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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.

Innovations in mobility are built upon a management of complex interactions between sub-systems and components. A need for CAE tools that are capable of system simulations is well recognized, as evidenced by a growing number of commercial packages. However impressive they are, the predictability of such simulations still rests on the representation of the base components. Among them, a wet clutch actuator continues to play a critical role in the next generation propulsion systems. It converts hydraulic pressure to mechanical force to control torque transmitted through a clutch pack. The actuator is typically modeled as a hydraulic piston opposed by a mechanical spring. Because the piston slides over a seal, some models have a framework to account for seal friction. However, there are few contributions to the literature that describe the effects of seals on clutch actuator behaviors.

A wet friction component continues to play a critical role in a step-ratio automatic transmission (AT) system. It is hydraulically actuated to alter planetary gear configurations for automatic shifting. During a shift event, its engagement torque is transmitted to AT output shaft, directly affecting vehicle shift quality. The friction component behaviors vary widely under different conditions. In a vehicle development process, unanticipated behaviors often lead to an inefficient trial-and-error approach for adjusting shift feel. Thus, a shift improvement process can benefit from upfront characterization of friction component behaviors. The so-called SAE#2 test system has served as the industry-standard since 1960's for evaluating friction components. It provides a useful means for evaluating friction component design variables. However, its standardized test conditions do not adequately capture dynamic effects of AT shift control variables.