How Gm's Hy-Wire Works

A brief look at GM's new concept car, the Hi-Wire.

With GM's new Hy-Wire concept car, you'll use drive-by-wire instead of physical linkages--that means controls are not related to what they control, so the steering wheel and the brake pedal may soon be things of the past. With the new Hy-Wire concept, the controls are simply computer controls, for example; instead of a steering wheel and brake pedals you may have a pair of joysticks. Instead of fuel gages and a speedometer, you might see a computer screen that will display whatever information you need. It's even possible that it will display diagnostic information about your car, or the images from a rear-mounted video camera.

When you turn the wheel of a car today, or step on the brake, you are moving physical objects that move other objects that control the car. This is a "˜physical linkage'. A bicycle is a good example of physical linkage control. You twist the handle bars and the wheel changes direction. Large modern airplanes, by contrast, rarely use direct physical linkages. Instead, the controls that the pilot uses send signals to computers. The computers then move the rudder, flaps, etc.

When you step on the brake pedal of a normal car, that pushes a plunger down in a cylinder forcing brake fluid into the system. That pushes the brakes against the drums in the wheels and stops the car. In a drive-by-wire car, you could push a button, pull a lever, or even speak to a voice control microphone to tell the computer to stop the car. Then the computer triggers the brakes. It grants the car's designer a great deal of flexibility in the passenger compartment.

In cars of today, the thing that makes it go is an internal combustion engine. They usually burn gasoline. To provide power to move the car, gasoline is mixed with air and injected into the cylinders. The spark plug provides a spark and the fuel/air mixture explodes, forcing the piston to the other end of the cylinder. The moving piston turns the crankshaft. The crankshaft turns the gears and finally the axle. It's a fairly complex process to turn the crankshaft spinning at high speed to wheels spinning at low speed.

The Hy-Wire uses fuel cells and electric motors. The entire system is much simpler. You still start with gasoline. But that passes through a "˜refiner', a device that splits off the hydrogen in gasoline and passes it to the fuel cell. The rest of the gasoline, oxygen and carbon, is released to the atmosphere in the form of carbon dioxide. In the fuel cell the hydrogen combines with oxygen to form water, electricity and a little heat. It is a surprisingly efficient process.

The electricity is then sent to motors in each wheel. Having each wheel powered independently, means that as long as one wheel has good traction, you can keep going. Instead of transferring motion from piston to crankshaft to gears to axle to wheels, the Hy-Wire transfers electricity to motors and the motors turn the wheels. It's also possible to reclaim energy while braking. In a conventional car, that energy just heats and wears break pads. In Hy-Wire, a lot of it can be reclaimed and stored in batteries for use later.

In the new Hy-Wire concept car, all of the motor, fuel cells, fuel storage, etc. is contained in a section called 'the skateboard'. It consists of the wheels, undercarriage and a platform a few inches thick. The passenger compartment is a separate section that is added later. All controls pass through a single junction box. That means that the same "˜skateboard' can run a two-seat sports car or a station wagon. Since all the controls are computer generated, they can be anywhere in the car. You could literally pass the wheel to someone.

Of course, this is a concept car. GM will use ideas from this in future autos, so it's entirely possible that someday soon you'll drive a car with a front window that reaches from your toes to the roof, while you steer the car with a joystick set in the arm of a comfortable chair.

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