Missile Autopilot Research Articles

Model predictive control for non-linear missiles

The present paper reports an attempt of applying model predictive control (MPC) to design an autopilot for a non-linear missile. The non-linear, fast dynamics of the missile raise three issues in the design of an MPC algorithm: the choice of the MPC performance index, in particular the terminal weighting term, to compromise the performance and the stability requirements; loss of the global minimum in the online optimization since it is a nonlinear optimization; and the computational time limitation imposed by the fast sampling requirement. For the first issue, a procedure is developed to determine the terminal weighting term using a new representation of the control sequence in the moving horizon. For the other two issues, a new initial control profile and an associated control strategy are adopted in each optimization routine. It is shown that the new MPC algorithm can guarantee stability, even when a local minimum is attained in the online optimization or the optimization process has to stop owing to the limitation of the sampling time. Simulation results carried on the missile show that good performance and stability are achieved by the new MPC algorithm, whereas four other current MPC algorithms lose their stability.

Missile autopilot design using quasi-LPV polynomial eigenstructure assignment

This paper presents the design of a missile autopilot over its flight envelop using quasi-linear parameter-varying polynomial eigenstructure assignment (PEA). The paper describes the extension of PEA to parameter-varying systems using a nonlinear missile model developed by Horton as an example. The autopilot is designed for a single-plane lateral acceleration control and a 5 degree of freedom (DOF) autopilot is also designed. Both lateral acceleration and augmented lateral acceleration outputs are considered. The lateral acceleration autopilot has nonminimum phase characteristics, and it is shown that the quasi-linear parameter-varying PEA approach can handle nonminimum phase systems unlike classic dynamic inversion techniques. Simulation results are presented over fast variations in Mach number and show that the design is robust.

Mixed [formula omitted] autopilot design of bank-to-turn missiles using fuzzy basis function networks

This paper presents a novel mixed H 2 / H ∞ autopilot design for bank-to-turn missiles. Based on sliding control theory, the proposed autopilot utilizes a fuzzy basis function network to approximate the unknown nonlinear functions of bank-to-.turn missile dynamics, enabling a mixed H 2 / H ∞ controller with weight updating laws to be applied to attenuate the effects of approximation errors and external disturbances. Moreover, the mixed H 2 / H ∞ autopilot design can minimize H 2 performance criteria under a desired H ∞ disturbance rejection constraint. Unlike general mixed H 2 / H ∞ control problems, the proposed H 2 / H ∞ autopilot with self-tuning fuzzy basis function network can avoid solving coupled Riccati equations by adequately selecting diagonal weighting matrices in the H 2 performance criterion and H ∞ constraint. Therefore, the proposed H 2 / H ∞ control approach can be implemented efficiently. Computer simulation results are presented to illustrate the effectiveness of the proposed mixed H 2 / H ∞ autopilot for BTT missiles.

Simulation of Missile Autopilot with Two-Rate Hybrid Neural Network System

Simulation of Missile Autopilot with Two-Rate Hybrid Neural Network System

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.

Sliding-Mode Control for Integrated Missile Autopilot Guidance

A sliding-mode controller is derived for an integrated missile autopilot and guidance loop. Motivated by a differential game formulation of the guidance problem, a single sliding surface, defined using the zero-effort miss distance, is used. The performance of the integrated controller is compared with that of two different two-loop designs. The latter use a sliding-mode controller for the inner autopilot loop and different guidance laws in the outer loop: one uses a standard differential game guidance law, and the other employs guidance logic based on the sliding-mode approach. To evaluate the performance of the various guidance and control solutions, a two-dimensional nonlinear simulation of the missile lateral dynamics and relative kinematics is used, while assuming first-order dynamics for the target evasive maneuvers. The benefits of the integrated design are studied in several endgame interception engagements. Its superiority is demonstrated especially in severe scenarios where spectral separation between guidance and flight control, implicitly assumed in any two-loop design, is less justified. The results validate the design approach of using the zero-effort miss distance to define the sliding surface.

Control and Maneuverability of a Square Cross-Section Missile

A study has been conducted into the aerodynamics, control, and performance of a square cross-section supersonic missile. Comparisons have been made with an equivalent circular cross-section baseline. This paper summarizesthe control and maneuverability findings and explores the relationship between airframe asymmetry and autopilot architecture. Missile autopilot designs based on classical, H ∞ , and nonlinear dynamic inversion methodologies are compared in terms of a robust stability requirement defined by Nichols exclusion regions, applied in a multiloop sense. Valuable insights into the required autopilot architecture are gained through this. Various other performance metrics are also proposed and used to explore the relative merits of the square cross-section body shape.

