The characteristic course 26 thus results essentially due to the friction of the torsion bar 9 and the associated elements of the steering device 2 ,

Of course, in the operating state hands_off, in which the driver turns the steering wheel 10 not served, also a different course than the course 26 form. In particular, the way pieces can be designed differently or arranged, as it is in the course 26 the case is. Of course, the measuring instructions as well as the Attachment of the corresponding sensor Influence on the formation of the corresponding course of the actual moment M over the steering position Pos. The second course 26 FIG. 12 illustrates an example of a characteristic curve indicating the hands_off operating state in which the driver controls the steering wheel 10 not served.

4 shows a diagram 28 in which a schematically illustrated course 29 is shown. The schematically illustrated course 29 includes a first type 30 a way piece and a second type 32 a stretch of road and a third type 34 a stretch of road and a fourth type 36 of a stretch of road. The time sequence of the types of stretchers and the underlying actual, not shown course is each characterized by an applied arrowhead. In contrast to the course 26 out 3 is the course 29 in 4 highly schematized in order to explain the recognition of the characteristic curve, in which the operating state hands_off, in which the driver does not operate the steering wheel.

The detection of the types 30 to 36 Of partitions can be done in different ways. So it is possible, for example, by a straight line interpolation of sections of the course 26 out 3 the different types 30 to 36 to recognize from parts of the way. Of course, there are also other methods for detecting the types 30 to 36 of parts of the way.

The first type 30 a span is recognized, for example, when substantially a first direction 38 the time course of the steering position Pos is present and in the same period substantially a first direction 40 the time course of the actual moment M is present. Accordingly, the second type becomes 32 a part of the way then recognized, if essentially a second direction 42 the time course of the steering position Pos is present and in the same period substantially a second direction 44 the time course of the actual moment M is present.

In an alternative or supplementary embodiment, the first or second type 30 . 32 the distance pieces then recognized when the steering position Pos a first range of values 46 or 48 covers and the actual moment M in the same period a second value range 50 sweeps. The first range of values 46 ranges from a value P8 to a value P9, where the first range of values 46 is smaller than the value range from a value P7 to a value P10. The first range of values 48 extends from a value P2 to a value P3 and is thus smaller than a value range from a value P1 to a value P4. The second value range 50 extends from a value M2 to a value M3 and is thus smaller than a value range from a value M1 to a value M4. The value ranges 46 . 48 and 50 thus indicate a minimum, that for the detection of the appropriate type 30 . 32 must be exceeded or overstretched by the corresponding course.

The value pairs P1 and M4, P4 and M1, P10 and M1 and P7 and M4 represent the corner points of the course shown schematically 29 represents.

The third type 34 the distance pieces is then recognized if either the steering position Pos a third range of values 52 overrides or essentially the first direction 38 the steering position Pos is present and the actual torque M remains substantially the same in the same period of time, wherein a substantially constant of the actual torque M means that the value of a corresponding course moves substantially by the value M4.

The fourth type 36 the distance pieces is then recognized if either the steering position Pos a third range of values 54 covers over or substantially the second direction of the steering position Pos is present and the actual moment M remains substantially the same in the same period, with a constant of the actual moment M in this context means that a corresponding course around or in a corridor to moves the value M1.

The third range of values 52 extends from the value P2 to a value P6. The third range of values 54 extends from a value P5 to the value P9. The third range of values 52 is therefore smaller than a range of values extending from the value P1 to the value P7. The third range of values 54 is therefore smaller than a range of values extending from the value P4 to the value P10.

In an alternative embodiment of the method, the first type 30 and the third guy 34 the stretches are then recognized together when the steering position Pos sweeps over a fourth range of values and in the same period essentially the first direction 38 the time course of the actual moment M is present. The fourth value range is in 4 not shown, but is at least equal to or less than a range of values from the value P10 to the value P1.

Accordingly, the second type 32 and the fourth guy 36 the distance pieces then recognized together when the steering position Pos sweeps over a further fourth range of values and in the same period at least temporarily the second direction 44 the time course of the actual moment M is present. The further fourth value range results according to the fourth value range and is less than or equal to a value range from the value P1 to the value P10.

The types 30 . 34 . 32 and 36 follow each other in this order and ideally continue, that is in an unoperated state hands_off the steering wheel, also in this order. This is the characteristic course 29 then before, if several temporally successive types 30 . 34 . 32 and 36 be recognized by parts of the way. This means, for example, that the characteristic course 29 exists only when there is a limit on the number of types 30 . 34 . 32 and 36 is recognized consecutively. Of course, the characteristic course 29 with each of the successive types 30 to 36 begin and end.

Another condition in which the operating state hands_off is recognized, in which the driver does not operate the steering wheel, is when the steering position in one direction is a fifth range of values in one direction 38 or 42 sweeps. The fifth range of values is not shown, but may for example extend from the value P1 to the value P10, or preferably be greater than this range. As a result, extreme gradients of the steering position, which are triggered by the driver assistance system, can be used in only one direction to immediately display the operating state hands_off, in which the driver does not have his hands on the steering wheel.

