Terminal Homing Phase Research Articles

탐색기 시야각 제한을 고려한 장거리 공대공 유도탄의 중기 궤적최적화

This paper describes a midcourse trajectory optimization for long-range missiles with a seeker field-of-view limit. Trajectory optimization is performed using convex programming, which is effective for real-time applications. Field-of-view limit, minimum dynamic pressure, and angle-of-attack limit are considered as path constraints. The terminal velocity is used as a performance index to ensure maneuverability in the terminal homing phase. The discontinuity of dynamics at the end of boost time is solved by separating the flight phase into a boost phase and a glide phase. The nonlinear dynamics are converted to input affine form using new input variables and partially linearized. The admissible input set is relaxed into a convex set through lossless convexification. Slack variables are introduced in the quadratic trust region and linearized path constraint, where they are augmented into the performance index for robust convergence. The transformed dynamics are discretized through a pseudo-spectral method and optimal trajectory is obtained using sequential convex programming. The effectiveness and robustness of the proposed method are verified through numerical simulation.

Rapid Homing Guidance Using Jerk Command and Time-Delay Estimation Method

For certain engagements against small and fast-moving targets at higher altitude, an available total flight time during the terminal homing phase is short due to the limited performance of onboard seekers to detect and track the target, and the autopilot performance of an aerodynamically controlled missile can degrade due to low air density and low dynamic pressure. To increase the lethality of warheads, sometimes terminal zero acceleration, corresponding to zero angle of attack at the instant of interception, is also required. This article proposes a new rapid homing guidance law, which can achieve the terminal zero miss-distance and zero-acceleration response under these severe engagements mentioned earlier. For deriving state feedback form commands that can be implemented to arbitrary order autopilot systems, the polynomial-function-based guidance design method and time-delay estimation method are adopted by introducing a jerk command and more general autopilot dynamics. The characteristics and performance of the proposed guidance law are demonstrated by performing various numerical linear simulations and adjoint simulations, including model uncertainties.

Underwater Docking Approach and Homing to Enable Persistent Operation.

One of the main limiting factors in deployment of marine robots is the issue of energy sustainability. This is particularly challenging for traditional propeller-driven autonomous underwater vehicles which operate using energy intensive thrusters. One emerging technology to enable persistent performance is the use of autonomous recharging and retasking through underwater docking stations. This paper presents an integrated navigational algorithm to facilitate reliable underwater docking of autonomous underwater vehicles. Specifically, the algorithm dynamically re-plans Dubins paths to create an efficient trajectory from the current vehicle position through approach into terminal homing. The path is followed using integral line of sight control until handoff to the terminal homing method. A light tracking algorithm drives the vehicle from the handoff location into the dock. In experimental testing using an Oceanserver Iver3 and Bluefin SandShark, the approach phase reached the target handoff within 2 m in 48 of 48 tests. The terminal homing phase was capable of handling up to 5 m offsets with approximately 70% accuracy (12 of 17 tests). In the event of failed docking, a Dubins path is generated to efficiently drive the vehicle to re-attempt docking. The vehicle should be able to successfully dock in the majority of foreseeable scenarios when re-attempts are considered. This method, when combined with recent work on docking station design, intelligent cooperative path planning, underwater communication, and underwater power transfer, will enable true persistent undersea operation in the extremely dynamic ocean environment.

A Novel Integral Sliding Mode-Type Continuous Guidance Law With Autopilot Lag for Intercepting Non-Cooperative Maneuvering Targets

This paper proposes an integral sliding mode guidance law with the constraints of the line-of-sight angle and its rate for the interception of a non-cooperative maneuvering target. The analytical guidance law is derived using an integral sliding mode control and an inertial delay control allowing for unknown uncertainties. The guidance law is further advanced to achieve exponential convergence and high terminal guidance accuracy with autopilot lag. This is accomplished by applying dynamic surface control and fractional order filters. Finally, the finite-time stability of the guidance law with and without missile autopilot lag is demonstrated. In addition to its robustness and precision, there are other benefits of this proposed guidance law. First, the proposed guidance law can effectively attenuate an abrupt change in guidance commands during the terminal homing phase in the presence of uncertainties without prior information. Second, the design parameters in the inertial delay control are decoupled with the integral sliding mode control. This decoupling supplies more degrees of freedom to regulate the performance of guidance commands. Third, the finite-time convergence of the proposed guidance law is guaranteed while accounting for the approximated second-order dynamics and uncertainties of the missile autopilot. Theoretical analysis and numerical simulations were conducted to demonstrate the efficiency of the proposed guidance law.

