Hyeong-Geun Kim

Missile Guidance Law Considering Constraints on Impact Angle and Terminal Angle of Attack

This paper proposes a guidance law considering constraints on impact angle and terminal angle of attack for a homing missile. In the proposed structure, the guidance law generates angle of attack command and the controller tracks the generated command. For deriving the angle of attack command, the differential game problem with terminal boundary conditions is proposed and solved. Then, the sliding mode control is applied in order to derive the actual command input from the guidance command. Because the guidance command is the angle of attack, the terminal angle of attack constraint can be easily handled and the controller needs not deal with non-minimum phase characteristics. This capability to control the terminal angle of attack is the main contribution of the paper. The performance of the proposed law is evaluated using a two-dimensional nonlinear simulation. The result demonstrates that the proposed law allows the missile to intercept the maneuvering target with the constraints on impact angle and terminal angle of attack.

Impact time control guidance considering seeker's field-of-view limits

This paper proposes a guidance law that achieves the desired terminal impact time without violating a seekers field-of-view (FOV) limits. In order to derive the guidance law, kinematic conditions for impact time control are defined, and the backstepping control technique is applied for the satisfaction of the conditions. As a virtual control input for the backstepping structure, the relative closing velocity is used and its magnitude is limited by a prescribed limit. Then, the seekers look angle can also be confined within a specific range because the look angle is mainly determined by the difference between the line-of-sight (LOS) and the velocity vector. This capability to confine the seekers look angle with achievement of the desired impact time is the main contribution of the paper. To evaluate the performance of the proposed law, numerical simulation is conducted. The result demonstrates that the proposed guidance law enables the missile to simultaneously achieve the zero miss distance and desired impact time without violating the prespecified FOV limits.

Robust Control of an Equipment-Added Multirotor Using Disturbance Observer

Modifications of multirotor unmanned aerial vehicles are increasingly popular by integrating tools, sensors, or a robotic arm depending on types of applications. In these circumstances, precise motion control against model uncertainty and disturbance is essential. This brief presents an inner-loop control structure to recover the dynamics of a multirotor combined with additional objects similar to the bare multirotor using disturbance observer (DOB)-based approach. In addition, in the process of the inner-loop controller design and the associated stability proof, it is revealed that the safe operation bounds of the modified multirotor in accordance with the amount of inertia added to the multirotor. The proposed control design is validated with flight experiments using a multirotor integrated with a four-DOF robotic arm, where the multirotor is commanded to follow a desired trajectory while the robotic arm is in motion. The results show superior tracking performance of the proposed structure in comparison with backstepping control without DOB.

All-aspect Guidance with Impact Angle Constraint against Unknown Target Maneuver

This paper presents an all-aspect guidance law that allows the missile to achieve the interception of a target at the prescribed impact angle for any initial conditions. The proposed guidance law is designed to intercept a maneuvering target without requiring information of the normal acceleration of the target. In order to develop a guidance law that ensures all-aspect capability, the kinematic conditions that always guarantee the interception of the maneuvering target at the desired impact angle are defined. The defined kinematic conditions are expressed as two error variables for simultaneously satisfying the homing and impact angle control, and the guidance law is derived by stabilizing both error variables near zero based on the backstepping control technique. The analysis of the overall closed-loop dynamics verifies that the proposed law achieves the interception of the maneuvering target at the prescribed impact angle from any initial heading and boresight conditions, despite the absence of the information of the target acceleration. Numerical simulations also demonstrate that the proposed law achieves an acceptable miss distance at the desired impact angle for various initial conditions against different types of nonstationary targets: nonmaneuvering targets, constant-maneuvering targets, and weaving targets.

Integrated guidance and control of dual missiles considering trade-off between input usage and response speed

An integrated guidance and control law for agile dual missiles is proposed using sliding mode control. For tight integration, engagement kinematics and missile dynamics are combined without linearization. Then, two sliding surfaces are defined because dual missiles have two degrees of freedom for control. One surface is defined for making line of sight (LOS) angle rate converge, and the other for fast response of the missile. Response speed of the missile is adjusted flexibly with the control. If heading error exists, a fast controller that consumes large input is applied. On the contrary, a relatively slow controller consuming smaller input is applied when heading error is zero. For this strategy, transition control technique is applied. As a result, an integrated guidance and control law with fast response speed is derived. Performance of the proposed integrated law is evaluated with highly maneuverable target using nonlinear simulations.

Robust adaptive control with a reduced order controller

The adaptive control of a stable plant with a ROC (reduced-order controller) which is marginally stable is addressed. The ROC is obtained from a ROM (reduced-order model) of the plant, which approximates the frequency response of the estimated plant. The ROC which stabilizes both the ROM and the estimated plant is designed by the pole placement scheme with some modification in order to satisfy the specifications on the gain and phase margins of the overall system. The proposed adaptive control algorithm takes the gain and phase margins into consideration in the design process to increase the robustness of the control. Simulation results show that the proposed algorithm is more robust than previous algorithms.<<ETX>>