motorware 13 PID controller only contains a PI controller

in MotorWare there are modules for both PI and PID

We use the modules for PID in everything we do. You can see they are included in the project files and we use PID_ functions in ctrl.c, and all the objects have APIs that access the Kd term.

  // set the default Id PID controller parameters
  Kp = _IQ(0.1);
  Ki = _IQ(pUserParams->ctrlPeriod_sec/0.004);
  Kd = _IQ(0.0);
  outMin = _IQ(-0.95);
  outMax = _IQ(0.95);

  PID_setGains(obj->pidHandle_Id,Kp,Ki,Kd);
  CTRL_setGains(handle,CTRL_Type_PID_Id,Kp,Ki,Kd);

But you are correct that with current and speed loops the D term is set to 0 so you are really just using PI controls. It brings no benefits to these types of control loops.  In motor/motion control they are typically only used in position control systems.

Dave Wilson has a series of blogs about PI/PID controls that may interest you.

http://e2e.ti.com/members/1452723/blogs/default.aspx

Hello Chris,

Please check this code that is copied from pid.h. I believe this is also used by the controller.

//! \brief     Runs the PID controller

//! \param[in] handle      The PID controller handle

//! \param[in] refValue    The reference value to the controller

//! \param[in] fbackValue  The feedback value to the controller

//! \param[in] pOutValue   The pointer to the controller output value

static inline void PID_run(PID_Handle handle,const _iq refValue,const _iq fbackValue,_iq *pOutValue)

{

  PID_Obj *obj = (PID_Obj *)handle;

  _iq Error;

  _iq Up,Ui;

  Error = refValue - fbackValue;

  Ui = obj->Ui;                                                  // load the previous integral output

  Up = _IQmpy(obj->Kp,Error);                                    // Compute the proportional output

  Ui = _IQsat(Ui + _IQmpy(obj->Ki,Up),obj->outMax,obj->outMin);  // Compute the integral output

  obj->Ui = Ui;                                                  // store the intetral output

  obj->refValue = refValue;

  obj->fbackValue = fbackValue;

  *pOutValue = _IQsat(Up + Ui,obj->outMax,obj->outMin);          // Saturate the output

  return;

} // end of PID_run() function

In this code Kd is not used.

Anyway, my problem is not that, but when i add a variable to the pid object, the all kind of strange things happen.

//! \brief Defines the PID controller object

//!

typedef struct _PID_Obj_

{

  _iq Kp;                     //!< the proportional gain for the PID controller

  _iq Ki;                     //!< the integral gain for the PID controller

  _iq Kd;                     //!< the derivative gain for the PID controller

  _iq Ui;                     //!< the integrator start value for the PID controller

  _iq refValue;               //!< the reference input value

  _iq fbackValue;             //!< the feedback input value

  _iq outMin;                 //!< the minimum output value allowed for the PID controller

  _iq outMax;                 //!< the maximum output value allowed for the PID controller

  _ie last_error;         

} PID_Obj;

Like in the code above.

Thanks,

Paul

Paul van Ruth said:

In this code Kd is not used.

You are correct. Kd is in the structure but is not used. I'll file this as a bug. I agree that if this is a PID controller the Kd term needs to be in the control law in case Kd != 0.

Paul van Ruth said:

Anyway, my problem is not that, but when i add a variable to the pid object, the all kind of strange things happen.

Are you using a lab where pid.c/.h is in your user code and is NOT being called from the on-chip ROM?

Thank you for your response.

I'm using lab12b. This runs the ctrl and pid.c/h from ram, right?

Regards,

Paul

correct. only 2a uses the forward FOC control in ROM.

I don't understand why adding another member to the PID structure would be causing issues. what exactly is happening?