Slip Speed and Drive Torque Planning of Multivariable Controller for an Electrified Vehicle with Dual Clutch Transmission

Abstract

Demand for electrified vehicles is increasing due to increased environmental pollution regulations and interest in highly efficient vehicles. According to these demands, research on electrified vehicles equipped with Dual Clutch Transmission (DCT) has been actively conducted for the purpose of improving energy efficiency of electrified powertrain, maximizing acceleration performance, and increasing maximum speed. However, since DCT requires clutch to clutch shifting, it is difficult to control drive torque and slip speed using two clutch actuators and a power source input. In order to solve this, a study on a multivariable shift controller has been conducted. However, this study chose a heuristic planning method to control the two outputs. However, since the slip speed and drive torque are coupled, it is necessary to tune the reference for every shift scenario, as well as create unnecessary control inputs or degrade shift control performance. Therefore, this study proposes a reference planning method considering powertrain dynamics. Specifically, by using the powertrain modeling of the electrified vehicle, a reference composed of power source input, slip speed, and drive torque can be constructed while satisfying dynamics. Using the proposed method, the slip speed is uniquely determined when the reduction ratio of the power source torque and the inertia phase time are predetermined. In order to verify the proposed planning method in this paper, an electrified powertrain simulator designed with a multivariable controller was constructed with MATLAB/SIMULINK. Afterwards, the heuristic reference planning method of the previous study and the method proposed in this paper were simulated in a vehicle composed of the same shift controller and powertrain. As a result, not only the reference automatically generated without tuning, but the energy consumption of the clutch actuator is reduced by about 10% in the control result with the same ride quality.