Bhavin Kharadi

The Euro New Car Assessment Program (NCAP) recently updated their standards for radar to improve driver assistance features in new cars.

NCAP standards vary by region; in the U.S., our NCAP is governed by the National Highway and Traffic Safety Administration a.k.a. NHTSA and the Global NCAP is a centralized organization. However, all organizations have the same goal: to set standards that make cars and driving safer. The organizations provide ratings in the form of 0-5 stars to help consumers make informed new car buying decisions.

In many cases, Euro NCAP has been the first to set standards that raise the bar for the auto industry worldwide. The latest regulation, No. 79, specifies the minimum distance and operation speed for radar in blind-spot detection and lane-change assistance.

For radar, "Minimum distance and minimum operation speed" (section 5.6.4.8) section, helps finding the minimum operation speed Vsmin, down to which the ACSF of Category C is permitted to perform a lane change maneuver, with minimum distance Srear which radar can support.

In other words, it helps to identify how far blind spot detection radar sensor should detect at a minimal operating speed of 20km/h for ACSF of Category C doing LCM.

Making It Safer to Change Lanes

A safe lane change maneuver is one where the approaching vehicle has sufficient time to react (decelerate) to ensure at all time a safe driving distance between the two vehicles. Specifically, the R79 regulation (in section 5.6.4.7) defines a potential lane change maneuver by an ego vehicle as critical if an approaching vehicle in the target lane would have to decelerate at a higher level than 3m/s², 0.4 seconds after the lane change maneuver has started, to ensure the distance between the two vehicles is never less than that the distance the ego vehicle travels in 1 second.

With knowledge of the distance and speed of the approaching vehicle and the speed of the ego vehicle it is possible to calculate the critical distance S_critical (Section 5.6.4.7.1) between the two vehicles at the start of the lane change. A lane change maneuver is not permitted if the distance at the start of the maneuver between the two vehicles is less than S_critical.  Figure 1 below plots S_critical as a function of the speed of the ego vehicle. Note that for an ego vehicle speed of 20kmph, the critical distance is close to 180m.

Thus, detecting an approaching vehicle and estimating its distance is key to an effective lane change. As described in Section 5.6.4.8 of the regulations, every manufacturer has to declare the minimum distance (S_rear) at which the vehicle can reliably detect an approach from the rear in the adjacent lane (the regulations require a two-wheeler to be used for testing S_rear). Based on the declared S_rear, the regulation then defines a minimum operation speed (V_smin) which is computed as lowest speed at which the ego-vehicle can perform a lane change, with an approaching vehicle at a distance of S_rear and speed of 130 kmph as showing in Figure 2.

In the absence of any detection by the ego vehicle of an approaching vehicle in the adjacent lane, the regulations make a worst-case assumption that there is an undetected approaching vehicle at a distance of S_rear with a speed of 130kmph. In this circumstance no lane change is permitted at speed below V_smin. However, should the ego vehicle detect an approaching target at a distance less than S_rear, then a lane change can be initiated at a speed less than V_smin provided the situation is not deemed critical (i.e. the distance between the approaching vehicle and the ego-vehicle is more than S_critical (as defined in 5.6.4.7.1))

TI’s AWR2944 is the first ever single-chip corner radar sensor enabling carmakers to meet these NCAP safety requirements. It provides unmatched corner radar performance with best in class RF performance enabled by a 4^th transmitter for 33% higher angular resolution than traditional 3 transmitter devices. Here are the test results with some use case conditions:

Meet NCAP Requirements with TI mmWave Radar Sensors for Corner Radar

With longer range, high-resolution radar, cars can sense oncoming vehicles faster with detection at farther distances to more safely change lanes and navigate intersections. By helping automakers meet the latest NCAP safety requirements, TI’s corner radar can make driving safer worldwide.

Additional Resources:

• AWR2944 Product Folder
• High-End Corner Radar Reference Design
• Buy anAWR2944 Evaluation Board
• Order AWR2944 Device Samples
• Power the AWR2944 with the LP87745-Q1 PMIC.