93 Design of the Controls

Traditional mechanical controls can be used in a traditional way, i.e. steering wheel, and floor mounted accelerator and brake (there is no need for a clutch with an electric vehicle). However some modern vehicles, such as the GM Hy-wire (shown in Figure 8.16) use more sophisticated modern systems using 'drive by wire'. This is a system which has come from the aircraft industry where it is know as 'fly by wire'. In this system the controls are effectively movement transducers that convert movement into an electrical signal. The electrical signal is normally fed into an electronic controller, or a computer, which in turn controls servos on the brakes, steering, throttle, etc.

There are various configurations for the controls, and they can be configured perfectly normally: steering wheel, accelerator and brake pedals, and the type of 'gear lever' normally found on an automatic transmission car. However, with an all-electric car it is possible to break out of this standard, and use different systems such as the stick controller illustrated in Figure 9.4. Normally a four quadrant electronic controller is used to control the motor, the first quadrant providing forward power and the second providing regenerative braking (the other two quadrants are used in reverse). Because one electronic controller is used for both acceleration and normal braking it is easier to use one lever to accelerate and brake the vehicle. The mechanical brakes could then be added to the extreme lever position. Some manufacturers have experimented with a one stick control, which incorporates both the steering, accelerator and brakes. A stick control fitted to an experimental vehicle is shown in Figure 9.5.

A stick controller can also be used where it is coupled mechanically to the brakes and steering. Normally it is servo-assisted. This system has the advantage that some mechanical control is kept in the event of a breakdown of the power-assisted servos. 'Drive by wire' normally brings out fears of what happens in the event of a failure, but it should be borne in mind that 'fly by wire' has been used successfully on aircraft for years.

An advantage of more modern types of control system that are appropriate for electric vehicles is that computer systems could be used to over-ride user commands. For example, the motor power of a vehicle is normally fixed to allow it to ascend steep hills at reasonable speed, but this power can be used to provide excessive acceleration and speed which wastes energy and reduces range. It is quite practical to provide electronic speed control

Figure 9.4 Stick controller
Figure 9.5 Stick controller fitted to a vehicle

so that excessive speeds and acceleration are avoided. This could also be linked to satellite navigation systems to ensure that the car never exceeded statutory speed restrictions, increasing road safety as well as maximising vehicle range.

With electric vehicles, where the aim is always to save energy, onboard computers coupled to satellite navigation systems can be even more advantageous. The latter can keep journeys to a minimum by giving precise directions to any destination. They could also direct drivers to nearby charging points.

Hybrid Cars The Whole Truth Revealed

Hybrid Cars The Whole Truth Revealed

Hybrid Cars! Man! Is that a HOT topic right now! There are some good reasons why hybrids are so hot. If you’ve pulled your present car or SUV or truck up next to a gas pumpand inserted the nozzle, you know exactly what I mean! I written this book to give you some basic information on some things<br />you may have been wondering about.

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