Abstract
By linearizing the non-linear simultaneous equations of Part III in the vicinity of an equilibrium state, the state equations of tractor-trailer combinations (TTC) was derived. To investigate the verity of the state equations, the theoretical results of the step and impulse responses were compared with tested result of the ones. The controllability, observability and stability of TTC control system were investigated, too. To estimate all of the state variables including the inaccessible ones, a state observer was designed. The conclusions were as follows: (1) TTC control system is controllable and observable. (2) In the case of backing, high speed and steering motions, TTC control system is instable. (3) The tested results of the step and impulse responses agree well with the theoretical results, (4) All of the state variables can be estimated by state observer.
