函数返回值一直为0的问题

沉默遇上寡言 · 发表于 2013-4-22 13:28:03

下面的函数返回值一直为0是怎么回事    我主函数里ceshi=IncPIDCalc(15);    出来结果也是0

int IncPIDCalc(int NextPoint)//PID算法
{
int iError,iIncpid; //当前误差
iError = sptr->SetPoint - NextPoint; //增量计算
  iIncpid = sptr->Proportion * iError //E[k]项
         -sptr->Integral * sptr->LastError //E[k－1]项
         + sptr->Derivative * sptr->PrevError; //E[k－2]项
sptr->PrevError = sptr->LastError; //存储误差，用于下次计算
sptr->LastError = iError;
return(iIncpid);
//返回增量值
}

沉默遇上寡言 · 发表于 2013-4-22 15:18:07

249176669 发表于 2013-4-22 14:53
结构体使用方法不正确？

我是看不出有啥问题你们看看去掉结构体就OK了不知道是我哪里弄错了

typedef struct PID
{
int SetPoint; //设定目标 Desired Value
int Proportion; //比例常数 Proportional Const
int Integral; //积分常数 Integral Const
int Derivative; //微分常数 Derivative Const
int LastError; //Error[-1]
int PrevError; //Error[-2]
} PID;
#define P_DATA 2
#define I_DATA 0
#define D_DATA 0
#define HAVE_NEW_VELOCITY 0X01//反馈

static PID sPID;
static PID *sptr = &sPID;

void IncPIDInit(void)//初始化PID
{
sptr->LastError = 0; //Error[-1]
sptr->PrevError = 0; //Error[-2]
sptr->Proportion = P_DATA; //比例常数 Proportional Const
sptr->Integral = I_DATA; //积分常数Integral Const
sptr->Derivative = D_DATA; //微分常数 Derivative Const
sptr->SetPoint =10; //目标是100
}

int IncPIDCalc(int NextPoint )//PID算法
{
int iError;int iIncpid; //当前误差
  iError = sptr->SetPoint - NextPoint; //增量计算
  iIncpid = sptr->Proportion * iError //误差
         -sptr->Integral * sptr->LastError //前次误差
         + sptr->Derivative * sptr->PrevError; //前前次误差
sptr->PrevError = sptr->LastError; //存储误差，用于下次计算
sptr->LastError = iError;
return(iIncpid);
//返回增量值
}