ایمان محمدزمان

A linear matrix inequality (LMI)-based algorithm is developed to design a robust state-feedback controller using integral quadratic constraints (IQCs) for an uncertain linear parameter varying system (LPVS). The uncertain LPVS is described by an interconnection of a nominal LPVS which is solely dependent on the measurable parameters and a block-structured uncertainty. The IQC approach is implemented to model the input/output behavior of the uncertainties. In general, the robust synthesis method and the IQC stability analysis for the uncertain LPVS lead to a non-convex problem and are solved by the iterative algorithms. However, in the proposed method, the problem is converted into a convex problem. Therefore, the LPV synthesis for the nominal LPVS and the IQC analysis for handling uncertainties are performed simultaneously. Consequently, without any constraints on nominal system matrices, the proposed method might achieve a better performance and less computational burden. Furthermore, the object is to minimize the l 2 -gain, H ∞  control, when the closed-loop asymptotical stability is also guaranteed. The performance and effectiveness of the proposed method are demonstrated based on two examples

In this paper, a new approach is presented to design a gain-scheduled state-feedback controller for uncertain linear parameter-varying systems. It is supposed that the state-space matrices of them are the linear combination of the uncertain scheduling parameters. It is assumed that the existed uncertainties are of type of time-invariant parametric uncertainties with specified intervals. Simultaneous presence of the concepts of the gain-scheduling and the time-invariant uncertainties is a serious challenge. Because, the philosophy of the gain-scheduling is variability with time. But, the time-invariant parametric uncertainties are constant and unknown. To obviate this challenge, a robust state-feedback law is proposed that is robust against the time-invariant uncertainties. In this method, the arbitrary values are selected for the uncertainties from the defined intervals. But, the selected values are not necessarily equal to the true ones. Hence, the new scheduling parameters are presented to calculate the proposed controller. Finally, the proof of the proposed scheme is presented based on Lyapunov concept. To show the effectiveness of the final controller, the proposed method is simulated to stabilize the roll rate of a typical missile. Also, the simulation results are compared with the experimental ones in the presence of the INS (Inertial Navigation System) module.

Because of refraction of the incoming wave in the radar-guided interceptors, the radome can cause large miss distance and even having a destabilizing effect on the guidance system. On the other hand, the radome imposes an unwanted feedback that is not similar to the conventional feedback loops, in which output must follow a desired control signal. In this paper, the destructive effect of radome in guidance loop stability and performance is analyzed at first. Then, proposing a virtual integrator operator, the problem is transformed to a conventional tracking control problem so that the performance indexes can be defined in control aspect. Regarding the parametric uncertainty of the radome slope, µ-synthesis approach is used to design a robust compensator. Simulation results and stability analysis show that the designed compensator improves the guidance system performance in the presence of the radome, while the stability is guaranteed.

In this paper a robust autopilot is designed using fuzzy gain scheduling. At first the flight envelop is divided to sub regions using v-gap metric and a suitable operating point is selected in each region and robust static H∞ loop shaping controller is designed for the linearized model. Finally, fuzzy gain scheduling is used to interpolate the local controllers. Simulation results show the generality and effectiveness of the proposed control strategy in terms of the performance and robustness of the system.

In this paper, a novel integrated guidance and control (IGC) approach is designed using the combination of backstepping and sliding mode control methods. In contrast to the traditional methods combining the kinematic and dynamic equations and deriving a state space model as an integrated unit model, the proposed method designs the guidance and control problem in a single loop. This algorithm is robust with respect to the uncertainties in the target acceleration and missile dynamic model. Simulation results using six-degrees-of-freedom simulation aerodynamic model (6DOF) and three-dimension (3-D) engagement show that the proposed IGC design, with guidance and control dynamic synergism, eventuates interception with the maneuvering target.

Radome causes refraction of the incoming rardar wave in radar-guided interceptors, thus having a destabilizing effect on the guidance loop, especially at high altitudes. Therefore, a compensator is required to maintain the stability of the guidance loop and causes minimum miss distance in the presence of radome error. From the control perspective, Radome causes an unwanted feedback that is not similar to the conventional feedback loops, in which output must follow a desired control signal. In this paper, the desired closed-loop response is determined first, then a novel approach is proposed to shape the frequency response of the feedforward path so that the stability and performance requirements are satisfied . Frequency response is shaped by linear matrix inequality (LMI) tools and v-gap metric is used to select the best frequency response. Simulation results show that the designed compensator drastically decreases the miss distance, while the stability is guaranteed.

This paper presents a new stability preserving interpolation technique for robust gain scheduling autopilot design. The interpolation method is based on interpolation in the common stability region of local controllers and generates a gain-scheduled controller that is stabilizing at every operating point of a closed loop system. For selection of stability region of local controllers, the notion of the v-gap metric and its connection to robust loop-shaping theory is used. The proposed method facilitates the design of gain-scheduled controllers that preserves stability of the closed loop system. The simulation results given show the generality and effectivneness of the proposed control strategy in terms of the stability, performance and robustness, of the system.

In this paper a robust autopilot is designed for a low altitude and short range interceptor. Operating point is selected with v-gap metric tool and robust static H∞ loop shaping controller is designed for the linearized model. Propose method does not use gain scheduling approach and guarantees stability of the interceptor’s nonlinear dynamics in the whole flight envelope. Also an algorithm is proposed in order to reduce complexity synthesis of the weights in the loop shaping controller. In this algorithm the weights are optimized in order to maximize the robust stability margin. It is shown that robust stability margin which achieved by the controller can guarantee the stability of interceptor in the whole flight envelope.

In this paper, a two point guidance law for homing interceptors using finite time second order sliding mode control and based on parallel navigation is proposed. In the proposedguidance law, sliding surface is selected as the line of sight rate and the target maneuvers are considered as an uncertainty which only needs the upper bound of these maneuvers. Furthermore, the proposed algorithm can guarantee the finite time convergence of the LOS rate to zero or a small neighborhood of zero. Therefore, the performance and stability of guidance loop against maneuvering targets are increased.

In this paper, a PI guidance law with finite time convergence is proposed to nullify the LOS rate in finite time. With the new guidance law, the line-of-sight angular rate will converge to zero or a small neighborhood of zero before the final time of the guidance process. Furthermore, the proposed PI guidance law is extended to the first order pursuit dynamics which can guarantee the stability of the guidance loop and finite time convergence of the LOS rate. In this case, high derivatives of the LOS rate are appeared in the guidance law. Simulation results show the effectiveness and robustness of the proposed guidance law against maneuvering target as compared with finite time PN and true proportional navigation guidance law.

In this paper, a PI guidance law is proposed to nullify the LOS rate. Stability of the guidance dynamics including autopilot and seeker dynamics is analyzed by employing circle criterion. Stability conditions give an analytical bound for the time of the flight up to which stability can be assured. The stability bound of the new guidance law is less conservatism than PN guidance law. Also, this approach can be used as a tool for Guidance, Autopilot and seeker parameters design. Simulation results show the effectiveness and robustness of the proposed guidance law against maneuvering target as compared to PN.

In this paper a new guidance law is proposed to guarantee the stability of the guidance loop considering first order pursuit dynamics using short time stability theorem. As homing guidance is operates over a finite time, short time stability criterion which is defined over a specified time interval can be used effectively in guidance loop stability analysis. Proposed guidance law utilizes line of sight angular rate and pursuit acceleration measurements. Stability region which depends on the pursuit dynamics and guidance gains is an analytical expression in terms of time to go. Stability condition of the new guidance law is less conservatism than classical proportional navigation guidance law.