Gear Shift Control of Dual Clutch Transmissions with a Torque Rate Limitation Trajectory Abstract— Gearshift control is one of the main functions of automotive transmissions。 The proposed control utilizes the functionality of Dual Clutch Transmissions (DCTs) that two control inputs are available incorporating each other。 During gearshift operation, each clutch is controlled uni-directionally to prevent undesirable effects such as dead zone nonlinearity, saturation, and etc。 Even though they have such a constraint, the desired clutch profile is tracked well via cross-coupling effect of two actuators。 In addition, engine torque is reduced based upon the predetermined target engine speed。 A simple proportional-integrative (PI) controller is implemented for a feedback control of the proposed gear shifting management。 Simulation results show that gear shifting is performed without excessive oscillations of the shaft  torque。73743

I。 INTRODUCTION

Recently, advanced transmission technologies are intro- duced to improve fuel efficiency。 Since planetary type Au- tomatic Transmissions (ATs) generally require torque con- verters to connect the engine with the transmission with few exceptions, it is inevitable that there are energy losses in spite of smooth gear shifting。 Automated Manual Transmissions (AMTs) have a servo-controlled clutch and gear actuators along with mechanism of Manual Transmissions (MTs)。 However, AMTs have a limitation of shift quality due to severe torque interruption [1], [2], [3],  [4]。

On the other hand, Dual Clutch Transmissions (DCTs) combine high efficiency of MTs with convenience of auto- matic transmissions by using two clutches for engagement and release, simultaneously。 Thus, shift quality and driving comfort can be significantly improved even without lack of torque transmission。 In spite of such advantages, controlla- bility plays a crucial role in determining overall performance of DCTs。 There have been some researches on the modeling and analysis of dynamic characteristics of DCTs [5], [6], [7], [8]。 The methods suggested in several researches are open- loop based control and PID controller with experimental calibration [9], [10]。 Since DCT vehicles are not equipped with a torque converter, it is difficult to achieve sophisticated torque control in the real  environment。

Thus, the upper level controller for gear shifting man- agement, that generates a clutch profile accurately to the lower controller for actuator control, should provide a desired control input to the electric or hydraulic actuators。 Moreover, gear  shifting  should  be  performed  in  a  short  period    of

time to prevent the vehicle from having torque interruption。 Compared with a launch control of standing vehicles, it requires very fast engagement and release of a clutch in order to avoid torque interruption so that actuators are needed to have quick response。

In this paper, the gearshift control management system will be presented to utilize the unique characteristic of dual clutch systems。 Section II presents the driveline model equipped with the DCT。 In Section III, the open-loop based control will be introduced for comparison with the proposed method。 In IV, the gearshift control strategy using a torque rate limitation is proposed based on the convexity of control inputs。 The engine controller is also introduced to reduce the engine torque。 Simulation results and some concluding remarks are drawn in Section V and VI,  respectively。

II。 DRIVELINE MODEL

In a gear shift operation, a driveline model with the dual clutch transmission is needed to describe dynamic behavior of the system because DCTs do not have a torque converter that dampens shift impact compared with ATs。 The schematic of the driveline model is shown in Fig。   1。