Yoon-Hwan Kim

Three-Axis Autopilot Design for a High Angle-Of-Attack Missile Using Mixed H 2 /H ∞ Control

We report on the design of a three-axis missile autopilot using multi-objective control synthesis via linear matrix inequality techniques. This autopilot design guarantees H₂/H ∞ performance criteria for a set of finite linear models. These models are linearized at different aerodynamic roll angle conditions over the flight envelope to capture uncertainties that occur in the high-angle-of-attack regime. Simulation results are presented for different aerodynamic roll angle variations and show that the performance of the controller is very satisfactory.

Optimal UAV formation guidance laws with timing constraint

In this paper, optimal guidance laws for multiple vehicles formation flight are addressed. The proposed laws are obtained as state-feedback solutions of linear quadratic optimal control problems to minimize the time varying energy cost with terminal constraints on position and velocity. Since the proposed laws are able to control the flight time, they are possible to make all vehicles join the formation concurrently at a specified time. A method to compensate the acceleration or maneuver of the formation leader is included in the guidance laws. And an inter-vehicle collision avoidance scheme is also considered. The performance of the guidance laws is tested via various numerical simulations.

Composite Guidance Scheme for Impact Angle Control Against a Nonmaneuvering Moving Target

I N ADVANCED guidance law designs, impact angle control has been widely required to maximize the effect of thewarhead and to achieve a high kill probability. Since the first paper for impact angle control [1] was published, to the best of our knowledge, many guidance laws with impact angle constraint have been studied. Ryoo et al. [2] proposed a pure energy optimal guidance law with impact angle constraint. As an extension of this work, Ryoo et al. [3] proposed an optimal impact angle control guidance law minimizing the time-to-go weighted energy cost function. Lu et al. [4] developed three-dimensional guidance laws, which were based on proportional navigation (PN) with adaptive guidance parameters, to achieve impact angle requirements. Ratnoo and Ghose proposed a two-phase guidance law for capturing all possible impact angles against a stationary target [5] and a nonstationary nonmaneuvering target [6]. The proposed guidance law used PN with N < 2 for the initial phase to cover impact angles from zero to −π through an orientation trajectory and PNwithN ≥ 2 for the final phase to intercept the target with the desired impact angle. Erer andMerttopcuoglu [7] proposed a similar two-phase guidance law switching from biased PN to PN when the integral value of the bias met a certain value determined by engagement conditions. Most of research mentioned has focused on the impact angle as well as a zero terminal miss distance. The impact angle control, however, made the missile trajectory highly curved, which might have then missed the target within the seeker’s lookangle limit. Since this leads to the mission failure, it is very important to consider the missile’s physical constraints, such as the seeker’s look-angle and maximum acceleration limits. Recently, studies considering the look-angle limits as well as the impact angle have been carried out. Park et al. [8] proposed a composite guidance law comprising PN with N 1 to maintain the constant look angle and PNwithN ≥ 2 to intercept the target with the desired impact angle. In [9], the error feedback loop of the look angle was included in PN with N 1 for robustness and converging from the arbitrary look angle to the desired one. In [10], a pure energy optimal guidance lawwith an impact angle constraint and the seeker’s look-angle limit was developed using optimal control theory with state variable inequality constraint. Kim et al. [11] proposed a biasshaping method, based on the work in [7], to consider the look-angle and acceleration limits. Tekin and Erer [12] presented a two-phase guidance law with a numerical process for calculating navigation gains to handle the look-angle limits and acceleration constraints. Also, Erer et al. [13] proposed another two-phase guidance scheme to address the look-angle constraint problem, which can select an initial phase guidance lawbetween PNandbiasedPN.Ratnoo [14] dealt with a similar problem to [8] and showed analytic guarantees for achieving all impact angles with any finite field-of-view (FOV) limit. These works have been studied against stationary targets, so the impact angle errors may appear at the instant of interception if the guidance laws presented in [8–14] are applied to the case of moving targets. In this Note, a composite guidance scheme, studied in [8,9], is extended to the case of a nonmaneuvering moving target. The proposed guidance scheme is composed of modified deviated pure pursuit (DPP) with the error feedback loop of the look angle for the initial guidance phase and PN with N ≥ 3 for the final guidance phase: the first phase is to maintain the constant look angle of the seeker, and the second is to intercept themoving targetwith a terminal angle constraint. The switching of guidance phases occurs when satisfying a specific line-of-sight (LOS) angle determined by engagement conditions. Guidelines on the gain tuning of modified DPP and calculation of themaximumachievable impact angle, which is calculated by taking into account the seeker’s look-angle and maximum acceleration limits, are also investigated for guidance designers.

