WheelEncoders (UORB message)

Wheel encoder readings.

Angular speed, unwrapped angle and raw encoder counts for up to four wheels. Published by the Roboclaw driver (one instance per controller, two encoder channels each) and by the Gazebo bridge in simulation. Streamed to MAVLink as WHEEL_DISTANCE, logged, and exported over uXRCE-DDS.

Wheel order follows the PX4 motor index: entry i is the wheel driven by Motor(i+1) in the rover's actuator configuration.

• Mecanum: 0 = front right, 1 = front left, 2 = rear right, 3 = rear left
• Differential: 0 = right, 1 = left (2 and 3 unused)
• Ackermann: 0 = drivetrain (motor or drive shaft, reported as wheel rotation), 1-3 unused

Unused entries have counts_per_rev = 0.

The WHEEL_DISTANCE stream supports a single publisher: with several instances (e.g. two Roboclaw controllers) they all fill the same slots and only the most recently updated instance is streamed.

TOPICS: wheel_encoders

Fields

Name	Type	Unit [Frame]	Range/Enum	Description
timestamp	uint64	us		Time since system start
wheel_speed	float32[4]	rad/s		Wheel angular speed. Positive is forward rotation.
wheel_angle	float32[4]	rad		Unwrapped wheel angle since boot, 2 _ pi _ encoder_counts / counts_per_rev
counts_per_rev	uint32[4]			Encoder counts per wheel revolution
encoder_counts	int64[4]			Wheel position in encoder counts since boot. Positive is forward rotation; negative is reverse rotation.

Source Message

Source file (GitHub)

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# Wheel encoder readings
#
# Angular speed, unwrapped angle and raw encoder counts for up to four wheels.
# Published by the Roboclaw driver (one instance per controller, two encoder channels each)
# and by the Gazebo bridge in simulation.
# Streamed to MAVLink as WHEEL_DISTANCE, logged, and exported over uXRCE-DDS.
#
# Wheel order follows the PX4 motor index: entry i is the wheel driven by Motor(i+1) in the
# rover's actuator configuration.
# - Mecanum: 0 = front right, 1 = front left, 2 = rear right, 3 = rear left
# - Differential: 0 = right, 1 = left (2 and 3 unused)
# - Ackermann: 0 = drivetrain (motor or drive shaft, reported as wheel rotation), 1-3 unused
#
# Unused entries have counts_per_rev = 0.
#
# The WHEEL_DISTANCE stream supports a single publisher: with several instances (e.g. two Roboclaw
# controllers) they all fill the same slots and only the most recently updated instance is streamed.

uint64 timestamp # [us] Time since system start
float32[4] wheel_speed # [rad/s] Wheel angular speed. Positive is forward rotation.
float32[4] wheel_angle # [rad] Unwrapped wheel angle since boot, 2 * pi * encoder_counts / counts_per_rev
uint32[4] counts_per_rev # [-] Encoder counts per wheel revolution
int64[4] encoder_counts # [-] Wheel position in encoder counts since boot. Positive is forward rotation; negative is reverse rotation.