It is known from German Patent Application No. DE 39 09 644 to perform a measurement of the inherent velocity of a vehicle in accordance with the Doppler radar principle, a signal reflected from the ground being utilized.
The apparatus according to the present invention for determining inherent vehicle velocity has the advantage that the evaluation of inherent vehicle velocity by means of a pre-crash sensor suite on the basis of signals reflected from the ground is used only when a predefined operating state exists. This predefined operating state may be, for example, locked wheels, slipping wheels, or wheels suspended in the air. The reason is that these operating states mean that a measurement of the inherent velocity by way of wheel rotation speed fails. The inherent velocity measurement is therefore then performed using the pre-crash sensor suite on the basis of signals reflected from the ground.
It is particularly advantageous that the pre-crash sensor suite has a radar sensor suite. It is furthermore advantageous that the apparatus compares the signal reflected from an object with the inherent vehicle velocity in such a way as to classify the object. Specifically, if the object possesses, on the basis of the reflected signals, a relative motion with respect to the vehicle that is equal to the inherent velocity, it is then a stationary object. That stationary object could then also be used to determine the inherent velocity.
In an airbag algorithm at present, signals from impact sensors such as acceleration sensors are evaluated. The relative velocity between the vehicle and a crash object, as well as the inherent velocity, are important parameters for obtaining a better determination of the triggering time. These parameters can be ascertained by means of a pre-crash sensor suite. Usually, however, the inherent velocity is determined in the ESP/ABS control unit by means of wheel rotation speeds. This information is no longer correct, however, in certain operating states such as locked or spinning or suspended wheels.
The inherent velocity is an important variable for ESP/ABS function. An exact estimate in critical situations, e.g. locked wheels, thus also improves vehicle stability.
It is consequently provided according to the present invention to determine the inherent vehicle velocity in such operating states by means of the pre-crash sensor suite. This is accomplished on the basis of signals reflected from the ground, i.e. from the road surface. Because the distance and angle of the radar beams with respect to the road surface is constant, the signal time from transmission to reception is an indication of the inherent velocity of the vehicle.
Because of the wide opening angle of the pre-crash sensor, in addition to the actual usable signals from oncoming or stationary obstacles, signal components deriving from the road are also obtained. From these constantly present signal components, the inherent velocity of the vehicle can then be calculated. The pre-crash sensor suite can advantageously use a radar sensor suite here, but it is also possible to use an ultrasonic sensor suite or lidar technology, or other signals that are emitted and reflected back.
When the beam component reflected back from the road is evaluated, what is obtained is an object that is always at the same distance in front of the vehicle. It is made up of a sequence of objects that are moving toward the vehicle. When the velocity of the object sequence is then evaluated, it is then found to correspond to the inherent velocity. Because of the fixed distance of the object and the object velocity that is directed toward the vehicle, the object can be distinguished from crash-relevant objects and thus employed for determination of the inherent velocity.
Number | Date | Country | Kind |
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103 31 965.4 | Jul 2003 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/DE04/01480 | 7/8/2004 | WO | 12/13/2005 |