Air-to-Air Combat Tactics Synthesis and Analysis Program Based on an Adaptive Maneuvering Logic

Abstract

Two digital computer programs synthesizing optimal maneuvers in one-on-one air-to-air combat situations are described. The method develops intelligently interactive maneuvers without relying on human pilot experience. One program drives one of the interacting aircraft, thus replacing one of the human pilots on the NASA Langley Research Center's Differential Maneuvering Simulator, this in real time. The other program operates in a normal batch processing mode. Both programs use the same technique which maps the physical situation of the two aircraft into a quantized, abstract situation space. The outcome in this situation space is predicted for several trial maneuvers, a value is associated with the outcome of each trial maneuver, and finally, the maneuver with the highest predicted value is executed.

These programs, operating with six degrees of freedom and realistic aerodynamic representation for both aircraft, provide a means for objective evaluation of weapons systems and pilot performance.     

基于Hamilton-Jacobi方程的飞行器机动动作可达集分析

为了给驾驶员完成标准机动动作提供决策支持, 提出一种使用哈密尔顿-雅克比(Hamilton-Jacobi)方程求解机动动作可行状态空间的研究方法.使用关键点将机动动作划分为不同阶段, 将各关键点的标准状态约束作为目标集, 逆时间求解目标集对应的可达集得到各阶段的边界状态范围, 目标集和可达集均由零水平集表示.使用该方法得到斤斗动作三维度运动模型下各阶段的可达集及斤斗动作的可行状态空间, 为了使运动模型的控制量与驾驶员实际操纵更为接近, 构建了以迎角变化率为控制量的四维度运动模型, 在此基础上对斤斗动作各阶段的可达集进行了分析.     

Low cost IMU–Odometer–GPS ego localization for unusual maneuvers

This paper presents the problem of outdoor vehicle localization during unusual maneuvers with the Interacting Multiple Model (IMM) and Extended Kalman Filter (EKF) approaches. IMM, contrary to classical methods, is based on the discretization of the vehicle evolution space into simple maneuvers. Each maneuver is represented by a simple dynamic model such as a constant velocity or a constant turning model. This allows the method to be optimized for highly dynamic vehicles. In this work, we focus on unusual vehicle maneuvers during some special driving situations, including very strong accelerations, high speed turnings or backwards driving with stop stages. The presented results are based on real measurements collected from different scenarios. Based on an EKF vs. IMM comparison, these results show a real interest of using the IMM method in order to take into account unusual maneuvers.     

Visualizing complexities: the human limits of air traffic control

Air traffic management is organized into filters in order to prevent tactical controllers from dealing with complex conflicting situations. In this article, we describe an experiment showing that a dynamic conflict display could improve human performance on complex conflict situations. Specifically, we designed a display tool that represents the conflicting portions of aircraft trajectories and the evolution of the conflict zone when the user adds a maneuver to an aircraft. The tool allows the user to dynamically check the potential conflicting zones with the computer mouse before making a maneuver decision. We tested its utility on a population of forty students: twenty air traffic controller (ATC) students at the end of their initial training and twenty engineering students with the same background but no ATC training. They had to solve conflicts involving 2–5 aircraft with a basic display and with the dynamic visualization tool. Results show that in easy situations (2 aircraft), performance is similar with both displays. However, as the complexity of the situations grows (from 3 to 5 aircraft), the dynamic visualization tool enables users to solve the conflicts more efficiently. Using the tool leads to fewer unsolved conflicts and shorter delays. No significant differences are found between the two test groups except for delays: ATC students give maneuvers that generate less delays than engineering students. These results suggest that humans are better able to manage complex situations with the help of our conflict visualization tool.     

