Recent research and development has led to the next generation hybrid fuel automobile, depicted in Figure 1.20. The hybrid fuel vehicle utilizes a conventional internal combustion engine in combination with a battery (or other energy storage
device such as a fuel cell or flywheel) and an electric motor to achieve a propulsion
system capable of doubling the fuel economy over conventional automobiles. Although these hybrid vehicles will never be zero-emission vehicles (since they have
internal combustion engines), they can reduce the level of harmful emissions from
one-third to one-half, and with improvements envisioned in the future, these emissions may reduce even further. As stated earlier, the modern automobile requires
many advanced control systems to operate. The control systems must regulate the
performance of the engine, including fuel–air mixtures, valve timing, transmissions,
wheel traction control, antilock brakes, and electronically controlled suspensions,
among many other responsibilities. On the hybrid fuel vehicle, there are additional
control functions that must be satisfied. Especially necessary is the control of
power between the internal combustion engine and the electric motor, determining
power storage needs and implementing the battery charging, and preparing the vehicle for low-emission start-ups. The overall effectiveness of the hybrid fuel vehicle
depends on the combination of power units that are selected (e.g., battery versus
fuel cell for power storage). Ultimately, however, the control strategy that integrates the various electrical and mechanical components into a viable transportation system strongly influences the acceptability of the hybrid fuel vehicle concept
in the marketplace.