Autopilot Loop Research Articles

L1 Adaptive Control for Small-Scale Unmanned Helicopters: Enhancing Speed Regulation

This paper focuses on the application of L1 adaptive control to the speed autopilot loop of small-scale unmanned helicopters. The L1 adaptive control technique is investigated for its potential to provide reliable speed control, particularly in handling external disturbances and model uncertainties. Although L1 adaptive control has been widely studied, its application to small-scale unmanned helicopters remains relatively unexplored. Through numerical simulations and a preliminary experimental test campaign conducted on a small rotary-wing platform, this paper contributes to validating L1 adaptive control as a promising solution for speed regulation in unmanned helicopter platforms.

Design of an Gain-Scheduled Guidance Scheme for a Guided Projectile

This paper addresses the design of a two-dimensional guidance scheme in the vertical plane, using robust and gain-scheduling control methods, for a fin-stabilized canard-guided projectile. Given that the conventional proportional navigation guidance (PNG) is not completely adequate for target interception with a control-authority-limited weapon, the proposed guidance law is offered as an improvement compared with PNG while respecting a similar parallel navigation guidance principle. The projectile-target engagement kinematics full nonlinear model is discussed, and a linear parameter-varying model, necessary for guidance design, is derived without any approximation. A set of reduced-order mixed-sensitivity controllers with an additional reference model following constraint is designed using a specific computation procedure. The resulting homing closed-loop system is assessed through linear and nonlinear simulations of either nominal or perturbed scenarios. These scenarios include noise or uncertain launch initial conditions, and they also take a simplified or a more realistic autopilot loop into account. The gain-scheduled guidance scheme is finally compared with PNG, and with three other recent guidance laws considering limitations on the acceleration command.

Linearization of Anti-Tank Guided Missile

Anti-tank surface to surface guided missile systems are considered to be one of the most powerful weapons in the modern war. Due to their effectiveness against either fortifications or tanks in addition to their relative low weight, they are deployed in the field easily. One of the most challenges the engineers face while designing a guided missile is the autopilot design. The autopilot loop or the inner loop of the missile should steer the missile during its spatial flight till hitting the target even it is moving or stationary. A higher maneuver target was hit by the missile, the more reliable autopilot you design. On designing a mature autopilot, a promising mathematical model of the missile should be in hand and mathematical linearized model should be derived. This paper presents a mathematical representation of an anti-tank guided missile the mathematical linearized model as well so that the design of the missile autopilot is presented in the future work.

Full-state autopilot-guidance design under a linear quadratic differential game formulation

Full-state single-loop and full-state two-loop autopilot-guidance architectures are derived under a linear quadratic differential game formulation. In the full-state single-loop case, the guidance command is injected directly to the actuator, whereas in the full-state two-loop case, it is the input to the autopilot loop. To prevent impractical end-game scenarios, where the states diverge to unacceptable values, a cost function that includes appropriate running cost terms on some of the states is proposed. The conditions for obtaining an equivalence relation between the full-state single-loop and full-state two-loop architectures are derived under a linear quadratic differential game formulation and the proposed cost function. Under such a formulation, the two full-state architectures are identical if and only if the number of guidance commands matches the number of available controllers. The guidance laws performance is illustrated using an interceptor missile having forward and aft controls in linear and nonlinear settings, while considering two types of evasion strategies. The first strategy is a linear controller based on the linear quadratic differential game solution. The second strategy is a “bang–bang” controller based on the optimal evasion solution. It is shown that the linear evasion strategy may not be suitable to represent a realistic evading strategy. In addition, the conditions for the existence of a saddle point solution are analyzed for the two full-state guidance laws.

Single Versus Two-Loop Full-State Guidance and Control

Full-state approach to designing nonlinear autopilot and guidance systems with bounded controls (servo command or acceleration command) is presented. Two types of full-state architectures are considered: full-state single-loop and full-state two-loop. In the full-state single-loop case, the guidance command is injected directly to the actuator, whereas in the full-state two-loop case, it is the input to the autopilot loop. It is proven that the two full-state architectures are equivalent for nonlinear systems for any cost function if there is a unique mapping from the servo command and state sets into the guidance command set. This result encourages the use of the full-state two-loop architecture over the full-state single-loop one because it ensures a stabilized vehicle if the guidance loop is inactive. The theorem and guidance laws are illustrated via a dual-control missile in an endo-atmospheric interception scenario.

