Adaptive cruise control: New Siemens development detects fog and poor visibility

Adaptive cruise control in its next generation:

Siemens VDO has developed an adaptive cruise control (ACC) system that alerts the driver when there is insufficient distance to the vehicle ahead during poor visibility conditions. The automotive supplier uses an optical sensor (LIDAR) with exceptionally powerful evaluation electronics to accomplish this. Within the scope of pro.pilot – the Siemens VDO driver assistance network – deployment of the cost-efficient sensors will be realized in new medium-sized and compact car models in the near future, as early as 2008.

A nightmare during the morning drive on the freeway: lines of traffic at high speeds with little space between the cars. A fog bank reduces your vision and only with great effort can you brake your own car just before hitting the brake lights of the car ahead. Lucky! Unfortunately, there are still far too many accidents in which the driver realized too late how critical the situation was – often with deadly consequences. For comfortable, convenient and safe driving, Siemens VDO is currently developing pro.pilot, a network of driver assistance systems. Pro.pilot provides enhanced comfort, convenience and safety for drivers and promptly alerts them to accident hazards. One feature of pro.pilot is an adaptive cruise control (ACC) function based on LIDAR sensors (LIght Detection And Ranging). In contrast to a radar sensor, the LIDAR sensor can also detect rain, fog, snow and spray. In accordance with driver preference, in poor visibility conditions, the electronics reduce the speed and increase the distance to the car ahead.

The LIDAR sensor from Siemens VDO consists of infrared emitters, a photodiode as a receiver for the bundled invisible infrared light and the evaluation electronics. The sensor continuously measures the propagation time of the transmitted infrared rays. The time the light needs to travel from the sensor to the vehicle ahead and back again is measured. Based on
these propagation times, the electronics calculate the distance to the next vehicle ahead. The electronic image differentiates between objects, which means it can distinguish cars, trucks or motorcycles from stationary objects. Since the LIDAR sensor works on a wavelength similar to visible
light, it can recognize visibility restrictions caused by weather; the driver alert and speed adjustment functions are based on this.

Up to now, automatic distance controls have been installed almost exclusively in luxury automobiles. Expensive radar sensors are used there as the data source for the ACC and cannot make visibility range measurements.
Siemens VDO is pursuing the goal of making driver assistance systems available for a wide range of vehicles. To this end, the corporation already started developing ready-for-production LIDAR sensor systems back in 2003 for use in all automobiles, since these are much less expensive than radar sensor systems.

In actual application, the LIDAR-based ACC, with a range of 250 meters, does not otherwise differ from the existing radar systems already used in the luxury class vehicles: the driver specifies the desired cruise control speed and the car maintains this speed until the system detects another road user in the same lane. The speed is then reduced as much as necessary until the preset safety distance is maintained. This safety clearance is not oriented on an absolute distance, but is rather automatically adjusted to the speed being driven.

As a system supplier in the driver assistance sector, Siemens VDO considers, along with the electronic recognition and evaluation of the vehicle's surroundings, the most important development challenge is the convenient interaction between the driver and the system. The human-machine interface will be decisive in terms of whether drivers actually accept driver-assistance systems and thus prevent accidents.

Related news: Foursprung, P4MR, adaptive cruise control

Source: Siemens VDO

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