Motus Reference Manual
Page 46 of 146
Version 1.1
29/11/2019
problem for time based data such as velocities and accelerations where aliasing will
occur at the lower rate. To prevent this problem, if the output rate is lower than 1000
Hz, Motus will low pass filter the values of the time dependent data between packets
to prevent aliasing. This is only the case when a packet is set up to output at a certain
rate. If the packet is simply requested no anti aliasing will occur. Additionally there is
no anti aliasing for non time dependent fields such as position.
11.7
Vehicle Profiles
Motus supports a number of different vehicle profiles. These vehicle profiles impose
constraints upon the filter that can increase performance. If your application matches
one of the available vehicle profiles, it is recommended to select it for use in the Filter
Options dialogue in Motus Manager, see section 12.8.2. For a list of the different
vehicle profiles please see section 16.10.5.1. Please note that if the wrong vehicle
profile is selected it can cause a significant decrease in performance.
11.8
Odometer Pulse Length
For Motus to use a wheel speed sensor or odometer input, it must know the pulse
length of the signal. The pulse length is the distance in metres between low to high
transitions of the signal. The odometer pulse length can either be entered manually or
automatically calibrated by Motus. To enter the pulse length manually, please use the
Odometer configuration dialogue in Motus Manager, see section 12.8.7. To
automatically calibrate the odometer pulse length please use the procedure listed
below in section 11.8.1. By default the odometer will automatically calibrate itself.
11.8.1
Odometer Automatic Pulse Length Calibration Procedure
1. Ensure that the signal is connected correctly and that the GPIO pin is configured
as an odometer input using the GPIO configuration dialogue in Motus Manager,
see section 12.8.6.
2. Open Motus Manager, connect to Motus and open the Odometer configuration
dialogue. In the Odometer configuration dialogue tick the automatic pulse
length calibration check box and press the write button, see section 12.8.7.
3. Wait until Motus has a continuous GNSS fix and then drive 1000 metres over flat
terrain with as little turning as possible.
4. If Motus loses a GNSS fix for any extended period of time during the calibration,
the distance travelled will be reset. The distance travelled can be checked in the
Odometer configuration dialogue to ensure that it has passed 1000 metres.
5. Once 1000 metres has been driven, press the read button and check that the
automatic pulse length check box becomes un-ticked and the pulse length value
is read.
11.9
Reversing Detection
Reversing detection is an algorithm that can detect when the vehicle is travelling in
reverse. Knowledge of reverse motion is important when using velocity heading or
odometer input to provide correct results. If Motus is fitted to a vehicle that does not
