A system may include a controller that may control operations of a device according to a control loop and characterize a frequency response of the device while the device is operating. The controller may characterize the frequency response by adding a perturbation signal to any signal in the control loop. The controller may then determine a first transformed signal by performing a first discrete Fourier transform on a first signal in the control loop at a frequency of the perturbation signal and determine a second transformed signal by performing a second discrete Fourier transform on a second signal in the control loop at the frequency of the perturbation signal. The controller may then determine the frequency response at the frequency by comparing a first amplitude and a first phase of the first transformed signal to a second amplitude and a second phase of the second transformed signal.