Conversion to Chained Form
Many controllable 2 input systems can be converted to chained form using a nonlinear change of coordinates and a feedback input transformation .
Necessary and sufficient conditions for convertibility exist in the form of an algebraic test (Murray, ‘92).
There is a systematic (but tedious!) method of finding the appropriate coordinate and input transformations (Tilbury, Murray, and Sastry, ‘94)
For the robot/trailer system, the transformations are: