DC Motor: I-V Identification and torque control


This demo shows how to set up a procedure for identification of a DC Motor with permanent magnets aimed at digital torque control.

The application is divided into two parts:

  • In the first part the dsPIC implements a simultaneous sampling of voltage and current and sends the data via serial bus to a remote PC (sampling time equal to approximately 4e-5 sec, number of samples 12800 * 2,signal voltage type PRBS)
  • In the second part the PI controller, designed on the model identified, is used to control the current (directly) and the torque (indirectly) with appropriate characteristics of strength (sampling time of 6.4e-5 sec)

On the PC side, the data are processed with a specific software for the system identification.

The applied methods are:

  • Subspaces Method (with generic I/O data)
  • PEM method (to refine the model)
  • Residual Analysis (to validate the model)





  • Dario Di Stefano (Engineer)


On the FLEX side, the software is divided in 2 simple C applications for identification and control.
On the PC side, you need 2 specific softwares to receive data via serial COM port and to implements identification and control analysis.


This is the list of hardware components needed to reproduce the demo:

  • FLEX board (light or full)
  • 3 home made PCBs (for H-Bridge circuit, anti-alias filters, RS-232 adapter);
  • a few resistences, ICs and connectors
  • a DC motor
  • a PC


(click for full versions)

In the figures below you can see: 1) the accuracy of the model identified (red line) compared to the real motor output (blue line) during the initial phase of the experiment; and 2) the conceptual diagram.


1) Experiment




2) Conceptual diagram




Source code and documentation about the electronic components

External links

Dario Di Stefano