Replacement and ADAS Calibrations: Safety and Success are in the Details
By Allison Whitney
An Insurance Institute for Highway Safety (IIHS) study on the risk of uncalibrated windshield cameras and their effects on Advanced Driver Assistance Systems (ADAS) such as Lane Keep Assistance and Front Collison Warning systems highlighted many vital issues. But one stands out: the importance of following OE specifications to the letter to ensure successful calibrations.
Investigating the Failures
The study involved testing replaced windshield-mounted cameras. In one vehicle test, the autobraking system failed because the technician did not follow the vehicle manufacturer’s calibration instructions, including positioning the vehicle from the target at the exact specified distance. In the words of the IIHS senior test coordinator, “they were just eyeballing it.”
The IIHS used a Honda Civic for this test. The vehicle was brought to the dealer to replace its windshield, and get the camera remounted. IIHS tested the auto-braking of the Civic traveling at 25 mph.
The system, when working correctly, would emit an audible warning at 124 feet or 3.4 seconds before impact and begin braking automatically if the driver took no action, at 53 feet or 1.5 seconds before impact.
This test vehicle didn’t alert the driver until 102 feet from impact, leaving the driver with just 2.8 seconds to respond. The vehicle didn’t start autobraking until 32 feet and 0.9 seconds from impact, resulting in a collision with the obstacle at 20 mph.
IIHS’s test coordinator went back to the technician and found he failed to follow many steps in the static calibration. The test coordinator quoted in the study said, “the center of the car needs to be determined and projected out in front of it, and then the camera told where that is. This was the step the dealer failed to do until I helped them.”
This story speaks to a very human failure; we sometimes dismiss needed but often time-consuming procedures and instructions if we do not understand the reason behind them.
To this end, let’s review what happens during a front-facing camera calibration and try to understand the “whys” behind the facility requirements, the vehicle conditions, and the procedural instructions set forth by most vehicle manufacturers.
The typical static calibration requirements insist that the vehicle is on a flat, level surface. And in the case of camera calibration, it should be performed in a bright, controlled lighting environment. The area behind the calibration targets should be clear and clutter-free. In the case of radar calibration, no metal objects should be within the calibration space.
Behind the Why
The “whys” of these requirements seem straightforward. We are calibrating a camera with a target that has a white background and a black image upon it. We want to create an ideal setting for the cameras to “see” the targets. Dim, uneven lighting or glare will hinder the camera’s ability to recognize the targets. Additionally, there should be no clutter, signs, or photos behind the target as they might “confuse” the camera. If we calibrate radar devices—components meant to detect metal objects— we don’t want other metal objects in the vicinity of the vehicle’s radar unit and the positioned calibrator. In a shop environment, this might mean moving metal garbage pails, tire machines, or toolboxes to another space in the shop.
And how important is it that the calibration is performed on a flat, leveled surface? Important, as one aspect of the positioning of the target to the vehicle, is dependent on the vehicle’s rear driveline. An uneven floor might throw off the vehicle’s pitch and may result in an improper calibration.
Condition Checklist
The next step before calibration is to ensure the vehicle meets a list of conditions. These include: making sure all the fluids are at recommended levels, the gas tank is full, the tire pressure on all tires is at the placard-listed psi, and that vehicle carries no additional load—no groceries, no luggage, no heavy equipment.
The “why” here is perhaps a little less straightforward, but our head ADAS trainer George Lesniak offers the best rationale that these prescribed conditions seek to emulate the “stance” of the vehicle when it left the factory floor and went on to be calibrated.
The OE is saying the vehicle met these conditions when initially calibrated. And to ensure these input components perform as designed–to inform the system’s operation–these original pre-calibration conditions must be met. Failure to meet these conditions may compromise the calibration and, therefore, compromise the safety system’s effectiveness overall.
Additional prescribed conditions include ensuring that all lights are off in the vehicle and all doors are closed. This is so the vehicle battery is not drained during the calibration. For the same reason, a battery maintainer should be used.
The next step prior to the calibration is to ensure that target is positioned correctly to the vehicle. Our standard calibration frame system uses lasers, mirrors, rear-wheel clamps, and a tape measure to position the frame to the vehicle. The technician uses the center laser on the frame to detect the vehicle’s centerline. A measuring tape is used to ensure the frame is at the OE-specified distance to the vehicle. Next, the rear wheel clamps
with lasers are used with the frame to ensure that the crossbar (and subsequently the OE-specific target when attached) is perpendicular to the vehicle’s rear axle. The clamps and frame are also used to ensure the angle of the frame is positioned to the vehicle’s driveline.
Why are all these steps performed? Because the thrust angle, the angle generated from the vehicle’s rear axle, dictates the car’s direction as it ventures down the road. Our frame is positioned to the reference point of the vehicle thrust angle.
This pre-calibration is the most timing-consuming step of the entire calibration procedure, and the actual camera calibration takes just minutes.
One thing missing from the IIHS study was the technician’s lack of reason for not following the OE directives. Perhaps he didn’t have the right tools or equipment or found the measuring process too time-consuming or tedious and decided to take a shortcut. And why the excuse is unimportant, it’s true, the setup processes for the ADAS calibrations can be time-consuming and tedious.
Calibration systems developers have heard technicians lament and answered with new systems or adaptions for existing ones that drastically cut the setup time and ensure more precise vehicle positioning: no plumb bobs, no chalk, no measuring tape.
But as Lesniak said, “a calibration technician must be able to read, understand, interpret and follow detailed instructions without skipping steps … the accuracy of the calibration depends upon the person setting up the targets.”
Allison Whitney is the content manager for Autel. You can reach her at allisonw@autel.com
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