As the energy and environment crisis increase severely, developing cleaner and more fuel efficient vehicles have become a research hot spot of automobile industry. In recent years HEV (hybrid electric vehicle) and EV (electric vehicle) are widely considered as two of the most viable solutions to the world’s need for cleaner and more fuel-efficient vehicles.
This project aims to further improve the performance and fuel efficiency of EVs/HEVs for real application of urban driving. The thesis can be divided in to two major studies: EMB (Electro-Mechanical Brake) system development and HEV power management, which are two hot topics in the latest researches of EVs/HEVs.
The brake system plays an important role in vehicles. As the X-by-wire technology develops, EMB can realize individual control of braking force on each wheel; which makes it very suitable for electrified vehicles. In this thesis a compact design of EMB actuator is proposed. To investigate the control of EMB system, a down scaled EMB test rig has been set up and an EMB motor control system has been developed. In the section of clamping force control of EMB system, in order to achieve fully control of braking force, a low cost sensor less clamping force control method is proposed. It is noted that in real applications of EVs/HEVs the EMB system is normally cooperated with regenerative braking system during braking process, in this thesis the co-operative control of hybrid brake system is investigated as well to improve the braking performance and regenerative braking efficiency.
In order to overcome the drawbacks of the conventional gasoline vehicles, HEVs encompass two power sources (internal combustion engine and electric motor) to drive the vehicle. Due to existence of the double power sources, HEVs normally have multiple operation modes. The objective of HEV power management is to find the optimal power distribution on each power source to meet the power requirement with minimum fuel consumption. In this thesis to improve the fuel efficiency and keep the balance of battery SOC (state of charge) simultaneously during urban driving, a revised dynamic programming (DP)-optimized HEV power management control strategy is proposed. The DP algorithm is applied to obtain the optimal engine/motor power distribution and utilized for the design of the fuzzy control strategy. The traditional DP algorithm is modified with the consideration of SOC balance for HEVs. In the analysis of DP simulation results, rules of torque slip behaviors have been found, which are directly utilized in the design of fuzzy control strategy. In order to improve the practicality of the control strategy to meet the diversities of city driving patterns, an urban driving pattern recognition method is presented. To evaluate the control performance, the proposed control strategy is also compared with the conventional rule-based strategy. The simulation results indicate that by adopting the proposed strategy the fuel efficiency of HEV is improved, and the SOC of the battery is kept in balance during different urban driving cycles.
|Date of Award
|15 Mar 2018
- Univerisity of Nottingham
|John Xu (Supervisor) & Dunant Halim (Supervisor)