User's Manual

P330 Data Sheet / User Guide 45
DRAFT
approximately 150mm although it is not unusual to find individuals which are different by more than
300mm. It is also important to note that the bias also varies over temperature. Furthermore, this is
slightly nonlinear and even with a single order compensation, the user can expect residual bias errors
on the order of +/- 2 to 3 cm.
An example of bias performance over temperature of nine units is provided in Figure 6-6 below.
Fig. 6-6: DW1000 Bias performance over temperature.
While bias calibration is relatively straightforward it is very important that it is handled appropriately.
If not, then the user will experience significant errors when attempting to localize.
Decawave’s documentation and application notes provide several suggestions as to how these
changes in bias with temperature can be best accommodated.
Once Time Domain has completely characterizes the behavior of a few hundred units, it is our
intention to provide temperature compensated range measurement. In the meantime, the P330
provides the user with a means of measuring the board temperature. This allows the user the
opportunity to implement a temperature compensation routine.
6.4.4 Accuracy
Range accuracy is a function of precision and bias. If ranges are used to determine location, then the
location accuracy will be a function of the accuracy of the constituent range measurements. To a first
order, the accuracy of the DW1000 will be approximately 5-10cm. For many applications this will be
more than sufficient.
For applications that require more accuracy, it will be necessary to do a more complete analysis.
Such an analysis would include evaluation of the environment in which the equipment is to be used,
determination of the maximum rate at which a P330 would move, and consider the effects of
averaging. Basically, a “bad” environment and “fast” moving mobiles will degrade accuracy. On
the other hand, most errors are Gaussian so any form of averaging will improve accuracy. Averaging
can be the result of taking many range readings on a particular link and averaging them over time or it
could come in the form of taking many range readings to a large infrastructure of anchors (reference
units). Other forms of averaging are also possible.
Finally, the accuracy and reliability of a system can be greatly increased if the system relies on the
combined outputs of multiple types of sensors. For example, integrating measurements from a UWB
ranging, inertial sensors and, if the device is a robot, wheel odometry will greatly improve the overall
system performance.
15.0000
15.1000
15.2000
15.3000
15.4000
15.5000
15.6000
15.7000
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-40 -20 0 20 40 60 80
Meters
Temp C