Dongsoo Cho

Nonsingular Sliding Mode Guidance for Impact Time Control

A guidance problem for impact time control applicable to salvo attacks is considered based on the sliding mode control. To prevent the singularity of the guidance command, a positive continuous nonlinear function of the lead angle is introduced to the guidance command, which makes the Lyapunov stability negative-semidefinite. This issue is also resolved by the additional component of the guidance command, which makes the sliding mode be the only attractor still without the singularity. The capturability analysis is presented regardless of the initial launching conditions of missiles, which can guarantee a wide range of the capture region. The proposed guidance law is easily extended to a nonmaneuvering target using the predicted interception point. Simulation results confirm the effectiveness of the proposed guidance against a nonmaneuvering target as well as a stationary target with absence and presence of measurement noise.

Impact angle constrained sliding mode guidance against maneuvering target with unknown acceleration

In this paper, a sliding mode guidance law for impact angle control is proposed against a maneuvering target with unknown acceleration, which is capable of achieving the acceptable miss distance and a wide range of the desired impact angle. The main idea is to separate the switching surfaces for the impact angle constraint and the homing constraint, then to associate the two surfaces by introducing an appropriate virtual controller. Because of the unknown target acceleration, an adaptive procedure is designed to select the gain of the switching controller which accounts for the uncertainty bound regarding the target acceleration. The stability of the proposed approach is analyzed by Lyapunov theory, and the capturability analysis is also presented. Simulation results confirm the effectiveness of the proposed guidance against a maneuvering target as well as a nonmaneuvering target with absence and presence of noise.

Adaptive Dynamic Surface Control based on Neural Network for Missile Autopilot

In this paper, we investigate a roll-pitch-yaw integrated autopilot for a short-range air-to-air missile (SRAAM) in the presence of uncertainties in total aerodynamic forces and moments. To design an adaptive controller for command following of angle of attack, sideslip angle, and roll angle, adaptive dynamic surface control (DSC) is developed using neural network. The explosion of complexity in conventional backstepping design is avoided by using DSC. Uncertain nonlinearity is represented by neural network under universal approximation. To achieve adaptive performance, the neural network is learned by updating the weight matrices and gains on-line through adaptation rules that are derived from Lypunov stability theory. It is shown that the proposed control design can guarantee the uniformly ultimate boundedness of all the signals in the closed-loop system, and make the tracking error arbitrarily small. The six-degree of freedom nonlinear missile simulation results validate the feasibility of the proposed control law.

Fast adaptive guidance against highly maneuvering targets

An adaptive guidance law applicable to a short-range homing missile is investigated against a highly maneuvering target that has the same maximum maneuver acceleration as the missile. In practice, it is difficult to measure the target acceleration with precision and without time delay. The objective of this study is to design a guidance law that can intercept a target within the acceptable miss distance in the presence of unknown target acceleration and guidance command saturation. For this, the main idea of this paper is to apply the fast adaptive control approach to estimating the tangential component of the unknown target acceleration. Moreover, the auxiliary signal is introduced to prevent the presence of the guidance command saturation from destroying the desired adaptive performance. The proposed guidance law can be classified as an augmented proportional navigation guidance (PNG) law with the actual target acceleration component being replaced by its accurate estimate. Simulation results illustrate the satisfactory performance of the proposed guidance law in comparison with other guidance laws with the absence and presence of measurement noise.

Force and moment blending control for agile dual missiles

This paper presents a force and moment blending control scheme for a dual-controlled missile with tail fins and reaction jets, which is especially aimed at a fast response. A dual missile can be controlled by forces and moments independently, when the reaction jet is located in front of the center of gravity of the missile. Controlling the net force of aerodynamic lift and jet thrust yields much a faster response compared with controlling the net moment, but it uses large control efforts caused by divergence of angle of attack, especially the jet thrust. Here, force control is implemented by using sliding mode control. Large input usage is alleviated by shaping angle of attack. The proposed blending scheme begins with force control and then makes a transition to moment control. Both control strategies are demonstrated by a nonlinear missile system. The smooth transition from force control to moment control is demonstrated. The proposed approach shows a very fast response, while its input usage is almost same as the conventional moment control.

Fast adaptation for an uncertain nonlinear system using adaptive feedback linearization with optimal control modification

In this paper, we investigate an adaptive control for fast adaptation without high-frequency oscillation, using feedback linearization and optimal control modification. Generally, a large adaptive gain is used to achieve fast adaptation and this can cause high-frequency oscillations in standard model-reference adaptive control. The fast adaptation approach is based on an optimal control problem to minimize L2 norm of the tracking error. Through the adaptive feedback linearization-based technique with first-order filters, optimal control modification can be applied to more general nonlinear systems having unmatched uncertainties. Uniformly ultimate boundedness of the overall closed-loop system is analyzed by the Lyapunov stability theory. Simulation results validate the performance of the proposed control approach.

Force and moment blending control for fast response of agile dual missiles

This paper presents a blending principle of tail fins and reaction jets to achieve a fast response for a dual-controlled missile under a slew-rate limit. The blending principle can be categorized as controlling either the net force or the net moment according to how the two actuators cooperate with each other. When compared with controlling the net moment, controlling the net force of aerodynamic lift and jet thrust allows direct control of the acceleration, thus enabling a much faster response but at the expense of large control effort. In this work, for the initial transient period a force controller is designed to achieve fast response under the slew-rate limit, then the transition control is proposed, which begins with force control and makes a transition to moment control to reduce the control usage. This transition does not involve switching from one controller to the other. Rather, the angle of attack is properly shaped corresponding to the desired moment, allowing a smooth and stable transition from force control to moment control. The smooth transition by the proposed strategy from force control to moment control is demonstrated with nonlinear missile dynamics. The proposed approach shows a very fast response, while its input usage is almost same as the conventional moment control.

Adaptive Sliding Mode Control for Dual Missile Using RBF Neural Network

This paper presents an adaptive sliding mode control for a dual-controlled missile with tail fins and reaction jets. An RBF(Radial Basis Function) neural network is used to adaptively compensate for the uncertainties. The network adaptation rule is derived from Lyapunov stability theory. It is shown that the proposed control design achieves uniformly ultimate boundedness. The proposed controller is demonstrated by nonlinear missile dynamics and it shows a stable response against uncertainty.

Adaptive output feedback control using optimal control modification

In this paper, an observer-based adaptive output feedback controller is developed for a class of strict-feedback nonlinear systems having unmatched uncertainties with unmeasured states. We transform an unmatched uncertain nonlinear system into the system having matched uncertainty through system transformation that forms lumped uncertainties. Since only the output is measurable, we design an adaptive observer based on the transformed nonlinear system to make the output track the given desired trajectory. The adaptive laws are derived using optimal control modification, which allows the use of a large adaptive gain for fast adaptation. This approach is based on an optimal control problem to minimize ℒ2 norm of the tracking error. Uniformly ultimate boundedness of the overall closed-loop system is analyzed by the Lyapunov stability theory. Simulation results validate the performance of the proposed control approach.