Byung-Eul Jun

Roll-Pitch-Yaw Integrated Robust Autopilot Design for a High Angle-of-Attack Missile

This paper explores the feasibility of roll-pitch-yaw integrated autopilots for a high angle-of-attack missile. Investigation of the aerodynamic characteristics indicates strong cross-coupling effects between the motions in longitudinal and lateral directions. Robust control techniques based on H ∞ synthesis are employed to design roll- pitch-yaw integrated autopilots. The performance of the proposed roll-pitch-yaw integrated controller is tested in high-fidelity nonlinear 5-degree-of-freedom simulations. The proposed controllers are scheduled as a function of total angle of attack in a linear parameter varying framework with proportional navigation guidance laws. The integrated controller demonstrates satisfactory performance that cannot be achieved by the controller designed in a decoupled manner.

Extended least-correlation estimates for errors-in-variables non-linear models

This paper introduces a method of parameter estimation working on errors-in-variables polynomial non-linear models in which all measurements are corrupted by noise. The first step is to develop the linear regression models which are equivalent to polynomial non-linear systems. A main idea is to extend the parameter vector by even-order components of noise and to augment the regression vector by appropriate constants or measurements. Applying the method of least correlation, which has a capability to cope with errors-in-variables linear models, to the equivalent model with extended parameters and augmented regressors yields an extended least-correlation estimator. Analysis shows that, for non-linear systems with third or lower order polynomials, the parameters estimated by the proposed method asymptotically converge to the true values. Numerical examples also support analytical results. Applications of the approach to Volterra models, Hammerstein models and Weiner non-linear systems are included.

Sliding-Mode-Based Missile-Integrated Attitude Control Schemes Considering Velocity Change

A sliding-mode-based control scheme is proposed for integrated roll–pitch–yaw attitude control of a fin-controlled skid-to-turn missile during the boost phase. The missile aerodynamics accompany nonlinear, partially unstable, and cross-coupling effects among input channels so that integrated control is required. A mathematical model of the attitude dynamics and aerodynamics is constructed regarding the inertial property variations. Two possible architectures (the single-loop control scheme employing the higher-order sliding mode controller and the separated control scheme based on the traditional sliding mode controller) are proposed. For the integrated attitude control of the missile, multiple sliding surfaces are chosen for simultaneous tracking of the attitude commands. To demonstrate the performance of the proposed control scheme, numerical simulations are performed using a nonlinear six degrees-of-freedom missile model in the presence of uncertainties.

Integrated pitch/yaw acceleration controller for projectile with rotating canards using linear quadratic control methodology

In this paper, an integrated pitch/yaw autopilot for the acceleration control of the projectile with rotating canards is proposed based on the linear quadratic control methodology. The pitch/yaw motions of such munitions are highly coupled so that it is not easy to control both pitch and yaw accelerations. As a remedy, we propose the integrated pitch/yaw output feedback structures based on the classical three-loop topology. Then, the optimal control gains are determined by solving the linear quadratic regulator (LQR) problem. The proposed autopilot is tested with nonlinear simulations to investigate its performance.

Sliding mode based attitude and acceleration controller for a velocity-varying skid-to-turn missile

Sliding mode based roll-pitch-yaw integrated attitude and acceleration controller for a fin-controlled skid-to-turn(STT) missile is proposed. In terms of aerodynamics, the missile model has severe nonlinearities and coupling effect between input channels and roll-pitch-yaw angles that make the controller design challenging. Moreover, the controller should be designed for the entire flight envelope consisting of boost-phase and gliding-phase where rapid velocity variation exists, and therefore parametric robustness with respect to rapid velocity change is strongly required. The attitude autopilot controls the Euler angles of the missile, and is configured as a single-loop. On the other hand, the acceleration autopilot, which is of two-loop structure, is used for the control of STT maneuver. The proposed autopilots use multiple sliding surfaces to generate control inputs for multiple channels simultaneously. Numerical simulation is performed to verify the performance of the proposed controllers.

Nonlinear missile autopilot design via three loop topology and time-delay adaptation scheme

In this paper, a new missile acceleration controller is proposed, based on the three loop control structure with the feedback linearization control law and time-delay adaptive law. In order to avoid the nonminimum characteristics of conventional missile systems, an approximate system and three loop topology are considered. Under this control structure, the feedback linearization methodology is applied to relieve difficulties of aerodynamic nonlinearity. Finally, this controller is augmented by the time-delay adaptation scheme to compensate for the model uncertainties. The performance of proposed autopilot is tested using a nonlinear missile model with uncertainties, by imposing step commands.

A Nonlinear Roll Autopilot based on 5-DOF Models of Missiles

This paper suggests a nonlinear control law to stabilize the rolling motion of missiles. Based on the analysis of rolling moment characteristics due to pitch/yaw control cross-coupling, we propose a conjecture that the moment is described by the bilinear form of pitch/yaw acceleration and yaw/pitch control. The conjecture fits a set of wind tunnel test data and leads to a bilinear control law. An important point is that the control law is implemented by using pitch/yaw accelerations and control signals. Simulations show that the new control law stabilizes rolling motions which cannot be stabilized by linear feedback control laws.

Performance analysis of sign-sign algorithm for transversal adaptive filters

Abstract The sign-sign algorithm (SSA), which is obtained by clipping both the reference input and the estimation error of the least mean square (LMS) algorithm, is analysed for transversal adaptive filters with correlated Gaussian data. The analysis focuses on the expected behaviours of the filter coefficients and the mean square error of the filter. The previous analysis of this type for the SSA is based on the assumption that the input data of adaptive filters are independent, identically distributed Gaussian, but this restriction is removed in our analysis. The analytical results are verified numerically through computer simulations for two examples - an adaptive linear predictor and an adaptive system identification.

Design of missile autopilot using PI and approximate feedback linearization control with time-delay adaptation scheme

A straight forward application of feedback linearization to the missile autopilot design for acceleration control may be limited due to the nonminimum characteristics and the model uncertainties. As a remedy, this paper presents a cascade structure of an acceleration controller based on approximate feedback linearization methodology with a time-delay adaptation scheme. The inner loop controller is constructed by applying feedback linearization to the approximate system which is a minimum phase system and provides the desired acceleration signal caused by the angle-of-attack. This controller is augmented by the time-delay adaptive scheme and the outer loop PI (proportional-integral) controller in order to adaptively compensate for feedback linearization error because of model uncertainty and in order to track the desired acceleration signal. The performance of the proposed method is examined through numerical simulations.

A 3-Loop Autopilot Design for a Missile using an Automated MDO Environment

A 3-loop missile autopilot design method using an automated MDO (Multi-Disciplinary Optimization) environment is proposed. The classical 3-loop characteristics are analyzed and the 5 DOF simulation technique is introduced for evaluating the designed autopilot system. Several performance indices and constraints are considered for the environment in order to achieve the design goals. Numerical simulations are performed for verifying the developed environment fidelity and other applications are illustrated for showing the effectivenss of the developed optimal environment.