  Existing works on control of tractor-trailers systems only consider the
kinematics model without taking dynamics into account. Also, most of them treat
the issue as a pure control theory problem whose solutions are difficult to
implement. This paper presents a trajectory tracking control approach for a
full-scale industrial tractor-trailers vehicle composed of a car-like tractor
and arbitrary number of passive full trailers. To deal with dynamic effects of
trailing units, a force sensor is innovatively installed at the connection
between the tractor and the first trailer to measure the forces acting on the
tractor. The tractor's dynamic model that explicitly accounts for the measured
forces is derived. A tracking controller that compensates the pulling/pushing
forces in real time and simultaneously drives the system onto desired
trajectories is proposed. The propulsion map between throttle opening and the
propulsion force is proposed to be modeled with a fifth-order polynomial. The
parameters are estimated by fitting experimental data, in order to provide
accurate driving force. Stability of the control algorithm is rigorously proved
by Lyapunov methods. Experiments of full-size vehicles are conducted to
validate the performance of the control approach.