Two-Dimensional Continuous Terminal Interception Guidance Law With Predefined Convergence Performance

This paper derives a new terminal homing guidance law for missiles to intercept non-cooperative maneuvering targets subject to the constraint of terminal line-of-sight angle. The new guidance law avoids abrupt and large changes in guidance commands, while allows the control gains to be determined analytically or chosed loosely to ease the design of guidance law. This is achieved by combining the advantages of sliding mode, prescribed performance, and inertial delay controllers. The prescribed performance controller is designed by a new two-phased prescribed performance function with an improved continuous dynamic property, which drives the predefined state error-based sliding mode variable to a small residual set around zero. The inertial delay controller is adopted to suppress the system uncertainty. Thus, the new guidance law yields continuous guidance commands over the entire terminal homing phase while eliminating abrupt and large changes in the initial phase, resulting from the initial state errors in the prescribed performance function. The newly proposed guidance law improves the prescribed performance control that dominates the gains of the proposed guidance law. Theoretical analyses and numerical simulations are conducted to verify the robustness and preciseness of the proposed guidance law.

Prescribed performance interceptor guidance with terminal line of sight angle constraint accounting for missile autopilot lag

A prescribed performance guidance law during the terminal homing phase is proposed to intercept a non-cooperative maneuvering target in this paper. First, on the basis of sliding mode control, a prescribed performance control method based on a revised prescribed performance function is proposed to drive the sliding mode variable to zero. It leads to smooth guidance commands to fulfill the terminal line of sight angle constraint. Then, taking the autopilot's dynamics and its uncertainties into account, a robust controller is designed using dynamic surface control, sliding mode control and inertial delay control, which guarantees the reference guidance commands to be precisely tracked. The highlights of the proposed guidance law are: 1) the transient performance of guidance commands is improved, so that excessive large changes are avoided in the initial phase, 2) parameters that dominant the convergence of the predetermined sliding mode variable can be analytically determined based on the predesigned terminal tolerance, it is more convenient to achieve the prescribed convergence, 3) although uncertainties are existing in the dynamics of missile autopilot, the proposed guidance law could guarantee the terminal interception accuracy. All of the improvements are shown in numerical simulation results.

Prescribed performance slide mode guidance law with terminal line-of-sight angle constraint against maneuvering targets

This paper proposes a new terminal homing guidance law with line-of-sight angle constraint for a missile to intercept a noncooperative maneuvering target by integrating prescribed performance control with sliding mode control. The newly proposed guidance law is derived analytically with a prescribed performance controller in combination with the continuous nonsingular terminal sliding mode manifold and the disturbance observer. The prescribed performance controller is designed with a new prescribed performance function to avoid undesired abrupt change in the derivative of prescribed performance variable. In addition to its robustness and preciseness, this new homing guidance law is able to attenuate a largely abrupt change in guidance commands due to driving the sliding mode variable whose initial derivative is close to zero to a desired residual set at the beginning of the terminal homing phase. Furthermore, the time-varying control gain of the new guidance law is analytically determined by terminal tolerance. Theoretical analysis and numerical simulations are conducted to demonstrate the effectiveness of this new guidance law.

Differential Game Guidance Law for Interceptor Missiles with a Time-varying Lateral Acceleration Limit

A guidance law for an interceptor missile with a time-varying lateral acceleration limit is developed using differential games formulation with bounded controls. If an interceptor has axial acceleration and its lateral acceleration is generated by the aerodynamic lift, its lateral acceleration limit will vary with time due to its time-varying speed and the air density varying with altitude. This time-varying lateral acceleration limit property can also be obtained by designs of the time-varying sum of jets’ thrust when the interceptor is steered by divert reaction jets. The effect of this time-varying limit is investigated in this paper. The results indicate that the time-varying design of this limit leads to cooperation between the mid-course and terminal homing phase, and yields an improvement in homing accuracy. The effectiveness of this guidance law is demonstrated in a realistic ballistic missile defense scenario. It is shown that the proposed guidance law guarantees admissible accuracy, and is robust for the target maneuver commands and the delay in the estimation process of the target maneuvers. Furthermore, it provides better homing performance compared to the conventional law if the estimation delay is longer than a certain degree.