The actual moment M and / or the steering position Pos are low-pass filtered before the recognition of the operating state hands_off or hands_on, in order to bring about a smoothing of the respective signals and thus to an improved recognition of the types 30 to 36 to contribute to the paths.

5 shows a schematically illustrated state transition diagram 56 with the two operating states hands_off and hands_on. According to the course 22 from the 2 is assumed according to the methods described here of the operating state hands_on, in which the driver is the steering wheel 10 served. Now, according to the method described above, the characteristic course 29 out 4 recognized, then according to the arrow 58 in the operating state hands_off passed, in which the driver turns the steering wheel 10 not served. In the operating state hands_off is lingered until one of the characteristic course 29 deviating course results, whereupon according to the arrow 62 in the operating state hands_on is passed.

6 shows a schematic block diagram 64 with a block 66 , The block 66 the actual torque M and the steering position Pos are supplied. The block 66 determined according to the method described above from the actual moment M and the steering position Pos a signal 70 , where the signal 70 two states according to the operating conditions hands_off and hands_on can take. The block 66 is especially as a computer program for the digital computing device 4 designed to be on the storage medium for the control unit 3 of the steering system 1 to be saved and executed.

Claims (14)

Method for detecting an operating state (hands_off; hands_on) of a steering wheel ( 10 ) in a steering system ( 1 ) of a motor vehicle, the operating state (hands_off; hands_on) describing whether a driver is turning the steering wheel ( 10 ), wherein an actual moment (M) on a torsion bar ( 9 ) of the steering system ( 1 ) and a steering position (Pos) of the steering system ( 1 ), characterized in that the operating state (hands_off), in which the driver controls the steering wheel ( 10 ) is not served, then it is detected when the actual moment (M) on the torsion bar ( 9 ) of the steering system ( 1 ) above the steering position (Pos) of the steering system ( 1 ) a characteristic course ( 26 ; 29 ) having. Method according to claim 1, characterized in that the characteristic profile ( 26 ; 29 ) is present when several temporally successive types ( 30 . 32 . 34 . 36 ) are recognized by parts of the way. Method according to claim 2, characterized in that the characteristic curve ( 26 ; 29 ) has a substantially trapezoidal, in particular substantially hysteresis-like arrangement of the stretchers. Method according to Claim 1, 2 or 3, characterized in that the operating state (hands_off) in which the driver drives the steering wheel ( 10 ) is not served, then it is recognized if the characteristic course ( 26 ; 29 ) is present for more than a predetermined period of time, in particular longer than 25 seconds. Method according to one of claims 2 to 4, characterized in that a first type ( 30 ) of a path is detected when substantially a first direction ( 38 ) of the time course of the steering position (Pos) is present and in the same period substantially a first direction ( 40 ) of the time characteristic of the actual torque (M) is present, and wherein a second type ( 32 ) of a path is detected when substantially a second direction ( 42 ) of the time course of the steering position (Pos) is present and in the same period essentially a second direction ( 44 ) of the time course of the actual moment (M) is present. Method according to one of claims 2 to 5, characterized in that a first or second type ( 30 ; 32 ) the distance pieces is then recognized when the steering position (Pos) a first range of values ( 46 ; 48 ) and the actual moment (M) over the same period of time covers a second value range ( 50 ). Method according to one of claims 2 to 6, characterized in that a third or fourth type ( 34 ; 36 ) the distance pieces is then recognized when either the steering position (Pos) a third range of values ( 52 ; 54 ) or essentially the second or third ( 38 ; 42 ) Direction of the steering position (Pos) is present and the actual torque (M) remains substantially the same in the same period. Method according to one of claims 2 to 4, characterized in that a first and third type ( 30 . 34 ) of the stretches are then recognized together when the steering position (Pos) covers a fourth range of values and in the same period at least temporarily substantially the first direction ( 40 ) of the time course of the actual moment (M) is present, and wherein a second and fourth type ( 32 . 36 ) of the stretches are then recognized together when the steering position (Pos) sweeps over a further fourth range of values and in the same period at least temporarily the second direction ( 44 ) of the time course of the actual moment (M) is present. Method according to one of the preceding claims, characterized in that the operating state (hands_off) in which the driver controls the steering wheel ( 10 ) is not operated, then it is detected when the steering position (Pos) in one direction only ( 38 ; 42 ) covers a fifth range of values. Method according to one of the preceding claims, characterized in that the actual torque (M) and / or the steering position (Pos) are low-pass filtered before the detection of the operating state (hands_on; hands_off). Method according to one of the preceding claims, characterized in that the actual torque (M) a sensor signal of a torque sensor ( 16 ), and wherein the steering position (Pos) a rotation angle of the torsion bar ( 9 ) or a rack position. Computer program for a digital computing device ( 4 ) which is adapted to carry out a method according to any one of the preceding claims. Control unit ( 3 ) for a steering system ( 1 ) of a motor vehicle, which is provided with a digital computing device, in particular a microprocessor, on which a computer program according to claim 12 is executable. Storage medium for a control unit ( 3 ) of a steering system ( 1 ) according to claim 13 on which a computer program according to claim 12 is stored.

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