Communications: electrical – Land vehicle alarms or indicators – Of collision or contact with external object
Reexamination Certificate
1999-07-12
2001-11-27
Hofsass, Jeffery (Department: 2632)
Communications: electrical
Land vehicle alarms or indicators
Of collision or contact with external object
C340S435000, C340S465000, C340S576000, C340S903000
Reexamination Certificate
active
06323763
ABSTRACT:
BACKGROUND OF THE INVENTION
This application claims the priority of German application 198 31 071.4, filed in Germany on Jul. 10, 1998, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a steering system for motor vehicles, a steering handle, for example, steering handwheel, capable of being operated by the driver, a steering actuating drive for the steering adjustment of steerable vehicle wheels, with a steering-angle desired-value encoder capable of being operated by the steering handle, a steering-angle actual-value encoder capable of being operated by the steerable vehicle wheels, and a regulating and control arrangement operating the steering actuating drive as a function of a comparison of the desired and actual values of the steering angle.
A steering system of the foregoing type may be designed, in particular, for steer-by-wire operation, in which, where appropriate, a mechanical steering column, customary in conventional steering systems, can be replaced by another mechanical system or else by a hydraulic system, in particular a hydrostatic system.
Car manufacturers are making great efforts, based on various concepts, to increase vehicle safety and, consequently, the safety of vehicle occupants. According to one of these concepts, measures are indicated, by means of which, for example, the risk of collision of the vehicle with an obstacle is reduced. Collisions of this kind may occur, for example, when, if a first vehicle changes lane, a second vehicle is in the so-called “blind spot” of the first vehicle. Collisions when the vehicle is being manoeuvred are less serious, but are all the more frequent. Also, the fear of collisions, for example when the vehicle is being parked, often means that, when parking spaces are tight, drivers often do not even attempt to park the vehicle.
Electronic parking aids are known for manoeuvring the vehicle. These aids generate an acoustic signal, and warn the driver, on the basis of range-measuring sensor technology, when a critical distance between the vehicle and an obstacle is reached. At higher speeds, parking aids of this type are unsuitable for avoiding collisions, for example during a change of lane.
EP 0,738,647 A2 discloses a conventional power steering system with a rigid steering column which has a servomotor for assisting a manual steering force exerted by the driver. Moreover, the known power steering system has means for deciding whether there is the possibility of a collision between the vehicle and an obstacle detected in the steering direction. When the risk of a collision is detected in the known power steering system, there is a reduction in the power assistance, so that a collision course can be controlled only by increased manual steering force. At the same time, in order to avoid a collision, the known power steering system may work as sluggishly as a conventional power steering system in which the power assistance has failed.
The collision avoidance principle used in the known power steering system can be applied, however, only to a steering system having a rigid steering column. It is not possible to use it in a steering system which works by steer-by-wire operation or in a steering system with an open steering column, that is to say a steering system without a rigid steering column, for example a steering system with a hydraulic rod, a steering column with couplings, planetary assemblies or other gearings which interrupt the rigid drive-through from the steering wheel to the steered wheels. This is because, in steering systems of this type without a rigid coupling between the steering handle and the steered wheels, such a reduction in the power assistance would not be noticed on the steering handwheel by the driver. Thus, if lateral wheel forces act on the steered wheels, changes in direction of travel which can no longer be controlled by the driver may occur.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a steering system in which a risk of collision between a vehicle equipped with it and an obstacle is reduced, while, at the same time, the steering system is to continue to be suitable for steer-by-wire operation.
This problem has been solved according to the present invention by providing a steering system comprising a steering handle arranged to be operated by a vehicle driver, a steering actuating drive operatively arranged for steering adjustment of steerable vehicle wheels, a steering-angle desired-value encoder operatively associated with the steering handle; a steering-angle actual-value encoder operatively associated with the steerable vehicle wheels; a regulating and control arrangement arranged to operate the steering actuating drive as a function of a comparison of desired and actual values of the steering angle; and a collision prevention apparatus, configured to determine steering angles defining a collision path between the motor vehicle and an obstacle, wherein the regulating and control arrangement is operatively arranged to hinder or prevent the setting of a desired steering angle coinciding with one of the collision steering angles.
The invention is based on the general recognition of acting on the steering system such that the driver is hindered or even prevented from setting a desired steering angle coinciding with a collision steering angle. With the aid of this measure, faulty steering manoeuvres leading to collisions are intercepted or reduced as early as on the desired-value side of the steering system, and the actual-value side of the steering system can remain unchanged.
In particular, the steering actuating drive can transmit the same high stabilizing actuating forces to the steerable vehicle wheels. When the setting of a desired steering angle coinciding with one of the collision angles is hindered or prevented, it follows from the unchanged dependence of the actual steering angle on the desired steering angle that an actual steering angle coinciding with one of the collision steering angles also can be set only with difficulty, or not at all. Thereby, in actual fact, a collision course of the vehicle with a detected obstacle is impeded or avoided.
Since the actual-value side of the steering system is unchanged, for example, lateral forces acting on the steerable vehicle wheels cannot cause any uncontrolled steering manoeuvre. The steering system according to the invention is therefore particularly suitable for steer-by-wire operation.
Moreover, the invention provides that the regulating and control arrangement is configured to operate the steering actuating drive to prevent an actual steering angle from coinciding with one of the collision steering angles.
The invention is also based on the recognition, particularly in a steering system working by steer-by-wire operation, that the dependence of the actual steering angle on the desired steering angle is modified, to the effect that an actual steering angle predetermined by a desired steering angle is set only as long as the set actual steering angle does not correspond to one of the detected collision steering angles.
Desired steering angles exceeding the desired steering angle are then ignored. This measure also results in the effective prevention of a collision between the vehicle and a detected obstacle. Since, in this system too, the actuating forces for steering the steerable vehicle wheels are unchanged, uncontrolled steering movements cannot occur, in this embodiment either, in the event of lateral forces acting on the steerable vehicle wheels, as a result of which this steering system, too, can be used with steer-by-wire operation.
While this solution gives the steering system or the vehicle priority over the driver's wishes, the above-mentioned solution adopts a different approach and leaves ultimate control over the vehicle to the driver.
Particularly in a development of the first-mentioned embodiment of the steering system according to the invention, countersteering apparatus can be provided. Thereby, the steering handle capable of being opera
Bohner Hubert
Freitag Rainer
Moser Martin
Schneckenburger Reinhold
Crowell & Moring LLP
Daimler-Chrysler AG
Hofsass Jeffery
Nguyen Hung
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