I am a beginner in robotics and I have just come across the concepts of differential and steer drive. I don't understand them very clearly yet.
I found the following write up describing differential drive as follows:
If the angular velocities are identical in terms of both values and direction, i.e. if both the wheels are driven at the same speed and same direction (either clockwise or anticlockwise) then the robot tends to spin around its vertical axis. This complete turn capability is one of the greatest advantages of a differentially driven robot (a.k.a zero radius turn).
Being a complete beginner, I concede I could be entirely incorrect in disagreeing with the above. I just imagine that "both wheels" driving at the same speed and direction (clockwise or anticlockwise) would mean a robot is travelling along linearly i:e straight ahead. I don't understand why the writer says the robot is actually spinning around it's Z axis.
If I'm wrong, please explain what I'm missing.
And please, let me have links to material that would help me understand differential and steer drive.
Thanks in advance.