Estimation of Articulation Angle for Tractor Semi-trailer Based on State Observer

Jackknife is an unstable state of tractor semi-trailer combination, and there is no sensor available to detect the jackknife or measure the hitch articulation angle. A state observer is designed to estimate the articulation angle, where a 3 DOF tractor semi-trailer linear model is used. The steering wheel angle sensors, lateral acceleration sensor, yaw rate sensor and axle load sensor of electronic stability control system for commercial vehicle are available here, and the signals are used in the state observer. Utilized road adhesion coefficient is estimated with lateral acceleration to correct the linear tire model. The observer is validated on a 21 DOF tractor semi-trailer nonlinear model, the simulation results shown that the estimated articulation angle is accurate in either linear area or nonlinear area of tire lateral force model.