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© Volvo Car Group

It’s just a windscreen…

By Andrew Marsh, 08.03.16
Posted in: Featured | Public | Technology Trends

Volvo XC90 introduced with the new Scalable Product Architecture (SPA) and the Volvo Engine Architecture (VEA). These building blocks have allowed the subsequent S90 and V90 to use many components as well as assemblies, so reducing investment was well as piece cost.

One development was a new feature – instead of a RADAR module fitted to the very front of the vehicle shielded by materials transparent to electro-magnetic wave transmission / reception, along with a LiDAR module fitted behind the windscreen for short range measurement – the forward distance measurement module is a twin range RADAR module fitted.…. behind the windscreen. This module also includes the CMOS camera for object classification, and was developed by Delphi.

The standard array of IntelliSafe for XC90 includes:

  • Recognition of road signs and speed limit alerts (CMOS camera).
  • Speed limiter – linked to road sign recognition (CMOS camera).
  • Lane keeping alert (CMOS camera).
  • Lane departure warning if indicators are not deployed (CMOS camera).
  • Driver alert (CMOS camera and steering input monitoring).
  • Adaptive cruise control (twin forward facing RADAR unit).
  • Run-off mitigation which includes selective deployment of seat belt tensioners, closing windows, and activation of the braking system (CMOS camera with twin forward facing RADAR unit).
  • Autonomous braking (CMOS camera with twin forward facing RADAR unit).
  • Autonomous lane keeping and distance control up to 80 mph / 130 kmh (CMOS camera with twin forward facing RADAR unit).

Further options include:

  • Blind spot detection (two rear mounted RADAR modules)
  • Additional door mirror mounted and tailgate mounted cameras for 360 degree viewing.
  • Reversing auto brake when traffic drives past (tailgate mounted camera).

From this extensive list the most important sensors face forwards, and server multiple safety system functions. The forward facing CMOS camera is built into the twin RADAR module. © Volvo Car Group

The RADAR module has two fields of view - short range (up to 40m ahead, 30 degrees either side of centre line) and longer range (up to 200m, 10 degrees either side of centre line). The short range RADAR eliminates the need for a LiDAR sensor. © Volvo Car Group

The RADAR module is specifically calibrated to take into account the return signal degradation caused by the glass (which is angled relative to the RADAR, so presenting a greater thickness of glass) and even the shroud around the module. The latter item is more likely to be an interlock since the heat generated by the RADAR module is significant – hence it has its own cooling fan. The heating element on the front screen serves to keep the view ahead of the CMOS camera free from condensation – the RADAR module can cope without needing screen heating, since this would reduce the electromagnetic wave transmission / reception almost useless.

Since the RADAR module is placed in a sub-optimal position – behind glass instead of ‘near transparent to electromagnetic waves’ plastic, that the glass properties are super critical. Making a laminated screen with different interlayer and different glass formulation will reduce the autonomous braking system performance.

The RADAR module emits over quite a large area of the central screen as shown by the riged zone shown above. This precludes fitting tinting film (illegal in Europe anyway), things hanging off the rear view mirror and more. © Volvo Car Group

Volvo have demonstrated that the RADAR module can be placed in a ‘safe’ area behind glass, and that the technology combined with CMOS camera can replace the previous forward facing RADAR / LIDAR / CMOS camera systems used by Volvo. The RADAR / CMOS camera module is connected to the vehicle electronic system via two CAN BUS and one FlexRay data transmission system.

The module is attached to a base plate bonded to the windscreen. The only mechanical adjustment is to ensure it is set vertically by use of a special tool with a level as shown above – the windscreen has to be set into the body aperture with spacer blocks to ensure it is seated symmetrically relative to the vehicle longitudinal centre line. Once set up and after the screen bonding agent has cured, the module is commissioned via the diagnostics tool. © Volvo Car Group

Due to the angle of incidence with the windscreen means that Volvo recommend:

  • Only replace windscreens with those sourced from Volvo or the original manufacturer.
  • Replace the windscreen if it is chipped or cracked in the critical zone ahead of the sensor module, where the defect limit is 3mm x 0.5mm. If the defect is in the ‘zone’ and bigger than this size, the screen must be replaced.





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