Method and control unit for recognizing critical driving situations of a two-wheeled motor vehicle

Abstract

A method/control unit for recognizing critical driving situations of a two-wheeled motor vehicle (MV), including: ascertaining an instantaneous slip angle (ISA) and differential slip angle (DSA) of the front/rear wheels; ascertaining an instantaneous roll angle (IRA); comparing the ascertained SAs and DSAs to predetermined values (PV) of maximum allowable slip angles (MASA) or DSAs; comparing the IRA to PVs of a maximum allowable roll angle (MARA); and generating a criticality signal when one of the ISAs is greater than the PV of the MASA, at least one of the instantaneous DSAs is greater than the PV of the maximum allowable DSA, and the IRA is greater than the PV of the MARA. Critical driving situations are recognized with the method, and measures for stabilizing the two-wheeled MV or other safety-enhancing measures may be performed. Special driving situations (driving over low- patches or braking while negotiating a curve) may be considered.

Claims

1. A method for recognizing critical driving situations of a two-wheeled motor vehicle that includes a front wheel and a rear wheel, the method comprising: ascertaining an instantaneous slip angle and an instantaneous differential slip angle of the front wheel and/or an instantaneous slip angle and an instantaneous differential slip angle of the rear wheel; ascertaining an instantaneous roll angle of the two-wheeled motor vehicle; comparing the ascertained slip angles and the differential slip angles to respective corresponding predetermined values of maximum allowable slip angles or maximum allowable differential slip angles; comparing the instantaneous roll angle to a predetermined value of a maximum allowable roll angle; and generating a criticality signal when at least one of the instantaneous slip angles is greater than the associated predetermined value of the maximum allowable slip angle, at least one of the instantaneous differential slip angles is greater than the associated predetermined value of the maximum allowable differential slip angle, and the instantaneous roll angle is greater than the predetermined value of the maximum allowable roll angle.

2. The method of claim 1, wherein the instantaneous slip angle and the instantaneous differential slip angle are ascertained for both the front wheel and the rear wheel, and the predetermined value of the maximum allowable slip angle of the front wheel is increased to a higher value of a maximum allowable slip angle of the front wheel, provided that the ascertained instantaneous slip angle of the rear wheel is smaller than a reduced predetermined value of the maximum allowable slip angle of the rear wheel.

3. The method of claim 1, further comprising: ascertaining whether a brake of the two-wheeled motor vehicle is actuated, and when an actuation of the brake is recognized, the predetermined value of the maximum allowable roll angle is reduced to a lower value of the maximum allowable roll angle.

4. The method of claim 1, wherein the instantaneous slip angle of the front wheel and/or of the rear wheel is ascertained based on a measurement of an instantaneous sideslip angle of the two-wheeled motor vehicle.

5. The method of claim 1, wherein the instantaneous slip angle of the front wheel is ascertained based on a measurement of an instantaneous sideslip angle of the two-wheeled motor vehicle, and taking into account an ascertained instantaneous steering angle of the two-wheeled motor vehicle.

6. A control unit for a two-wheeled motor vehicle, comprising: a controller for recognizing critical driving situations of the two-wheeled motor vehicle, which includes a front wheel and a rear wheel, and configured to perform the following: ascertaining an instantaneous slip angle and an instantaneous differential slip angle of the front wheel and/or an instantaneous slip angle and an instantaneous differential slip angle of the rear wheel; ascertaining an instantaneous roll angle of the two-wheeled motor vehicle; comparing the ascertained slip angles and the differential slip angles to respective corresponding predetermined values of maximum allowable slip angles or maximum allowable differential slip angles; comparing the instantaneous roll angle to a predetermined value of a maximum allowable roll angle; and generating a criticality signal when at least one of the instantaneous slip angles is greater than the associated predetermined value of the maximum allowable slip angle, at least one of the instantaneous differential slip angles is greater than the associated predetermined value of the maximum allowable differential slip angle, and the instantaneous roll angle is greater than the predetermined value of the maximum allowable roll angle.

7. A two-wheeled motor vehicle, comprising: a control unit for recognizing critical driving situations of the two-wheeled motor vehicle, which includes a front wheel and a rear wheel, and configured to perform the following: ascertaining an instantaneous slip angle and an instantaneous differential slip angle of the front wheel and/or an instantaneous slip angle and an instantaneous differential slip angle of the rear wheel; ascertaining an instantaneous roll angle of the two-wheeled motor vehicle; comparing the ascertained slip angles and the differential slip angles to respective corresponding predetermined values of maximum allowable slip angles or maximum allowable differential slip angles; comparing the instantaneous roll angle to a predetermined value of a maximum allowable roll angle; and generating a criticality signal when at least one of the instantaneous slip angles is greater than the associated predetermined value of the maximum allowable slip angle, at least one of the instantaneous differential slip angles is greater than the associated predetermined value of the maximum allowable differential slip angle, and the instantaneous roll angle is greater than the predetermined value of the maximum allowable roll angle.

