Sungyeon Ko

Development of Brake System and Regenerative Braking Cooperative Control Algorithm for Automatic-Transmission-Based Hybrid Electric Vehicles

In this paper, a brake system for an automatic transmission(AT)-based hybrid electric vehicle (HEV) is developed, and a regenerative braking cooperative control algorithm is proposed, with consideration of the characteristics of the brake system. The brake system does not require a pedal simulator or a fail-safe device, because a hydraulic brake is equipped on the rear wheels, and an electronic wedge brake (EWB) is equipped on the front wheels of the vehicle. Dynamic models of the HEV equipped with the brake system developed in this study are obtained, and a performance simulator is developed. Furthermore, a regenerative braking cooperative control algorithm, which can increase the regenerative braking energy recovery, is suggested by considering the characteristics of the proposed hydraulic brake system. A simulation and a vehicle test show that the brake system and the regenerative braking cooperative control algorithm satisfy the demanded braking force by performing cooperative control between regenerative braking and friction braking. The regenerative braking cooperative control algorithm can increase energy recovery of the regenerative braking by increasing the gradient of the demanded braking force against the pedal stroke. The gradient of the demanded braking force needs to be determined with consideration of the drivers braking characteristics, regenerative braking energy, and the driving comfort.

Development of co-operative control algorithm for parallel HEV with electric booster brake during regenerative braking

In this study, a co-operative regenerative braking control algorithm for the HEV with an electric booster brake was proposed and its performance was evaluated. A dynamic model for the electric booster brake system was derived to develop the electric booster brake performance simulator and its performance was investigated. In addition, a dynamic model for the 6-speed AT-based hybrid vehicle was established to develop a performance simulator, and it was combined with the electric booster brake performance simulator. Considering the electric booster structure, a strategy was proposed to distribute the braking force and regenerative braking force using the electric booster. A co-operative control algorithm was proposed, wherein the regenerative torque is cut off to ensure ride comfort and maintain the braking force during downshift for braking, and then the regenerative torque is controlled considering the electric booster brake response characteristic. The combined performance simulator was used to evaluate the performance of the electric booster brake and the co-operative control algorithm, and the results indicated that the desired braking force was maintained and that the deceleration change decreased.

Comparative study on power characteristics and control strategies for plug-in HEV

A comparative study was performed for two types of plug-in hybrid electric vehicles (PHEVs): GM Volt and Toyota Prius Plug-in Hybrid. First, powertrain models of the two vehicles were derived. Based on the dynamic models, a detailed component control algorithm was developed for each PHEV. Especially, a control algorithm was proposed for motor generator 1 (MG1) and MG2 to achieve optimal engine operation. In addition, an energy management strategy for selecting the operation mode was developed from the viewpoint of fuel economy, using the battery state of charge and vehicle velocity. Based on the performed simulation results, a comparative study was performed, and it was found that the role and capacity of MG1 and MG2, and the mode selection algorithm, must be determined depending on the configuration of the PHEV.

A Study on In-wheel Motor Control to Improve Vehicle Stability Using Human-in-the-Loop Simulation

In this study, an integrated motor control algorithm for an in-wheel electric vehicle is suggested. It consists of slip control that controls the in-wheel motor torque using the road friction coefficient and slip ratio; yaw rate control that controls the in-wheel motor torque according to the road friction coefficient and the yaw rate error; and velocity control that controls the vehicle velocity by a weight factor based on the road friction coefficient and the yaw rate error. A co-simulator was developed, which combined the vehicle performance simulator based on MATLAB/Simulink and the vehicle model of CarSim. Based on the co-simulator, a human-in-the-loop simulation environment was constructed, in which a driver can directly control the steering wheel, the accelerator pedal, and the brake pedal in real time. The performance of the integrated motor control algorithm for the in-wheel electric vehicle was evaluated through human-in-the-loop simulations.

Development of a vehicle stability control algorithm using velocity and yaw rate for an in-wheel drive vehicle

This paper proposes a vehicle stability control algorithm that uses velocity and yaw rate during cornering for an in-wheel independent drive vehicle. The vehicle velocity control at the cornering determines the velocity limit that the vehicle can sustain the given cornering radius and controls the vehicle velocity for safe cornering if the vehicle velocity is faster than the velocity limit. The yaw rate control determines whether the vehicle is under steer or over steer during cornering and directly generates a yaw moment by independently driving and braking the in-wheel motor of each wheel. To evaluate the validity of the vehicle stability control algorithm, a co-simulator that integrated the CarSim vehicle model and MATLAB/Simulink controller model was developed.

Development of a route information-based control algorithm of a range extender for an RE-EV

In a range-extended electric vehicle (RE-EV), the system efficiency decreases when the engine power is transmitted to the driving motor through the battery due to the charging and discharging energy conversion efficiency. To improve the system efficiency, a control algorithm is proposed using the route information. The control algorithm calculates the threshold power based on the battery charging amount and the demanded vehicle power from the target route. Using the threshold power, more engine power can be transmitted directly from the engine to the driving motor without charge and discharge process through the battery. It was found that the proposed algorithm reduces the fuel consumption of the target RE-EV, compared with the existing CD/CS control.

Development of regenerative braking co-operative control system for automatic transmission-based hybrid electric vehicle using electronic wedge brake

This research proposes a regenerative braking co-operative control system for the automatic transmission (AT)-based hybrid electric vehicle (HEV). The brake system of the subject HEV consists of the regenerative braking and the electronic wedge brake (EWB) friction braking for the front wheel, and the hydraulic friction braking for the rear wheel. A regenerative braking co-operative control algorithm is suggested for the regenerative braking and friction braking, which distributes the braking torque according to the drivers demand. A vehicle test was performed to evaluate the proposed braking system and cooperative control algorithm.