Uncertainty Quantification of Wet Clutch Actuator Behaviors in P2 Hybrid Engine Restart Process
2022-01-0791
03/29/2022
- Content
- Advanced features in automotive systems often necessitate the management of complex interactions between system components. To accomplish this task, closed-loop feedback is commonly used for effective real-time controls. Alternatively, open-loop schemes with adaptive parameters can be applied when real-time feedback is infeasible. Although these strategies possess certain levels of robustness, their performance can deteriorate in the presence of significant uncertainties, resulting in undesirable system behaviors. This limitation is often further amplified in systems with complex nonlinear dynamics. A hydro-mechanical clutch actuator is among those systems whose behaviors are highly sensitive to variations in sub-component characteristics and operating environment. In a P2 hybrid system, a wet clutch is utilized for cranking the engine during EV-HEV mode switching. It is critical that a controller is capable of stroking hydro-mechanical clutch actuator as quickly and as consistently as possible under all conditions. Thus, during the control development process, it is desired to quantify the effects of uncertainties on the clutch actuator behaviors. In this paper, a predictive hydro-mechanical clutch actuator model is first presented. The equation of motion for the actuator piston includes a parametric representation of squeeze film and friction material compression for damping effects. The hydraulic line dynamics is modeled with a series of lumped volumes connected through orifices. Clutch torque is computed based on the Coulomb friction assumption. The model behaviors are qualitatively validated with experimental vehicle data. Monte Caro simulations are conducted to investigate the effects of uncertainties in input signal, bulk modulus of the fluid, piston seal friction, and piston damping. The mean behavior of piston pressure changes considerably when the presence of uncertainty is accounted for, which significantly affects the piston motion and clutch torque predictions. The results demonstrate that uncertainty quantification offers valuable insights into system behaviors that are not obtainable through conventional deterministic analyses.
- Citation
- Yang, H., Fujii, Y., Zhang, Y., Haria, H. et al., "Uncertainty Quantification of Wet Clutch Actuator Behaviors in P2 Hybrid Engine Restart Process," SAE Technical Paper 2022-01-0791, 2022, .