Braking performance is rigorously checked before factory release and during periodic inspections. Road testing with a portable instrument complements brake-bench testing where some parameters cannot be measured adequately.
Operating principle
Hardware
A portable instrument comprises an acceleration sensor, pedal-force sensor, flexible pedal switch, acquisition host, power supply and microprinter. The illustrations show Naiou braking-system arrangements.
Measurement
The acceleration sensor is the principal sensing component. It measures deceleration during braking, and the acquisition host processes the signal to calculate stopping distance, braking time, initial speed, maximum deceleration and MFDD.
Use
Install the acceleration sensor in the vehicle and make the required instrument settings. On a smooth road, drive at the specified initial speed and apply emergency braking to standstill. The instrument measures braking-system performance.
Precautions
- Calculated stopping distance may differ from direct measurement because of the site, weather, vehicle condition and driver operation, although the results should be broadly similar.
- Better road and vehicle conditions improve repeatability and stability.
- The source reports lower pass rates with a 10 km/h initial speed and higher pass rates at 20 km/h, but says 20 km/h may not reveal directional deviation correctly. At 30 km/h, it reports both higher pass rates and better assessment of deviation; some vehicles that remain straight at 20 km/h deviate at 30 km/h.
- Do not steer during the test, otherwise valid measurement data cannot be obtained.
- The pedal contact switch is fitted to the brake pedal. Resting a foot on it while driving may trigger it early and cause an incorrect measurement.
- Install the acceleration sensor horizontally with its arrow pointing in the direction of travel and tighten the screws. Incorrect installation can create large errors.
- The vehicle must be fully stationary before entering measurement-ready mode.
- Do not press the brake pedal after entering ready mode.
Luoyang Naiou Electric develops road-test systems and matching sensors for vehicle performance measurements. Please leave an enquiry or contact customer service.