*First test run.
There's something wrong with steering, the radius of left turn is much less than right turn.
Can you tell the difference between right turn and left turn? No wonder my first test run went fail.......
*Steering system
This video shows how the steering system works.
*Second test run.
I fixed the problem that I had found at the first test run.
Despite of a little drift when making a sharp turn, the machine is controllable and the second test run went much better.