Missile Autopilot Design Research Articles

Three-Axis Autopilot Design for a High Angle-Of-Attack Missile Using Mixed H2/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 <TEX>$H_2/H_{\infty}$</TEX> 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.

A composite sliding mode autopilot design

Sliding mode control has been applied to the design of many missile autopilots. In this paper, a control method with the primary feedback being proportional to the switching is developed for eliminating the disturbance effect due to model uncertainty. With this control method, a sliding mode autopilot is analysed. Then, a composite sliding mode control strategy is discussed to reduce the switching frequency. Numerical simulation results show a good performance of the composite control system.

Missile Autopilot Design: Gain-Scheduling and the Gap Metric

This paper presents a systematic methodology for the synthesis of global gain-scheduled controllers for nonlinear time-varying systems. A controller of this type is used to compute the pitch-axis autopilot of an air-air missile. The missile model used is considered a benchmark for testing autopilot controllers in the academic and industrial communities. The missile's dynamics are linearized at a small set of operating points for which proportional― integral/proportional-type controllers are designed, to shape the frequency response of the linear plants' dynamics. A new set of operating points is computed afterward using the connection between the gap metric and the H ∞ loop-shaping theory. Then, reduced-order, static, H ∞ loop-shaping controllers are designed for this set of points using linear matrix inequality optimization techniques. Finally, the global gain-scheduled controller is obtained by interpolating the proportional―integral/proportional and the loop-shaping controllers' gains over the missile's flight envelope. The simulation results given show the generality and effectiveness ofthe proposed control strategy in terms of the operating point selection, stability, performance and robustness, of the closed loop.

Global stabilizing controller design for linear time-varying systems and its application on BTT missiles

A parametric method for the gain-scheduled controller design of a linear time-varying system is given. According to the proposed scheduling method, the performance between adjacent characteristic points is preserved by the invariant eigenvalues and the gradually varying eigenvectors. A sufficient stability criterion is given by constructing a series of Lyapunov functions based on the selected discrete characteristic points. An important contribution is that it provides a simple and feasible approach for the design of gain-scheduled controllers for linear time-varying systems, which can guarantee both the global stability and the desired closed-loop performance of the resulted system. The method is applied to the design of a BTT missile autopilot and the simulation results show that the method is superior to the traditional one in sense of either global stability or system performance.

Integrated Roil-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.

Integrated Guidance and Control of Homing Missiles Against Ground Fixed Targets

This paper presents a scheme of integrated guidance and autopilot design for homing missiles against ground fixed targets. An integrated guidance and control model in the pitch plane is formulated and further changed into a normal form by nonlinear coordinate transformation. By adopting the sliding mode control approach, an adaptive nonlinear control law of the system is designed so that the missile can hit the target accurately with a desired impact attitude angle. The stability analysis of the closed-loop system is also conducted. The numerical simulation has confirmed the usefulness of the proposed design scheme.

Fuzzy gain-scheduled missile autopilot design using evolutionary algorithms

The paper presents the lateral acceleration control design of a missile model using the evolution strategy (ES). The nonlinear fixed-structure-like controller is represented by the singleton fuzzy model. This allows a variation of shapes of the gain functions to be explored, and subsequent modification is fairly easy. Instead of finding an optimal decomposition of the fuzzy controller, a set of fuzzy rules is unconventionally optimized for the overall gain surfaces that guarantee acceptable performances for the closed-loop system over the whole operating envelope. The simulation results show that the designed fuzzy gain-scheduled controller is a robust tracking controller for all perturbation vertices

Polynomial approach for design and robust analysis of Lateral missile control

A polynomial approach is presented for the design and analysis of a sideslip velocity missile autopilot. The controller is designed using polynomial eigenstructure assignment (PEA). The missile model is described by linear parameter varying (LPV) matrices. The design renders to a closed-loop system independent of the choice of equilibria. Thus, if the operating points are in the vicinity of the equilibria, then only one linear model will describe closed-loop dynamics, regardless of the rate of change of the operating points. Parametric stability margins for uncertainty in the controller parameters and aerodynamic derivatives are analysed using a finite version of the Nyquist Theorem. The Finite Nyquist Theorem (FNT) exploits the polynomial framework to assess robustness for a parametric uncertain system with the Finite Inclusion Theorem (FIT). The design and analysis approach is applied to a single-input single-output (SISO) tail-controlled missile in the cruciform fin configuration. Simulations show good tracking of sideslip velocity with closed-loop system, fast responses and good parametric robustness against six uncertain parameters.

