The invention relates to a driver assistance device having a plurality of ultrasound sensors. Moreover, the invention also relates to a vehicle having such a driver assistance device as well as a method for operating a driver assistance device.
A plurality of different driver assistance systems or driver assistance devices for motor vehicles is known. A number of such driver assistance devices operate on the basis of ultrasound sensors that are designed for detecting the surroundings of a vehicle. Specific actions are carried out depending on this information, which is detected by means of the ultrasound sensors, e.g. information is output to the driver of the vehicle and/or at least one semi-autonomous process is carried out for driving the vehicle by the driver assistance device.
With current parking assistance systems or parking assistance devices the distance between an object and the vehicle is determined using the transition time of previously transmitted ultrasound signals. An ultrasound sensor transmits a defined number of ultrasound signals, which in turn are received by one or a plurality of the ultrasound sensors. These are always the same ultrasound signals. It is therefore not possible for adjacent ultrasound sensors to transmit simultaneously, because the received ultrasound signals cannot otherwise be unambiguously assigned.
Moreover, a method of operating an ultrasound sensor array is known from DE 101 06 142 A1. Said array comprises at least two transmitting units distributed along the circumference of the motor vehicle for transmitting ultrasound pulses, and at least one receiving unit for receiving ultrasound pulses reflected at an object in the monitoring area. A plurality of transmitting units can be operated in parallel and at the same time transmit ultrasound pulses that are encoded relative to each other. For encoding, carrier signals of the ultrasound pulses are frequency modulated differently for the individual simultaneously operated transmitting units at least during the pulse period and the received encoded ultrasound pulses are assigned to individual simultaneously operated transmitting units by the at least one receiving unit using the encoding.
Regarding the encoding of ultrasound signals, a plurality of options and procedures are mentioned in said DE 101 06 142 A1. Besides frequency encoding, in which the frequency of the carrier signal of a first transmitting unit is upward modulated and the frequency of the carrier signal of a second transmitting unit is downward modulated, amplitude modulation can also be carried out over one or a plurality of pulses.
Such ultrasound sensors, which transmit encoded ultrasound signals, are however relatively expensive.
Moreover, it is not necessary for each function of a driver assistance system to transmit such encoded ultrasound signals, but conventional unencoded signals are also sufficient.
The object of the present invention is to provide a driver assistance device with whose ultrasound sensors high functionality in respect of safe and reliable detection of the surroundings is guaranteed and which can be implemented inexpensively.
This object is achieved by a driver assistance device, a vehicle having such a driver assistance device and a method for operating such a driver assistance device according to the independent claims.