Methodology Development for Multibody Simulation to Understand Shift Shock Behaviour

One of the critical challenges for transmission design is to predict the gear shift dynamics accurately and to ensure smooth gear shift quality for different driver behaviors while shifting. This calls for detailed understanding of the RWUPs. Through prototype testing, understanding the influence of different parameters is costly and time consuming. Also, the testing does not provide necessary visualization of exact physics and the identification of issues is difficult. One of such typical concerns is shift shock while shifting the gear. Sudden gear engagement or disengagement leads to impact torque in drivetrain during shifting of gears, which in turn results in winding and unwinding of powertrain due to vehicle Inertia. This induces noise and vibration that affects driver comfort. The paper presents, the methodology to frontload prediction of dynamics of gear shifting that leads to shift shock behavior. A multi-body dynamics model of transmission with synchronizer is modeled in MSC ADAMS VIEW. The paper details out the high-fidelity multibody simulation modeling in terms of different connections, contact parameters, gear modelling, appropriate discretization of driveline systems - stiffness and inertia modelling, damping and friction considerations. Different model fidelity levels are discussed in the paper and the influence of different parameters on the shift shock phenomenon is presented. Three different numerical integrators HHT, GSTIFF and Newmark are studied, and results are presented. It is observed that the simulation results with HHT integrator are in good agreement with the test result.