159 lines
3.7 KiB
C
159 lines
3.7 KiB
C
/*
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Modified from
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https://github.com/PX4/Firmware/blob/master/src/lib/pid/pid.cpp
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参考资料：
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https://github.com/PX4/Firmware/issues/12362
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https://dev.px4.io/master/en/flight_stack/controller_diagrams.html
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https://docs.px4.io/master/en/config_mc/pid_tuning_guide_multicopter.html#standard_form
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https://www.controleng.com/articles/not-all-pid-controllers-are-the-same/
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https://en.wikipedia.org/wiki/PID_controller
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http://brettbeauregard.com/blog/2011/04/improving-the-beginner%E2%80%99s-pid-derivative-kick/
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*/
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#include "pid.h"
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#define SIGMA 0.000001f
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/**
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* @brief 初始化PID
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*
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* @param pid PID结构体
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* @param mode PID模式
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* @param sample_freq 采样频率
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* @param param PID参数
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* @return int8_t 0对应没有错误
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*/
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int8_t PID_Init(KPID_t *pid, KPID_Mode_t mode, float sample_freq,
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const KPID_Params_t *param) {
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if (pid == NULL) return -1;
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if (!isfinite(param->p)) return -1;
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if (!isfinite(param->i)) return -1;
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if (!isfinite(param->d)) return -1;
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if (!isfinite(param->i_limit)) return -1;
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if (!isfinite(param->out_limit)) return -1;
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pid->param = param;
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float dt_min = 1.0f / sample_freq;
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if (isfinite(dt_min))
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pid->dt_min = dt_min;
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else
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return -1;
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LowPassFilter2p_Init(&(pid->dfilter), sample_freq, pid->param->d_cutoff_freq);
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pid->mode = mode;
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PID_Reset(pid);
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return 0;
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}
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/**
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* @brief PID计算
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*
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* @param pid PID结构体
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* @param sp 设定值
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* @param fb 反馈值
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* @param fb_dot 反馈值微分
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* @param dt 间隔时间
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* @return float 计算的输出
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*/
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float PID_Calc(KPID_t *pid, float sp, float fb, float fb_dot, float dt) {
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if (!isfinite(sp) || !isfinite(fb) || !isfinite(fb_dot) || !isfinite(dt)) {
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return pid->last.out;
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}
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/* 计算误差值 */
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const float err = CircleError(sp, fb, pid->param->range);
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/* 计算P项 */
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const float k_err = err * pid->param->k;
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/* 计算D项 */
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const float k_fb = pid->param->k * fb;
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const float filtered_k_fb = LowPassFilter2p_Apply(&(pid->dfilter), k_fb);
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float d;
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switch (pid->mode) {
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case KPID_MODE_CALC_D:
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/* 通过fb计算D，避免了由于sp变化导致err突变的问题 */
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/* 当sp不变时，err的微分等于负的fb的微分 */
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d = (filtered_k_fb - pid->last.k_fb) / fmaxf(dt, pid->dt_min);
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break;
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case KPID_MODE_SET_D:
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d = fb_dot;
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break;
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case KPID_MODE_NO_D:
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d = 0.0f;
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break;
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}
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pid->last.err = err;
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pid->last.k_fb = filtered_k_fb;
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if (!isfinite(d)) d = 0.0f;
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/* 计算PD输出 */
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float output = (k_err * pid->param->p) - (d * pid->param->d);
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/* 计算I项 */
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const float i = pid->i + (k_err * dt);
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const float i_out = i * pid->param->i;
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if (pid->param->i > SIGMA) {
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/* 检查是否饱和 */
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if (isfinite(i)) {
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if ((fabsf(output + i_out) <= pid->param->out_limit) &&
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(fabsf(i) <= pid->param->i_limit)) {
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/* 未饱和，使用新积分 */
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pid->i = i;
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}
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}
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}
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/* 计算PID输出 */
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output += i_out;
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/* 限制输出 */
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if (isfinite(output)) {
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if (pid->param->out_limit > SIGMA) {
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output = AbsClip(output, pid->param->out_limit);
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}
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pid->last.out = output;
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}
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return pid->last.out;
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}
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/**
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* @brief 重置微分项
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*
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* @param pid PID结构体
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* @return int8_t 0对应没有错误
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*/
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int8_t PID_ResetIntegral(KPID_t *pid) {
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if (pid == NULL) return -1;
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pid->i = 0.0f;
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return 0;
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}
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/**
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* @brief 重置PID
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*
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* @param pid PID结构体
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* @return int8_t 0对应没有错误
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*/
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int8_t PID_Reset(KPID_t *pid) {
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if (pid == NULL) return -1;
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pid->i = 0.0f;
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pid->last.err = 0.0f;
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pid->last.k_fb = 0.0f;
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pid->last.out = 0.0f;
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LowPassFilter2p_Reset(&(pid->dfilter), 0.0f);
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return 0;
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}
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