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Code Issues Releases Activity

Add a 1-tap IIR filter into the gyros in the feedback path. This will make the

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stabilization output a bit more resilient to the high frequency noise from
gyros.  However this value shouldn't be too high as it will increase the phase
delay of the feedback loop and decrease stability.  Default is 5 ms.

Note: this resests the stabilizationsettings object.  Sorry guys.
This commit is contained in:
James Cotton 2011-06-21 19:49:20 -05:00
parent d1104d3fdc
commit 373689207a
2 changed files with 22 additions and 2 deletions
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20
flight/Modules/Stabilization/stabilization.c
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@ -77,6 +77,8 @@ static xTaskHandle taskHandle;
static StabilizationSettingsData settings;
static xQueueHandle queue;
float dT = 1;
float gyro_alpha = 0;
float gyro_filtered[3] = {0,0,0};
pid_type pids[PID_MAX];
// Private functions
@ -193,6 +195,11 @@ static void stabilizationTask(void* parameters)
local_error[2] = fmod(local_error[2] + 180, 360) - 180;
#endif
for(uint8_t i = 0; i < MAX_AXES; i++) {
gyro_filtered[i] = gyro_filtered[i] * gyro_alpha + attitudeRaw.gyros[i] * (1 - gyro_alpha);
}
float *attitudeDesiredAxis = &stabDesired.Roll;
float *actuatorDesiredAxis = &actuatorDesired.Roll;
float *rateDesiredAxis = &rateDesired.Roll;
@ -234,7 +241,7 @@ static void stabilizationTask(void* parameters)
case STABILIZATIONDESIRED_STABILIZATIONMODE_RATE:
case STABILIZATIONDESIRED_STABILIZATIONMODE_ATTITUDE:
{
float command = ApplyPid(&pids[PID_RATE_ROLL + ct], rateDesiredAxis[ct]-attitudeRaw.gyros[ct]);
float command = ApplyPid(&pids[PID_RATE_ROLL + ct], rateDesiredAxis[ct] - gyro_filtered[ct]);
actuatorDesiredAxis[ct] = bound(command);
break;
}
@ -336,6 +343,17 @@ static void SettingsUpdatedCb(UAVObjEvent * ev)
pids[pid].i = *data++;
pids[pid].iLim = *data++;
}
// The dT has some jitter iteration to iteration that we don't want to
// make thie result unpredictable. Still, it's nicer to specify the constant
// based on a time (in ms) rather than a fixed multiplier. The error between
// update rates on OP (~300 Hz) and CC (~475 Hz) is negligible for this
// calculation
const float fakeDt = 0.0025;
if(settings.GyroTau < 0.0001)
gyro_alpha = 0; // not trusting this to resolve to 0
else
gyro_alpha = exp(-fakeDt / settings.GyroTau);
}

4
shared/uavobjectdefinition/stabilizationsettings.xml
View File

@ -13,7 +13,9 @@
<field name="RollPI" units="" type="float" elementnames="Kp,Ki,ILimit" defaultvalue="2,0,50"/>
<field name="PitchPI" units="" type="float" elementnames="Kp,Ki,ILimit" defaultvalue="2,0,50"/>
<field name="YawPI" units="" type="float" elementnames="Kp,Ki,ILimit" defaultvalue="2,0,50"/>
<field name="GyroTau" units="" type="float" elements="1" defaultvalue="0.005"/>
<access gcs="readwrite" flight="readwrite"/>
<telemetrygcs acked="true" updatemode="onchange" period="0"/>
<telemetryflight acked="true" updatemode="onchange" period="0"/>