Development of a Parallel Hybrid Energy Management Strategy with Consideration of Drive Quality and State of Charge Dynamics

• Main Author: Legg, Thomas David
• Other Authors: Mechanical Engineering
• Format: Others
• Published: Virginia Tech 2021
• Subjects: hybrid; vehicle; simulation; drive quality; battery management
• Online Access: http://hdl.handle.net/10919/103422

The development of a rule-based hybrid energy management strategy for a parallel P4 full hybrid without access to a functional prototype is presented. A simulation model is developed using component bench data and validated using EPA-reported fuel economy test data, including a proposal for complete criteria for valid test results using EPA speed error and SAE J2951 parameters. A combined Willans line model is proposed for the engine and transmission, with control modes based on efficiency-derived power thresholds. Algorithms are proposed for battery state of charge (SOC) management including engine loading and one pedal strategies. Vehicle drive quality with the hybrid control strategy is analyzed, with acceleration and jerk managed through axle torque rate limits and filters. The simulated control strategy for the hybrid vehicle has an energy consumption reduction of 20% for the Hot 505, 3.6% for the HWFET, and 12% for the US06 compared to the stock vehicle. For standard drive cycles, battery SOC is maintained within 20% to 80% safe limits, with charge balanced behavior achieved. Jerk contributions of the hybrid powertrain are generally kept below a 10 m/s3 tolerable limit, with peaks of 15 m/s3 tuned for vehicle launch drive quality. The complete energy management strategy proposed improves fuel economy compared to baseline data while maintaining vehicle drive quality and is considered well-rounded and ready for in-vehicle testing and implementation. === Master of Science === A hybrid electric vehicle with an engine on the front axle and an electric motor on the rear axle is analyzed. A control strategy is developed based on a set of rules with different modes depending on the vehicle speed and accelerator pedal position, switching between using only the electric motor, only the engine, and a combination of both. The control strategy increases fuel economy while maintaining the charge level of the hybrid battery pack and providing a smooth and enjoyable driving experience.