"Getting Started with smart cars"-location-and incremental-PID implementation code

PID control is the most common algorithm in the production of intelligent car, it mainly divided into two kinds: position and increment. The following is a discussion of the characteristics of these two types of PID and code implementation.

1. Position-type PID

Features: position pid is used to integrate all the error values in the past, so it is related to the whole state of the past.

Code implementation:

typedef struct PID//define struct body

{

float LastError; Last Error

float Sumerror; Error integral term

} PID;

Static PID SPID;

Static PID *sptr=&spid;

void Pid_init (void)//pointer initialization

{

Sptr->lasterror = 0;

Sptr->sumerror = 0;

}

Float Pidcalc (float nextpoint)

{

float Derror,error;

Error = Setpoint-nextpoint; Deviation

Sptr->sumerror + = Error; Integral

Derror = error-sptr->preverror; Current differential

Sptr->lasterror = Error;

Return (kp* Error//scale item

+ki * Sptr->sumerror//Points

+kd* derror); Differential term

}

   

 

 

 

2. Incremental PID

Features: the increment of PID output is the increment of control quantity, the influence of misoperation is small

Code implementation:

Typedefstruct PID

{

float V_lasterror; ERROR[-1]

float V_preserror; Error[-2]

}pid;

Staticpid SPID;

Staticpid *sptr=&spid;

Voidpid_init (void)//pointer initialization

{

Sptr->v_lasterror = 0; ERROR[-1]

Sptr->v_preserror = 0; Error[-2]

}

Voidpid_caculate (U16 set_value,float Get_value)

{

float g_fdirectioncontrolout1=0;

V_error=get_value-set_value;

g_fdirectioncontrolout1= P * (v_error-sptr->v_lasterror) + I * v_error + D (V_ERROR-2*SPTR-&G T V_LASTERROR+SPTR->V_PRESERROR);//calculate current output increment

Sptr->v_preserror =sptr->v_lasterror; Storage error, for next calculation

Sptr->v_lasterror = V_error;

G_fdirectioncontrolout2 + = g_fdirectioncontrolout1;//Last output plus current output increment

G_fdirectioncontroloutold = g_fdirectioncontroloutnew;

G_fdirectioncontroloutnew =g_fdirectioncontrolout2;

}

 

The choice of P, I, d three links, generally only use PI control or PD control, such as speed control requires steady state error, then the integral link, so the use of Pi control, and the use of direction control, because there is no need for steady state error, so the use of PD control can be, The function of D is to eliminate the oscillation caused by the P link.

 

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