Data processing: vehicles – navigation – and relative location – Relative location – Collision avoidance
Reexamination Certificate
1999-12-17
2001-05-01
Nguyen, Tan (Department: 3661)
Data processing: vehicles, navigation, and relative location
Relative location
Collision avoidance
C701S096000, C340S436000, C340S903000
Reexamination Certificate
active
06226593
ABSTRACT:
The invention relates to a method and an appliance for braking a motor vehicle in the immediate vicinity of an obstacle.
An automatic brake control system for a vehicle, which automatically generates a braking force if the distance and/or relative speed between the vehicle and a preceding vehicle falls below a certain limiting value, is known from the publication DE 43 10 354 A1. For this purpose, the distance apart and the speeds of the two vehicles are determined and compared, in a calculation device, with specified limiting values. If the measured distance apart and/or the relative speed is below the limiting values, braking signals are generated in a control device for controlling the brake system, by means of which signals the vehicle is retarded to such an extent that the distance and/or the relative speed required is restored.
This publication does not however show how, in the immediate vicinity, braking procedures can be optimized at small distances and relative speeds between the vehicle and the obstacle. In driving manoeuvres of this type—for example during parking—the problem exists that, because of the small distance apart (which may only be a few centimetres in certain cases), a rapid driver reaction is required for the change from accelerator to brake pedal in order to avoid collisions with the obstacle. In the case of restricted space relationships, it is often necessary to manoeuvre the vehicle with minimum distance to the obstacle, in which case—despite the usually low speed for these manoeuvres—even a slightly delayed reaction by the driver can lead to damage. In addition, faulty and panic reactions on the part of the driver, for example excessively powerful pedal actuations which cause a vehicle movement not desired by the driver and which can also involve fairly large-scale damage, cannot be excluded.
SUMMARY OF THE INVENTION
The invention is based on the problem of minimizing the reaction time in the case of the slow approach to an obstacle.
In accordance with the novel method, the approach to an obstacle is subdivided into two phases as a function of the distance between vehicle and obstacle. Although, in the first phase, the vehicle is located at a short distance from the obstacle, the distance is still large enough to permit the vehicle to travel at low speed. In this phase, the distance between vehicle and obstacle lies between two specified or calculated limiting values, the proximity limit, where the first phase begins when the distance falls below it, and the stop limit, where the second phase begins when the distance falls below it and in which the vehicle is brought into its final position and the vehicle speed is usually reduced to zero.
In the first phase—after the distance falls below the proximity limit and provided the vehicle speed has also fallen below a specified or calculated threshold value—both the braking torque decelerating the vehicle and the engine torque accelerating it are set to values greater than zero but under the additional condition that the value of the engine torque shall exceed the value of the braking torque. In this phase, the vehicle is acted on by opposing torques; because of the larger engine torque, however, the vehicle remains in motion and the vehicle is prevented from coming to rest before the final position has been reached. At the same time, however, the brake has already been applied.
Because both a braking torque and an engine torque act on the vehicle in the first phase, reaction times of the brake system and the engine to changes in the braking and/or engine torque are limited to a minimum value because there are no delays due to inertia and no transmission time losses. The vehicle reacts more spontaneously and, in addition, the external space relationships present can be exploited in an optimum manner.
Due to further approach of the vehicle to the obstacle, the distance falls below the stop limit and the second phase begins. In the second phase, the qualitative relationship between the braking torque and the engine torque reverses. The braking torque now exceeds the engine torque, with the result that the vehicle speed is reduced and a collision with the obstacle is avoided. The reversal of the relationship between the braking torque and the engine torque can be achieved by either increasing the braking torque or reducing the engine torque, or by a combination of the two. The decision as to whether an intervention in the brake system or an intervention in the engine management system (to adjust the engine drive torque) takes place can be made as a function of parameters and condition variables such as the remaining distance, relative speed, relative deceleration, type and size of the obstacle, type of the driving manoeuvre, specified braking function, etc.
Intervention to produce change in both the wheel brake and engine control systems can take place in the shortest possible time because both components are already acted upon by braking torque and engine torque and there are, therefore, no delays in building up a type of torque. Immediate-vicinity driving manoeuvres in particular, for example parking procedures, which necessitate braking the vehicle at a small distance from obstacles, can therefore be carried out in an optimized manner. It is possible to carry out continuous braking until the vehicle comes to rest, while avoiding deceleration jumps and jolts with, at the same time, the best possible utilization of space. The uniform deceleration helps to avoid undesirable driver reactions. In vehicles with brake-by-wire systems, furthermore, an automatic brake intervention can be undertaken which is not noticed by the driver, it being possible to intensify or moderate the brake pressure generated by the driver via the brake pedal by means of an automatically generated brake pressure.
In expedient developments of the method, the braking torque and the engine torque are adjusted in the first phase, in the distance range between the proximity limit and stop limit, in such a way that the vehicle moves at a constant speed which, particularly during parking, is located in a speed range up to a maximum of approximately 5 km/h.
In a preferred configuration, an obstacle recognition system is employed which can recognize the size and type of an obstacle and, as a function of these parameters, calculate a steering deflection or a steering angle travel in order to avoid the relevant obstacle or to realize an optimum driving function which takes account of the obstacle. The steering deflection or the steering angle travel can either be indicated to the driver optically and/or acoustically or can be undertaken automatically with the aid of servoelements. In the latter case, it can be expedient to intensify or moderate the steering angle intervention carried out by the driver in order to permit the vehicle to follow the optimum, calculated function. During the braking intervention and during the steering angle intervention, it can be advantageous to permit the deviation from the value specified by the driver within specified limits only in order to leave the driver with the final decision on the vehicle behaviour and, in addition, to provide him—for safety reasons—with the feeling that the vehicle reactions are exclusively attributable to him.
In accordance with an advantageous appliance, which is particularly suitable for carrying out the novel method, devices are provided for determining the distance and for determining the relative speed between the vehicle and the obstacle. In addition, the appliance includes a closed-loop and open-chain control device for determining an optimum braking strategy, a brake actuation device for actuation, independent of the driver, of a brake system and, if appropriate, a steering angle sensor including servo-element for adjusting the steering angle.
Appropriate signals, which can be supplied to the closed-loop and open-chain control device as input signals for further processing, are generated in the devices for determining the distance apart and the relative speed. These input signa
Kurz Gerhard
Muller Armin
Rohrig-Gericke Thomas
Schob Reinhold
Troster Harry
Calcaterra Mark P.
Daimler-Chrysler AG
Nguyen Tan
LandOfFree
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