Lab 7b Tips: Brushless DC Motor

Pre-Lab

• Sample predicted torque vs. speed plot.
  

In-Lab

• λ ≈ 0.0037 Nm/A or Vs/rad
• Sample torque vs. position and torque vs. speed plots.
  
• You can replace your bdctorq.m file with the code below to convert the torque to Nm and rename your variables from position and torque to qrmx and torquex respectively (x = a, b, or c).
  % M-file for EE323 LAB
% date : 04/08/2010
% Function for saving data in a MAT file
% bdctorq('filename', var1, var2)
% 'filename' should be of the form 'tx.mat'.
% You need the single quotes.
% var1 is saved as qrmx
% var2 is saved as torquex
% where x should be a, b, or c

function bdctorq(u,position,torque)
[position,i] = sort(position);
torque = torque(i)/141.6; % convert from oz-in to Nm

phase = u(2);
eval(sprintf('qrm%s=position;',phase));
eval(sprintf('torque%s=torque;',phase));

save (u, sprintf('qrm%s',phase), sprintf('torque%s',phase),'-MAT');