Multi-body Dynamics Modeling And Digital Simulating Of A Off-road Vehicle

As the science develops, the performance of automobile is need more. And competition makes it more important to adopt new technique and new ways to improve the conducts. Virtual prototype technique can build models, simulate models and optimize them, then it can shorten the developing periods, save money, improve quality, finally improve the competition of the product.ADAMS is one of the software that is widely used in mechanics dynamic analysis. Virtual prototype technique is used in ADAMS, which provides the function of big displacement and non-linear solver, convenient interface and powerful postprocessing system. ADAMS/CAR is one of the professional modules, which is mainly used for dynamic simulating and analyzing of vehicle (including full vehicle and assemblies).This paper was based on multi-body dynamic theory and the software ADAMS/CAR. According to the off-road vehicle, which is in the initial design stage, the three-dimensional CAD models were afforded, so the key hardpoints, mass, moment of inertia, etc. were gotten. Because of the structure of 4WD, a driveline template was built which supported 4WD and based on the original template in ADAMS/CAR. The off-road vehicle is drived on the bad road in most of the situation, so in order to solve this problem, ASCL wheel-axle model was adopted in building the full vehicle model, too. It's very meaningful in improving the validity of the model and consummating the driveline template in ADAMS/CAR. Other subsystems of the full vehicle models were built by modifying the parameters in the ADAMS/CAR templates, such as vehicle body model, front and rear double wishbone independent suspension, brake system and steering model.The research on suspension kinematics were about the parameters, such as wheel orientation, body lifting and diving that related to suspension which were caused by the relative movement of vehicle body and wheels. So, in order to research on the kinematics of suspension, a kind of movement was imported to the suspension system, then the output results were researched and evaluated. The research on suspension dynamics were about wheel orientation, etc. which were caused by the lateral or longitudinal force or torque acting on the suspension system. So, the way to research and evaluate the suspension dynamics was to import force or torque to the suspension system. So the kinematics and dynamics simulation analysis were made to the front double-wishbone suspension of thisoff-road vehicle. These simulations were: kinematics analysis caused by the parallel jump of the left and right wheels; kinematics analysis caused by the rolling movement of the vehicle body; dynamics analysis caused by the external forces. Finally, the suspension of the initial stage off-road vehicle could be analyzed. As the speed of the vehicle increased, better controllability and stability performance of the vehicle were required, not only cars, but also off-road vehicles. So, according to the national controllability and stability test for automobiles test procedure, six simulation tests were made, including: steer wheel angle step input test, steer wheel angle pulse input test, returnability test, steady static circular test, steering efforts test and pylon course slalom test. Then, according to the national standards, these tests were scored and full vehicle performance were scored, too. It turned out that this off-road vehicle model performed well in controllability and stability. It was very important to check the models. According to the results data of this initial design off-road automobile in steady static circular test, compare of the results between the virtual prototype model and the real vehicle under the condition of same vehicle speed were made, it turned out that the results were basically well matched and the trend was consistent. Because of the complex condition of roads that the vehicle traveled, special simulations were made to this off-road vehicle, including driving the vehicle through vertical step, pothole and grade. The results identified that the vehicle could go through these obstacles, and proved the validity of the 4WD driveline model built before.