reflow-oven-control-sw/stm-firmware/include/reflow-controller/pid-controller.h

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/* Reflow Oven Controller
*
* Copyright (C) 2020 Mario Hüttel <mario.huettel@gmx.net>
*
* This file is part of the Reflow Oven Controller Project.
*
* The reflow oven controller is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* The Reflow Oven Control Firmware is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with the reflow oven controller project.
* If not, see <http://www.gnu.org/licenses/>.
*/
/** @addtogroup pid-controller
* @{
*/
#ifndef __PID_CONTROLLER_H__
#define __PID_CONTROLLER_H__
/**
* @brief Representation of a PID controller
*/
struct pid_controller {
/**
* @brief Derivate term @f$k_d@f$
*/
float k_deriv;
/**
* @brief Integral term @f$k_i@f$
*/
float k_int;
/**
* @brief Proportional term @f$k_p@f$
*/
float k_p;
/**
* @brief Internally precalculated auxiliary value. @f$k_{i_t} = \frac{1}{2}k_{i} \cdot T_s@f$
*
* This value is caluclated during the @ref pid_init function to reduce calculations during the continous
* PID sampling.
*/
float k_int_t;
/**
* @brief Internally precalculated auxiliary value. @f$k_{d_t} = 2\frac{k_{d}}{T_s + 2 k_{d\tau}}@f$
*
* This value is caluclated during the @ref pid_init function to reduce calculations during the continous
* PID sampling.
*/
float k_deriv_t;
/**
* @brief Internally precalculated auxiliary value. @f$\overline{k_{d_t}} = \frac{2 k_{d\tau} - T_s}{ 2k_{d\tau} + T_s}@f$
*
* This value is caluclated during the @ref pid_init function to reduce calculations during the continous
* PID sampling.
*/
float k_inv_deriv_t;
/**
* @brief Saturation of output value
* @note This value is set to 100 (corresponding to 100%) for the temperature controller
*/
float output_sat_max;
/**
* @brief Minumum saturation of PID output value.
* @note This value is set to 0 for the temperature controller as the oven driver is not able to cool
*/
float output_sat_min;
/**
* @brief Maximum value @f$i_{max}@f$ the inegrator in the PID controller can reach.
*
* The output of the integral term of the PID controller is limited to @f$\pm i_{max}@f$
*
*/
float integral_max;
/**
* @brief Sampling period @f$T_s@f$ of the PID controller in seconds
*/
float sample_period;
/**
* @brief Output value of the PID controller
*/
volatile float control_output;
/**
* @brief Internal state variable holding the last input value.
*/
volatile float last_in;
/**
* @brief integral term's value
*/
volatile float integral;
/**
* @brief derivate term's value
*/
volatile float derivate;
};
/**
* @brief Initialize a @ref pid_controller struct
* @param pid Struct to initilaize
* @param k_deriv Derivate term
* @param k_int integral term
* @param k_p Proportional term
* @param output_sat_min Minimum output saturation
* @param output_sat_max Maximum output saturation
* @param integral_max Maximum integral term
* @param kd_tau Time constant of derivate term low pass filter
* @param sample_period Sample time in seconds
*/
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void pid_init(struct pid_controller *pid, float k_deriv, float k_int, float k_p,
float output_sat_min, float output_sat_max, float integral_max, float kd_tau, float sample_period);
/**
* @brief Reset a PID controller.
*
* This sets all internal states to 0.
*
* @param pid Controller
*/
void pid_zero(struct pid_controller *pid);
/**
* @brief Execute a tiome step of the PID controller. This function must be periodically called in an pid_controller::sample_period interval
* @note This function does not check its calling interval. It must be ensured by the caller.
* @param pid Pid controller to execute
* @param deviation Input deviation
* @return Current controller output after the calculated time step
*/
float pid_sample(struct pid_controller *pid, float deviation);
/**
* @brief Retrieve the controller's current output
* @param pid Pid controller
* @return Output
*/
float pid_get_control_output(const struct pid_controller *pid);
/**
* @brief Duplicate a PID controller
* @param dest destination controller
* @param src Source controller
* @return 0 if successful
*/
int pid_copy(struct pid_controller *dest, const struct pid_controller *src);
#endif /* __PID_CONTROLLER_H__ */
/** @} */