Optimization of nanofiber scaffold properties towards nerve guidance channel design

Nerve guidance channels are limited by lack of topographical guidance：Treatment of sizeable nerve gaps remains problematic following peripheral nerve injury.Functional outcomes are good when neurorrhaphy,or direct end-to-end suture repair,is possible.The problem arises when there is significant segmental loss,which can occur following trauma as well as oncological procedures.

Extended optimal guidance law with impact angle and acceleration constriants

The extended optima straints of miss distance and Schwartz inequality. To reduce guidance law with terminal conmpact angle is derived by the terminal acceleration and eliminate gravity disturbance absolutely, the object function, which designs the weight of control command to be the power function of time-to-go＇s reciprocal, is given. And the gravity is considered when building the state equation. Based on the parsing express of the guidance command change with varying time and adjoint system analysis method, the command characteristics and the non-dimensional miss distance of the guidance law are analyzed, a design principle of guidance order coefficients is discussed. Finally, based on the requirement of engineering, the method to calculate the guidance condition and maximal required acceleration of the guidance law is given. The simulation demonstrates that not only the guidance law can satisfy the terminal position and impact angle constraints, but also the terminal acceleration can be converged toward zero, which will support a good situation for the terminal angle of attacking control.

Adaptive weighting impact angle optimal guidance law considering seeker's FOV angle constraints

In this paper, a new adaptive optimal guidance law with impact angle and seeker’s field-of-view(FOV) angle constraints is proposed. To this end, the generalized optimal guidance law is derived first. A changeable impact angle weighting(IAW) coefficient is introduced and used to modify the guidance law to make it adaptive for all guidance constraints. After integrating the closed-form solution of the guidance command with linearized engagement kinematics, the analytic predictive models of impact angle and FOV angle are built, and the available range of IAW corresponding to constraints is certain. Next, a calculation scheme is presented to acquire the real-time value of IAW during the entire guidance process. When applying the proposed guidance law, the IAW will keep small to avoid a trajectory climbing up to limit FOV angle at an initial time but will increase with the closing target to improve impact position and angle accuracy, thereby ensuring that the guidance law can juggle orders of guidance accuracy and constraints control.

Design of Closed Loop Optimal Guidance Law Using Neural Networks

It is generally impossible to obtain the analytic optimal guidance law for complex nonlinear guidance systems of homing missiles,and the open loop optimal guidance law is often obtained by numerical methods,which can not be used directly in practice.The neural networks are trained off line using the optimal trajectory of the missile produced by the numerical open loop optimal guidance law,and then,the converged neural networks are used on line as the feedback optimal guidance law in real time.The research shows that different selections of the neural networks inputs,such as the system state variables or the rate of LOS(line of sight),may have great effect on the performances of the guidance systems for homing missiles.The robustness for several guidance laws is investigated by simulations,and the modular neural networks architectures are used to increase the approximating and generalizing abilities in the large state space.Some useful conclusions are obtained by simulation results.

Advanced optimal guidance law with maneuvering targets

Based on optimal theory, the advanced optimal guidance law （AOGL） is derived for the interception endgame of maneuvering targets in step mode. The guidance system dynamics, target maneuvering dynamics and acceleration, gravity acceleration are considered and their effects are dy- namically cancelled out in guidance law. A four states Kalman filter is designed to estimate the re- quired states for AOGL. Simulation results show the AOGL is less sensitive to errors caused by target maneuvering and guidance system lag, and it needs less missile acceleration in most time of guidance especially at the end of intercept than other guidance laws. Especially its acceleration is zero at the end of intercept when attacking maneuvering target.

Kinetic Optimal Midcourse Guidance Law for Air-to-Air Missiles

A new kinetic optimal midcourse guidance law is derived based on optimal control formulation. A new simplified Runge-Kutta grade numerical method is proposed to find the optimal trajectory. Real data of an Mr-to-air missile is referred to for comparing results using the kinetic optimal midcourse guidance law with those under both the kinematic optimal guidance law and singular perturbation sub-optimal guidance law, wherein the latter two laws are modified in this paper by adding a vertical g-bias command to each law for the sake of trajectory shaping. Simulation results show that using the new kinetic optimal mideourse guidance law can help save energy and maximize terminal velocity effectively.

