Fuji Heavy Industries Ltd is exhibiting a next-generation Active Driving Assist (ADA) system to ensure pre-crash safety, etc by using images shot with only two CCD cameras at the 40th Tokyo Motor Show.
Price cut in half
Fuji Heavy Industries' new ADA system will be sold at "about half the price" of its existing system priced at about ¥350,000 (US$3,048) composed of a stereo camera and a millimeter wave radar, according to a demonstrator from the company.
The price reduction was achieved by eliminating the millimeter wave radar and providing a dedicated ASIC and commercially available microprocessor incorporated in the camera module to perform image processing. The company plans to employ the new system in Legacy sometime around spring 2008.
Stereo camera made by Hitachi
The camera uses a monochrome CCD image sensor with a resolution of approximately 300,000 pixels and a frame rate of 30fps. The sensor can recognize an object up to 100m ahead.
The company "paid particular attention to the detection capability for the middle distance," the demonstrator said. Thus, when the obstacle is located 2m ahead of the vehicle, the camera can detect the distance to the obstacle with an error within several centimeters.
Although the error increases to several meters in long-distance detection, "there is no real necessity for high-precision recognition in long-distance detection because vehicle control that requires long-distance information is almost limited to the on/off control of the accelerator," the demonstrator said.
The stereo camera was developed by Hitachi Ltd, and the product is on display at Hitachi's booth. The camera is reportedly equipped with a product from the SH-4 series, a line of image processing microprocessors available from Renesas Technology Corp.
Hardware-based 3D rendering
The main feature of the image processing performed by the latest system is that images shot with two cameras are processed by hardware with the use of ASIC incorporated in the camera module.
"Although 3D rendering imposes a heavy computational load, its algorithm is simple," the demonstrator said. "The programs are successively executed by a serial circuit just like a flow process on a conveyor belt."
When performing calculations to recognize the distance to the vehicle driving in front, obstacles ahead, lane lines, shaking of the vehicle, etc based on the resultant 3D images, arithmetic operations are performed on the microprocessor with the use of the company's proprietary image processing software. The shaking of the vehicle is determined mainly based on the frequency of the vibrations of the images with respect to the lane line used as the reference.
In addition, the system is equipped with another algorithm to correct the misalignment of images due to the variation in camera installation positions while the vehicle is driving. The details of this algorithm, "is confidential because it is an important know-how," the demonstrator said.
Use in night fog being considered
The latest system senses the information outside of the vehicle with stereo cameras alone without the use of a millimeter wave radar. In general, a millimeter wave radar is said to be better suited to recognize obstacles ahead in snow, fog or other bad weather conditions compared with a camera.
The existing ADA system employs the combination of a radar and a stereo camera in consideration of such capability. However, the latest system can "recognize obstacles ahead in fog, snow or other conditions at night with the use of the camera alone," the demonstrator said.
"The performance is better than many users would expect thanks to our proprietary sensitivity and image processing methods used in the camera," he added.
Meanwhile, the company is less willing to utilize the next-generation ADA in a situation "where obstacles ahead cannot be recognized by the driver's eye," the demonstrator said.
"It is difficult to decide whether the driving assist system is really required in such circumstances," the demonstrator added.
Linkage with other systems via CAN
The linkage between the next-generation ADA system and other systems, including the brake control system, is enabled via CAN communication. The ADA system determines whether or not to intervene in other systems, and sends a trigger signal upon intervention.
"The amount of data to be transmitted is not so large because the system doses not send image signals to CAN," the demonstrator said.
The employed CAN may be divided into two parts: one for vehicle body system and the other for driving control system, Fuji Heavy Industries said.