Digital Signal Processing Reference
In-Depth Information
3.
FREQUENCY-DOMAIN ANALYSIS
To avoid the temporal effects, we have decided to study the problem in the
frequency-domain with the hopes of extracting feature sets for driver
individuality in a precise, robust and consistent manner. Towards that end,
we have explored the variations in the long-term spectra of the accelerator
pedal and the brake pedal for several drivers, which are illustrated in Figure
17.1. Spectra are computed from the signals over a period of approximately
twelve minutes for each driver. As it can be observed that the amplitudes are
greater in the low-frequency region, which implies that these pedal pressures
tend to change relatively slowly. In spite of significant driver-to-driver
differences there is no clear-cut indication of driver individuality form these
long-term frequency spectra. We think that the long-term spectra do not take
into account the non-stationary characteristics of moving vehicles, traffic, the
road conditions, and the driver behavior as response to these. Therefore, we
have decided to focus on other signal processing avenues.
4.
PEDAL PRESSURE STATISTICS
After observing non-conclusive results from long-term spectral analysis,
we have turned our attention to the probability theory by computing the
distributions of the accelerator and brake pedal pressures among drivers -
both female and male. These are displayed in Figure 17-2. These plots show
the relative frequency as a function of pressure readings in kilogram-force
per centimeter square for the accelerator pedal and the break pedal,
respectively --1.0 kgf is equal to 9.8 Newtons. It is worth noting that these
readings are taken from sensors attached to the pedals.
There are noticeable differences among drivers the way they press each
pedal. Their habits in applying pressure to these two pedals in handling a
vehicle differ significantly as well. Some drivers accelerate in multiple
stages, whereas others tend to press the accelerator in a continuous and
smooth manner.
