Professional_Tool_And_Equipment_News_February_2020 - 50

Calibrating forwardfacing radar sensors
With more vehicles featuring ADAS, it is important for
technicians to learn the basics for calibrating the sensitive
components that make these systems work.
By Scott Brown
and PTEN staff

he forward-facing radar sensor is
an integral part of the advanced
driver assistance system
(ADAS) on many vehicles. When
calibrating the sensor, it is important
to have some basic knowledge about
how it works, system integration, and
why it needs to have specific calibration
routines performed.
In basic terms, a radar sensor works
by bouncing radiation waves off objects
within a space in front of the vehicle.
This wave-like pattern operates in the
"millimeter" spectrum and is considered
to only operate via line of sight. Distances
can be calculated by the time it takes the
waves to travel to the object and back
to the sensor, and location can be factored by the incident angles, a process
known as triangulation. Finally, speed
can be estimated using the Doppler
effect - the change in frequency and
wavelength of the waves in relation to the
sensor's position.
Depending on the manufacturer, the
radar sensor is typically part of a sensor suite used by the ADAS to "sense"
the world around the vehicle and aid
the driver by reducing certain driving
tasks. Today, these systems are intended
for assistance only, meaning the driver is
ultimately responsible for the safe operation of the vehicle at all times.
A radar sensor is a delicate device
operating in a harsh environment.
Forward-facing radar is usually mounted
at the front of the vehicle, which can lead
to multiple challenges.
Calibration requirements for these

PTEN

FEBRUARY 2020

sensors vary by manufacturer and may
be updated over time. The component
manufacturer relies on several calibrations for the sensor to function properly in all conditions. Some of these
calibrations need to be re-established
after certain services are performed on
the vehicle.
Technicians have little to no control
over some of these calibrations, however.
For instance, some internal calibrations
cover the sensitivity of the sensor in relation to temperature and typically don't
require any field calibration. However,
it is possible that the manufacturer may
discover issues with these calibrations
that could potentially be resolved by
updating the sensor's firmware. It is

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Fig. 1 - Forward-facing radar on
a 2019 Nissan Altima.

important that the technician checks
for applicable technical service bulletins and available software updates
for these systems prior to performing
field calibration.
When it comes to service, the technician will be responsible for performing
certain calibrations as prescribed by the
vehicle manufacturer. Field calibration
typically relies on the technician establishing certain baseline values, so the
sensor knows its position relative to 3D
space (world coordinates) and the vehicle
it is attached to.
Vehicles may require certain specifications prior to calibration, such as a

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