This is an old revision of the document!
PID-functions
Set of helper functions to initiate and update a PID control loop
Description
PID_new( pid[], Float:in, Float:out )
PID_dir( pid[], direction )
PID_set( pid[], Float:set )
PID_tune( pid[], Float:Kp, Float:Ki, Float:Kd )
PID_tune( pid[], Float:min, Float:max )
PID_update( pid[], Float:in )
Parameters
in | Feedback value |
out | Initial output value |
direction | 1 (normal) or -1 (reverse) |
set | setpoint / target |
Kp | Proportional component |
Ki | Integral response component |
Kd | Derivative response component |
min | Smallest output value allowed |
max | Largest output value allowed |
Return value
The PID_update function returns the calculated output value.
Example usage
new p[PID]; // create a PID main() { // Initialize the PID with mid range input and no output PID_new(p, 50.0, 0.0); // Limit output to +/- 10 PID_limits(p, -10.0, 10.0); // Set the tuning parameters PID_tune(p, 0.2, 0.04, 0.01); // Set update speed to 100ms SetTickInterval( 100 ); } @Tick(uptime) { new Float:psi; new Float:v; // Read and scale a sensor input (0-100psi from 4-20mA sensor) psi = 100.0 * ((GetInputValue(1, INVAL_RAW)-4000)/16000); // Update the PID with the feedback value v = PID_update(p, psi); // Apply to output SetOutput(4, fround(v+50)); }
NOTE: The values used in the above example are not from a real world setup. Please make sure you understand how PID works and how to correctly tune the variables if you use any of the PID functions.