8. The two-wheeled motor vehicle of claim 7, further comprising: a sensor system to ascertain the instantaneous slip angle of the front wheel and/or of the rear wheel, the instantaneous differential slip angle of the front wheel and/or of the rear wheel, and the instantaneous roll angle of the two-wheeled motor vehicle; a data memory to store predetermined values of maximum allowable slip angles, predetermined values of maximum allowable differential slip angles, and the predetermined value of the maximum allowable roll angle; a data processing unit to compare the instantaneous slip angle to the associated predetermined value of a maximum allowable slip angle, for comparing the instantaneous differential slip angle to the associated predetermined value of a maximum allowable differential slip angle, and for comparing the instantaneous roll angle to the predetermined value of a maximum allowable roll angle; and a signal generation unit to generate the criticality signal when at least one of the ascertained instantaneous slip angles is greater than the associated predetermined value of the maximum allowable slip angle, and at least one of the ascertained instantaneous differential slip angles is greater than the associated predetermined value of the maximum allowable differential slip angle, and the ascertained instantaneous roll angle is greater than the predetermined value of the maximum allowable roll angle.

9. The two-wheeled motor vehicle of claim 8, wherein the sensor system includes a steering angle sensor for ascertaining an instantaneous steering angle of the front wheel of the two-wheeled motor vehicle, and a sideslip angle sensor for ascertaining an instantaneous sideslip angle of the two-wheeled motor vehicle, and wherein the data processing unit is configured for deriving the instantaneous slip angles and the instantaneous differential slip angles based on sideslip angles ascertained by the sideslip angle sensor, taking into account steering angles ascertained by the steering angle sensor.

10. The two-wheeled motor vehicle of claim 7, further comprising: a safety device which includes one of: a traction control system, an anti-lock braking system, a device for generating additional stabilizing lateral forces, a device for increasing contact forces, a device for outputting warning signals, a device for activating safety units, and/or a device for outputting an electronic assistance call; wherein the controller is configured to activate the safety device with the generated criticality signal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a two-wheeled motor vehicle according to one specific embodiment of the present invention.

(2) FIG. 2 shows a schematic view, from above, of a two-wheeled motor vehicle for illustrating steering angles and sideslip angles.

(3) FIG. 3 shows a schematic view, from the front, of a two-wheeled motor vehicle for illustrating a roll angle.

DETAILED DESCRIPTION

(4) FIG. 1 shows a two-wheeled motor vehicle 1 that is configured for carrying out the method provided herein for recognizing critical driving situations, with the aid of a specially configured control unit 3. Two-wheeled motor vehicle 1 includes a sensor system 5, which may be configured in particular in the form of an inertial sensor system, and with the aid of which a data processing unit 6 of control unit 3 is enabled to ascertain instantaneous slip angles of front wheel 7 or of rear wheel 9 of two-wheeled motor vehicle 1, changes in these slip angles over time, and an instantaneous roll angle of two-wheeled motor vehicle 1. In particular the sensor system may be configured for measuring or determining an instantaneous sideslip angle of two-wheeled motor vehicle 1, and may thus act as a sideslip angle sensor 21. In the illustrated example, sensor system 5 is shown as a separate component; however, it may also be integrated into control unit 3. Two-wheeled motor vehicle 1 also includes a steering angle sensor 11, with the aid of which an instantaneous steering angle, at which front wheel 7 is steered, may be determined. In addition, a data memory 13 that is integrated into control unit 3 or configured as a separate component is provided, in which predetermined values of maximum allowable slip angles, maximum allowable values for differential slip angles, and maximum allowable values for the roll angle may be stored. A wheel speed sensor 15, 17 is also provided for front wheel 7 and rear wheel 9, respectively. In addition, a signal generation unit 19 is provided in control unit 3 for outputting a criticality signal when a critical driving situation is recognized. The criticality signal may activate a safety device 23 of the two-wheeled motor vehicle, for example for stabilizing the driving situation.

(5) The schematic top view from above of two-wheeled motor vehicle 1 illustrated in FIG. 2 shows a steering angle between a vehicle longitudinal axis 19 and a direction in which front wheel 7 is steered at that moment, and a sideslip angle , between vehicle longitudinal axis 19 and a movement direction 21 at the center of gravity of two-wheeled motor vehicle 1. A slip angle between a velocity vector at the wheel contact point and an intersection line between the wheel center plane and the roadway plane may be ascertained or estimated with knowledge of instantaneous steering angle and instantaneous sideslip angle .

(6) It is pointed out that the angles in question are illustrated for simplified representation of an upright two-wheeled motor vehicle 1, and in particular may be illustrated differently for a two-wheeled motor vehicle 1 that is negotiating a curve.

(7) The schematic front view of two-wheeled motor vehicle 1 illustrated in FIG. 3 shows a roll angle between two-wheeled motor vehicle 1 and a vertical direction 23.

(8) A method, i.e., a recognition algorithm, has been developed that is able to reliably distinguish between stable and unstable driving states. For this purpose, slip angle and differential slip angle d of at least one of the wheels, as well as roll angle , are continuously or periodically monitored and compared to associated maximum allowable values, and when the limiting values for all three variables are simultaneously exceeded, the presence of instability is assumed and a criticality signal is output.

