void pid_Cal(void)
{
//float index = 0;
IncPid * p = NULL;
p = &g_PID_Inc;
p->SetVal = sys_para.given_temp;
p->ActualVal = g_pt100.f_real_value;
p->err = p->SetVal - p->ActualVal;
if(work_temp_phase == work_phase_43C_level)
{
if(FAN_Speed_Status == FAN_Speed_LOW)
{
if(fabs(p->err) >= 6.0f)
{
p->Kp = 0; //0.45
p->Ki = 0.4; //0.05
p->Kd = 0;
}
else
{
p->Kp = 1.8; //0.4 0.475
p->Ki = 0.4; //0.05 0.07
p->Kd = 0; //0.2
}
}
else if(FAN_Speed_Status == FAN_Speed_HIGH)
{
if(fabs(p->err) >= 6.0f)
{
p->Kp = 0; //0.45
p->Ki = 0.4; //0.05
p->Kd = 0;
}
else
{
p->Kp = 1.75; //0.4 0.475
p->Ki = 0.38; //0.05 0.07
p->Kd = 0; //0.2
}
}
}
else if(work_temp_phase == work_phase_38C_level)
{
if(FAN_Speed_Status == FAN_Speed_LOW)
{
if(fabs(p->err) >= 6.0f)
{
p->Kp = 0; //0.45
p->Ki = 0.4; //0.05
p->Kd = 0;
}
else
{
p->Kp = 1.8; //0.4 0.475
p->Ki = 0.4; //0.05 0.07
p->Kd = 0; //0.2
}
}
else if(FAN_Speed_Status == FAN_Speed_HIGH)
{
if(fabs(p->err) >= 6.0f)
{
p->Kp = 0; //0.45
p->Ki = 0.4; //0.05
p->Kd = 0;
}
else
{
p->Kp = 1.75; //0.4 0.475
p->Ki = 0.38; //0.05 0.07
p->Kd = 0; //0.2
}
}
}
else if(work_temp_phase == work_phase_32C_level)
{
if(FAN_Speed_Status == FAN_Speed_LOW)
{
if(fabs(p->err) >= 6.0f)
{
p->Kp = 0; //0.45
p->Ki = 0.4; //0.05
p->Kd = 0;
}
else
{
p->Kp = 1.8; //0.4 0.475
p->Ki = 0.4; //0.05 0.07
p->Kd = 0; //0.2
}
}
else if(FAN_Speed_Status == FAN_Speed_HIGH)
{
if(fabs(p->err) >= 6.0f)
{
p->Kp = 0; //0.45
p->Ki = 0.4; //0.05
p->Kd = 0;
}
else
{
p->Kp = 1.75; //0.4 0.475
p->Ki = 0.38; //0.05 0.07
p->Kd = 0; //0.2
}
}
}
p->IncrementVal = (p->Kp * (p->err - p->err_next))
+ (p->Ki * p->err)
+ (p->Kd * (p->err - 2 * p->err_next + p->err_last));
p->err_last = p->err_next;
p->err_next = p->err;
}
可以看出，首先调整的是P控制，代码中为Ki，因为增量式pid的ki参数相当于位置式的p控制，所以首先调整ki，是的温度出现震荡，然后添加kp（位置式的d控制），这样就可以使系统稳定。
同时，也是用了微分分离的思想，就是温差比较大的时候，不要微控制，即kp=0；，到了一定稳定范围了，才使用pd控制。