Variable Load Factor Guidance for Low-Altitude Fly-to-Point Maneuvers of a Jet Fighter Aircraft

This paper describes the formulation andnumerical investigation of a variable load factor guidance algorithm(variable n-guidance) that allows an aircraft pilotto approximate minimum-time low-altitude quasi-level fly-to-pointmaneuvers of a jet fighter aircraft. The maneuvers studied consistof flight to a point at a radial distance of 50 kft from thestarting point, with the final position vector oriented at 45,90, 135, 180 deg from the initial course and with the requirementthat the initial and final altitudes be the same.First, the fly-to-point maneuver is optimized from the time viewpointwith respect to three controls (angle of attack, power setting,angle of bank) via the sequential gradient-restoration algorithm.Then, from the study of the optimal trajectories, a variablen-guidance algorithm is developed, connecting theload factor to the turn-to-go. This algorithm is implementedvia feedback control and tested. For comparison purposes, a constantn-guidance scheme is also tested. The main conclusionis that the variable n-guidance algorithm producestrajectories that approximate closely the optimal trajectories.On the other hand, the constant n-guidance schemedoes not approximate well the optimal trajectories.     

拦截机动目标的范数型协同微分对策制导律

针对多个拦截弹协同拦截单个机动目标的情况,提出了一种范数型的协同微分对策制导律。在拦截弹和目标的控制系统均具有理想动力学特性且法向加速度均有界的条件下,对追逃对策问题进行分析,建立了线性化的多对一追逃对策运动模型,基于微分对策理论选取范数型的性能指标,推导得出了一种具有"bang-bang"结构的最优制导策略。上述制导律无需预先对目标的机动规律做假设,且可避免出现因加速度饱和而导致制导律失去最优性的现象。最后通过对拦截多种机动形式的目标进行仿真,验证了上述方法的有效性。     

Two-dimensional merging path generation using model predictive control

A merging path generation method for automated vehicle merging is proposed. This method can make the relevant vehicles cooperate with each other with constraint accelerations, keep the vehicles in their lanes and generate collision free merging path. The merging problem is considered in the two-dimensional space. We set up the mathematic model of the system, formulate the two-dimensional merging problem as an optimization problem and solve it by model predictive control (MPC). To compare the simulation results with the practice, three typical cases were researched. In order to be more practical, the initial conditions of the cases were set according to the data obtained through analyzing the helicopter-shot video. The results represent that the MPC-controlled merging maneuver carried out safely and smoothly, and the relative positions after merging is also the same with the practical results in all the three representative conditions considered. The absolute values of the accelerations of the vehicles are all kept below a practical value 3 m/s². The importance of cooperation in merging maneuver can also be noticed in the simulation results. By letting the relevant vehicles cooperate, this control algorithm would generate collision free merging path even in the very severe condition. The computational time for the three cases is also short enough for the method to be implemented in actual situation.     

Nonlinear Adaptive Close Formation Control of Unmanned Aerial Vehicles

This paper treats the question of formationflight control of multiple unmanned aerial vehicles (UAVs). Inclose formation the wing UAV motion is affected by the vortexof the adjacent lead aircraft. The forces produced by these vorticesare complex functions of the relative position coordinates ofthe UAVs. In this paper, these forces are treated as unknownfunctions. For simplicity, it is assumed that the UAVs have autopilotsfor heading-, altitude-, and Mach-hold in the inner loops. Anadaptive control law is derived for the position control of thewing aircraft based on a backstepping design technique. In theclosed-loop system, commanded separation trajectories are asymptoticallytracked by each wing aircraft while the lead UAV is maneuvering.It is seen that an overparametrization in the design is essentialfor the decentralization of the control system. These resultsare applied to formation flight control of two UAVs and simulationresults are obtained. These results show that the wing UAV followsprecisely the reference separation trajectories in spite of theuncertainties in the aerodynamic coefficients, while the leadaircraft maneuvers.     

