## PID Controller in MATLAB

I’ve had several people ask me for a MATLAB implementation of a PID controller. I took my previous PID controller post and ported it to MATLAB. Because MATLAB is not designed for software like this, I made a single PID instance code set. In other words, the following code only represents one controller.

Here is the code for the update function (you must place it in a file named pid_update.m)

function pid_update(curr_error, dt) global windupGuard; global proportional_gain; global integral_gain; global derivative_gain; global prev_error; global int_error; global control; % integration int_error = int_error + (curr_error * dt); % integration windup guarding if (int_error < -(windupGuard)) int_error = -(windupGuard); elseif (int_error > windupGuard) int_error = windupGuard; end % differentiation diff = ((curr_error - prev_error) / dt); % scaling p_term = (proportional_gain * curr_error); i_term = (integral_gain * int_error); d_term = (derivative_gain * diff); % summation of terms control = p_term + i_term + d_term; % save current error as previous error for next iteration prev_error = curr_error;

Here is some VERY basic code just used to call the update function once.

global windupGuard; global proportional_gain; global integral_gain; global derivative_gain; global prev_error; global int_error; global control; % set these as needed windupGuard = 10.0; proportional_gain = 4.0; integral_gain = 5.0; derivative_gain = 3.0; % this is the zeroize function prev_error = 0.0; int_error = 0.0; % call update function pid_update(19, 1.0)

Here’s a question for those of you here reading this: Why on earth are you using MATLAB for a PID controller?