A system for a type of nonholonomic wheeled mobile robots equipped with an uncalibrated camera fixed to the ceiling is investigated.Based on the visual feedback and the state-input transformation,models of uncertain chained form systems are presented for the robot-camera systems.Then,new smooth time-varying feedback controllers are proposed to exponentially stabilize the uncertain chained system by using state-scaling and control theories for two cases.The exponential stabilities of the closed-loop uncertain systems are rigorously proved.Simulation results demonstrate the effectiveness of the proposed strategies. A system for a type of nonholonomic wheeled mobile robots equipped with an uncalibrated camera fixed to the ceiling is investigated.Based on the visual feedback and the state-input transformation, models of uncertain chained form systems are presented for the robot-camera systems. , new smooth time-varying feedback controllers are proposed to exponentially stabilize the uncertain chained system by using state-scaling and control theories for two cases. The exponential stabilities of the closed-loop uncertain systems are rigorously proved. Simulation results demonstrate the effectiveness of the proposed strategies.