Online safety calculations for glide-slope recapture

As unmanned aerial vehicles (UAVs) increase in popularity and usage, an appropriate increase in confidence in their behavior is expected. This research addresses a particular portion of the flight of an aircraft (whether autonomous, unmanned, or manned): specifically, the recapture of the glide slope after a wave-off maneuver during landing. While this situation is rare in commercial aircraft, its applicability toward unmanned aircraft has been limited due to the complexity of the calculations of safety of the maneuvers. In this paper, we present several control laws for this glide-slope recapture, and inferences into their convergence to the glide slope, as well as reachability calculations which show their guaranteed safety. We also present a methodology which theoretically allows us to apply these offline-computed safety data to all kinds of unmanned fixed-wing aerial vehicles while online, permitting the use of the controllers to reduce wait times during landing. Finally, we detail the live aircraft application demonstration which was done to show feasibility of the controller, and give the results of offline simulations which show the correctness of online decisions at that demonstration.This work was sponsored by the Large National Science Foundation Grant for Information Technology Research (NSF ITR) ‘‘Foundations of Hybrid and Embedded Software Systems’’, Award #0225610, and by Defense Advanced Research Projects Administration (DARPA) ‘‘Software Enabled Control’’ (SEC) Program, under contract #F33615-98-C-3614.     

Decentralized nonlinear robust control of UAVs in close formation

This paper treats the design of a decentralized nonlinear robust control system for formation flying of multiple unmanned aerial vehicles (UAVs). In close formation, it is assumed that vortex of any UAV affects the motion of all the UAVs behind it. The forces produced by these vortices are complex functions of relative position co‐ordinates of the UAVs. In this paper, these forces are treated as unknown functions, which cannot be parameterized. Since the system is not invertible in the wind axes system, a simplified co‐ordinate system obtained from the wind axes system for which the velocity roll (bank angle) is zero, is considered for the design of the control system. A nonlinear robust control system for the separation trajectory control of the wing aircraft in the simplified wind coordinate system is derived. Uncertain functions and unmeasured variables are estimated using a high‐gain observer for the synthesis of the control system. Each wing UAV synthesizes its control law using its own state variables and the relative position of the preceding UAV with respect to the wing UAV. Thus the control system is decentralized since each UAV has to communicate (depending on sensors for position measurement) with at most one (preceding) UAV, and no data transmission from the remaining vehicles is required. Simulation results for two UAVs are presented which show precise separation trajectory control of each wing UAV in spite of the presence of unknown and unstructured vortex forces, while the lead aircraft maneuvers. Furthermore, these results confirm that when the wing aircraft is positioned properly in the vortex of the lead aircraft, it experiences reduction in its required flight power. Copyright © 2003 John Wiley & Sons, Ltd.     

Communication free leader–follower formation control of unmanned aircraft systems

This paper proposes a formation control strategy for unmanned aircraft under which there is no need to information exchange among aircraft. Based on the measurement of relative information such as distances and orientations obtained from practical sensors, the formation is realized by employing the feedback linearization approach. By considering the leader maneuver to be unknown, a nonlinear estimator is designed and the stability of the combined controller–estimator is guaranteed. Simulation results confirm the effectiveness of the proposed formation flight control strategy.     

Dynamics and control of a spatial disorientation trainer

Modern combat aircraft can fly at unusual orientations. The spatial disorientation trainer (SDT) examines a pilot's ability to recognise these orientations, to adapt to unusual positions and to persuade the pilot to believe in the aircraft instruments for orientation and not in his own senses. The SDT is designed as a four-degree-of-freedom (4DoF) manipulator with rotational axes. Through rotations about these axes, different orientations can be achieved; different acceleration forces acting on the pilot can also be simulated. In this paper, a control algorithm of an SDT that improves the quality and safety of the SDT motion while improving position accuracy and reducing servo errors is proposed. This control algorithm uses approximate inverse dynamics based on the recursive Newton–Euler algorithm, which accounts for the motors present in the system; it calculates motor torques, as well as the forces and moments acting on the SDT links based on the achievable velocities and accelerations of the robot links. This algorithm enables accurate dimensioning of the axes bearings and links as well. The maximum possible accelerations of the SDT links are calculated in each interpolation period based on the total moments of inertia for the axes of rotation of these links, mutual influences of the link accelerations on each other, and motor capabilities. The forces, moments and torques that act on the SDT links obtained with the suggested algorithm have lower magnitude and smoother profile. In this study, the forces and angular velocities that act on the simulator pilot in the SDT are calculated along with the roll and pitch angles of the gondola for these forces.     

