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Flexible fusion
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12/09/2006
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The extensive use of electronic systems by the automotive market is well documented. Of the many applications enabled by electronic technology, driver assistance systems have come to the fore as 24GHz radar systems for passenger cars have been introduced. In addition to lane change assistance and blind spot sensors, applications like adaptive cruise control (ACC) and an extension of this, ACC Stop and Go, are now being addressed by oems and sensor manufacturers.
Indeed, car manufacturers are now becoming interested in implementing multi-sensor approaches, sometimes termed as sensor data fusion. These systems enable the car to monitor the whole environment. One of the requirements resulting from this approach is a new distribution of signal processing blocks between sensor(s) and a central ecu. As this ‘fusion ecu’ becomes responsible for data validation, object recognition, object tracing and communication with the car network, the sensor itself becomes a simple data acquisition unit.
Ideally, the sensor would transfer all data to the central ecu for processing. Assuming a typical cycle time of 30 to 40ms, this could result in data rates up to 2.9Mbit/s per sensor. This bandwidth isn’t available with today’s car networks; therefore some data pre processing and data reduction has to be performed in the sensor. One approach is to implement the required signal processing in an fpga. With their internal multipliers and ram blocks, they offer unbeatable dsp performance at a moderate frequency. An fpga’s architecture is suitable for the whole algorithm including offset correction, fft and digital beam forming – even tasks like threshold calculation and spectral peak detection can be performed within the fpga. The inherent flexibility of an fpga also means that the system can be adapted to the available bus, be it CAN, FlexRay or a proprietary bus, without changing the system architecture and adding external components. A soft processor core optimised for the fpga can be used as a system controller and also as a host controller for CAN or FlexRay. Using an fpga to implement new multi sensor systems allows costs to be kept low, making the new 24GHz radar systems affordable for customers and thus improving road safety.
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Author
Dr Axel Zimmerman
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