An Algorithm for Robust Routing Strategies in Networks

In this article, the authors address the problem of optimal guidance of road network users. In the literature, several routing algorithms have been proposed under different approaches to solve this problem. Most adaptive algorithms for optimal path are based on the least expected travel time. Another approach has emerged named the SOTA （stochastic on time arrival）. This approach based on the idea of Frank （1969）, which aims to maximize the probability of arriving to a destination node parting from a given node in the network and with a given time budget. The authors＇ contribution consists here in extending this approach in order to introduce robustness towards path failure, in the guidance optimization. The authors propose a model that includes the existence as well as the performance of detours for selected paths, in the calculus of the travel time reliability. This new way of calculating travel time reliability guarantees a kind of robustness of the optimal guidance strategy.

Neighboring optimal guidance using higher-order dynamics approximation with application to orbital injection problem

Neighboring optimal guidance,a method to obtain a suboptimal guidance law by approximately solving the first-order necessary conditions based on a nominal trajectory,is widely used in the aerospace field due to its high computational efficiency and low resource usage.For more advanced scenarios,the existing methods still have a problem that the guidance accuracy and optimality will seriously degrade when the actual state largely deviates from the nominal trajectory.This is mainly caused by the approximate description of the first-order conditions in terms of total flight time and nonlinear constraints.To address this problem,a higher-order neighboring optimal guidance method is proposed.First,a novel total flight time updating strategy,together with a normalized time scale,is presented that transforms the optimal problem with free total flight time into a more tractable optimal problem with fixed total flight time.Then,using the vector partial derivative method,a higher-order approximation is adopted,instead of the first-order approximation,to accurately describe the nonlinear dynamical and terminal constraints,thus obtaining a polynomially constrained quadratic optimal problem.Finally,to numerically solve the polynomially constrained quadratic optimal problem,a Newton-type iterative algorithm based on the orthogonal decomposition is designed.Through the iterative solution within each guidance period,the corrections to control quantities and total flight time are generated.The proposed method is applied to a launch vehicle orbital injection problem,and simulation results show that it achieves high accuracy of orbital injection and optimality of performance index.

Optimal guidance against active defense ballistic missiles via differential game strategies

The optimal guidance problem for an interceptor against a ballistic missile with active defense is investigated in this paper.A class of optimal guidance schemes are proposed based on linear quadratic differential game method and numerical solution of Riccati differential equation.By choosing proper parameters, the proposed guidance schemes are able to drive the interceptor to the target and away from the defender simultaneously.Additionally, fuel cost, control saturation,chattering phenomenon and parameters selection were taken into account.Satisfaction of the proposed guidance schemes of the saddle point condition is proven theoretically.Finally, nonlinear numerical examples are included to demonstrate the effectiveness and performance of the developed guidance approaches.Comparison of control performance between different guidance schemes are presented and analysis.

Time-optimal guidance for intercepting moving targets with impact-angle constraints

The minimum-time path for intercepting a moving target with a prescribed impact angle is studied in the paper.The candidate paths from Pontryagin’s maximum principle are synthesized,so that each candidate is related to a zero of a real-valued function.It is found that the real-valued functions or their first-order derivatives can be converted to polynomials of at most fourth degree.As a result,each candidate path can be computed within a constant time by embedding a standard polynomial solver into the typical bisection method.The control strategy along the shortest candidate eventually gives rise to the time-optimal guidance law.Finally,the developments of the paper are illustrated and verified by three numerical examples.