Input–output invertibility and sliding mode control for close formation flying of multiple UAVs

This paper treats the question of invertibility of input–output maps and the design of a robust control system for formation flying of multiple unmanned aerial vehicles (UAVs). In close formation, the wing UAV motion is affected by the vortex of the adjacent lead aircraft. The forces produced by these vortices are complex functions of relative position coordinates of the UAVs. In this paper, these forces are treated as unknown functions. For trajectory tracking, invertibility of certain input–output maps in the wind axes system are examined. Interestingly, in the wind axes system, the system is not invertible, but in a simplified co‐ordinate system obtained from the wind axes system for which the velocity roll is zero, inverse control of separation co‐ordinates is possible. Variable structure control laws are derived for separation trajectory control of wing aircraft in the simplified wind co‐ordinate system and for the flight control of the lead aircraft. Simulation results for two UAVs are presented which show precise separation trajectory control in spite of the presence of unknown vortex forces, while the lead aircraft maneuvers. Furthermore, these results confirm that when the wing aircraft is positioned properly in the vortex of the lead aircraft, there is a reduction in the required flight power. Published in 2000 by John Wiley & Sons, Ltd.     

Pre-LOI trajectory maneuvers of the CHANG’E-2 libration point mission

This paper addresses pre-LOI (before Lissajous orbit insertion) trajectory maneuvers for the libration point mission of CHANG’E-2,which is the first Chinese satellite to fly to the Sun-Earth L2 libration point and the first satellite ever to fly to the L2 point from lunar orbit.First,a transfer trajectory for the mission is designed based on InterPlanetary Superhighway theory under the constraint of the remaining propellant,TT&C (telemetry,track and command) and sunlight conditions.The effects of trajectory maneuver errors on the mission are also analyzed.Second,based on the analysis results,the article investigates the trajectory maneuver schemes for the lunar escape and transfer trajectory maneuvers employing mathematical models and operational strategies.The mission status based on our maneuver schemes is then presented,and the results of control operation and corresponding analysis are provided in detail.Finally,the future trajectory maneuver in the Lissajous orbit is discussed.According to the analysis of the CHANG’E-2 TT&C data,the trajectory maneuver schemes proposed in the article work properly and efficiently.     

Vision Based Control for Fixed Wing UAVs Inspecting Locally Linear Infrastructure Using Skid-to-Turn Maneuvers

The following paper proposes a novel application of Skid-to-Turn maneuvers for fixed wing Unmanned Aerial Vehicles (UAVs) inspecting locally linear infrastructure. Fixed wing UAVs, following the design of manned aircraft, commonly employ Bank-to-Turn maneuvers to change heading and thus direction of travel. Whilst effective, banking an aircraft during the inspection of ground based features hinders data collection, with body fixed sensors angled away from the direction of turn and a panning motion induced through roll rate that can reduce data quality. By adopting Skid-to-Turn maneuvers, the aircraft can change heading whilst maintaining wings level flight, thus allowing body fixed sensors to maintain a downward facing orientation. An Image-Based Visual Servo controller is developed to directly control the position of features as captured by onboard inspection sensors. This improves on the indirect approach taken by other tracking controllers where a course over ground directly above the feature is assumed to capture it centered in the field of view. Performance of the proposed controller is compared against that of a Bank-to-Turn tracking controller driven by GPS derived cross track error in a simulation environment developed to replicate the field of view of a body fixed camera.     

Optimal transition maneuvers for a class of V/STOL aircraft

This paper focuses on the problem of computing optimal transition maneuvers for a particular class of tail-sitter aircraft able to switch their flight configuration from hover to level flight and vice versa. Both minimum-time and minimum-energy optimal transition problems are formulated and solved numerically in order to compute reference maneuvers to be employed by the onboard flight control system to change the current flight condition. In order to guide the numerical computation and to validate its results, in a first stage approximated solutions are obtained as a combination of a finite number of motion primitives corresponding to analytical trajectories of approximated dynamic models. The approximated solution is then employed to generate an initial guess for the numerical computation applied to a more accurate dynamic model. Numerical trajectories computed for a small scale prototype of tail-sitter aircraft are finally presented, showing the effectiveness of the proposed methodology to deal with the complex dynamics governing this kind of systems.     

