This paper presents a methodology of performance assessment for precision guided system. Hierarchical performance index system is established with a tree-like structure. Scheme of performance evaluation platform design is presented with four main parts, such as process management system, vehicle guidance simulation system, data processing system, and evaluation system. Based on the scheme, performance assessment platform is developed via Visual C++ codes. Numerical simulation method based on Monte Carlo simulation is used to get the values of the lowest level indexes. AHP method is used to compute the values of upper level indexes. An example of precision guided system performance assessment is given. And Simulation results suggest that the methodology presented in this paper is effective.

For the entry guidance based on a nominal trajectory, trajectory tracking is an important part, by which the nominal trajectory is followed and several constraints can be observed. In order to reject disturbance and achieve good tracking performance in trajectory tracking, a finite-time trajectory tracking method is presented. Utilizing the differential flatness theory, a linear tracking error system can be derived from the nonlinear point-mass dynamics of an entry vehicle. A disturbance compensator is designed based on linear extended state observers. The compensator observes the disturbances in the tracking error system, and then compensates the disturbances in the following tracking law. To track the nominal trajectory, a finite-time tracking law with disturbance compensation is derived using a linear finite-time stabilization method. This method ensures that the tracking error is finite-time stable and the settling time of the tracking error is within a specified range. Numerical simulation demonstrates the proposed trajectory tracking law. Under various disturbances, good tracking performance is achieved and all constraints are observed. The proposed trajectory tracking method is effective.

A new aerodynamic parameter fitting approach is proposed to avoid online aerodynamic parameter interpolation for advanced flight vehicle trajectory generation, guidance and control. Due to its ability to fit any nonlinear function and simple structure, BP neural network was chosen as the tool to fit the aerodynamic parameters which are the function of Mach number, angle of attack and other variables. A weight value learning method based on hybrid genetic algorithm and support vector machines optimization algorithm is presented in order to overcome the shortcoming of reaching local minimal values of the BP neural network. Simulation results show that aerodynamic parameter fitting time is less than aerodynamic parameter interpolation and the proposed approach is a way to save computation time during trajectory design, guidance and control, and numeric simulation process.

In terminal guidance phase, only partial information concerning the interception geometry is available. To intercept a target in specified direction under this condition, an impact angle constrained guidance law is proposed based on the dynamic output feedback. The guidance law doesn't use the rate of line-of-sight angle, and can guarantee convergence speed of the closed-loop system. Utilizing the parametric algebraic Riccati equation, a dynamic output feedback controller is designed. The controller contains a feedback law and an observer is obtained. Through integrated design of the parameters of the feedback law and the observer, the closed-loop system can be transformed to a new system, whose system matrix is a Jordan matrix. Using Lyapunov approach, desired convergence speed of the new system can be obtained by tuning its poles. And the same convergence speed of the original closed-loop system can also be achieved. Based on the dynamic output feedback controller, an impact angle constrained guidance law is derived. The guidance law is demonstrated by numerical simulation. Convergence speed can be guaranteed by the guidance law, and high guidance precision is achieved.

In view of efficient models and equipments integration, a distributed simulation method orienting homing missiles GNC demonstration and performance assessment is presented. GNC system of homing missile is introduced briefly as foundation. Distributed simulation method of GNC demonstration is presented. Operation principle, time promoting, and model operation sequence are discussed. Base on this method, a distributed simulation system is developed for GNC demonstration and performance assessment. Architecture of the simulation system, including hardware structure and software structure, is illustrated. Utilizing this system, GNC system of an infrared imaging homing missile is demonstrated with consideration of laser active jamming, disturbances and model uncertainties. Simulation results are obtained for GNC performance assessment. Demonstration and performance assessment of GNC are efficient and economical by the distributed simulation method.

A three-dimensional constrained trajectory generation algorithm, orienting onboard implementation and large-crossrange missions, is presented for near space hypersonic vehicles. In this algorithm, an altitude vs. velocity profile of a three-dimensional trajectory is planned directly according to initial conditions, terminal conditions and trajectory constraints. Based on the altitude profile and an admissible attack angle profile, flight-path angles and bank angles are computed analytically with consideration of lateral motion. Other states of the trajectory are generated by trajectory propagation. And terminal rangeto-go of the trajectory is computed. Then, trajectory generation problem is simplified to a one-parameter search problem. To solve this problem, a design variable of the altitude profile is adjusted, by which error of terminal range-to-go is eliminated and desired crossrange and downrange of the trajectory are achieved. In addition, attack angle profile design is also discussed. An attack angle profile, which adapts to various missions, can be obtained. The algorithm is demonstrated for various cases in numerical simulation. The algorithm is able to generate constrained three-dimensional trajectories rapidly. And large crossrange can be achieved. The rapid three-dimensional constrained trajectory generation algorithm is effective and efficient.

A rapid trajectory planning methodology orienting onboard application is presented for entry vehicles with medium and higher L/D ratios. In this methodology, a parameterized altitude vs. velocity profile of an entry trajectory is designed according to initial conditions, terminal conditions, and trajectory constraints. And flight-path angles and bank angles are computed analytically with an admissible angle of attack profile. These constitute key concepts of the methodology. Following the concepts, trajectory planning is simplified to a one-parameter search problem. In this problem, a parameter of the altitude profile is adjusted to acquire desired range of the trajectory. The one-parameter search problem can be solved quickly, because of a monotonic relationship between design variable of the altitude profile and range of the trajectory. In numerical simulation, the trajectory planning algorithm is demonstrated for various cases, in which the vehicle is guided to a fixed target or a moving target with desired terminal conditions. In these cases, the algorithm is able to plan entry trajectories observing trajectory constraints and terminal constraints rapidly. Simulation results suggest the methodology presented in this paper is effective.

The guidance and control for near space vehicles are subjected to multiple constraints. To actualize the goals of guidance and achieve the flight mission, a guidance method for near space vehicles under the consideration of multiple constraints is proposed in this paper. The guidance problem is decomposed into two subproblems, a trajectory planning subproblem and a trajectory tracking subproblem. Based on the parameterized modeling to angle of attack and the optimizing process of these parameters, the optimized longitudinal reference trajectory with the longest range is obtained. Then, a tracking law is designed to follow this longitudinal reference trajectory, and the robustness is reinforced via the double-loops structure of the tracking system. Finally, the guidance method is demonstrated by simulation, and the detailed analyses are given at the end of this paper.

In the entry phase, aero-environment is extremely complex for Reusable Launch Vehicles (RLVs). This brings a huge challenge to design the entry guidance law for RLVs. In this paper, an entry trajectory planning method for RLVs is researched and the algorithm is improved to ensure the continuity and smoothness of the longitudinal reference trajectory. Meanwhile, the skipping of trajectory control is decreased, and the flyability of trajectory is enhanced. Moreover, a new lateral guidance logic is proposed to reinforce the reliability of the algorithm. At the end of this paper, simulation and analysis are given to demonstrate the guidance method.