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Disable the PID output constraint for the attitude PIDs (rate/angle) … #194

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Jan 31, 2017
+19 −24
Merged

Disable the PID output constraint for the attitude PIDs (rate/angle) … #194

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10 changes: 6 additions & 4 deletions src/modules/interface/pid.h
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Original file line number Diff line number Diff line change
Expand Up @@ -63,7 +63,8 @@
#define PID_YAW_INTEGRATION_LIMIT 360.0


#define DEFAULT_PID_INTEGRATION_LIMIT 5000.0
#define DEFAULT_PID_INTEGRATION_LIMIT 5000.0
#define DEFAULT_PID_OUTPUT_LIMIT 0.0

#else

Expand Down Expand Up @@ -98,7 +99,8 @@
#define PID_YAW_INTEGRATION_LIMIT 360.0


#define DEFAULT_PID_INTEGRATION_LIMIT 10000.0
#define DEFAULT_PID_INTEGRATION_LIMIT 10000.0
#define DEFAULT_PID_OUTPUT_LIMIT 0.0

#endif

Expand All @@ -115,8 +117,8 @@ typedef struct
float outP; //< proportional output (debugging)
float outI; //< integral output (debugging)
float outD; //< derivative output (debugging)
float iLimit; //< integral limit
float outputLimit; //< output limit
float iLimit; //< integral limit, absolute value. '0' means no limit.
float outputLimit; //< total PID output limit, absolute value. '0' means no limit.
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I still don't think it's a great idea to have the outputLimit functionality at all -- if the output of the PID needs to be limited, that suggests the coefficients need to be tuned instead. However, the current position controller makes use of this functionality, and I don't have a way to test out changes to that layer, so I've left it in.

See my comments on issue #185 for some more details.

float dt; //< delta-time dt
lpf2pData dFilter; //< filter for D term
bool enableDFilter; //< filter for D term enable flag
Expand Down
14 changes: 0 additions & 14 deletions src/modules/src/attitude_pid_controller.c
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Expand Up @@ -60,10 +60,6 @@ static int16_t rollOutput;
static int16_t pitchOutput;
static int16_t yawOutput;

static float rpRateLimit = 150.0f;
static float yawRateLimit = 150.0f;
static float rpyRateLimitOverhead = 1.1f;

static bool isInit;

void attitudeControllerInit(const float updateDt)
Expand Down Expand Up @@ -94,10 +90,6 @@ void attitudeControllerInit(const float updateDt)
pidSetIntegralLimit(&pidPitch, PID_PITCH_INTEGRATION_LIMIT);
pidSetIntegralLimit(&pidYaw, PID_YAW_INTEGRATION_LIMIT);

pidRollRate.outputLimit = INT16_MAX;
pidPitchRate.outputLimit = INT16_MAX;
pidYawRate.outputLimit = INT16_MAX;

isInit = true;
}

Expand Down Expand Up @@ -125,10 +117,6 @@ void attitudeControllerCorrectAttitudePID(
float eulerRollDesired, float eulerPitchDesired, float eulerYawDesired,
float* rollRateDesired, float* pitchRateDesired, float* yawRateDesired)
{
pidRoll.outputLimit = rpRateLimit * rpyRateLimitOverhead;
pidPitch.outputLimit = rpRateLimit * rpyRateLimitOverhead;
pidYaw.outputLimit = yawRateLimit * rpyRateLimitOverhead;

pidSetDesired(&pidRoll, eulerRollDesired);
*rollRateDesired = pidUpdate(&pidRoll, eulerRollActual, true);

Expand Down Expand Up @@ -201,8 +189,6 @@ PARAM_ADD(PARAM_FLOAT, yaw_kd, &pidYaw.kd)
PARAM_GROUP_STOP(pid_attitude)

PARAM_GROUP_START(pid_rate)
PARAM_ADD(PARAM_FLOAT, rpRateLimit, &rpRateLimit)
PARAM_ADD(PARAM_FLOAT, yawRateLimit, &yawRateLimit)
PARAM_ADD(PARAM_FLOAT, roll_kp, &pidRollRate.kp)
PARAM_ADD(PARAM_FLOAT, roll_ki, &pidRollRate.ki)
PARAM_ADD(PARAM_FLOAT, roll_kd, &pidRollRate.kd)
Expand Down
19 changes: 13 additions & 6 deletions src/modules/src/pid.c
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Expand Up @@ -43,7 +43,7 @@ void pidInit(PidObject* pid, const float desired, const float kp,
pid->ki = ki;
pid->kd = kd;
pid->iLimit = DEFAULT_PID_INTEGRATION_LIMIT;
pid->outputLimit = DEFAULT_PID_INTEGRATION_LIMIT;
pid->outputLimit = DEFAULT_PID_OUTPUT_LIMIT;
pid->dt = dt;
pid->enableDFilter = enableDFilter;
if (pid->enableDFilter)
Expand Down Expand Up @@ -77,16 +77,23 @@ float pidUpdate(PidObject* pid, const float measured, const bool updateError)
pid->outD = pid->kd * pid->deriv;
output += pid->outD;

float i = pid->integ + pid->error * pid->dt;
// Check if integral is saturated
if (abs(i) <= pid->iLimit || abs(pid->ki * i + output) <= pid->outputLimit) {
pid->integ = i;
pid->integ += pid->error * pid->dt;

// Constrain the integral (unless the iLimit is zero)
if(pid->iLimit != 0)
{
pid->integ = constrain(pid->integ, -pid->iLimit, pid->iLimit);
}

pid->outI = pid->ki * pid->integ;
output += pid->outI;

output = constrain(output, -pid->outputLimit, pid->outputLimit);
// Constrain the total PID output (unless the outputLimit is zero)
if(pid->outputLimit != 0)
{
output = constrain(output, -pid->outputLimit, pid->outputLimit);
}


pid->prevError = pid->error;

Expand Down