This　paper　presents　an　optical　flow　based　novel　technique　to　perceive　the　instant　motion　velocity　of　mobile　robots.　The　primary　focus　of　this　study　is　to　determine　the　robot＇s　ego-motion　using　displacement　field　in　temporally　consecutive　image　pairs.　In　contrast　to　most　previous　approaches　for　estimating　velocity,　we　employ　a　polynomial　expansion　based　dense　optical　flow　approach　and　propose　a　quadratic　model　based　RANSAC　refinement　of　flow　fields　to　render　our　method　more　robust　with　respect　to　noise　and　outliers.　Accordingly,　techniques　for　geometrical　transformation　and　interpretation　of　the　inter-frame　motion　are　presented.　Advantages　of　our　proposal　are　validated　by　real　experimental　results　conducted　on　Pioneer　robot.