| Purpose |
To set up the
parameters for a Proportional, Integral and Derivative (PID) Controller function. The
function PIDcompute( ) will make use of the parameters defined here for the
corresponding channel ch. ch = channel number (1-16)
lmt = Maximum (saturation) limit for the computed result.
P
= Proportional Gain (KP)
I
= Integral Gain (KI )
D
= Differential Gain (KD)
Transfer Function of a PID Controller are defined as follow:
All four parameters: lmt, P, I
& D can be either 16 or 32-bit integer constants or integer variables. For the lmt
term, the computed controller output value by the PIDcompute( ) function is not allowed
beyond the + lmt value (i.e. lmt represents the saturation point of the computed
controller output). PIDcompute( ) function implements "Integrator anti-windup"
feature, which will avoid integrating the error signal when output is already saturated .
Important: When this statement
is run, the integral and differential terms of channel ch is set to zero. Hence
PIDdef should be run only once during initialization and not repeatedly executed.
Otherwise the PIDcompute( ) function will not run properly because of the loss of integral
and differential data. |
