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Unformatted text preview: ar wheel controller/anti-lock brake system
Regulate velocity of rear wheel Brake pressed
Gradually increase amount of breaking
If skidding (front wheel is moving much faster than rear wheel)
then temporarily reduce amount of breaking brake pedal pressed Inputs
Front wheel speed
Rear wheel speed brake on/off micro
controller front wheel velocity move rear wheel rear wheel velocity Outputs
Pulse-width modulation rear wheel velocity
Pulse-width modulation brake on/off * / .
0 1 ) 2
+ # Check if brake pedal pressed – or interrupt Move rear wheel
write (rearWheel, onOff) Use automatic detection capability of processor brake pedal pressed rear wheel velocity $ Brake pedal port
Need to make sure not to forget to do so (use timer) write (brakePort, onOff) GPIO
port 3 Software must repeatedly check brakePressed = read (brakePedalPort) Turn brake on/off front wheel velocity , micro
port brake on/off
move rear wheel Connect brake pedal to input capture or external interrupt pin
Interrupt on level change
Interrupt handler for brake pedal
brake pedal pressed GPIO
controller 2 #$ %& $ + ) / ) $ $ Use timer to turn brake on and off To pump the brakes gradually increase the duty-cycle
(ton) until car stops Apply brake
Set timer to interrupt after “on” time
Set time to interrupt after “off” time
Repeat How do we tell which interrupt is which?
set timer to go off at each edge...
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This document was uploaded on 04/04/2014.
- Fall '09