To improve applicability and adaptability of the impact time control guidance (ITCG) in practical engineering, a two-stage ITCG law with simple but effective structure is proposed based on the hybrid proportional navigation, namely, the pure-proportional-navigation and the retro-proportional-navigation. For the case with the impact time error less than zero, the first stage of the guided trajectory is driven by the retro-proportional-navigation and the second one is driven by the pure-proportional-navigation. When the impact time error is greater than zero, both of the stages are generated by the pure-proportional-navigation but using different navigation gains. It is demonstrated by two-and three-dimensional numerical simulations that the proposed guidance law at least has comparable results to existing proportional-navigation-based ITCG laws and is shown to be advant-ageous in certain circumstances in that the proposed guidance law alleviates its dependence on the time-to-go estimation, consumes less control energy, and adapts itself to more boundary conditions and constraints. The results of this research are expected to be supplementary to the current research literature.

In a bid to take advantage of natural characteristics of the proportional navigation guidance (PNG) in practical engineering, the PNG-based impact time control guidance (ITCG) continues to be a popular alternative for achieving the desired impact time of a missile. For most such ITCG, the performance is dependent on the accuracy of the time-to-go estimation. Along the lines of the development of PNG-based ITCG in earlier studies, a nonsingular ITCG is proposed on the basis of nonlinear formulations. It is demonstrated that, by theoretical analysis and numerical simulation, this proposed ITCG is shown to be advantageous in certain circumstances. By deriving a novel additional acceleration command, the proposed law is of lower dependence on time-to-go estimate and is capable of eliminating some singularities, leading to wider adjustable range of the desired impact time and better adaptability to more conditions. This research is expected to be supplementary to those presented in the current research literature.

In this paper, a novel composite efficiency factor model has been proposed for the trajectory optimization of gun-launched gliding guided projectiles. The composite efficiency factor is based on the reduction of glide efficiency associated with the maneuvering capability. The influences of the composite efficiency factor on flight parameters have been investigated. Both the constant composite efficiency factor and an equilibrium glide assumption are simulated, and both are feasible by adjusting the composite efficiency factor with no terminal constraints. Additionally, the optimized composite efficiency factor model with a tightened constraint of the canard deflection angle has been performed and has demonstrated its applicability and effectiveness through case studies with different impact constraints, which can effectively eliminate the oscillatory phenomenon produced by only optimizing the glide efficiency. In comparison with several traditional optimization indices, the validity and superior features of optimizing the composite efficiency factor have also been analyzed in detail. Moreover, a simple simulation of the shaping optimization of the composite efficiency factor demonstrates an excellent improvement in the reserved terminal glide, the maneuvering capabilities, and the damage effect. These results demonstrate that the proposed approach provides a feasible application and potential workhorse for trajectory design and optimization.

A novel polynomial guidance law is proposed for flight vehicle terminal guidance, subject to multiple constraints including launch angle, impact angle, impact time, and zero terminal acceleration. This approach reconstructs the flight path angle profile into two components. One component satisfies the constraints. The other ensures target interception. The constraint-oriented component is formulated as a polynomial function of the relative range-to-go. Based on this reconstruction framework, a new linearization approach is introduced to handle the nonlinear engagement kinematics. A closed-form guidance law is then derived to satisfy multiple constraints, and its convergence is analyzed theoretically. To optimize the control effort, a data-driven method is subsequently incorporated into the framework. Numerical simulation results show that the proposed guidance law achieves multiple constraints with high precision. Compared with existing methods, it also requires less control effort. Specifically, the impact angle error is within 0.02°, and the impact time error is within 0.05 s.