| With the rapid development of Chinese economy and gradually improving inter-regional logistics, the nation's demand for heavy-duty truck is increasing. At the same time, the modern logistics industry not only requires deliver the goods to destination efficiently and safely, but also demands high dynamics performances of all aspects of heavy-duty truck, which is closely followed with interest by automobile manufacturers. Consequently, how to improve the structure and dynamics performances of heavy-duty truck will become the pursuing target for vehicle manufacturers and research institutionsThis paper was completed based on the research of "Chassis Matching and Performance Optimization of Heavy-duty Truck", which was a subproject of National High-tech R&D Plan (863 Plan) of China"Integrated Advanced Technology of Heavy-duty Truck Development" (No.2006AA110105-6). Based on multi-body dynamic method and virtual prototype technology, a rigid-flexible coupling model of a heavy-duty truck was built in ADAMS/Car software environment, including full-floating cab mount system, taper-leaf-spring suspension system, braking system with two disc brakes and four drum brakes, air spring suspension system, steering system, powertrain system, etc., at the same time, the frame and cab were generated as elastic parts with FEA method.In accordance with National Standard GB/T 4970-1996, "Method of random input running test automotive ride comfort", GB/T6323.3-94～GB/T6323.6-94, "Controllability and stability test procedure for automobiles", GB 12676-1999, "Structure, performance and test methods of automotive braking system" and ECE R13, some simulation calculations of heavy-duty truck were implemented in ADAMS/Car and the validity of rigid-flexible coupling model was verified by comparing the simulation results with experiment data.The frame flexibility was increased and decreased through modifying the elastic modulus of frame. It was studied how the ride comfort and controllability and stability of heavy-duty truck were influenced by different frame flexibility. The result shows that increasing frame stiffness properly is very helpful to improve ride comfort and under-steer characteristic, and is able to reduce the value of resonant peak level, but the roll angle will increase with large frame flexibility.Based on the analysis of force of vehicle with multi-axles during brake, the mathematical models of axle loads and brake forces were established, and then the ideal braking forces distribution curve with multi-axles (space curve I) was deduced, in addition, the braking process that the multi-axles vehicle traveled on different adhesive road surface was analyzed and discussed. According to the conclusions above, the loaded and unloaded space curve I of heavy-duty truck built in this paper were acquired. Meantime, the surface groups of braking force relationship on different adhesive road surface under condition of one of axles locked(f,m,r surface group) were obtained.Actual loaded and unloaded braking force distribution curves (space curveβ) of heavy-duty truck were designed and devised and their validity were verified by analysising the braking process on different adhesive road surface. In addition, space curveβwere programmed in virtual prototyping software with ADAMS/Solver functions, and then some simulation were performed in ADAMS/Car software environment to analyze heavy-duty truck braking performance on high and low adhesive road surface under different load conditions. The simulation results met the requirements of ECE regulations, and the percentage of utilization of maximum tractive force of each axle was improved.Logic threshold control strategies were developed that the heavy-duty truck brakes on high and low adhesive road surface and the road surface with adhesion coefficients ranged from low to high and high to low, and the corresponding controller model was established in MATLAB/Stateflow. Simultaneously, reference speed estimation model and brake chamber model were built in MATLAB/Simulink, and then three-axles pneumatic brake system model of heavy-duty truck with ABS was accomplished.A rigid-flexible coupling model of a heavy-duty truck with ABS was completed in the virtual environment with ADAMS/Car and MATLAB/Smulink, and the Co-simulation calculations were implemented under different road surface conditions. The results demonstrated that braking efficiency was improved with ABS, and this controller provides a basis for further guide in ABS product R&D stage.
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