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AC_PID: save 8 bytes per AC_PID object

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we don't need the _derivative or _output variables
This commit is contained in:
Andrew Tridgell 2012-11-27 18:06:22 +11:00
parent b8d5a5904a
commit bbd6c5154e
2 changed files with 5 additions and 48 deletions
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51
libraries/AC_PID/AC_PID.cpp
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@ -55,19 +55,19 @@ int32_t AC_PID::get_leaky_i(int32_t error, float dt, float leak_rate)
int32_t AC_PID::get_d(int32_t input, float dt) int32_t AC_PID::get_d(int32_t input, float dt)
{ {
if ((_kd != 0) && (dt != 0)) { if ((_kd != 0) && (dt != 0)) {
_derivative = (input - _last_input) / dt; float derivative = (input - _last_input) / dt;
// discrete low pass filter, cuts out the // discrete low pass filter, cuts out the
// high frequency noise that can drive the controller crazy // high frequency noise that can drive the controller crazy
_derivative = _last_derivative + derivative = _last_derivative +
(dt / ( _filter + dt)) * (_derivative - _last_derivative); (dt / ( _filter + dt)) * (derivative - _last_derivative);
// update state // update state
_last_input = input; _last_input = input;
_last_derivative = _derivative; _last_derivative = derivative;
// add in derivative component // add in derivative component
return _kd * _derivative; return _kd * derivative;
} }
return 0; return 0;
} }
@ -83,47 +83,6 @@ int32_t AC_PID::get_pid(int32_t error, float dt)
return get_p(error) + get_i(error, dt) + get_d(error, dt); return get_p(error) + get_i(error, dt) + get_d(error, dt);
} }
/*
* int32_t AC_PID::get_pid(int32_t error, float dt)
* {
* // Compute proportional component
* _output = error * _kp;
*
* // Compute derivative component if time has elapsed
* if ((fabs(_kd) > 0) && (dt > 0)) {
* _derivative = (error - _last_error) / dt;
*
* // discrete low pass filter, cuts out the
* // high frequency noise that can drive the controller crazy
* _derivative = _last_derivative +
* (dt / ( _filter + dt)) * (_derivative - _last_derivative);
*
* // update state
* _last_error = error;
* _last_derivative = _derivative;
*
* // add in derivative component
* _output += _kd * _derivative;
* }
*
* // Compute integral component if time has elapsed
* if ((fabs(_ki) > 0) && (dt > 0)) {
* _integrator += (error * _ki) * dt;
* if (_integrator < -_imax) {
* _integrator = -_imax;
* } else if (_integrator > _imax) {
* _integrator = _imax;
* }
* _output += _integrator;
* }
*
* return _output;
* }
*/
void void
AC_PID::reset_I() AC_PID::reset_I()
{ {

2
libraries/AC_PID/AC_PID.h
View File

@ -124,8 +124,6 @@ private:
float _integrator; ///< integrator value float _integrator; ///< integrator value
int32_t _last_input; ///< last input for derivative int32_t _last_input; ///< last input for derivative
float _last_derivative; ///< last derivative for low-pass filter float _last_derivative; ///< last derivative for low-pass filter
float _output;
float _derivative;
/// Low pass filter cut frequency for derivative calculation. /// Low pass filter cut frequency for derivative calculation.
/// ///