Dissertation

Hardware Architecture and Smart Control for Human-Electric Serial Hybrid Powertrains

Author:

Mohamad Ali Daher

Pages:

159

DOI:

https://doi.org/10.18154/RWTH-2025-00815

Keywords:

cycling, human-hybrid, powertrain control, series hybrid

Year:

2025

Language:

english

Format:

ebook

The globally increasing need for mobility poses elementary challenges to society, politics, and the economy. There is a growing urgency to reduce emissions from the transportation sector. Electric vehicles are crucial for achieving climate neutrality but face limitations such as range and cost issues. Smaller vehicles like pedelecs offer potential solutions but lack safety, performance and comfort. This thesis addresses these challenges through the development of human hybrid powertrains. The research focuses on three key aspects. Firstly, it aims to understand the performance characteristics of nonprofessional cyclists and how these insights can be leveraged to enhance the powertrain. Secondly, it seeks to identify the optimal human hybrid powertrain topology and parameterize its components. Finally, it explores factors influencing the controllability and acceptance of human hybrid powertrains. Preliminary findings indicate that amateur cyclists exhibit unique driving behaviors. They have a preferred cadence range, irrespective of vehicle speed. Also, drivers maintain a constant power output, adjusting torque as cadence increases. The comfortable power output limit is 120 W for extended durations, which can temporarily surge to over 300 W for short bursts. A human digital model is developed to accurately predict human performance, including heart rate, power output limits, cadence and torque profiles. This digital model plays a crucial role in designing the powertrain and control algorithms by modeling human behavior. A serial hybrid powertrain configuration is chosen for its control advantages and adaptability to driver preferences. A novel control architecture is implemented to mimic the natural feel of cycling while accommodating user preferences. It includes features like automatic nonlinear speed control and torque amplification, supplementary functions like electronic one-way clutch and heart rate-based control to enhance functionality, safety and efficiency. The powertrain components are dimensioned to enable compliance with L7e regulations while achieving performance comparable to small M-class vehicles, including top speed, range and acceleration. Importantly, energy demand remains minimal at 4.58 kWh/100km for the Urban Driving Cycle. Field tests demonstrate that varying cadence and torque affect driver power output, “driver energy share” (DES), pedal unit and human body efficiency. DES ranges from 5 % to 15 % for a 300 kg vehicle. Field study participants indicated high levels of acceptance, influenced by driver experience, control strategy and hardware performance. The overall efficiency of the human hybrid powertrain, combining driver and battery efficiency, is found to be highest in the serial hybrid configuration (85.9 %) compared to the parallel hybrid (71.7 %), making it the preferred option for low DES levels.