This research presents theoretically an automated vehicle merging control which is an important subsystem of AHS. The goal of the system is to automatically control the vehicle merging from ramp to the AHS lane in an efficient, smooth and safe manner. The entire merging process is divided the a speed adjustment stage and a lane merging stage. Three important parameters; acceptability, availability and pursuability are analyzed to characterize the AHS lane gap features. Three control guidance laws (linear, optimal and parabolic speed profile) are developed to describe the desired behaviors of the merging vehicle based on the merging quality and safety consideration. The desired states of the merging vehicle are generated through the outer loop by specified control guidance law. The tracking errors compared with desired states are eliminated by the proper design of controllers in the inner loop. Both longitudinal and lateral controller are designed using the sliding mode control theory which can handle the model nonlinearities and uncertainties of the vehicle dynamics. Two new sliding mode methods are proposed in the design of the lateral controller. The proposed system is evaluated and validated through computer simulations. The simulation results show that system performance is satisfactory under the various merging conditions for a smooth, efficient and safe merging. The system also supplies a basis for the further research on the multiple merging control system and the lane changing control system. / Ph. D.