Odometer

The 3DM-GQ7 Navigation Filter supports external speed measurements, either through a hardware encoder interface or digital message input. Speed aiding can greatly increase navigation performance during GNSS outage scenarios. In order to configure the odometer interface, complete the following steps:

  1. Configure the GPIO for encoder input using the GPIO Configuration (0x0C,0x41) command. Ensure that both input pins are set to the correction GPIO mode. See Main/Aux for more details on the connector interface. Note: The GQ7 currently only supports quadrature encoders but single ended encoder support may be added.

    NOTE: Odometer "A" input must be put on GPIO 1 (main pin 7). Odometer "B" input must be put on GPIO 2 (main pin 9). See Main/Aux for more details.

  2. Configure the odometer scaling and uncertainty using the Odometer Settings (0x0C,0x43) command.

  3. Set the odometer lever arm using the Measurement speed lever arm (0x0D,0x61) command. This lever arm also applies to external speed measurements input with the Input speed measurement (0x0D,0x60) command.

  4. To use the odometer measurement in the Navigation Filter, ensure that the Filter Aiding Measurements are properly configured.

 

Recommended Odometer System

The 3DM-GQ7 has been tested with the following odometer:

Michigan Scientific High Resolution Wheel Pulse Transducer E512