Skid-to-turn missile autopilot design using scheduled eigenstructure assignment technique

This paper presents an application of adaptive control techniques to the design of skid-to-turn missile autopilot. The involved simplified adaptive controller is developed by combining gain scheduling approach with the eigenstructure assignment control design. A linear interpolation method is proposed to generate linear parameter-varying controller from a finite set of linear time-invariant controllers. Results of simulations are reported to demonstrate the performance, stability, and robustness of the considered autopilot.

AUTOPILOT DESIGN FOR AGILE MISSILE USING LTV CONTROL AND NONLINEAR DYNAMIC INVERSION

This paper is concerned with autopilot design for an agile missile with aerodynamic fins, thrust vectoring control, and side-jet thrusters. Two-time scale dynamic inversion is used as a nonlinear flight control law. To deal with the inherently weak robustness property of dynamic inversion, Ackermann-like formula which is a time-varying version of Ackermann formula for LTI systems is applied to control the aerodynamic fins to stabilize LTV tracking error dynamics. In addition, control allocation algorithms for the effective distribution of the required total control efforts to the individual actuators are suggested, which are capable of extracting the maximum performance by combining each control effector. Finally, the main results are validated through nonlinear simulations with aerodynamic data.

Adaptive flight control design for nonlinear missile

The focus of this work is to investigate the possible benefits of modern nonlinear control design methods for missile autopilot design. The basic requirement for an autopilot is firstly fast responses because of the short amount of time involved in the end-game. A slow response could easily cause a miss if the target has the capacity to perform high-g evasive manoeuvers. Secondly, minimum error is an obvious requirement if the missile is to achieve a kill. Finally, robustness to model uncertainties is important in order for the missile to achieve its objective in the physical environment. In the first part of this paper input–output approximate linearisation of a nonlinear missile has been studied. A method for controlling the nonlinear system that is input–output linearisable is examined that retains the order of the system in the linearisation process, hence producing a linearised system with no internal or zero dynamics. Desired tracking performance for lateral acceleration of the missile is achieved by using a nonlinear control law that has been derived by selecting the lateral velocity as the linearisation output. Simulation results are shown to exercise the final design and show that the linearisation and controller design are satisfactory. Then an adaptive nonlinear controller is designed that guarantees tracking performance when the uncertain parameters vary within a stability bound. An autopilot combining an indirect adaptive controller with approximate feedback linearisation is proposed in order to achieve asymptotic tracking. Adaptation is introduced to enhance closed-loop robustness, while approximate feedback linearisation is used to overcome the problem of unstable zero dynamics. Computer simulations show that this approach offers a possible autopilot design for nonlinear missiles with uncertain parameters.

Nonlinear Missile Autopilot Design with Theta-D Technique

In this paper, a new nonlinear control method is used to design a full-envelope, hybrid bank-to-turn (BTT)/skidto-turn (STT) autopilot for an airbreathing air-to-air missile. Through this new approach, called the θ − D method, we find approximate solutions to the Hamilton‐Jacobi Bellman (HJB) equation. As a result, the resulting nonlinear feedback law can be expressed in a closed form. In this paper, a θ − D outer-loop and inner-loop controller structure is used in an autopilot design. A hybrid BTT/STT autopilot command logic is used to convert the commanded accelerations from the guidance laws to reference angle commands for the autopilot. The outer-loop θ − D controller converts the angle-of-attack, sideslip, and bank-angle commands to body-rate commands for the inner loop. An inner-loop θ − D controller converts the body-rate commands to fin commands. This design is evaluated using a detailed six-degrees-of-freedom simulation. Numerical results show that the new controllers achieve excellent tracking performance and exhibit insensitivity to parameter variations over a wide flight envelope.

A robust adaptive nonlinear control approach to missile autopilot design

In this paper, an adaptive nonlinear control design technique is applied to the pitch controller for a missile model, which is aerodynamically controlled. Missile motion is modelled to be nonlinear with unknown parameters and uncertainties. Both unknown parameters and uncertainty bounds are estimated and, based on these estimates, controller parameters are updated at each step. We adopt a design procedure, basically an adaptive backstepping method, which gives the adaptive scheme guaranteeing uniform ultimate boundedness despite of model uncertainties. Computer simulations show that this approach is very promising for the autopilot design for missiles which are highly nonlinear in aerodynamics with unknown parameters.

