Virtual development and torque control optimization of a hybrid-electric motorbike

Abstract

Hybridizing a road motorcycle poses significant challenges due to strict constraints on weight, dimensions, and cost, requiring innovative solutions tailored to motorcycle-specific features. This study focuses on a stock motorcycle with a 54 kW engine and 200 kg curb weight, aiming to reduce fuel consumption and CO₂ emissions without compromising performance or ride quality. The proposed hybrid powertrain introduces key innovations: an extremely downsized thermal engine (from a two-cylinder 690 cc to a single-cylinder 250 cc), a compact axial flux electric motor, and a 2 kWh optimized battery. These elements allow seamless integration into the stock motorcycle while meeting design targets. Additionally, positioning the electric motor post-clutch and gearbox (P3) enables full-electric operation, decoupling the internal combustion engine. Performance comparisons between the original and hybrid configurations, using a MATLAB-Simulink model, reveal several key findings: (1) downsizing the engine is a very effective solution for minimizing the overall dimensions and weight of a motorcycle hybrid powertrain; (2) optimal control involves deactivating the thermal engine below 65 km/h and recharging the battery when the engine can operate at maximum brake thermal efficiency; (3) hybridization achieves a 27% reduction in fuel consumption and a 45% decrease in CO₂ equivalent emissions during the Worldwide Motorcycle Test Cycle (WMTC); (4) the smaller engine shortens catalyst light-off time by 20%, lowering pollutant emissions; (5) the hybrid motorcycle offers a full-electric range of 24 km at 100% state of charge (SOC); (6) full performance parity with the stock motorcycle is achieved only with a fully charged battery, though the thermal engine alone can still meet standard performance levels, including the WMTC velocity schedule. This study demonstrates the technical feasibility of hybridizing motorcycles in this category, achieving significant environmental benefits without sacrificing functionality.