ABSTRACT To improve shift quality of vehicle with clutch-to-clutch gear shifts, a two-degree-of-freedom controller, including a clutch pressure estimator, is designed for clutch slip control during the inertia phase of the shift process. The controller is designed based on a low order linear model which is derived from dynamics of the proportional pressure control valve and the vehicle drive line. Then the calculated controller is evaluated on the constructed nonlinear powertrain simulation model. Simulation results show that the rotational speed difference of clutch can track the desired trajectory well, and shift shock can be reduced by designing suitable feedforward compensator. INTRODUCTION To improve fuel economy, reduce emission and enhance driving performance, many new technologies have been introduced in the transmission area in recent years, such as Dual Clutch Transmission (DCT) and new Automatic Transmissions (AT) controlling the clutches independently [1]. In both transmissions, the change of speed ratio can be regarded as a process of one clutch to be engaged while another being disengaged, namely, clutch-to-clutch shifts. How to make the process smooth and efficient relies on th e clutch slip control, accordingly, the control of cylinder pressure becomes very important. In recent years, the small size but large flow rate proportional valve was developed for direct clutch pressure control without using the pilot duty solenoid valve [2]. New Automatic Transmission can use it to improve the ability of the transmission to adapt to different driving co nditions, as well as reduce the cost and improve packaging. Clutch-to-clutch shift of this kind of Automatic Transmission involves electronic control of both the oncoming and offgoing clutches, thus guarantee the timing and coordination between them, which are assured by the hydraulic logic circuits in the case of traditional AT. The elimination of some shift valves and accumulators, etc. greatly simplifies the transmission mechanical content, but makes the robust control of clutch-to-clutch shifts a challenge [1, 3]. Furthermore, the sensors for measuring the pressure of clutch cylinder are seldom used because of the cost and durability. If system state feedback is to be used to enhance system control quality, the cylinder pressure needs to be estimated [4]. Two-degree-of-freedom controller design is suitable to many automotive control systems for it can fulfill good tracking performance and robustness simultaneously [5]. In [6], a two-degree-of-freedom controller was designed for the speed control of a braking mechanism, in which the feedback gain was calculated by /g80 synthesis. This paper, therefore, use the two-degree-of-freedom controller design method to carry out the clutch slip control of an Automatic Transmission with proportional pressure control valves. Th e clutch cylin der pressure, which is necessary for state feedback control is estimated by a reduced-order state observer. The feedback gain is calculated by robust pole assignment methods while the feedfo rward compensator aims to improve the system response. Not only the rotational speed can track the desired trajectory well, but also can shift shock be reduced by choosing suitable feedforward compensator. The designed controller, including the pressure estimator is evalu ated on a wh ole powertrain simulation model. In particular, the simulation of gear shift process with engine control shows the robustness of the controller. 2008-01-0537 Two-Degree-of-Freedom Controller Design for Clutch Slip Control of Automatic Transmission Bingzhao Gao Jilin University, China Yokohama National University, Japan Hong Chen Jilin University, China Kazushi Sanada Yokohama National University, Japan Copyright © 2008 SAE International SAE Int. J. Passeng. Cars - Mech. Syst. | Volume 1 | Issue 1 430Downloaded from SAE International by Univ of Cal