spintac velocity control problem

I want to use spintac to control the velocity, and this is achieved, but I can not change the acceleration, below is my code :

void ST_runVelCtl(ST_Handle handle,OBSERVER_Handle observerHandle, CTRL_Handle ctrlHandle,ENC_Handle encHandle)
{
    _iq speedFeedback, iqReference;
    ST_Obj *stObj = (ST_Obj *)handle;
    CTRL_Obj *ctrlObj = (CTRL_Obj *)ctrlHandle;

    speedFeedback = _IQmpy(ENC_getFilteredSpeed(encHandle), _IQ(ST_SPEED_KRPM_PER_PU));

    STVELCTL_setVelocityReference(stObj->velCtlHandle, gMotorVars.SpeedRef_krpm);
    STVELCTL_setAccelerationReference(stObj->velCtlHandle,_IQmpy(MAX_ACCEL_KRPMPS_SF,gMotorVars.MaxAccel_krpmps));    // Internal ramp generator does not provide Acceleration Reference
    STVELCTL_setVelocityFeedback(stObj->velCtlHandle, speedFeedback);
    STVELCTL_run(stObj->velCtlHandle);

    // select SpinTAC Velocity Controller
    iqReference = STVELCTL_getTorqueReference(stObj->velCtlHandle);

    // Set the Iq reference that came out of SpinTAC Velocity Control
    CTRL_setIq_ref_pu(ctrlHandle, iqReference);
}

I am using  encoder to get the velocity. the velocity can be changed accuartly.