Fuel-optimal control for soft lunar landing based on a quadratic regularization approach.

• The fuel-optimal control problem is formulated as a constrained nonlinear system optimal control problem. • A novel piecewise state linear feedback controller is introduced. • A quadratic regularization approach is developed for solving the optimal control problem. • Convergence results indicate that the proposed algorithm is convergent. • Numerical results show that the proposed method is effective. This paper considers a fuel-optimal control problem for soft lunar landing. Firstly, the fuel-optimal control problem is formulated as an optimal control problem of constrained nonlinear systems with a novel piecewise state linear feedback controller, which can be transformed into an optimal control problem of switched systems. However, it is difficult to solve this fuel-optimal control problem analytically by using conventional optimization techniques due to its nonlinear nature and the existence of the continuous-time inequality constraint. Next, to obtain the numerical solution of the fuel-optimal control problem, a numerical computation method is developed by using a quadratic regularization approach with a cubic sufficient-descent condition. Convergence results indicate that the proposed algorithm is convergent. Finally, a numerical experiment shows that the proposed algorithm is more effective than the existing method. [ABSTRACT FROM AUTHOR]