NexvioraDocumented target: Ubuntu 24.04 · ROS 2 Jazzy · Gazebo Harmonic where used. Browser labs tested; ROS/Ubuntu/hardware execution not performed here.
What you will understand
- Compute forward/yaw velocity.
- Explain straight and turning cases.
- Recognize slip assumptions.
Prerequisites: Configure, launch and diagnose a system and its stated environment.
The idea, made clear.
For wheel radius r, separation L and angular speeds ωL and ωR, forward speed is v = r(ωL + ωR)/2 and yaw rate is ω = r(ωR − ωL)/L. Equal speeds give straight travel. Opposite speeds rotate around the centre. These are kinematic equations, not a motor torque model.
The model assumes rolling without lateral slip. Soft tyres, uneven floors and skid steering break this assumption. Wheel odometry estimates motion; it does not prove where a robot went. Measure geometry separately from controller tuning.
Use metres, seconds and radians. Positive planar yaw is counterclockwise in a right-handed frame. A small fixed integration step limits numerical error. In the browser lab, the pose is calculated from wheel inputs; it is not received from hardware.
Try it, step by step.
Calculate a straight command
Run in Python.
r = 0.05
L = 0.30
left = right = 4.0
v = r * (left + right) / 2
w = r * (right - left) / L
print(v, w)Expected: 0.2 m/s and 0 rad/s.
Explore a turn
Set left to 2 and right to 4 rad/s in the lab.
Expected: 0.15 m/s and about 0.333 rad/s.
Compare measurements
On hardware, only after safe commissioning, compare a measured path with the model.
Expected: Explicit calibration evidence; no physical test is claimed here.
If something goes wrong
- Turn sign reversed
- Check labels, motor polarity and sign conventions.
- Distance drifts
- Review radius, encoder scale and slip before increasing gains.
Check your understanding
Make it yours
Calculate a circle radius v/ω and compare with the lab.
Optional progress stays in this browser. No account needed.
Go to the source documentation
Commands are educational examples for the stated environment, not a transcript of local ROS execution. Verify actual behavior on your machine.