The invention relates to a method for carrying out an avoidance maneuver of a motor vehicle. In a first method step, an object in the surroundings of the motor vehicle with which the motor vehicle is on a collision course is detected. A warning is then output to the vehicle driver, to the effect that the motor vehicle is on a collision course, and the steering activity of the vehicle driver is detected. An externally actuable rear-wheel steering device is subsequently switched in such a way that the front wheels and the rear wheels of the motor vehicle are controlled in the same direction. The invention also relates to a device for carrying out an avoidance maneuver.
Such a method is known from DE 10 2008 013 988 A1, which is incorporated by reference. In the previously known method, a path for the avoidance maneuver of the motor vehicle determined and the steering system of the motor vehicle is influenced as a function of the determined path. In this context, the previously known method provides that the steering system combines a front-wheel steering function and a rear-wheel steering function in such a way that the front wheels and the rear wheels of the motor vehicle are controlled in the same direction. The effect which is brought about is that actuation of the front wheels and of the rear wheels in the same direction gives rise to a more stable driving behavior during the avoidance maneuver. However, at the same time increased steering effort is necessary for the vehicle driver than is the case with rear wheels which are not steered or are steered in an opposing direction.
An aspect of the present invention is therefore to improve a method of the type mentioned at the beginning and a device for carrying out the method to the effect that an avoidance maneuver continues to be capable of being controlled by the vehicle driver using front wheels and rear wheels which are controlled in the same direction.
There is provision here that the vehicle movement dynamics effects of the actuation of the externally actuable rear-wheel steering device in the same direction are compensated. This compensation provides that a further warning is output to the vehicle driver in order to cause the vehicle driver to perform a greater steering activity which is necessary as a result of the actuation of the externally actuable rear-wheel steering device in the same direction.
In one particularly advantageous development of the method according to aspects of the invention, a path is calculated for the avoidance maneuver of the motor vehicle, and, when a deviation is present between the calculated steer angle which is necessary for avoidance and the steer angle which is set by the vehicle driver, the further warning is output to the vehicle driver in order to prompt him to correct the deviation.
A further advantageous development provides that the further warning to the vehicle driver be formed by a torque which is applied by a front-wheel steering device, which can be activated electro-mechanically, and can be felt by the vehicle driver at the steering wheel. The torque points in the direction of the calculated steer angle which is necessary for avoidance. In order to generate the torque, the front-wheel steering device which can be activated electro-mechanically is actuated with the effect of setting the calculated steer angle which is necessary for avoidance. In this context, the calculated steer angle which is necessary for avoidance is set by the front-wheel steering device which can be activated electro-mechanically, if the vehicle driver does not perform any opposing steering movements. If the vehicle driver has taken his hands away from the steering wheel, the calculated steer angle which is necessary for avoidance is therefore set. The vehicle driver is, however, capable at any time of overriding the proposed steer angle and steering in the other direction or locking the steering wheel further than is necessary for avoidance. In other words, the vehicle driver determines the locked steer angle and is merely assisted by the method.
In one development of the inventive idea, there is provision that the first warning to the vehicle driver is formed by vibration or oscillation which is applied by the front-wheel steering device, which can be activated electro-mechanically, and can be felt by the vehicle driver at the steering wheel.
One particularly advantageous development provides that the calculated steer angle which is necessary for avoidance is determined with the following steps:
In this context, the avoidance path is a circular path, a parabola, a trajectory or a combination of these geometric shapes.
In the case of the device which achieves the above-mentioned advantages, means are provided according to aspects of the invention which compensate the vehicle movement dynamics effects of the actuation of the externally actuable rear-wheel steering device in the same direction and output a further warning to the vehicle driver in order to cause the vehicle driver to perform a greater steering activity which is necessary as a result of the actuation of the externally actuable rear-wheel steering device in the same direction.
The means calculate a path for the avoidance maneuver of the motor vehicle and calculate a deviation between the calculated steer angle which is necessary for avoidance and the steer angle which is set by the vehicle driver, and in that, when a deviation is present, the means output a further warning to the vehicle driver in order to prompt him to correct the deviation. The further warning is generated by a front-wheel steering device which can be activated electro-mechanically and which, when actuation occurs, applies a torque which can be felt by the vehicle driver at the steering wheel.
The invention is best understood from the following detailed description when read in connection with the accompanying drawings. Included in the drawings is the following figures:
a shows a velocity diagram during an avoidance maneuver;
b shows a diagram of the steer angle δsetp, set by the vehicle driver, and the yaw rate during an avoidance maneuver;
c shows a diagram of a torque M which can be felt by the vehicle driver at the steering wheel;
d shows a diagram which illustrates the distance from the object O with which the motor vehicle is on a collision course, and
e shows a diagram of the lateral deviation during an avoidance maneuver.
Within the sense of the present invention, the steering wheel is representative of all the conceivable man/machine interfaces which a vehicle driver can operate in order to steer and control the motor vehicle, such as for example a joystick or a touchpad.
