A critical limitation preventing newer FSAE teams from improving
in the international rankings is that of the person-machine
interface, where driver inexperience and lack of training lead to
loss of traction. The Traction Control System (TCS) described here
uses closed-loop control of available engine power via spark
retardation. Two distinct, driver-selectable algorithms were
developed which govern TCS operation for either 1) launch control
for the straight line acceleration event, or 2) full traction
control for all other dynamic events.
Launch control uses a spark retard rev limit to allow the driver
to hold the engine at the ideal RPM for easy rev matching via flat
foot shifting. Wheel speeds are simultaneously monitored to achieve
ideal tire slip ratios. The full traction control algorithm uses
the launch control method as a basis, but also addresses potential
need for corner exit oversteer or engine braking. Front and rear
accelerometers determine when the car is in an oversteer condition.
Dynamometer data have been acquired off a tuned engine to assist in
the initial PID gains used on the track.
The vehicle was instrumented with 1) wheel encoders and Hall
effect sensors at every wheel, 2) potentiometers on the brake,
accelerator, and clutch pedals, and 3) two MEMs-based accelerometer
chips. These signals were sent to a Microchip® dsPIC® linked to the
ECU via CAN. These systems are all detailed along with their
functional requirements and engineering specifications; guidelines
for their implementation within a CAN-based vehicle network were
outlined. The preliminary results presented here are encouraging
and illustrate the effectiveness of this system, which is a work in
progress. Lessons learned from how this project was integrated
within the school curriculum are also presented.