Analysis of a station-keeping maneuver strategy for collocation of three geostationary satellites

A collocation strategy has been planned and analyzed for three geostationary satellites in the same longitude control box. The orbit determination error analysis is performed when only one ground station is used for the angle tracking and ranging. Based on the orbit determination errors, the station-keeping bands are allocated for seven-day East/West and 14-day North/South station-keeping maneuver cycles. The eccentricity control circle and inclination control box for individual satellites are allocated for the collocation. The eccentricity vector and inclination vector separation method is applied for the collocation, and the maneuver schedule is planned to minimize the operational load by avoiding simultaneous maneuvers. A total of fourteen weeks of station-keeping maneuvers are performed for three KOREASAT satellites, collocated in 116°E±0.05° longitude band.     

Pilot maneuver choice and workload in free flight

Two experiments examined pilots' maneuver choice and visual workload in a free-flight simulation. In Experiment 1, 12 pilots flew a high-fidelity flight simulator with a cockpit display of traffic information and maneuvered to avoid traffic in a simulated free-flight environment. Pilots' choices reflected a preference to make vertical rather than lateral avoidance maneuvers and to climb rather than descend. Pilots avoided both complex maneuvers and airspeed maneuvers. The data were modeled in terms of how pilots traded off factors related to safety, efficiency, mental effort, and prior habits. In Experiment 2, 10 pilots flew the same maneuvers as the pilots in Experiment 1 but followed ATC instructions rather than using the CDTI. The CDTI in Experiment 1 occupied 25% of the pilots' visual attention. A comparison of scanning with Experiment 2 suggested that the CDTI pulled visual attention away from the outside world, but this attention diversion did not leave pilots vulnerable to missing traffic not annunciated on the CDTI. Actual or potential applications of the results include understanding the safety implications of presenting traffic displays in the cockpit, and the impact of pilot maneuver preferences on airspace procedures.     

An output feedback nonlinear decentralized controller for unmanned vehicle co‐ordination

This paper presents vision‐based control strategies for decentralized stabilization of unmanned vehicle formations. Three leader–follower formation control algorithms, which ensure asymptotic co‐ordinated motion, are described and compared. The first algorithm is a full state feedback nonlinear controller that requires full knowledge of the leader's velocities and accelerations. The second algorithm is a robust state feedback nonlinear controller that requires knowledge of the rate of change of the relative position error. Finally, the third algorithm is an output feedback approach that uses a high‐gain observer to estimate the derivative of the unmanned vehicles' relative position. Thus, this algorithm only requires knowledge of the leader–follower relative distance and bearing angle. Both data are computed using measurements from a single camera, eliminating sensitivity to information flow between vehicles. Lyapunov's stability theory‐based analysis and numerical simulations in a realistic 3D environment show the stability properties of the control methodologies. Copyright © 2007 John Wiley & Sons, Ltd.     

A Novel LQG Controller of Active Suspension System for Vehicle Roll Safety

To improve vehicle roll safety during steering operation at high running speed, a new design approach for Linear Quadratic Gaussian (LQG) controller of active suspension system is proposed. Key steps of the new approach are as follows: 1) The front axle steered angle is written into a differential equation in accord with the minimum phase system and combines with the original system into the augmented system equation; 2) positive infinitesimals respectively including controls are added to the index; Thirdly, weights of the evaluating indicators of the LQG controller are determined by using analytic hierarchy process (AHP) and normalization methods based on vehicle motion statistics under the double-lane change maneuver as the typical steering maneuver. Performance comparisons are implemented between the active suspension system and the passive one under the double-lane change, slalom and fish-hook maneuvers. Results verify that the active suspension system with the proposed controller can achieve better vehicle roll safety and has a good adaptability under different steering maneuvers.