PIDAutoTuner Class Reference

Automatic PID tuning using the relay (Åström-Hägglund) method. More...

#include <PIDAutoTuner.h>

Classes
struct	Result

Public Member Functions
	PIDAutoTuner (float target, float relayAmp, float dt)
void	reset ()
float	update (float y)
bool	isFinished () const
Result	getResult () const
void	setHysteresis (float h)

Protected Types
enum class	State { INIT , RUNNING }

Protected Member Functions
void	detectPeaks (float y)
void	registerPeak (bool isMax)

Protected Attributes
float	target
float	relayAmp
float	dt
float	hysteresis = 0.01f
float	output = 0
float	time = 0
float	lastY = 0
float	maxY = -1e9
float	minY = 1e9
float	avgMax = 0
float	avgMin = 0
float	avgPeriod = 0
float	lastPeakTime = 0
int	peakCount = 0
bool	lastWasMax = false
bool	success = false
State	state = State::INIT

Detailed Description

Automatic PID tuning using the relay (Åström-Hägglund) method.

This class implements an automatic PID tuning algorithm based on the relay (bang-bang) method, also known as the Åström-Hägglund relay auto-tuning technique. It applies a relay (on/off) control to the system and analyzes the resulting oscillations to estimate the ultimate gain (Ku) and period (Tu). These values are then used to compute PID parameters using the Ziegler-Nichols tuning rules.

• The user specifies a target setpoint, relay amplitude, and sample time (dt).
• The tuner applies a relay output and detects peaks in the process variable.
• After sufficient oscillations, it calculates Ku, Tu, and recommended PID gains.
• The process can be monitored with isFinished() and the results retrieved with getResult().
• Hysteresis can be adjusted to avoid chattering.

Usage Example:

PIDAutoTuner tuner(target, relayAmp, dt);
while (!tuner.isFinished()) {
  float control = tuner.update(measuredValue);
  // Apply 'control' to actuator
}
auto result = tuner.getResult();
if (result.success) {
  // Use result.Kp, result.Ki, result.Kd
}

See also

setHysteresis, getResult, isFinished, update, reset

Author

Phil Schatzmann

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The documentation for this class was generated from the following file:

• src/TinyRobotics/control/PIDAutoTuner.h