Intel® Quiet System Technology (Intel® QST)
Thermal and Mechanical Design Guidelines 71
target temperature. As a result of its operation, the PID control algorithm can enable
an acoustic-friendly platform.
Figure
7-2. PID Controller Fundamentals
Proportional
Error
Derivative (Slope)
Integral (time averaged)
Proportional
Error
Derivative (Slope)
Integral (time averaged)
Proportional
Error
Derivative (Slope)
Integral (time averaged)
Proportional
Error
Derivative (Slope)
Integral (time averaged)
Time
Actual
Temperature
Actual
Temperature
Fan
Speed
Fan
Speed
Limit
Temperature
Limit
Temperature
For a PID algorithm to work limit temperatures are assigned for each temperature
sensor. For Intel QST, the T
CONTROL
for the processor and chipset are to be used as the
limit temperature. The ME will measure the error, slope and rate of change using the
following equations:
Proportional Error (P) = T
LIMIT
– T
ACTUAL
Integral (I) = Time averaged error
Derivative (D) = Temp / Time
Three gain values are used to control response of algorithm.
Kp = proportional gain
Ki = Integral gain
Kd = derivative gain
The Intel
®
Quiet System Technology (Intel
®
QST) Configuration and Tuning Manual
provides initial values for the each of the gain constants. In addition it provides a
methodology to tune these gain values based on system response.
Finally the fan speed change will be calculated using the following formula:
PWM = -P*(Kp) – I*(Ki) + D*(Kd)
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