The advantage of actuating the front wheels and rear wheels in the same direction during an avoidance maneuver is that a more stable driving behavior is achieved during the avoidance maneuver. However, at the same time a greater steering effort is required for the vehicle driver than is the case with rear wheels which are not steered or are steered in an opposing direction.
The present method therefore provides that the vehicle movement dynamics effects of the actuation of the externally actuable rear-wheel steering device H in the same direction are compensated. Since the vehicle driver is not prepared for the increased steering effort, it is therefore necessary to allow for the fact that the vehicle driver turns in too little to be able to safely drive around the object O. In order to compensate for the increased steering effort, a further warning X2 is output to the vehicle driver, which causes the vehicle driver to perform a necessary greater steering activity δv, which is necessary due to the actuation of the externally actuable rear-wheel steering device H and of the front-wheel steering device V in the same direction. The additional warning X2 to the vehicle driver which has just been mentioned is formed here by a torque M which is applied by the front-wheel steering device V which can be activated electro-mechanically. This torque M can be felt by the driver at the steering wheel of his motor vehicle 1. The front-wheel steering device V which can be activated electro-mechanically is actuated here in the direction of the necessary steer angle correction, as a result of which the vehicle driver feels, at the steering wheel, a torque M which suggests to him that he should perform a steer angle correction independently. If the vehicle driver takes his hands away from the steering wheel, the calculated steer angle which is necessary for avoidance is set. However, the vehicle driver is capable at any time of overriding the proposed steer angle and steering in the other direction or locking the steering wheel further than is necessary for avoidance. In other words, the vehicle driver determines the locked steer angle and is merely assisted by the method. What is a necessary steer angle correction here and how this is determined will be explained below: at the time at which a steering activity δv of the vehicle driver is detected, the difference d from the object O is determined and an avoidance path y(x) for the avoidance maneuver of the motor vehicle 1 is calculated. A circular path, a trajectory or a combination of a circular path and a trajectory is possible as an avoidance path y(x). The calculated steer angle δsetp, v which is necessary for avoidance is obtained directly from the calculated avoidance path y(x). Subsequently, the steer angle δact, v which is set by the vehicle driver is determined continuously and compared with the calculated steer angle δsetp, v which is necessary for avoidance. Given the presence of a deviation Δδv between the calculated steer angle δsetp, v which is necessary for avoidance and the steer angle δact, v which is set by the vehicle driver, the further warning X2 is output to the vehicle driver in order to prompt him to correct or minimize the deviation Δδv. In order to generate the warning X2, the front-wheel steering V, which can be activated electro-mechanically, is actuated with the effect of setting the calculated steer angle δsetp, v which is necessary for avoidance. The torque M which can be felt at the steering wheel therefore points in the direction of the calculated steer angle δsetp, v which is necessary for avoidance.
As is directly apparent from
Of course, it is conceivable to return the vehicle driver back to the position corresponding to the initial position after the avoidance. A further torque M is therefore predefined to the vehicle driver at the steering wheel, which further torque M returns him to his original direction of travel which he was following before the avoidance maneuver. If a further object with which the motor vehicle is on a collision course appears during the described method or subsequent thereto, the method is re-started.
A number of variables during an avoidance maneuver are contrasted in
c illustrates the time period in which the front-wheel steering device V is actively actuated in order to generate the torque M at the steering wheel.
e illustrates the first warning X1 which is output to the vehicle driver and is formed by means of vibration or oscillation at the steering wheel. Furthermore, the lateral deviation of the calculated avoidance path y(x) is illustrated, as is the detection of the steering activity δv of the vehicle driver.
In an alternative embodiment it is conceivable to apply an additional steer angle δadd instead of a further warning X2 in the form of a torque, which can be felt at the steering wheel and is in a predefined steering direction, which additional steer angle δadd reduces the deviation Δδv between the calculated steer angle δsetp, v which is necessary for avoidance and the steer angle δact, v which is set by the vehicle drive, so that the avoidance maneuver can be safely carried out. This additional steer angle δadd is therefore applied independently of the driver's request and forces the motor vehicle 1 onto the calculated avoidance path y(x). This correction in the event of deviation from the calculated avoidance path y(x) can be carried out with a variable ratio steering system as a front-wheel steering device. In this alternative embodiment, a further warning X2 to the vehicle driver is therefore dispensed with and instead the calculated steer angle δsetp, v which is necessary for avoidance is set. The vehicle driver is assisted in this alternative method to the effect that his vehicle is forced onto the avoidance path provided. In contrast, further changes compared to the method described in detail are not necessary since all the other method steps have an identical sequence.
The advantage of the described methods is that an avoidance maneuver is carried out safely and with a stable driving behavior and collisions are reliably avoided.
Number | Date | Country | Kind |
---|---|---|---|
10 2009 007 184.9 | Feb 2009 | DE | national |
This application is the U.S. National Phase Application of PCT International Application No. PCT/EP2010/051001, filed Jan. 28, 2010, which claims priority to German Patent Application No. 10 2009 007 184.9, filed Feb. 3, 2009, the contents of such applications being incorporated by reference herein.
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/EP2010/051001 | 1/28/2010 | WO | 00 | 7/29/2011 |