Three-dimensional multivariable integrated guidance and control design for maneuvering targets interception

This paper proposes a new three-dimensional integrated guidance and control (IGC) scheme for intercepting maneuvering targets based on backstepping technique, nonlinear disturbance observer (NDOB) and nonlinear differentiator. To this end, a realistic six degree-of-freedom model, considering aerodynamic uncertainties, cross-coupling effects, model uncertainties and target maneuvers, is constructed first. In order to achieve precise interception, a multivariable NDOB is designed based on second-order sliding mode technique to estimate the lumped uncertainties in finite time. By virtue of the proposed adaptive law, the upper bounds of the lumped uncertainties and their gradients are not required in NDOB design. Using the reconstructed information, a robust IGC law is then synthesized following a backstepping-like way. At each step of backstepping design, a nonlinear differentiator is adopted to avoid analytical differentiation of the virtual control laws and therefore the associated problem of 'explosion of terms' is completely addressed. Detailed stability analysis shows that the line-of-sight (LOS) angular rates will converge to zero asymptotically. Finally, the IGC algorithm is tested through numerical simulations against a maneuvering target.