3-D Biased PNG for Evasive Maneuver of Anti-Ship Missiles Against CIWS

Abstract In this paper, we propose advanced guidance laws for anti-ship missiles to enhance the survivability against ship-borne close-in weapon system in 3-dimensional space. The proposed guidance laws consist of a term of pure proportional navigation guidance to guarantee homing to target and a time varying bias term to cause evasive maneuver. As a time varying bias term, barrel-roll maneuvers are investigated. By using the Lyapunov stability theory, we prove the capturability of the proposed guidance laws against a non-maneuvering target. Evasion performance of the proposed guidance laws is compared to pure proportional navigation guidance via simulations.

Integrated Roll-Pitch-Yaw Autopilot Design for Missiles

An roll-pitch-yaw integrated autopilot for missiles is designed for compensation of dynamics coupling. The proposed autopilot is based on the classical control technique. The gains of the proposed autopilot are optimized by using co-evolutionary augmented Lagrangian method(CEALM). Several cost functions are compared in order to find feasible control gains. For a case that a bank angle of missiles is unknown, multiple models are used in the autopilot optimization. In nonlinear simulations as well as linear simulations, the proposed autopilot provided good performances.

Covariance analysis of spacecraft attitude control system

The covariance analysis is applied to the performance of spacecraft attitude control systems. Subsystem considered here are the spacecraft bus, attitude controller, reaction wheel assembly, star-tracker unit, inertial reference unit, and gyro drift estimator. The results computed by the covariance analysis are compared with the results computed by the Monte-Carlo simulation. The covariance analysis is shown to be useful for studying the effects of system parameters on attitude control performance.

Stability Analysis of Missiles with Strapdown Seeker

A missile with a strapdown seeker should properly estimate line-of-sight(LOS) rate using its attitude information and the look angle of the seeker because LOS rate information in an inertial coordinate system, which is used for a proportional navigation(PN) homing guidance, can not be obtained directly. However, an unnecessary feedback loop(Parasite Loop) is formed in the guidance and control loop, and it may cause the guidance performance degradation or even the unstability of the system(Parasite Effect). This paper presents estimation methods for the LOS rate information and effective ways to minimize the parasite effect using Routh-Hurwitz stability criterion. Various numerical simulations are also included to verify the proposed methods.

Capturability Analysis of PN Laws Using Lyapunov Stability Theory

The Lyapunov stability theory has been known inadequate to prove capturability of guidance laws because the equations of motion resulted from the guidance laws do not have the equilibrium points. By introducing a proper transformation of the range state, the original equations of motion for a stationary target can be converted into nonlinear equations with a specified equilibrium subspace that denotes the direction of missile velocity to the target. Applying the single Lyapunov function candidate to several PN laws, we show that either the equilibrium subspace is asymptotically stable or the nonlinear system is ultimately bounded. In our approach, there is no assumption of the constant speed missile. The proposed method is expected to provide a unified and simple scheme to prove the capturability of various guidance laws. Nomenclature ,, mm m rV a G G G = position, velocity, and acceleration vector of the missile r G = relative range vector from the target to the missile c r = specified radius of the sphere surrounding the target 0 r = initial range from the target to the missile s = 2 () c rr − V = Lyapunov function candidate , LL ψθ = azimuth and elevation angle of the LOS to the inertial reference frame , mm ψθ = azimuth and elevation angle of the missile velocity to the LOS reference frame BR ω = barrel-roll frequency

An Effectiveness Analysis of Anti-Ballisitic Missile Launcher Arrangement for the Lower Tier Defense against the Ballistic Missile

For a lower tier defense, the distance between a launcher and an engagement control station is quite important to estimate the proper defense area and to effectively arrange missile launchers. In this paper, we have analyzed an effectiveness of anti-ballistic missile launcher arrangement for the lower tier defense against the ballistic missile. The operation concept, specific configuration and aerodynamic characteristics of the ballistic missile such as SCUD-B/C, Nodong are considered in order to develop a realistic engagement simulation. The diverse engagement results through numerical simulations are provided to conduct the effectiveness analysis of anti-ballistic missiles.

Biased PNG with maximal-g barrel-roll for survivability enhancement of anti-ship missiles

In this paper, a guidance law for anti-ship missiles to enhance the survivability against ship-borne close-in weapon systems (CIWS) is investigated. As an evasive maneuver of the missile, a barrel-roll maneuver with a time-varying barrel-roll frequency is introduced. The barrel-roll frequency is determined to use all possible energy of the missile. The capturability of the proposed guidance law is proved by using the Lyapunov-like approach. Being compared with the biased PNG with a constant barrel-roll frequency, the proposed guidance law provided better evasion performance against CIWS.