Study On Structural Parameters And State Estimation Of Semi - Trailer

Accurate estimation of vehicle structural parameters and vehicle states are crucial for vehicle safety control system. This paper focuses on the issue of parameters and states estimation algorithms for the tractor-semitrailer combination. The estimated vehicle parameters and states are sent to vehicle stability control system to replace the nominal control parameters for precise control decision.An identification scheme for estimating tractor-semitrailer vehicle parameters such as mass and grade is designed and presented based on the longitudinal dynamics and recursive least square with multiple forgetting factors algorithm. Then, an improved algorithms for tractor-semitrailer vehicle parameters estimation using the longitudinal dynamics and acceleration deviation gradient model are discussed when grade changes rapidly. With the estimated mass information, trailer yaw moment of inertia can be obtained. Also, following the estimated mass and inertia parameters and the recursive least square method, the mass Centre of Gravity (CoG) such as longitudinal CoG positions and the height of trailer mass COG identifying scheme are formulated based on 4 Degrees of Freedom (4-DoF) and 6 Degrees of Freedom (6-DoF) tractor-semitrailer vehicle models. Then, trailer roll moment of inertia can be obtained. The proposed parameter identifying schemes are evaluated by simulation in TruckSim which is a famous commercial vehicle dynamics simulation platform. The results show that the estimated parameter values can well agree with the actual values.With the estimated parameters, the vertical load of every wheel of tractor-semitrailer vehicle can be calculated. An algorithm using Kalman Filter(KF) to estimate tractor-semitrailer vehicle states such as yaw rare, sideslip angle and articulated angle is designed based on a 4-DoF and 6-DoF tractor-semitrailer vehicle models. The proposed state identifying schemes are evaluated under ISO double lane test by simulation in TruckSim. The results show that the estimated states values can well agree with the actual values with estimator of 4-DoF in low speed conditions, however, estimator with 6-DoF can more adapt to the real states compared with the scheme with 4-DoF in high speed conditions.The stability control strategy and its reference model are established in Matlab/Simlink and designed the optimal steering Angle input to the reference model of closed loop stability control system in low adhesion conditions of road. The effect of parameter identification on control system is evaluated by TruckSim-Simulink co-simulation. Simulation results reveal that the control scheme with parameter identification can well adapt to the variation of vehicle load compared with the scheme with nominal design parameters especially driving in the low adhesion conditions of road, which lays a ground for vehicle safety control system of tractor-semitrailer vehicle.