Page 418 - Understanding Automotive Electronics

2735 | CH 11 Page 405 Tuesday, March 10, 1998 1:30 PM

FUTURE AUTOMOTIVE ELECTRONIC SYSTEMS 11

a tracking controller that outputs a control signal to a steering actuator.
Steering commands guide the vehicle to maintain the sensor over the guideway
wire.
Vehicle speed control is accomplished using an on-board radar sensor.
This sensor is located in front of the vehicle and directs a narrow radar beam
forward. The radar sensor system obtains a measurement of the range to a car in
front of the given car as well as the rate of change of that range. The sensor can
also measure vehicle ground speed via Doppler shift of radar signals reflected
from the ground.
The control system is a multiple-input/multiple-output controller that
generates control signals for a throttle actuator and a braking actuator.
Normally the controller will only activate the throttle; however, if the range to
the vehicle is decreasing even with a closed throttle, then braking is required.
The braking actuator pressurizes the brake lines automatically to slow the
vehicle as required. This action could occur if the platoon of cars were driving
down a long, relatively steep mountain or slope. It could also be required if an
obstacle were encountered that was stationary (as in the case of a car with a
breakdown). Panic-stop braking could actually be required in extreme cases.
Whenever manual control is required (e.g., when a given vehicle exits the
highway in order to reach a given destination), the driver takes control by
operating a control release switch.
There are many variations on the concept described above. Some will
prove to be feasible; others will not. At this time the automatic vehicle
guideway is an interesting experimental system with great potential for
maintaining optimum traffic flow on otherwise busy or congested highways.
It should be emphasized that many of the topics included in this final
chapter have an uncertain future in terms of production automobiles. Each idea
discussed here has had at least an experimental confirmation of its technical
feasibility. However, the final arbiter of the viability of each subsystem will be
the automobile consumer, who will vote with his or her dollars on whether any
given subsystem or feature is worth the incremental purchase price.

UNDERSTANDING AUTOMOTIVE ELECTRONICS 405