Daniel G. Smedley

Simulation Study of Dual Clutch Transmission for Medium Duty Truck Applications

Dual clutch based transmissions (DCT) have been developed for passenger vehicles in Europe. Compared to a single clutch based transmission (SCT), DCT eliminates torque interrupts during gear-shifting so that the vehicles can run as smooth as one using an automatic transmission (AT). Traditionally AT needs to use torque converters to transmit engine torque to drivelines. However, a torque converter is complicated and expensive, and offers lower driveline efficiency than SCT and DCT. DCT technology is a cost-effective avenue to achieve smooth shifting while taking advantage of the some beneficial features of both AT and SCT. This paper presents the results of an analysis of the application of DCT on medium duty (MD) trucks. First, we set up a 6-speed DCT with two groups of three gear ratios in correspondence to two ceramic dry clutches. Clutch dampers are included in the DCT model. For simplicity but without loss of generality, the synchronizers are not included for this study. Then, based on this DCT model, a complete powertrain for a MD truck is modeled from engine to wheels. The grade, rolling resistance and air resistances are considered in the model as well. A speed based shifting strategy is adopted for this simulation study. Finally, we run the DCT based model to show both transmission and vehicle dynamics. For comparison purposes, an SCT based vehicle model is built too with the same 6-speed ratios for DCT. The simulation results show that DCT can make smoother shifting than SCT and avoid engine flaring. Tentative conclusions will be presented in the final section.

Static Friction Models for Vehicle Simulation Study

The history of the challenge of friction modeling is briefly reviewed. Then this paper focuses on the modeling and simulation study of the friction related dynamics in the Simulink® environment, because Matlab®/Simulink® are popular engineering software tools for both industry and academia. Matlab® and Simulink® are the proprietary products of MathWorks, Inc. In this paper, the static friction models are studied through Simulink® by applying fixed and variable step sizes. The comparison shows that the static Karnopp model is not only numerically tractable but also can be inclusive of the fundamental friction characteristics of both stick slip and correct friction predictions. Finally this paper presents an improved Karnopp model for clutch modeling with the use of Simulink®, and the simulation shows that this model is computationally tractable with smooth dynamics.Copyright