ADAS covers anything from a single sensor system though to a group of systems,” Christian Doppler established the principle of using a pulsed transmission of energy, and measuring the time as well as position of the reflected energy. The Doppler effect is the core technology in all ADAS sensors, which allows distance as well as time to predict the closing speed to a potential object. Since the very first systems appeared nearly two decades ago the sensor cost has fallen dramatically, along with an equally dramatic improvement in performance. Whereas a ‘top end’ system from less than a decade ago would have one forward facing RADAR module, two rearward facing RADAR modules and one combined camera with LiDAR sensor behind the windscreen, this is now become the norm, with the exception LiDAR has been re-invented.
A top end system now has up to three RADAR modules at the front, a second-generation LiDAR sensor at the front, up to three RADAR modules at the rear, a CMOS camera behind the windscreen, four additional cameras around the vehicle and include up to six ultrasonic sensors at each end.
Advanced Driver Assistance Systems (ADAS) cover almost anything that alerts a driver to obstacles head or behind the vehicle whilst driving. The main components can include any or all of the following:
Location: Front and/or rear bumper skin. These emit a very high frequency sound wave and detect when the wave is reflected, calculating the time difference as a distance. These were typically used as parking sensors but now have been used by some OEMs as part of the ADAS sensor suite. The sensors that point forwards or rearwards typically have a range of 1.5m, with a sensing cone angle of 45 degrees, but the sensors pointing sideways have a range of 4.5m with 15 degrees cone angle. Remember, when the ultrasonic sensors are only ‘parking sensors’, they usually don’t act whilst the vehicle is being driven much above 10 km/h whereas if they are used for blind spot detection, they can be active at higher speeds. The sensors literally are dual purpose.
LiDAR (Light Detection And Ranging) sensor
Location: First generation units were fitted behind the windscreen, but more advanced units now appear behind the front bumper skin.
The sensor typically uses infrared light. The transmission light beam is chopped and receptors close to the emitter detect any reflected infrared light. Since the signal is transmitted on a fixed time base, the relative shift in time for the reflected signal allows the sensor to calculate if the obstacle is moving away, mowing towards or not moving at all. This uses the ‘Doppler’ effect to measure relative movement.
RADAR (Radio Detection And Ranging) sensor
Location: Usually fitted behind the front and / or rear bumper skin. One exception is Volvo (SPA – S60, V60, S90, V90, XC60, XC90, CMA – XC40) where the RADAR is integrated with the CMOS camera and fitted behind the windscreen – along with selected BMW models.
RADAR uses electromagnetic millimetric waves – the same as used for radio transmission. The radio transmission beam is chopped and receptors close to the emitter detect any reflected electro-magnetic waves. This also uses the ‘Doppler’ effect to measure relative movement.
C-MOS (Complementary Metal Oxide Semiconductor) camera
Location: This is typically fitted behind the windscreen, but lower resolution cameras can also be found on the boot/tailgate, under the door mirrors and even in the front grille.
C-MOS camera were largely developed from smart phones, as a relatively inexpensive ‘camera on a chip’ system. The clever part is not taking an image, but rather processing it. The technology to classify what the image could be, and to track it in real time, was developed for military use but was migrating into the automotive world from 1999 onwards.
Constant sensor and system evolution
All of these systems are undergoing continuous improvement, which means vehicle manufacturers have the opportunity to build in a range of ‘sensors’ from the first to the latest generation. For example, the forward-facing camera fitted to the windscreen has evolved over two decades, but all versions are in production right now.
First gen – single lens, single image by image processing. No possibility to measure distance, hence the addition of LiDAR to ‘fill in’ the near range shortfall from RADAR. Requires 100% instruction to set up.
Second gen – twin camera, single lens, single image by image processing. Can measure distance by image triangulation, thus deleting LiDAR in the windscreen to ‘fill in’ the near range shortfall from RADAR. Requires 100% instruction to set up.
Third gen – single lens, video stream processing. Can measure distance by image triangulation. Requires interactive test drive to set up.
Even in a single model life span the ADAS can be upgraded, and brand-new models can feature what is effectively technology from some time ago. Frequently, as part of a mid-life facelift, these systems can be upgraded which will involve changing sensors as well as the way the system works.
All of the sensors work together in a network, so altering or repairing one part of the vehicle may induce recalibration in an apparently undamaged area. There is a priority after the repair is completed:
1. Perform four-wheel alignment and adjust accordingly.
2. Perform ADAS calibration.
3. Check the diagnostics system at the end of the process.
The forward-facing sensors have long, narrow sensing areas, which means if they are not aligned to the vehicle longitudinal centre line, then they end up scanning irrelevant data. If the sensor(s) are not aligned correctly, then the detection range in the direction of travel will be reduced.
One example: A robot applies bonding agent to a windscreen and fits it to the vehicle shell during manufacture. In the aftermarket humans apply the bonding agent, and then place the windscreen onto the body. The forward-facing camera is fitted to the inside of the windscreen, the position it had in manufacturing might be different to the post-repair position, so it needs to be re-aligned.
Some vehicle manufacturers require an elaborate array of boards, four-wheel alignment sensors – which are not the same as used for four-wheel alignment – and more. Why? When a vehicle is built, the body, suspension and ADAS are all aligned. In repair, this has to be re-verified, to ensure the diagnostic system knows where the vehicle centre line is, and to aim the sensor accordingly. On older systems the sensor aiming is in part via mechanical adjustment, but for all systems the diagnostic tools are the only way to ensure the system is ‘awake’ and functioning properly.
Most importantly, assume nothing
Engage vehicle manufacturer repair information websites or sites like Ezi-Methods.
Check what is fitted to the vehicle – there is no need to calibrate if the system is not fitted.
Be aware – what could be fitted to a model when it first came to market is not what is fitted later on, especially when facelifted.
How do we calibrate these systems?
What will we cover in the follow up article?
The ADAS for our sector, because the system is fully integrated into the whole vehicle. It interacts with SRS, seat belts, window lifters, the brake system and even the powertrain. A malfunction in one area can flag as a fault in an apparently un-related area. That’s why it is so important for our sector.
There are no ‘industry’ trends nor standardisation / agreement on ADAS sensor types, function or performance. This model specific chaos is likely to continue for some years, until the future becomes clearer. Until then, we have to work with what is available, be aware of new developments and use methods to assist in solving problems, car by car. ADAS is just one aspect of a very, very bright future for the collision repair market.
uto Industry Consulting is an independent provider of technical information to the global collision repair industry via EziMethods, our online collision repair methods system. For more information please visit the website: www. ezimethods.com