CCS/TMS320F28379S: output of PID Control

Part Number: TMS320F28379S

Tool/software: Code Composer Studio

Hi,

I am using "DCL_runPID_C4" and I am doing  test for finding proper Kp. Ki and Kd value.

I set the parameter of PID as follow,

pid1.Kp = 5.0f;
pid1.Ki = 100;//0.015f;
pid1.Kd = 0;//1.35f;
pid1.Kr = 1.0f;
pid1.c1 = 188.0296600613396f;
pid1.c2 = 0.880296600613396f;
pid1.d2 = 0.0f;
pid1.d3 = 0.0f;
pid1.i10 = 0.0f;
pid1.i14 = 1.0f;
pid1.Umax = 1000.0f;
pid1.Umin = -1000.0f;
pid1.sps = &spid;
pid1.css = &cpid;

And my test control loop is as follow,

rk = 1000.0f; // initial value for control reference
lk = 0.0f; // control loop not saturated

while(1)
{
  pos = EQEP_getPosition(EQEP1_BASE);

  if (pos & 0x80000)
  {
     s_pos = (0xffffffff - pos);
  }
  else
  {
    s_pos = -pos;
  }
  yk = (float) s_pos;

// external clamp for anti-windup reset
DCL_runClamp_C1(&lk, 10.0f, -10.0f);

// run PID controller
uk = DCL_runPID_C4(&pid1, rk, yk, lk);
Duty = abs(uk) % 1001;

......

 }

But, uk becomes zero at yk is 21000.0000f

I expected uk was zero at yk that is same with rk(=1000.0f)

What is the wrong of my expectation?

BR

Paul