Cooperative Missile Guidance Strategies for Maritime Area Air Defence

Mid-course guidance phase classically refers to the procedure guiding the missile to a terminal handover point in order to acquire the target motion through its on-board sensor. The mid-course guidance law differs significantly from the guidance logic for the terminal homing phase due to the inherited characteristic of the midcourse guidance: it must not only find the best condition for the terminal homing phase, but also deliver the missile to that condition using only the target motion data updated by the external source such as a plane, ship, or ground base. In this paper we revisit the micourse guidance problem for maritime area air defense by mixing two contributions (one for mid course guidance law design and one for target allocation). The proposed solution is based on differential games (capturability considerations) for allocation of the missiles. The main idea is that a cooperative mid-course guidance strategy can defend the area as long as it assures that the depending area is always inside the defended area defined by earliest intercept geometry.

A Guidance Law with a Switching Logic for Maintaining Seeker's Lock-on for Stationary Targets

Modem anti-ship missiles employ complex and sophisticated guidance laws to hit the target and enhance their survivability by executing additional maneuvers. However, such maneuvers may cause the target to move out of the missile seeker's Field-Of-View (FOV). Maintaining seeker lock-on during an engagement is a critical factor for missile guidance. In this paper, a guidance law switching logic that maintains seeker lock-on and a simple guidance law that keeps the target look angle of the seeker constant is proposed. The proposed method can be used for the terminal homing phase, and can be switched from any kind of guidance laws if a proper switching condition is satisfied. The minimum and maximum flight time calculation method in consideration of the missile maneuver limit and the FOV of the seeker is also provided.

Using a Multiple-Model Adaptive Estimator in a Random Evasion Missile/Aircraft Encounter

The terminal phase (end game)of an encounter between an air-to-air missileequipped with an activemonopulse radar seeker and an evading e ghter aircraft, possibly employing electronic countermeasures in the form of electronic jinking, is addressed. The missile uses a guidance law derived from linear differential game theory, which is implemented by using a multiple-model adaptiveestimator (MMAE). TheMMAE identie es theevasion strategy of theaircraft, which consists of thecombination of evasion maneuverand electronic jinking. An extensivenumerical study is used to demonstrate the viability of the concept. In comparison with a previously proposed mixed strategy guidance methodology, the new MMAE-based approach leads to a substantial improvement in the guaranteed single-shot kill probability for the missile. ODERN air-to-air missiles, designed to intercept highly maneuverable aircraft equipped with electronic countermeasures (ECM), have to operate in a highly uncertain environment. This paper is concerned with the terminal phase (end game) of an encounter between a missile equipped with an active monopulse radar seeker and an evading e ghter aircraft having the option to use ECM. The terminal homing phase of the interception starts when the active seeker of the missile locks on its target, generating also a warning signal (including some threat identie cation ) in the aircraft. This warning is the only information the pilot has. At the moment when the warning is received, the pilot starts to execute a sequence ofperiodicalevasivemaneuvers.Simultaneously,toenhanceitssur

Trajectory Optimization for a Missile Using a Multitier Approach

A two-tier approach to the midcourse trajectory design for a surface-to-air missile to maximize the probability of hit is presented. The e rst tier represents the midcourse trajectory of the missile, and the second tier represents the terminal homing phase. The e rst-tier trajectory is optimized with an auxiliary constraint on the value of the approach angle to the intercept at handover to the terminal phase. The handover approach angle is used as the governing parameter in generating a e eld of optimum e rst-tier midcourse trajectories. The second-tier model estimates the probability of hit including a full suite of stochastic error sources on the seeker and missile. The optimal approach angleand midcoursetrajectory aredemonstrated to bedependent on the terminal homing noise contributors and the target maneuver.

An initial assessment of discriminant surface complexity for power law features

The detection of man-made objects in natural terrain is important in both the targeting and terminal homing phase of modern warfare. The presence of man-made objects in gray-scale images has been successfully detected using a new class of density estimation neural networks to analyze power law signatures. The complex nature of the discriminant surface relating these features has been elucidated using these adaptive mixture networks.