The　flexible　two-wheeled　balancing　robot　is　a　non-stable,　non-linear,　strong　coupling　system.　A　Kalman　filter　configuration　combining　a　gyroscope　and　an　inclinometer　is　implement　to　obtain　an　accurate　estimate　of　the　tilt　angle　and　its　derivate.　This　paper　also　presents　nonlinear　PID　controller　for　the　posture　balancing　control　of　FTWSBR,　The　experiment　results　demonstrate　that　the　control　method　is　effective　for　FTWSBR.　©　2011　IEEE.