Department of transportation
D.Suggested Additions to Test Procedures
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- Customer-Adjustable FCW Settings
- Sensor Axis Re-Alignment
- Multiple Events – Minimum and Maximum Time Between Events
- Time-to-Collision (TTC) Definition
D.Suggested Additions to Test ProceduresAccounting for Regenerative BrakingTesla expressed concern that the test procedures as currently written do not account for totally or partially electric vehicles that utilize regenerative braking to recharge batteries. Tesla urged NHTSA to clarify protocols for EV and hybrid vehicles, specifically regarding regenerative braking. Regenerative braking is an energy-preservation system used to convert kinetic (movement) energy back to another form, which in the case of an electric vehicle, is used to charge the battery. The reason it is called “braking” is that the vehicle is forced to decelerate by this regenerative system, once the driver’s foot is taken off of the throttle. This system is independent of the standard brake system but the result is the same; the vehicle slows down. NHTSA’s direct experience with testing a vehicle equipped with AEB and regenerative braking has been limited to the BMW i3. As expected, once the driver released the throttle pedal in response the FCW alert, regenerative braking did indeed slow the vehicle at a greater rate than for other vehicles not so equipped with regenerative braking. This had the effect of reducing maneuver severity since the SV speed at the time of AEB intervention was less than for vehicles not so-equipped. This is not considered problematic. For vehicles where the driver can select the magnitude of the vehicle’s regenerative braking (e.g., the Tesla Model S), the vehicle’s AEB system will be evaluated in its default mode (as originally configured by the vehicle manufacturer). Customer-Adjustable FCW SettingsThe Alliance noted that in some CIB and DBS applications, system performance may take into account the warning timing setting of the FCW system when the FCW system allows the consumer to manually set the warning threshold. To clarify, the Alliance recommended that the following language, which is adapted from the FCW NCAP test procedure (Section 12.0), be included in the CIB and DBS NCAP test procedure: “If the FCW system provides a warning timing adjustment for the driver, at least one setting must meet the criterion of the test procedure.” In its previous work involving FCW, the agency has allowed vehicle manufacturers to configure the systems with multiple performance level modes. This provided vehicle manufacturers flexibility in designing consumer acceptable configurations. The test procedure allowed an FCW mode that provides the earliest alert if the timing can be selected and used during agency testing. Additionally, the test procedures do not include resetting to the original setting after ignition cycles. NHTSA believes that as a consumer information program, we should test the vehicles as delivered. We also believe the performance level settings of the FCW systems within the AEB test program should now be set similar to the AEB. The Alliance requested that we have language in the test procedure specifying that if there are adjustments to the FCW system, one setting must meet the criterion of the test procedure. Vehicle manufacturers may provide multiple settings for the FCW systems. However, the agency will only use the factory default setting for both the FCW and the AEB systems in the AEB program.
NHTSA has seen two cases of sensor misalignment during the initial development of this program. In one case, the subject vehicle had visible grill damage because the AEB system did not activate and the test vehicle hit the SSV at full speed. In another case, the vehicle sensing system shut down after numerous runs; inspection also revealed visible grill damage to the subject vehicle. In both cases, the vehicles were returned to an authorized dealer, repaired and then returned to the test facility. The NCAP test program has instituted two new procedural improvements to monitor for system damage. First, we began testing with less-severe tests, such as the lead vehicle moving test first, to determine if the vehicle system is capable of passing any of the tests. Second, we have instituted more rigorous visual between-vehicle inspections by the contractor during the testing. Based on our observations in testing, we believe systems that have sensor damage will likely show visible grill damage. With the improvements in the AEB systems and refinement of our test protocol, we do not believe sensor misalignments will be a significant problem. We invite vehicle manufacturer representatives to attend each of our tests. We reserve the right to work with the vehicle manufacturers on a one-on-one basis if we have problems with the vehicles during the tests. Multiple Events – Minimum and Maximum Time Between EventsThe Alliance and Ford asked that the AEB test procedures specify a minimum time of 90 seconds and a maximum time of 10 minutes between each test run as in Euro NCAP AEBS test procedures. Some AEB systems initiate a fail-safe suppression mechanism when multiple activations are triggered in a short time. Most systems can be activated again with an ignition key cycle. In most cases activation of the suppression mechanism can be avoided by including a time interval between individual AEB activations or by cycling the ignition. The current test procedure addresses this by checking for diagnostic test codes (DTCs) to determine if any system suppression or error codes have occurred with the sensing system software. The agency agrees that there should be a minimum of 90 seconds between test runs and will modify the AEB test procedures to state this explicitly. We recognize that the algorithms in these vehicles look for conditions that are illogical, such as multiple activations in short periods of time, and within a single ignition cycle. The time needed to allow the subject vehicle brakes to cool and the test equipment to be reset between each test trial has always exceeded 90 seconds in the agency’s testing experience. . The agency will also specify in the test procedures that the vehicle ignition be cycled after every test run. The agency believes a maximum time between test runs of 10 minutes is too short to be feasible. The test engineers need sufficient time to review data, inspect the test equipment and set up for the next test run. Also recall that the test engineers need time to ensure the vehicle brake temperatures are within specification and the brake system is ready for the next test run. Additionally, it is impractical to specify that all of the tests must be completed within 10 minute cycles while conversely specify that testing be discontinued if ambient conditions are out of specifications. At this time, we are unaware of any algorithm-based reason why testing must be resumed in less than 10 minutes.
The agency acknowledges that the TTC calculations for the FCW test procedure are the same as these test procedures. The TTC calculations that are included in the NCAP FCW test procedures will be added to the AEB test procedures, as requested in the comments. This will make it clear that the TTC equations apply to the AEB test procedures as well. Directory: nhtsa nhtsa -> Speech to the 3rd Motor Vehicle Safety Symposium United Nations University Tokyo, Japan September 17, 2002 nhtsa -> Federal Automated Vehicles Policy Summary of Comments at December 12, 2016 Public Meeting nhtsa -> Department of transportation national Highway Traffic Safety Administration nhtsa -> Head restraints identification of Issues Relevant to nhtsa -> Department of transportation Download 138.42 Kb. Share with your friends:
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