Vehicle Dynamics Analysis Of Tractor-Semitrailer Based On Self-Steering

With the advancement of highway construction, especially the improvement of manufacturing level of heavy-duty truck, tractor-semitrailer takes full advantage of its transportation superiorities and has become the major form of road logistics transportation. Under the condition of meeting requirements of road regulation and axle load, most of vehicle manufacturers will increase trailer axles to raise transportation efficiency of tractor-semitrailer. The maneuverability, passing ability and handing stability will be deteriorated if increasing axle purely. And abnormal wear of tires will be aggravated. Currently, semi-trailer can only be equipped with three rigid axles.Self-steering axle is a useful method in handling turning difficulty and reducing tire wear of tractor-semitrailer when driving at low speeds. LL series self-steering axle of BPW Co.,Ltd is chosen as the research object. Firstly, the basic structure and steering principle of the self-steering axle were introduced. The center of fifth-wheel and trailer third axle was adopted as the research objects of path-following. With the analysis of curve driving, the relationship between the front axle steering angel and self-steering angle was built. To research the exciting force of self-steering axle, the normal force and steering torque were researched and solved.The basic structure and layout of self-steering axle were elaborated, especially the knuckle assembly part. The wave thrust washer models based on space cycloid were established, whose stress and deformation were analyzed in full load condition. According to the knowledge of theoretical mechanical, the steering resisting torque of parking maneuver was analyzed. Finally, the lock-opening torque of wave thrust washer was analyzed when turning at low-speed.Secondly, the simulation process of ADAMS/Car module was introduced. And the modeling coordinate was defined and the vehicle parameters were presented. Based on the analysis of tractor-semitrailer components, the templates of all subsystems were modeled in expert interface. The corresponding subsystems of vehicle were generated in standard interface. In order to establish the comparative vehicle models, including self-steering tractor-semitrailer model and conventional tractor-semitrailer model, the subsystems were assembled with test rig.Finally, several maneuverability cases were conducted with the two virtual prototypes, including 360-degree turning, 90-degree turning, step steering and ramp steering at the low-speed. The effect of self-steering axle on vehicle maneuverability and path-following was analyzed. The results show that, not only the side slip of semi-trailer is lightened, but also the maneuverability and path-following performance of tractor-semitrailer are improved if assembled a self-steering axle. Furthermore, several turning factors were researched, which may have influence on the performance of self-steering axle. The simulation results show small load, increasing speed in certain range, small steering angel and low steering speed will improve the performance of self-steering axle. Locked and unlocked self-steering axle has a direct impact on vehicle handing stability. According to national standard, the handing stability performance of the vehicle was analyzed. The simulation tests are mainly consisted of impulse input steering and single lane change steering. The vehicle yaw rate and lateral acceleration will be obviously increased if self-steering axle was unlocked, especially the body roll angle.