BMW’s exhaustive testing
“Flir has been providing thermal imaging cameras for thermal inspection to the BMW plant in Dingolfing since 1997,” says Robert Halbritter of Flir Systems’ sales partner and integrator, TOPA GMbH.
For most of the time, BMW has primarily used the cameras for electrothermography of switch cabinets and rooms. Hot components indicated a problem and were then replaced. This is the still the case today. But now BMW is using thermal imaging cameras for quality control too.
New vehicles are subjected to a number of individual and automated quality control measures including analysis in one of 10 separate roller dynamometers.
The entire process just takes a few minutes, during which each correct function has to be confirmed either automatically or by an inspector who sits in the vehicle monitoring displayed inspection data.
While cost and time-efficient testing is the common goal, identifying the optimum procedure for each inspection task needs individual consideration. This is the case, for example, when testing the exhaust flaps on a car’s dual exhaust system.
Twin tail pipes are a feature of the high performance BMW vehicles with eight-cylinder engines. On the BMW M5 model the requirement is different again, as the exhaust flap on the second tailpipe is only activated at a specified RPM.
The reason for this may be at first surprising as it’s all about acoustic design, the sound of a powerful engine should be impressive. Therefore a BMW M5 only opens the second tailpipe exhaust flap when it is really needed. Of course this feature has to be inspected, which is more complicated than it appears.
To check the efficiency of this operation, thermal imaging cameras – a different brand to Flir – were initially specified for each dynamometer rig. Their purpose was to visualise the thermal profile of the respective tailpipes in the dual pipe exhaust system.
Each system comprised two thermal imaging cameras, mounted to inspect the left and right tail pipes from above and the side. The solution was not only expensive, but costs also increased with time as the cameras required frequent repair over eight years of use.
Halbritter recommended a single, fix-mounted Flir A310 with a 45° lens for each dynamometer.
The advantage: that which was previously inspected using two cameras mounted on the sides could now be visualised using a single centrally positioned Flir camera.
This is possible as the field of view of the Flir A310 with 45° wide-angle lens is capable of showing the entire end of the vehicle from a distance of approximately two-metres. As a result, comprehensive inspection could be conducted by just 10 cameras, one for each dynamometer, instead of the 20 units required by the previous system.
The Flir A310 generates an analogue thermal imaging video
signal with a frame rate of 30Hz. This model is particularly suited to recording exhaust flow as it is simple to integrate and provides easy access to PAL video.
Christoph Hörnlen is responsible for fixed thermal imaging cameras for automation applications at Flir Systems GmbH.
“The Flir A310 has a digital output for alarms and for controlling external devices,” he says. “Additionally the data can be transmitted via TCP IP or Ethernet and the Flir A315 even supports the GigE Vision standard as well as the GeniCam protocol.”
The performance of the exhaust system is checked on a monitor in front of the vehicle that displays a thermal image. From this the inspector can see if the exhaust flap is functioning properly from changes in the thermal profile.
Left: BMW M5 cars made at a German car plant are being tested with the help of Flir thermal imaging cameras. Right: A thermal imaging camera from Flir shows vehicle inspectors whether one or both exhaust systems are working.