Systematic Gain‐Scheduling Control Design: A Missile Autopilot Example

ABSTRACTThe missile autopilot was designed using linear parameter‐varying (LPV) control techniques. The controller provides exponential stability guarantee and performance bound in terms of induced L2 norm for the missile plant. The systematic gain‐scheduling approach is motivated by the recent development in LPV control theory and provides a well founded and systematic procedure for high performance missile autopilot design problem.

A Missile Autopilot Based on Feedback Linearization

This paper is dealing with a missile autopilot design. The objective is to seek the approaches which significantly enhance the ability of an aerospace control engineer to deal with a practical nonlinear flight control problem. For this purpose, two nonlinear methods are considered: “approximate feedback” and “approximate dynamic feedback” with two time-scale separation. Both methodologies have been applied in order to overcome the difficulties caused by the non-minimum phase phenomenon of the missile. For the sake of realism, the implementation of the controller includes a nonlinear observer. The second method, which incorporates the classical industrial know how, has been shown to be better among the two in terms of both performance and complexity of the control law.

ADAPTIVE FLIGHT CONTROL DESIGN FOR NONLINEAR MISSILE

An autopilot combining an indirect adaptive controller with approximate feedback linearisation is proposed in order to achieve asymptotic tracking. Adaptation is introduced to enhance closed-loop robustness, while approximate feedback linearisation is used to overcome the problem of unstable zero dynamics. Computer simulations show that this approach offers a possible autopilot design for non-linear missiles with uncertain parameters.

Missile autopilot design via a multi‐channel LFT/LPV control method

AbstractIn this paper, the missile pitch‐axis autopilot design is revisited using a new and recently available linear parameter‐varying (LPV) control technique. The missile plant model is characterized by a linear fractional transformation (LFT) representation. The synthesis task is conducted by exploiting new capabilities of the LPV method: firstly, a set of H2/H∞ criteria defined channel‐wise is considered; secondly, different Lyapunov and scaling variables are used for each channel/specification which is known to reduce conserva tism; and finally, the controller gain‐scheduling function is constructed as affine matrix‐valued function in the polytopic co‐ordinates of the scheduled parameter. All these features are examined and evaluated in turn for the missile control problem. The method is shown to provide additional flexibility to tradeoff conflicting and demanding performance and robustness specifications for the missile while preserving the practical advantage of previous single‐objective LPV methods. Finally, the method is shown to perform very satisfactorily for the missile autopilot design over a wide range of operating conditions. Copyright © 2001 John Wiley &amp; Sons, Ltd.

Modern Missile Flight Control Design: An Overview

The requirement of high agility in the entire flight envelope will dominate the flight control design for future missile systems. The desin requirements for the next-generation autopilots will include not fast response to the required acceleration demands and extreme maneuvarability while maintaining stability, but also robustness over a wide range of mission profiles at all altitudes. An overview of different control techniques for missile autopilot design is presented in this paper.

Three-Axes Missile Autopilot Design: From Linear to Nonlinear Control Strategies

A three-axes skid-to-turn missile autopilot design is presented. The modeling is that of a missile developed by AerospatialeMatraMissiles.Variouscontrollawshavebeencomparedinordertoestimatetheirpotentialandtheir applicability: classical linear time-invariant control and static and dynamic approximate input-output linearizing feedbacks. The robustness is studied, and the best results, in terms of stability, performance, and robustness, are shown to be obtained by using a special type of nonlinear dynamic control. The simulation results are explained using a table of comparison.

Sliding Mode Control with Optimal Sliding Surfaces for Missile Autopilot Design

A new method is introduced to design sliding mode control with optimally selected sliding surfaces for a class of nonlinear systems. The nonlinear systems are recursively approximated as linear time-varying systems, and corresponding time-varyingsliding surfaces are designedfor each approximatedsystem so thatagivenoptimization criterion isminimized.The control input,which is designedbyusing an approximatedsystem, is then applied to the nonlinear system. The method is used to design an autopilot for a missile where the design requirement is to follow a given acceleration command. The sliding surface is selected such that a performance index formed as a function of angle of attack, pitch rate, and velocity error is minimized. It is shown that the response of the approximating sequence of linear time-varying systems converges to the response of the missile.