TABLE OF CONTENTS In mechanical-hybrid and parallel hybrid-electric vehicles, the mechanical power outputs from different power sources are combined using various devices that can be generically called "torque couplers." These include three-sprocket gears driven by belts or chains or direct coupling on the same shaft. The case of different prime movers that power different wheel axles is straightforward and not considered here.
The entry level to hybridization is the belt-driven architecture typically implemented by starter/generator "mild" hybrids. In this configuration, the traditional alternator is replaced by an electric machine capable of not only generating electricity but also acting as a motor to crank the engine, assisting it in powering, and driving auxiliary loads when the engine is off. Such an implementation requires a relatively low amount of modification to an ICE-based vehicle [101]. The engine and transmission do not require any modifications, nor does the space between them. Modifications are required to mount a larger electric machine: larger pulleys are needed on all belt-driven accessories, and an inverter.
Another concept for torque coupling is implemented in full parallel hybrids. It consists of mounting the rotor of the electric machine on the same engine shaft, between the engine and the final drive. The stator is mounted on the outer transmission housing or on a separate intervening housing [101]. This mounting allows the electric machine to be used as a damper to cancel oscillations at the drive train. This concept is realized in the ETH-Hybrid III [54], [230],...
