Abstract: Abstract：Aiming at the problem of Mars entry guidance, considering the constrained control and uncertainty of Mars atmosphere and detector’s parameters, the optimal robust guidance method with constrained control is proposed. Considering the parameter uncertainty of system, the optimal index of uncertain nonlinear system is transformed into an index of the nominal system. In consideration of the constrained control, a saturated function is introduced, and the guidance problem is transformed into solving the modified HJB equation. The neural network has the ability of approximation. The proposed HJB equation is solved with the neural network because the HJB equation is partial differential equation and there is a great deal of difficulty in solving it. The guidance method makes sure that the uncertain nonlinear systems have an optimal upper bound of performance index and that the method has robustness. Then, the method is applied to the Mars entry guidance. The simulation results show that the terminal conditions of Mars entry phase can be well guaranteed despite uncertainty of system, and that the control is in the constrained range, so the method is effective. Keywords： uncertain system; constrained control；HJB equation； Mars entry guidance

Key words: Keywords：uncertain system, constrained control；HJB equation； Mars entry guidance