A unified formulation of optimal guidance-to-collision law for accelerating and decelerating targets

This paper provides a unified formulation of optimal guidance-to-collision law for a target with an arbitrary acceleration or deceleration.The collision course for general target acceleration or deceleration is first determined from the engagement geometry in conjunction with the nonlinear engagement kinematics in the proposed approach.The heading error defined in the collision course is then adopted as a variable to be nullified for accomplishing the intercept condition.The proposed guidance law is derived based on the heading error dynamics and the optimal error dynamics to ensure optimality and finite-time convergence.As illustrative examples,the proposed guidance command for a constant target acceleration and a target deceleration in the form of a quadratic function of speed are provided.Additionally,the time-to-go prediction method is suggested for implementing the proposed method.The characteristics of the proposed guidance command are analytically investigated to provide insight into the proposed method.The key benefits of the proposed method lie in not producing unnecessary guidance commands near a target compared to other methods and ensuring optimality in guidance command even in the nonlinear engagement kinematics.Finally,numerical simulations are performed to validate the proposed method and to show our findings.

Optimal guidance of extended trajectory shaping

To control missile＇s miss distance as well as terminal impact angle, by involving the timeto-go-nth power in the cost function, an extended optimal guidance law against a constant maneuvering target or a stationary target is proposed using the linear quadratic optimal control theory.An extended trajectory shaping guidance（ETSG） law is then proposed under the assumption that the missile-target relative velocity is constant and the line of sight angle is small. For a lag-free ETSG system, closed-form solutions for the missile＇s acceleration command are derived by the method of Schwartz inequality and linear simulations are performed to verify the closed-form results. Normalized adjoint systems for miss distance and terminal impact angle error are presented independently for stationary targets and constant maneuvering targets, respectively. Detailed discussions about the terminal misses and impact angle errors induced by terminal impact angle constraint, initial heading error, seeker zero position errors and target maneuvering, are performed.

Aerial vehicle guidance based on passive machine learning technique

Purpose-The purpose of this paper is to develop a new guidance scheme for aerial vehicles based on artificial intelligence.The new guidance scheme must be able to intercept maneuvering targets with higher probability and precision compared to existing algorithms.Design/methodology/approach-A simulation setup of the aerial vehicle guidance problem is developed.A model-based machine learning technique known as Q-learning is used to develop a new guidance scheme.Several simulation experiments are conducted to train the new guidance scheme.Orthogonal arrays are used to define the training experiments to achieve faster convergence.A wellknown guidance scheme known as proportional navigation guidance(PNG)is used as a base model for training.The new guidance scheme is compared for performance against standard guidance schemes like PNG and augmented proportional navigation guidance schemes in presence of sensor noise and computational delays.Findings-A new guidance scheme for aerial vehicles is developed using Q-learning technique.This new guidance scheme has better miss distances and probability of intercept compared to standard guidance schemes.Research limitations/implications-The research uses simulation models to develop the new guidance scheme.The new guidance scheme is also evaluated in the simulation environment.The new guidance scheme performs better than standard existing guidance schemes.Practical implications-The new guidance scheme can be used in various aerial guidance applications to reach a dynamically moving target in three-dimensional space.Originality/value-The research paper proposes a completely new guidance scheme based on Q-learning whose performance is better than standard guidance schemes.

Optimal terminal-time determination for the ZEM/ZEV feedback guidance law with generalized performance index

This paper investigates a problem of determining the optimal terminal-time or time-to-go of the ZEM/ZEV(Zero-E ort-Miss/Zero-E ort-Velocity)feedback guidance law for a variety of orbital intercept or rendezvous maneuvers.A generalized ZEM/ZEV guidance problem,whose objective is to minimize a combination of the control energy and terminal time,is examined.Algebraic equations whose solution provides the optimal terminal-time of the orbital intercept/rendezvous problems are derived based on the optimal control theory.The e ectiveness of the proposed approach is demonstrated for various orbital maneuver problems.

Three-Dimensional Optimal Guidance with Lyapunov Redesign for UAV Interception

Three-dimensional guidance laws are designed to intercept non-maneuvering targets and maneuvering targets in this paper.An optimal control approach with constant or time-variant feedback gain is proposed for interception.The cost function is designed with considerations on energy-e±ciency and time-e±ciency in the transient process.Lyapunov redesign method is applied to treat the target acceleration,where the precise information of target accelerations is not necessarily required.E±cacy of the proposed guidance laws is proved theoretically and veri¯ed by simulation results.