An LQR Approach of Automatic Transmission Upshift Control Including Use of Off-Going Clutch within Inertia Phase 2020-01-0970
This paper considers using linear quadratic regulation (LQR) for multi-input control of the Automatic Transmission (AT) upshift inertia phase. The considered control inputs include the transmission input/engine torque, oncoming clutch torque, and traditionally not used off-going clutch torque. Use of the off-going clutch has been motivated by discussed Control Trajectory Optimization (CTO) results demonstrating that employing the off-going clutch during the inertia phase along with the main, oncoming clutch can improve the upshift control performance in terms of the shift duration and/or comfort by trading off the transmission efficiency and control simplicity to some extent. The proposed LQR approach provides setting an optimal trade-off between the conflicting criteria related to driving comfort and clutches thermal energy loss. It ensures tracking a linear-like profile of oncoming clutch slip speed reference, which was found to be nearly optimal based on control trajectory optimization results. A special attention is given on proper implementation of nonlinear energy loss term through LQR cost function cross term and using a clipped optimal control approach to provide that the clutches (described as torque source elements) can only dissipate energy. The LQR approach was applied to a fifth-order powertrain model and different upshift control scenarios ranging from the use of single clutch towards using both clutches and transmission input/engine torque reduction. It is shown that the LQR approach can reproduce Pareto frontiers obtained by multi-objective control parameter optimization demonstrating that apart from being used in closed loop controls, the proposed LQR approach can also be exploited for computationally efficient (off-line) optimization purposes.
Citation: Cvok, I., Deur, J., Ivanovic, V., Zhang, Y. et al., "An LQR Approach of Automatic Transmission Upshift Control Including Use of Off-Going Clutch within Inertia Phase," SAE Int. J. Adv. & Curr. Prac. in Mobility 2(4):2081-2091, 2020, https://doi.org/10.4271/2020-01-0970. Download Citation
Ivan Cvok, Josko Deur, Vladimir Ivanovic, Yijing Zhang, Yuji Fujii
University of Zagreb, Ford Motor Company
WCX SAE World Congress Experience
SAE International Journal of Advances and Current Practices in Mobility-V129-99EJ