112 lines
3.1 KiB
C
112 lines
3.1 KiB
C
/* Reflow Oven Controller
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*
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* Copyright (C) 2020 Mario Hüttel <mario.huettel@gmx.net>
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*
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* This file is part of the Reflow Oven Controller Project.
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*
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* The reflow oven controller is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* The Reflow Oven Control Firmware is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with the reflow oven controller project.
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* If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <reflow-controller/pid-controller.h>
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#include <string.h>
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void pid_init(struct pid_controller *pid, float k_deriv, float k_int, float k_p, float output_sat_min,
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float output_sat_max, float integral_max, float kd_tau, float sample_period)
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{
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if (!pid)
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return;
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pid->sample_period = sample_period;
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pid->k_p = k_p;
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pid->k_int = k_int;
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pid->k_deriv = k_deriv;
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pid->k_int_t = pid->k_int * pid->sample_period * 0.5f;
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pid->k_deriv_t = pid->k_deriv * 2.0f / (pid->sample_period + 2.0f * kd_tau);
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pid->k_inv_deriv_t = (2.0f * kd_tau - sample_period) / (2.0f * kd_tau + sample_period);
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pid->output_sat_max = output_sat_max;
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pid->output_sat_min = output_sat_min;
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pid->integral_max = integral_max;
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pid_zero(pid);
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}
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int pid_copy(struct pid_controller *dest, const struct pid_controller *src)
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{
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if (!dest || !src)
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return -1;
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memcpy(dest, src, sizeof(struct pid_controller));
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return 0;
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}
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void pid_zero(struct pid_controller *pid)
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{
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pid->control_output = 0.0f;
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pid->last_in = 0.0f;
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pid->integral = 0.0f;
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}
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static void calculate_integral(struct pid_controller *pid, float deviation)
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{
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pid->integral = pid->integral + pid->k_int_t * (deviation + pid->last_in);
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/* Saturate integral term to specified maximum */
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if (pid->integral > pid->integral_max)
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pid->integral = pid->integral_max;
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else if (pid->integral < 0.0f)
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pid->integral = 0.0f;
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}
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float pid_sample(struct pid_controller *pid, float deviation)
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{
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float output;
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if (!pid)
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return 0.0f;
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output = deviation * pid->k_p;
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/* PID runaway compensation */
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if (!(deviation > 0.0f && pid->control_output > pid->output_sat_max - 0.5f && pid->integral > 0) &&
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!(deviation < 0.0f && pid->control_output < pid->output_sat_min + 0.5f && pid->integral < 0)) {
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calculate_integral(pid, deviation);
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}
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/* Calculate derivative part */
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pid->derivate = pid->k_deriv_t * (deviation - pid->last_in) - pid->k_inv_deriv_t * pid->derivate;
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output += pid->derivate;
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output += pid->integral;
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/* Saturate output */
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if (output < pid->output_sat_min)
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output = pid->output_sat_min;
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else if (output > pid->output_sat_max)
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output = pid->output_sat_max;
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pid->control_output = output;
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pid->last_in = deviation;
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return output;
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}
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float pid_get_control_output(const struct pid_controller *pid)
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{
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if (!pid)
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return 0.0f;
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return pid->control_output;
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}
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