Brake testing is usually performed under the closed road conditions at a test track. The vehicle is accelerated to a speed above the desired starting point. Once the vehicle coasts down to the desired starting speed window, the brakes are applied and the pressure is modulated to give the desired average or sustained deceleration. The tests consist of a specific set sequence and include abuse and recovery procedures including fade tests and high speed effectiveness tests.
Modern electronically controlled braking systems are extremely efficient and are very close to reaching the optimum braking distances for a given tyre and road surface. It is therefore essential that the measurement of braking distances can be carried out with very high distance accuracy.
Due to their high precision, flexibility, and ease of installation, VBOX GPS data loggers are used by almost every automotive and tyre manufacturer in the world to carry out brake distance measurements. The VBOX can be moved from vehicle to vehicle in minutes making the setup and removal of the test equipment very quick maximising the time avaialble for testing.
There are two main kinds of braking test:
Distance travelled from the point the brakes are pressed to a standstill. This is the usual method used for certification (homologation) Brake Testing.
Conducting tests with a trigger ensures that the response time of the braking system is measured along with the performance of the tyres, brake pads, discs, and other components. However, during a trigger activated test, the car undergoes a complex change in attitude resulting in varying speeds across the body of the vehicle.
Centre of gravity corrections – or countering the 'lever-arm' effect - of testing tall vehicles with long suspension travel can be achieved with the combined use of GPS and an Inertial Measurement Unit.
Racelogic regularly verify the brake test measurements obtained by the VBOX unit against a light barrier, laser, and RTK DGPS setup with Base Station to confirm a positional accuracy of better than 2cm.
They also captured the test on their LabSat GPS simulator, which records the raw GPS signals and the brake trigger input, and allows them to replay it through any VBOX on the bench. This gives them a repeatable reference to check against any new firmware or hardware updates, and maintains a high standard of brake testing accuracy.
Learn more about GPS Accuracy here.