Missile Autopilot Design Using Discrete-Time Variable Structure Controller with Sliding Sector

In this paper a discrete variable structure controller with sliding sector is designed for tracking the lateral acceleration command for a dual-input air-to-air missile. A new algorithm is developed for the variable-width sliding-sector design by considering the dissipativeness property of the system. The width of the sliding sector is based on the norm of the linear uncertain system state and the reference input. The switching surface design is based on the reduced-order dynamics. The control law is designed such that the state trajectory from any initial point is driven into the sliding sector around the equilibrium point in the vicinity. of the the switching surface sigma(k) and thereafter remains inside it. The discrete sliding condition considered is parallel tosigma(k+1)parallel to parallel tosigma(k)parallel to.inside the sliding sector, the closed-loop system is dissipative with a linear control law. The uncertain missile plant with matched and mismatched uncertainty is considered, and the conditions on the norm-bound of the uncertainty are given for robust stability in the sense of Lyapunov. Simulation results of the missile autopilot are also included to show the efficacy of-the proposed controller.

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.

Combined H-Infinity Model-Matching Control and Dual-rate Digital Redesign for Missile Acceleration Autopilots

This paper proposes a missile acceleration autopilot obtained via H∞ model-matching control and dual-rate digital redesign. The first stage of the procedure consists in solving an H∞ model-matching problem in continuous-time. The second stage of the proposed approach is the conversion of the optimal continuous-time control system to a fast-inner-loop rate, slow-outer-loop rate digital control system using a dual-rate digital redesign approach which takes into account the closed-loop dynamics of the missile autopilot in the conversion. Reducing the order of the autopilot transfer functions and scheduling the controllers over the entire flight envelope constitute the last stages of the proposed approach. The proposed dual-rate missile acceleration autopilot is very useful in practice since it provides satisfactory closed-loop performances over an extended range of sampling rates, as compared with other digital autopilots. A nonlinear missile airframe dynamics model is used to demonstrate the application of ...

Modeling and H//sub∞/ control for switched linear parameter-varying missile autopilot

This paper presents a new method for designing a gain-scheduled missile autopilot. The nonlinear missile dynamics are modeled as a switched linear parameter-varying (SLPV) system, as is also common for many hybrid system models. A gain-scheduled autopilot for the SLPV system is then designed using a new synthesis technique that is based on a nonsmooth dissipation framework. The proposed algorithm extends previously published Lyapunov-based LPV approaches in three important ways: the SLPV system can provide a more accurate model of the missile dynamics; the nonsmooth Lyapunov function used in the synthesis is a more general class of Lyapunov functions; and the gridding technique typically used to solve the synthesis can be eliminated from the problem. As a result, the new approach yields a reliable gain-scheduled autopilot with better performance than the LPV controllers available in the literature.

A dynamically fuzzy gain – scheduled design for missile autopilot

AbstractA dynamic backpropagation training algorithm for an adaptive fuzzy gain scheduling feedback control scheme with the application to missile autopilots is developed. This novel design methodology uses a Takagi-Sugeno fuzzy system to represent the fuzzy relationship between the scheduling variables and controller parameters. Mach number and angle-of-attack are used as measured, time-varying exogenous scheduling variables injected into the control law. By incorporating scheduling parameter variation information, the adaptation law for controller parameters is derived. Results from extensive simulation studies show that the presented approach offers satisfactory controlled system performance.

Structured Multivariable Phase Margin Analysis with Applications to a Missile Autopilot

Structured Multivariable Phase Margin Analysis with Applications to a Missile Autopilot

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.

3-루프 가속도 오토파일롯 구조를 갖는 유도탄의 공력특성 연구

We study how the missile autopilot with three loop acceleration structure is related to the aerodynamic characteristics. First, the relationships between the response characteristics of wingless-tail controlled missile and aerodynamics are derived. Next the maximum allowable performance limit of autopilot and the design direction for a missile shape are indicated using the property of zero. The method proposed in this paper may give a help to the missile autopilot system design and determination of the shape of aerodynamic. Also, the validity of proposed method is demonstrated via numerical example.

AUTOPILOT STUDY FOR AN ASYMMETRIC AIRFRAME

We discuss the design of an autopilot for an asymmetric missile. The autopilot is obtained from controllers designed using H∞ synthesis. Due to important cross-coupling in the pitch, yaw and roll channels, it was not possible to work on a set of three decoupled models. A multivariable H∞ loop-shaping control law design is proposed at given operating points. The performance of the control law is evaluated through fully non-linear simulations and is found to be superior to that obtained from an LPV design in (Prempain et al., 2001).

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.