15-05-2014, 04:54 PM
THE HY-WIRE CARS
THE HY-WIRE.doc (Size: 1.47 MB / Downloads: 24)
Introduction
Cars are immensely complicated machines, but when you get down to it, they do an incredibly simple job. Most of the complex stuff in a car is dedicated to turning wheels, which grip the road to pull the car body and passengers along. The steering system tilts the wheels side to side to turn the car, and brake and acceleration systems control the speed of the wheels.
Given that the overall function of a car is so basic (it just needs to provide rotary motion to wheels), it seems a little strange that almost all cars have the same collection of complex devices crammed under the hood and the same general mass of mechanical and hydraulic linkages running throughout. Why do cars necessarily need a steering column, brake and acceleration pedals, a combustion engine, a catalytic converter and the rest of it?
According to many leading automotive engineers, they don't; and more to the point, in the near future, they won't. Most likely, a lot of us will be driving radically different cars within 20 years. And the difference won't just be under the hood -- owning and driving cars will change significantly, too.
In this article, we'll look at one interesting vision of the future, General Motor's remarkable concept car, the Hy-wire. General Motor may never actually sell the Hy-wire to the public, but it is certainly a good illustration of various ways cars might evolve in the near future.
Hy-wire Basics
Two basic elements largely dictate car design today: the internal combustion engine and mechanical and hydraulic linkages. If you've ever looked under the hood of a car, you know an internal combustion engine requires a lot of additional equipment to function correctly. No matter what else they do with a car, designers always have to make room for this equipment.
The same goes for mechanical and hydraulic linkages. The basic idea of this system is that the driver maneuvers the various actuators in the car (the wheels, brakes, etc.) more or less directly, by manipulating driving controls connected to those actuators by shafts, gears and hydraulics. In a rack-and-pinion steering system, for example, turning the steering wheel rotates a shaft connected to a pinion gear, which moves a rack gear connected to the car's front wheels. In addition to restricting how the car is built, the linkage concept also dictates how we drive: The steering wheel, pedal and gear-shift system were all designed around the linkage idea.
DESIGN
Due to hydrogen fuel cell drive system used by the Hy-wire, the conventional car layout has been revamped.Without the need for a conventional engine block and transmission system coupled to the steering column and pedals through mechanical linkage the car's power system and single electric motor are built into a flat skateboard configuration. Because all propulsion and energy storage systems are housed in the skateboard, designers are free to arrange the passenger compartment however they see fit.The skateboard itself contains crumple zones similar to those in conventional automobiles. The two basic elements that largely dictate car design today are: the internal combustion engine and mechanical and hydraulic linkages. If we look under the hood of a car, we can see that an internal combustion engine requires a lot of additional equipment to function correctly. The designers trying to bring out new luxurious and environment-friendly cars into the market always have to make room for this equipment.The same is the case with the mechanical and hydraulic linkages. The basic idea of using the linkages is that the driver can maneuver the various actuators in the car more or less directly, by manipulating driving controls connected to those actuators by shafts, gears and hydraulics. For example, in a rack and pinion steering system turning the steering wheel rotates a shaft connected to a pinion gear, which moves a rack gear connected to the carâ„¢s front wheels.The defining characteristic of the Hy-wire is that it doesnâ„¢t have either of those two things. Instead of an engine, it has a fuel cell stack, which powers an electric motor connected to the wheels. Instead of mechanical and hydraulic linkages, it has a drive by wire system where a computer actually operates the components that move the wheels, activate the brakes and so on, based on input from an electronic controller.
Power
The "Hy" in Hy-wire stands for hydrogen, the standard fuel for a fuel cell system. A fuel cell is an electrochemical energy conversion device that converts hydrogen and oxygen into water, producing electricity and heat in the process. A fuel cell provides a DC (direct current) voltage that can be used to power motors, lights or any number of electrical appliances. One can continually recharge a fuel cell by adding chemical fuel- hydrogen for an onboard storage tank.The type of fuel cell that is used in the Hy-wire car is the Proton exchange membrane fuel cell.Like batteries, fuel cells have a negatively charged terminal and a positively charged terminal that propels electrical charge through a circuit connected to each end. They are also similar to batteries in that they generate electricity from a chemical reaction. But unlike a battery, you can continually recharge a fuel cell by adding chemical fuel .In this case, hydrogen from an onboard storage tank and oxygen from the atmosphere.
The basic idea is to use a catalyst to split a hydrogen molecule (H2) into two H protons (H+, positively charged single hydrogen atoms) and two electrons (e-). Oxygen on the cathode (positively charged) side of the fuel cell draws H+ ions from the anode side through a proton exchange membrane, but blocks the flow of electrons. The electrons (which have a negative charge) are attracted to the protons (which have a positive charge) on the other side of the membrane, but they have to move through the electrical circuit to get there. The moving electrons make up the electrical current that powers the various loads in the circuit, such as motors and the computer system. On the cathode side of the cell, the hydrogen, oxygen and free electrons combine to form water (H2O), the system's only emission product.
Parts of a Fuel Cell
Polymer electrolyte membrane (PEM) fuel cells are the current focus of research for fuel cell vehicle applications. PEM fuel cells are made from several layers of different materials, as shown in the diagram. The three key layers in a PEM fuel cell include:
• Membrane electrode assembly
• Catalyst
• Hardware
Other layers of materials are designed to help draw fuel and air into the cell and to conduct electrical current through the cell.
Membrane Electrode Assembly
The electrodes (anode and cathode), catalyst, and polymer electrolyte membrane together form the membrane electrode assembly (MEA) of a PEM fuel cell.
• Anode. The anode, the negative side of the fuel cell, has several jobs. It conducts the electrons that are freed from the hydrogen molecules so they can be used in an external circuit. Channels etched into the anode disperse the hydrogen gas equally over the surface of the catalyst.
• Cathode. The cathode, the positive side of the fuel cell, also contains channels that distribute the oxygen to the surface of the catalyst. It conducts the electrons back from the external circuit to the catalyst, where they can recombine with the hydrogen ions and oxygen to form water.
Control
The Hy-wire's "brain" is a central computer housed in the middle of the chassis. It sends electronic signals to the motor control unit to vary the speed, the steering mechanism to maneuver the car, and the braking system to slow the car down.
The central computer is connected to an array of advanced sensors. Based on input from the driver, the computer activates the different actators to control the motion of the vehicle. The driver doesn’t actually drive the car directly: He or she gives instructions and the computer decides how to carry them out. The computer constantly makes adjustments on it to improve the driving performance the computer artificially creates a relatively smooth ride. The computer is connected to the body electronics through universal docking ports. The UDP transmits a constant stream of electronic command signals from the car controller to the central computer, as well as feedback signals from the computer to the controller.At the chassis level, the computer controls all aspects of driving and power use. But it takes its orders from a higher power -- namely, the driver in the car body.The central port works the same basic way as a USB port on a personal computer: It transmits a constant stream of electronic command signals from the car controller to the central computer. Additionally, it provides the electric power needed to operate all of the body onboard electronics.
Conclusion
The Hy-wire concept has so profoundly brought about changes in the automotive industry that GM and other auto makers are planning to move beyond the conventional car, towards a computerized environment friendly alternative. They are actually planning to launch such a vehicle for the public usage by the year 2020, hoping that they can overcome all the drawbacks faced by the Hy-wire car. Anyway, in all likelihood life on the highway will see some major changes within the next few decades.