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Drop 8 bytes per PID of unecessary information. Also trying to compute

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integral in ms instead of seconds to avoid rounding errors.
This commit is contained in:
James Cotton 2011-06-19 11:12:54 -05:00
parent 80709f356f
commit 9c1e523260
1 changed files with 7 additions and 13 deletions
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20
flight/Modules/Stabilization/stabilization.c
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@ -66,10 +66,8 @@ enum {ROLL,PITCH,YAW,MAX_AXES};
typedef struct {
float p;
float i;
float d;
float iLim;
float iAccumulator;
float lastErr;
} pid_type;
// Private variables
@ -287,17 +285,14 @@ static void stabilizationTask(void* parameters)
float ApplyPid(pid_type * pid, const float err)
{
float diff = (err - pid->lastErr);
pid->lastErr = err;
pid->iAccumulator += err * pid->i * dT;
if(fabs(pid->iAccumulator) > pid->iLim) {
if(pid->iAccumulator >0) {
pid->iAccumulator = pid->iLim;
} else {
pid->iAccumulator = -pid->iLim;
}
// Scale up accumulator by 1000 while computing to avoid losing precision
pid->iAccumulator += err * (pid->i * dT * 1000);
if(pid->iAccumulator > (pid->iLim * 1000)) {
pid->iAccumulator = pid->iLim * 1000;
} else if (pid->iAccumulator < -(pid->iLim * 1000)) {
pid->iAccumulator = -pid->iLim * 1000;
}
return ((err * pid->p) + pid->iAccumulator + (diff * pid->d / dT));
return (err * pid->p) + pid->iAccumulator / 1000;
}
@ -305,7 +300,6 @@ static void ZeroPids(void)
{
for(int8_t ct = 0; ct < PID_MAX; ct++) {
pids[ct].iAccumulator = 0;
pids[ct].lastErr = 0;
}
}