Electrification of Transportation
This chapter discusses applications of power electronics and motor drives in chassis systems, and it distinguishes three major classes of applications: power converters used in brake systems, power converters used in steering systems, and power converters used in suspension systems. The term “chassis” is used to designate the complete car less the body. It therefore consists of the engine, power-transmission system, and suspension system. These systems are attached to, or suspended from, a structurally independent frame, with the separation of the body and chassis as mechanical parts, various power electronics systems are associated with each. It is worthwhile to note that in rare cases both the body and chassis are welded together, forming a single unit.
If the buzzword for body systems was “mechatronics,” here we are excited by “all-electric vehicle” or “more electric vehicle,” which is a replacement for pneumat- ics/hydraulics witli electrical drives. This contemporary electrification of the transportation process also takes place in marine and aviation applications.
The evolutionary technological steps for all three main applications related to chassis systems subsequently include:
- • Direct driver/operator action.
- • Assisting operator action with an auxiliary energy source derived from the engine through either manifold or belts and a hydraulic system of sorts.
- • Replacing the engine-based energy source with electrical energy through an electromagnetic device, still within the hydraulic system.
- • All-electric solution (or more electric vehicle), with direct action of the motor drive instead of hydraulics or mechanical systems.
Even if this is the evolution, contemporary designs can reside in any of these categories, depending on the particular complexity of the motor vehicle.
Ancillary Energy Sources Derived from the Engine
The above-mentioned chassis applications of motor drives require a higher energy level than each of the body systems introduced in the previous chapter. Since the need and the desire to implement these precluded the larger alternators in operation, designers had to find other energy sources inside the car, preferably derived from the operation of the internal combustion engine.
The conventional car burns gas or diesel to produce mechanical power. Various equipment systems—that need energy for their displacement—had to derive energy from the internal combustion engine’s operation. The engine’s energy may be directly tapped through a mechanical connection with belts or gears, with a notable example of the air conditioning compressor.
Similarly, an alternator offers the possibility of using a higher energy generator to supply various electrically controlled accessories. While the construction and operation of a conventional alternator are explained in Chapter 3, newer designs may increase the installed power within the generator and supply more electrical loads. This is the trend taken up with the electrification in transportation process, and it can be sustained with energy stored in battery banks. In the future, the high-energy batteries used in hybrid and all-electrical vehicles can shift the balance of technologies even further in the direction of electrically powered accessories.
Other sources of energy consist of the hydraulic links from a pump, mechanically driven by the engine, with the most notable example of the power steering. Several interesting expansions to body systems were also considered. For instance, the French company Citroen devised a high-pressure hydraulics system for cars, which was used for all manner of systems, even power-adjustable seats. Also, the 1999-2004 Jeep Grand Cherokee had a hydraulically driven radiator fan, powered by the SUV’s (Sport Utility Vehicle) power steering pump. Finally, it is worthwhile to mention that most hard-top convertible cars use engine-driven hydraulics.
A distinct source of energy was briefly mentioned with the cruise control body system. The partial vacuum available at the intake manifold is used, with the most notable application in chassis systems being the booster for the power brake system.
Compressed air is rarely used in passenger cars and widely used in large vehicles Cremember the hissing bus door?).