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JOURNAL OF GUIDANCE
Volume 38, Number 12December 2015
Agency for Defense Development, Daejeon 34186, Republic of Korea
Seoul National University, Seoul 08826, Republic of Korea
Department of Aerospace and Mechanical Engineering, Korea Aerospace University
A three-dimensional nonlinear guidance law for path-following is proposed using differential geometry of space curves. The proposed guidance law makes a vehicle converge to and then follow a given desired path of general shape, which does not require strict restrictions on initial position and velocity. To take the advantages of the look-ahead effect for precise and robust path-following, the proposed guidance law takes the form of pure pursuit guidance, which is designed to align the velocity of the vehicle with the look-ahead vector. The look-ahead angle and the radially shifted distance are designed using differential geometry of the desired path. The proposed guidance law generates the normal acceleration command required for exact path-following and finally overcomes the limitations of previously developed look-ahead point-based methods in the case of general three-dimensional path-following. Stability analysis on the guidance law to follow constant-curvature planar paths is performed. The performance of the proposed guidance law is demonstrated by numerical simulations for various types of desired paths.