Using incremental rotary encoders

Note: This is an experimental feature to support rotary encoders. We do not guarantee the support of all rotary encoders.

Overview

Input velocity measurements for one or two wheels.
Mode: 40ms (25 Hz) averaging of received forward and backwards ticks
Only works with incremental rotary encoders that provide the correct quadrature signals (sometimes referred to as A/B signals), such as the CUI devices AMT103-V.

Note:
The rotary encoders themselves must be configured (electrically) or installed (reduction gears) so that they generate a good number of ticks per time. It should not be too many and not too few. Finding the sweet spot is tricky. Generally, the tick interval should be small enough to cover small movements (say, a few millimetres) and large enough to not generate too many ticks at maximum velocity (say, less than 2kHz).

Configuration

Stop Fusion.
Enable the Incremental Rotary Encoder. This can be done on the ‘Configuration > Measurements’ page of the web interface.
Enable or disable the second wheel sensor according to your setup.
Depending on the position and orientation of the encoder in the vehicle, the Translation and Rotation in must be measured and configured accordingly.

Layout

The signals connected to the VRTK2 AUX connector must be 3V3 logic level. Higher voltages will not work and may destroy the sensor.

The 5.1V supply voltage from the AUX connector Pin 1 can be used to supply the encoder or a level shifter. Note that the maximum current must not exceed 200mA.

The connection is as follows:

AUX connector pin 4 (GND) = ground
AUX connector pin 5 = rotary encoder first wheel “A” signal, 3V3 logic level
AUX connector pin 6 = rotary encoder first wheel “B” signal, 3V3 logic level
AUX connector pin 7 = rotary encoder second wheel “A” signal, 3V3 logic level
AUX connector pin 8 = rotary encoder second wheel “B” signal, 3V3 logic level

Note: The Vision-RTK 2 has no way of detecting if a encoder is connected or not. This means that Sensor and measurements status reports good measurements (of magnitude 0.0) in case there is no encoder connected on the ‘System > Info’ page of the web interface.