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Automobile drivers/passengers perceive automatic transmission (AT) shift quality through the torque transferred by transmission output shaft, so that torque regulation is critical in transmission shift control and etc. However, since a physical torque sensor is expensive, current shift control in AT is usually achieved by tracking a turbine speed profile due to the lack of the transmission output torque information. A direct torque feedback has long been desired for transmission shift control enhancement. This paper addresses a “virtual” torque sensor (VTS) algorithm that can provide an accurate estimate on the torque variation in the vehicle transmission output shaft using (existing) speed sensors. We have developed the algorithm using both the transmission output speed sensor and anti-lock braking system speed sensors. Practical solutions are provided to enhance the accuracy of the algorithm. The algorithm has been successfully implemented on both FWD and RWD vehicles.

The mechanical behavior of a passenger car disc brake sliding caliper is analyzed in order to better understand the parameters that influence rotor/pad pressure distribution. The analysis uses proven techniques for solving free boundary contact problems. Complementarity equations for a gap between adjacent nodes are formulated in terms of the contact compliances for the inboard and outboard pad/rotor interfaces and for the piston/inboard-shoe interface. These equations also capture the influence of rigid-body motion of the various caliper components resulting from the translation and rotation needed to satisfy static equilibrium. The finite element method is employed to calculate the compliance matrices for all the contact interfaces. An iteration scheme is developed to solve the nonlinear system of complementarity equations for each of the three contact problems.

This paper presents four different modeling approaches for the thermal analyses of disc brakes. The models, ranging from a simple lumped-parameter model to a complex three-dimensional model, have all been found to be useful depending on the need at hand. A lumped-parameter (zero-dimensional) rotor model predicts transient bulk rotor temperatures, while a one-dimensional model provides peak surface as well as bulk temperatures. A steady-state, two-dimensional model of the entire brake system predicts plateau temperatures during a multi-stop driving schedule. Finally, a complex three-dimensional transient model can be used to obtain detailed local rotor temperature distributions for any stoping sequence. Each modeling approach is presented here with experimental validation of the predicted results.

For the conventional 6 speed automatic transmission with engine stop-start powertrain, an electrically-driven auxiliary pump is implemented to maintain the transmission line pressure as required to lock-up the CB1234 clutch during engine auto-stop conditions. Upon releasing the brake pedal, the transmission engages into first gear with the objective to accelerate the vehicle in a responsive manner. In this study, a novel normally-engaged dual-piston clutch concept is designed to keep the CB1234 clutch locked-up during engine auto-stop conditions with the intention to eliminate the auxiliary pump without compromising vehicle performance. This dual piston clutch concept requires a relatively low line pressure to release the normally-engaged clutch when needed, thus, minimizing the hydraulic pumping work. To explore the functionality of this concept under a wide-open-throttle (WOT) auto-start transition, modeling and simulation of the normally-engaged dual-piston clutch is completed.