Integrated guidance and control based on block backstepping sliding mode and dynamic control allocation

A novel integrated guidance and control (IGC) design method based on the block backstepping sliding mode and extended state observer is proposed for the near space interceptor (NSI) with aerodynamic fins and reaction jets. Initially, the IGC model is employed by combining the interceptor-target relative motion model with the nonlinear dynamic of the NSI. Subsequently, the ESO is constructed to estimate the target acceleration and autopilot loop disturbance. Based on the estimated value and block backstepping sliding mode method, the IGC algorithm is given to obtain the virtual control moment. The stability of the closed-loop IGC system is also proven based on the Lyapunov theory. Moreover, a new dynamic control allocation algorithm is proposed to distribute the previously virtual control moment among the redundant actuators, while the actuator saturation and rate constraints are also taken into account. Finally, simulation results demonstrate that the proposed IGC algorithm can not only obtain a small miss distance, but also ensure the stability of the NSI dynamic.

Single Versus Two-Loop Full-State Multi-Input Missile Guidance

Two types of autopilot-guidance schemes for linear quadratic multi-input missile systems are compared: single- and two-loop configurations. In both cases, all the states are fed back into the guidance loop. In the two-loop case, the inner autopilot loop is designed separately from the outer guidance loop, whereas in the single-loop scheme, the guidance command is injected directly to the actuator, without a definite autopilot. It is proven that the two schemes achieve the same performance if and only if the number of guidance commands is identical to the number of available controllers. Thus, using the full-state two-loop scheme may be preferred, because it ensures a stabilized airframe whether the guidance loop is active or not. The theorem and guidance laws are illustrated using a dual-control missile model.

Linear Quadratic Integrated Versus Separated Autopilot-Guidance Design

Two types of guidance and control design concepts are explored: a traditional separated approach and an integrated one. Using the integrated approach, two different guidance systems are presented: a single-loop guidance law and a two-loop autopilot-guidance law. In the two-loop case, the autopilot loop is designed separately from the guidance one, but all the states are fed back into the guidance loop. It is proven that the integrated guidance laws achieve the same performance for single-input single-output systems. The performance of the three guidance laws is evaluated and compared via a thrust vector control missile. It is shown that the performance of the separated guidance law is inferior to that of the integrated laws.

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.

Introduction to robust ship track-keeping control design

The application of modern robust control techniques to the problem of surface ship track-keeping control will be considered. The system structure will be assessed and a control strategy proposed which exploits the intrinsic characteristics of the dynamics to provide a natural means of scheduling the controller with surge speed. The design philosophy enables the ship autopilot loop to be used with or without the outer track-keeping control action.

Teh Philosophy, Design, and Development of Miartes

"Miartes" is a code name for a Missile Autopilot Research and Teaching Simulator designed initially to satisfy the requirement for a special-purpose analog computer on which the principles of missile control and automatic control engineering could be taught simultaneously. The simulator is based on the roll autopilot suitable for the hypothetical missile "Flying Shrew." A sophisticated flight envelope, extending in altitude from sea-level to 70 000 feet and in speed from Mach 1.0 to Mach 2.0, necessitates a novel approach to the computer design if rescaling is to be avoided. The sophisticated ffight envelope chosen vividly illustrates the need for some form of adaptive autopilot loop. The simulator is intended to supplement more complex specialized computers, and general-purpose analog computers in an integrated course involving several specializations. It has been found that the use of the "Flying Shrew" mathematical model has enabled a thorough integration between lecture room and laboratory to be achieved. Calibration of the simulator is directly in terms of missile autopilot parameters, and, since rescaling is avoided, the effective student absorption rate is at least four times greater than with older methods of teaching. The simulator is also an excellent basis for student design and research projects.