(9) In the event of an instability, a further distinction is made concerning whether a roadway having a homogeneous friction coefficient is present, or whether the roadway has locations with a lower friction coefficient (low- patches). This may be important, since it determines the sequence in which front wheel 7 and rear wheel 9 become unstable. On roadways having a homogeneous friction coefficient, an instability generally occurs at rear wheel 9 first. Shortly thereafter, front wheel 7 becomes unstable and quickly turns, based on the steering kinematics, in the direction of the inner side of the curve.

(10) When traveling on a roadway having low- patches, front wheel 7 crosses a slick location first, followed by rear wheel 9. As a function of the length of the low- patch and the difference in friction coefficients between roadway surfaces that have good traction and that are slick, once again due to the steering kinematics, moderate to large steering angles and slip angles occur at front wheel 7, while rear wheel 9 has instability only in long low- patches having a large difference in friction coefficients. Moderately large front wheel slip angles .sub.1 do not always result in a fall, since front wheel 7 is often able to restabilize itself in the transition from the slick roadway surface to the roadway surface with good traction. However, the brief instability may result in a faulty recognition, and thus, unnecessary triggering of an intervention or a safety measure. To avoid the faulty recognition, intervention threshold .sub.1,max is increased, at least temporarily, to a larger value .sub.1,max,incr, provided that the rear axle has low slip angles .sub.2 that are less than a reduced value .sub.2,max,decr.

(11) In the event of a longer low- patch with a large difference in friction coefficients, rear wheel 9 also becomes unstable. It may then be advantageous to reduce the intervention threshold for .sub.1,max back to the normal value.

(12) Faulty intervention for brief instabilities is thus prevented by suitable selection of parameters; however, for longer instabilities a necessary intervention is triggered. The instability recognition at the front wheel 7 may thus also take place as a function of driving dynamic variables of rear wheel 9.

(13) To distinguish between unstable and stable driving states, it may also be advantageous to observe how quickly a slip angle .sub.1, .sub.2 increases at front and/or rear axle 7, 9. Simulations have shown that slip angles .sub.1, .sub.2 may safely reach maximum values .sub.1,max, .sub.2,max and even slightly exceed them, provided that the rate of the increase is low. For this reason, a linkage of slip angles .sub.1, .sub.2 to differential slip angles d.sub.1, d.sub.2 is implemented in the instability recognition logic system described herein.

(14) However, considerable slip angles .sub.1, .sub.2 may occur even during straight-ahead driving, due to ruts or when traveling over gravel or rough roads. The additional querying of motorcycle roll angle allows a recognition of the unstable state only when high transverse dynamics are also present. Faulty recognitions are thus avoided.

(15) As the result of braking operations at a high inclined position at front and/or rear axle 7, 9, two-wheeled motor vehicle 1 generally resumes an upright position relatively quickly. In this case, the threshold value of roll angle is reduced. It may therefore be advantageous to recognize a braking operation, for example by querying brake light switches, or by brake pressure sensors if present, and to subsequently reduce value .sub.max, at least temporarily, to a lower value .sub.max,decr, since necessary interventions would otherwise be prevented.

(16) One specific embodiment of a method described herein, i.e., an instability recognition logic system, as may be implemented in software and/or in hardware in a control unit, may therefore also be described by formulas, as follows:

(17) Instability of rear wheel when: |.sub.2|>.sub.2,max AND |d.sub.2|>d.sub.2,max AND ||>.sub.max

(18) Instability of front wheel when: ||>.sub.1,max AND |d.sub.1|>d.sub.1,max AND ||>.sub.max

(19) Changed parameters for low- patch situations:

(20) If |.sub.2|<.sub.2,max,decr, then .sub.1,max is increased to .sub.1,max,incr

(21) When the front and/or rear brake are/is actuated, the following applies:

(22) .sub.max is decreased to .sub.max,decr

(23) Variables:

(24) ||=absolute value of the motorcycle roll angle

(25) .sub.1=front wheel slip angle

(26) .sub.2=rear wheel slip angle

(27) d.sub.1=differential of .sub.1

(28) d.sub.2=differential of .sub.2

(29) Parameters:

(30) .sub.max [rad] value applies for unbraked driving maneuvers

(31) .sub.max,decr [rad] reduced value for braked driving maneuvers

(32) .sub.1,max [rad] maximum allowable front axle slip angle

(33) .sub.2,max [rad] maximum allowable rear axle slip angle

(34) .sub.1,max,incr [rad] increased value at front wheel for low- patch situations

(35) .sub.2,max,decr [rad] reduced value at rear wheel for low- patch situations

(36) d.sub.1,max [rad/s] maximum allowable differential front axle slip angle

(37) d.sub.2,max [rad/s] maximum allowable differential rear axle slip angle.

(38) In conclusion, it is noted that terms such as having, including, etc., do not exclude other elements or steps, and terms such as a or an do not exclude a plurality. Reference numerals in the claims are not to be construed as limiting.