Torque Control Using Monitoring Force C/C++ Code

The following example code is not necessarily complete, and may not compile if copied exactly. Refer to the examples folder on the NI-Motion CD for files that are complete and compile as is.

// Main function
void main(void)
{

   u8  boardID;            // Board identification number
   u8  axis;               // Axis number
   u16 csr   = 0;          // Communication status register
   u16 axisStatus;         // Axis status
   i32 constant;           // Constant force
   i16 adcValue;           // ADC value read
   
   // Variables for modal error handling
   u16 commandID;          // The commandID of the function
   u16 resourceID;         // The resource ID
   i32 errorCode;          // Error code


   ///////////////////////////////
   // Set the board ID
   boardID = 1;
   // Set the axis number
   axis = 1;
   // constant force needed to be maintained
   // corresponds to 5V for a +/- 5V ADC settings
   constant = 2047;
   ////////////////////////////////

   //-----------------------------------------------------------
   // Is is assumed that the axis being moved has an encoder
   // mapped as its primary feedback
   //-----------------------------------------------------------

   // Set the velocity for the move (in counts/sec)
   err = flex_load_velocity(boardID, axis, 10000, 0xFF);
   CheckError;

   // Set the acceleration for the move (in counts/sec^2)
   err = flex_load_acceleration(boardID, axis, NIMC_ACCELERATION, 100000, 0xFF);
   CheckError;

   // Set the deceleration for the move (in counts/sec^2)
   err = flex_load_acceleration(boardID, axis, NIMC_DECELERATION, 100000, 0xFF);
   CheckError;

   // Set the jerk (s-curve value) for the move (in sample periods)
   err = flex_load_scurve_time(boardID, axis, 100, 0xFF);
   CheckError;

   // Set the operation mode to velocity
   err = flex_set_op_mode(boardID, axis, NIMC_RELATIVE_POSITION);
   CheckError;

   do
   {

      // Read the ADC channel number 1 and calculate the position to be updated
      err = flex_read_adc_rtn(boardID, NIMC_ADC1, &adcValue);
      CheckError;

      if( (constant - adcValue) != 0){

         err = flex_load_target_pos(boardID, axis, (constant - adcValue), 0xFF);
         CheckError;

         // Move based on delta force
         err =  flex_start(boardID, axis, 0);
         CheckError;


      }

      // Check the move complete status/following error/axis off status
      err = flex_read_axis_status_rtn(boardID, axis, &axisStatus);
      CheckError;

      // Read the communication status register and check the modal errors
      err = flex_read_csr_rtn(boardID, &csr);
      CheckError;

      // Check the modal errors
      if (csr & NIMC_MODAL_ERROR_MSG)
      {
         err = csr & NIMC_MODAL_ERROR_MSG;
         CheckError;
      }

      Sleep (50); // Check every 10 ms

   }while (!(axisStatus & NIMC_AXIS_OFF_BIT)); // Exit on axis off

   return;      // Exit the Application


   /////////////////////////////////////////////////////////////////////////
   // Error Handling
   //
   nimcHandleError; //NIMCCATCHTHIS:
   
   // Check to see if there were any Modal Errors
   if (csr & NIMC_MODAL_ERROR_MSG){
      do{
         // Get the command ID, resource and the error code of the modal
         // error from the error stack on the board
         flex_read_error_msg_rtn(boardID,&commandID,&resourceID,&errorCode);
         nimcDisplayError(errorCode,commandID,resourceID);

         // Read the Communication Status Register
         flex_read_csr_rtn(boardID,&csr);

      }while(csr & NIMC_MODAL_ERROR_MSG);
   }
   else       // Display regular error
      nimcDisplayError(err,0,0);
   return;    // Exit the Application
}