Hitachi Unveils New Radar for Next-Generation Eaton VORAD ACC
IVsource.net
9 October 2000

The result of a partnership announced in early 1999, Hitachi Research Labs have successfully demonstrated a next-generation 76GHz radar for Eaton VORAD.  Performance results are provided here, along with implications for the market.

The two firms formed this partnership to develop products, applications, and a customer base for on-board vehicular radar.  The new capability is expected to provide enhanced performance for the next generation of Eaton VORAD's SmartCruise® ACC/collision warning product.

An Eye on the Automobile

The engineering effort included members of Hitachi's Semiconductor Division as well as the Research Lab.  In addition to the new radar development effort, major work went into refining Monolithic Microwave Integrated Circuit (MMIC) technology to create a sufficiently compact package.

Although not stated by either of the companies, it is likely that this new package is the "ticket" to take their product into the passenger car domain, since production costs are now lower, and the unit is more easily integrated into the front bumper of a car.   This development also brings EV into the millimeter wave domain; their earlier generation systems have operated at 24 GHz, effectively blocking them from the European market which has standardized on the 77 GHz range for vehicular radars.

Eaton VORAD is currently selling "thousands" of collision warning systems or adaptive cruise control systems each year to heavy truck fleets, according to sources within the company.  The products are available as a production option from most truck manufacturers in the US.

According to a technical paper -- authored by Hiroshi Kuroda and other Hitachi engineers and presented at the ITS 2000 Conference in Dearborn, Michigan in early October -- requirements levied on Hitachi engineers by Eaton VORAD included lightweight and compact packaging (for front bumper mounting), high reliability, and low cost.

The greatest challenge addressed was achieving high performance in the vehicle detection area.  The system aims to capture distance, azimuth angle, relative speed, and even lane positions of vehicles ahead to assess which vehicles are in the travel lane.  The ACC system as a whole is specified to have 'smooth' control up to the maximum distance; the ability to track target vehicles on curved roads; quick response to a vehicle cutting in front of the equipped vehicle; and operation at short distances to enable a stop-n-go system.

Needless to say, Eaton VORAD and Hitachi are choosing to keep most of the details to themselves, although some hard numbers were made available in the paper (see below).

The radar has three antennas -- one transmit antenna and two for receiving.  The power delivered to the transmit antenna is typically less than 10 milliwatts.  On the single MMIC module are three flat etched antennas on one side and electronics on the other side.  The unit receives inputs of yaw rate, vehicle speed, and braking signal; and outputs distance, relative speed, and azimuth for targets.  The waveform is frequency-shift-keyed monopulse to achieve Doppler radar performance.  A narrowband transmission protocol is used to achieve some immunity to jamming and interference from outside sources.

The two receive antennas give a "stereovision" perspective to detect the azimuth angle of targets.  The FSK waveform / monopulse approach enables the radar to detect and track multiple targets simultaneously and continuously.   The unit also includes a gyro sensor inside to measure the yaw rate of the host vehicle.

Range Requirements Exceeded in Testing

Test results showed that the radar detected a passenger car at over 160m (520 ft) while receding and around 140m (450 ft) while approaching.  Acceptable performance was also achieved at the minimum distance of one meter (3 feet).

New Algorithm Handles Stopped Objects

A particular challenge for FSK radars is in handling multiple stationary targets, such as cars in stopped traffic, due to multiple reflections and multipath interference.  Hitachi claims to have developed a new discrimination algorithm to handle this situation.

Hitachi's algorithm establishes three tracking filters: for the occupied lane, and for the lane on either side of the equipped car.  In testing with this approach, two parked vehicles in two adjacent lanes were successfully discriminated.  Being able to handle stationary targets is particularly important for achieving stop-n-go ACC operation in congested traffic.

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... see www.eaton.com/VORAD/.

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