Maximum likelihood estimations of force and mobility from short single   Brownian trajectories
  We describe a method to extract force and diffusion parameters from single trajectories of Brownian particles based on the principle of maximum likelihood. The analysis is well-suited for out-of-equilibrium trajectories, even when a limited amount of data is available and the dynamical parameters vary spatially. We substantiate this method with experimental and simulated data, and discuss its practical implementation, strengths, and limitations. 
Raphael Sarfati and Jerzy Blawzdziewicz and Eric R. Dufresne
cond-mat.soft