The placement of electric motors in hybrid electric vehicles (HEVs) significantly affects braking behavior through regenerative braking capability and mechanical coupling with the drivetrain:
1. Positional Influence on Energy Recovery
- P0/P1 (ICE-mounted): In positions connected directly to the engine crankshaft (P0) or between engine and transmission (P1), regenerative braking is limited. These motors primarily assist engine start-stop functions and mild hybrid operations, recovering minimal energy.
- P2/P3/P4 (transmission or axle-mounted):
- P2 (between transmission and wheels) allows direct mechanical coupling, enabling stronger regenerative braking by converting wheel momentum into electrical energy during deceleration.
- P3 (on the transmission output shaft) and P4 (integrated into the rear axle) provide even more efficient energy recovery, as they directly capture kinetic energy from wheel movement without relying on the engine-transmission path.
2. Two-Mode Hybrid Configurations
Systems like GM’s Two-Mode Hybrid use compound-split architectures with multiple clutches and planetary gearsets. This design allows:
- All-electric regenerative braking in Mode 1 (low-speed), maximizing energy recovery during urban driving.
- Hybrid braking blending in Mode 2 (high-speed), where mechanical and electrical braking forces are combined, optimizing energy recovery across speed ranges.
3. Series vs. Parallel Hybrid Dynamics
- Series hybrids (e.g., Nissan ePower) use motors as the sole drivetrain connection, enabling full regenerative braking capability since the ICE is mechanically decoupled from wheels. Braking energy is captured directly by the motor acting as a generator.
- Parallel hybrids (e.g., conventional P2 systems) require brake blending to balance friction brakes and regenerative braking, as the motor’s placement alongside the ICE introduces mechanical constraints.
Impact on Driver Experience
- Motor placement near wheels (P3/P4) provides smoother regenerative braking with less reliance on friction brakes, improving efficiency and pedal feel.
- ICE-coupled motors (P0/P1) often result in abrupt transitions between regenerative and friction braking, reducing energy recovery and driver comfort.
In summary, motor placement dictates regenerative braking efficiency by determining how directly kinetic energy can be converted to electrical energy during deceleration.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/how-does-the-placement-of-electric-motors-in-hevs-influence-braking-behavior/
