What are the different types of filter, and when should I use them?
On all current VBOX units, the amount of smoothing that can be applied at the source by the GPS engine to the velocity channel can be adjusted.
There are three preset levels of smoothing labelled as dynamic levels:
- High Dynamic Tests: This is the lowest level of smoothing and should be used for any Brake stops or high dynamic vehicle tests.
- Normal Dynamic Tests: This is an intermediate level of smoothing that will give a smoother velocity, for tests such as acceleration runs between two nonzero speeds.
- Low Dynamic Tests: This is the highest level of smoothing available and can be used where live velocity is required and needs to be as smooth as possible or for coastdown tests.
VBOX level filtering is a real-time filter, so once the data has been generated, the effect of the smoothing cannot be reversed. You can always use post-processing smoothing, which can be adjusted whilst reusing the same piece of original data. Further smoothing can be applied in the VBOX in real-time using a Kalman Filter, where available.
When should I apply filtering?
Increasing the level of filtering applied to data effectively reduces the bandwidth of the VBOX response and smooths the velocity and acceleration measurements.
During the measurement of data in high dynamic tests, the level of applied filtering should be kept to a minimum to capture fast transients, e.g. braking tests, lane change tests and steering response tests.
However, some tests that are of a lower dynamic nature can be made using higher levels of filtering to give smoother data, e.g. acceleration tests, circuit laps and coastdown tests.
See also