PID算法（c语言) #include
int pv; //integer that contains the process value 过程量 int sp; //integer that contains the set point 设定值 float integral; // 积分值 －－ 偏差累计值 float pgain; float igain; float dgain;
int deadband; //死区 int last_error; };
struct _pid warm,*pid;
int process_ point, set_point, dead_band; float p_gain, i_gain, d_gain, integral_val,new_integ;
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pid_init DESCRIPTION This function initializes the pointers in the _pid structure to the process variable and the setpoint. *pv and *sp are integer pointers. //－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－void pid_init(struct _pid *warm, int process_point, int set_point) {
struct _pid *pid; pid = warm;
pid->pv = process_point; pid->sp = set_point; }
//－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－pid_tune DESCRIPTION Sets the proportional gain (p_gain), integral gain (i_gain),
derivitive gain (d_gain), and the dead band (dead_band) of a pid control structure _pid.
设定PID参数 －－－－ P,I,D,死区
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void pid_tune(struct _pid *pid, float p_gain, float i_gain, float d_gain, int dead_band) {
pid->pgain = p_gain; pid->igain = i_gain; pid->dgain = d_gain;
pid->deadband = dead_band; pid->integral= integral_val; pid->last_error=0; }
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pid_setinteg DESCRIPTION Set a new value for the integral term of the pid equation.
This is useful for setting the initial output of the pid controller at start up.
设定输出初始值
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void pid_setinteg(struct _pid *pid,float new_integ) {
pid->integral = new_integ; pid->last_error = 0; }
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pid_bumpless DESCRIPTION Bumpless transfer algorithim.
When suddenly changing setpoints, or when restarting the PID equation after an extended pause,
the derivative of the equation can cause a bump in the controller output. This function will help smooth out that bump.
The process value in *pv should be the updated just before this function is used.
pid_bumpless 实现无扰切换
当突然改变设定值时，或重新启动后，将引起扰动输出。这个函数将能实现平顺扰动，在调用该函数之前需要先更新PV值
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void pid_bumpless(struct _pid *pid) {
pid->last_error = (pid->sp)-(pid->pv); //设定值与反馈值偏差 }
//－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－pid_calc DESCRIPTION Performs PID calculations for the _pid structure *a. This function uses the positional form of the pid equation, and incorporates an integral windup prevention algorithim.
Rectangular integration is used, so this function must be repeated on a consistent time basis for accurate control.
RETURN VALUE The new output value for the pid loop. USAGE #include \
本函数使用位置式PID计算方式，并且采取了积分饱和限制运算
PID计算
//－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－float pid_calc(struct _pid *pid) {
int err;
float pterm, dterm, result, ferror;
// 计算偏差
err = (pid->sp) - (pid->pv);
// 判断是否大于死区
if (abs(err) > pid->deadband) {
ferror = (float) err; //do integer to float conversion only once 数据类型转换
// 比例项
pterm = pid->pgain * ferror;
if (pterm > 100 || pterm < -100) {
pid->integral = 0.0; } else {
// 积分项
pid->integral += pid->igain * ferror;
// 输出为0－－100%
// 如果计算结果大于100，则等于100 if (pid->integral > 100.0) {
pid->integral = 100.0; }
// 如果计算结果小于0.0，则等于0 else if (pid->integral < 0.0) pid->integral = 0.0;
}
// 微分项
dterm = ((float)(err - pid->last_error)) * pid->dgain;
result = pterm + pid->integral + dterm; } else
result = pid->integral; // 在死区范围内，保持现有输出
// 保存上次偏差 pid->last_error = err;
// 输出PID值(0-100) return (result); }
//－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－void main(void) {
float display_value; int count=0; pid = &warm;
// printf(\// scanf(\
&d_gain);
// 初始化参数 process_point = 30; set_point = 40;
p_gain = (float)(5.2); i_gain = (float)(0.77); d_gain = (float)(0.18); dead_band = 2;
integral_val =(float)(0.01);
printf(\printf(\d_gain);
printf(\while(count<=20) {
scanf(\
// 设定PV,SP值
pid_init(&warm, process_point, set_point);
// 初始化PID参数值
pid_tune(&warm, p_gain,i_gain,d_gain,dead_band);
// 初始化PID输出值 pid_setinteg(&warm,0.0); //pid_setinteg(&warm,30.0);
//Get input value for process point pid_bumpless(&warm);
// how to display output
display_value = pid_calc(&warm);
printf(\
//printf(\
count++; } }