Tiny modules measure tire treads

Like many other countries, Germany mandates that all vehicles must go through regular inspection by authorized, independent agencies at specified time intervals. Some countries east and southeast of Germany are not as strict in controlling vehicle roadworthiness.

The European Union is sponsoring a joint project involving nine European countries as well as India to implement automatic testing of vehicle conditions in normal traffic on the road. Prior to the initiation of this project, police in these countries would set up mobile stations in rest areas and flag down vehicles for random checks, an expensive and inefficient process.

On May 6, the first automatic checking installation opened on the Autobahn from Salzburg, Austria, to Munich, Germany. Sensing and measuring equipment for this system is buried underneath the road, along the roadside, and on overhead structures. All passing vehicles, without exception, are automatically checked for weight, tire tread depth, smuggled cigarettes, and other factors. Monitoring tire tread depth is an important safety measure to identify problems such as aquaplaning, long braking distance, and vehicle alignment issues.

This automatic checking installation uses an image processing system from ProContour that can measure tire tread patterns contact-free in moving traffic, even at speeds of up to 120 km/h (75 mph). A DIN-rail ThinkIO-Duo computer from Kontron handles the calculations in real time.

The ProContour H3-D (Figure 1) measures tire tread depth with four measuring heads embedded in shafts or ducts in the road. Each measuring module covers a breadth of approximately 380 mm (15") to 670 mm (25") using one or two laser diodes, a laser beam controller, and CMOS sensor-controlled digital cameras. I/O channels (four analog, two digital) to and from the laser equipment underneath the road are provided via 750 Series I/O modules from WAGO that interface with the ThinkIO computer. Connection to a supervising system is possible via fieldbus or Ethernet connections on the ThinkIO module.

Figure 1: The H-3D laser scanner unit from ProContour is installed in manholes as part of the automatic vehicle checking installation along the Autobahn.
(Click graphic to zoom)

ProContour H3-D uses an efficient algorithm for laser triangulation of up to 16,000 images per second in less than 2.4 milliseconds at a resolution of 1536 x 512 pixels. This algorithm enables the use of a medium-performance commercial PC processor to complete calculations in real time. In this application, either a 1.20 GHz Intel Core Duo U2500 processor or a 1.06 GHz Intel Celeron M ULV 423 processor is used in conjunction with a standard PC-type interface and graphics chipset.

ProContour received the Innovation Award 2008 for its H3-D design at the biannual REIFEN (tires) trade fair in Essen, the world’s leading event for tire technology. Because the company submitted the H3-D system to the Physical-Technical Institute (the national metrology institute providing scientific and technical services) for approval, its results can be used in court as evidence of vehicle regulation violations.