Robust missile autopilot design based on dynamic surface control

Since the dynamical system and control system of the missile are typically nonlinear, an effective acceleration tracking autopilot is designed using the dynamic surface control(DSC)technique in order to make the missile control system more robust despite the uncertainty of the dynamical parameters and the presence of disturbances. Firstly, the nonlinear mathematical model of the tail-controlled missile is decomposed into slow acceleration dynamics and fast pitch rate dynamics based on the natura...     

Research for the orientation detection system using L-shape reticle

The basic scheme of the orientation detection system using L-shape reticle is introduced. The dimension of the patterns on the reticle of the system in practical applications is designed and an analysis of the principle of abstracting the orientation information of the target and the effects and formation method of self-adapting tracking gate is presented. The research result shows that the orientation detection system using L-shape reticle has a good effect on space-filtering, the signals that the orientation detection system sends out are easy to be processed by computer, its self-adapting tracking gate has a strong anti-interference ability, and the whole system＇s searching and tracking performances are quite high.     

Convergence of Self-Tuning Regulators under Conditional Heteroscedastic Noises with Unknown High-Frequency Gain

In the classical theory of self-tuning regulators, it always requires that the conditional variances of the systems noises are bounded. However, such a requirement may not be satisfied when modeling many practical systems, and one significant example is the well-known ARCH(autoregressive conditional heteroscedasticity) model in econometrics. The aim of this paper is to consider self-tuning regulators of linear stochastic systems with both unknown parameters and conditional heteroscedastic noises, where the adaptive controller will be designed based on both the weighted least-squares algorithm and the certainty equivalence principle. The authors will show that under some natural conditions on the system structure and the noises with unbounded conditional variances, the closed-loop adaptive control system will be globally stable and the tracking error will be asymptotically optimal.Thus, this paper provides a significant extension of the classical theory on self-tuning regulators with expanded applicability.     

Robust stability analysis for a cruise missile

A global controller design methodology for a flight stage of the cruise missile is proposed. This methodology is based on the method of least squares, To prove robust stability in the full airspace with parameter disturbances, the concepts of convex polytopic models and quadratic stability are introduced, The effect of aerodynamic parameters on system performance is analyzed. The designed controller is applied to track the overloading signal of the cruise segment of the cruise missile, avoiding system disturbance owing to controller switching, Simulation results demonstrate the validity of the proposed method.     

Adaptive robust control of mobile satellite communication system with disturbance and model uncertainties

The tracking and stable control of a typical shipmounted mobile satellite communication system(MSCS) is studied.Unlike the former studies based on simplified single-axis models,a tri-axis nonlinear model including the kinematic and dynamic features of the MSCS is used as the control object.An adaptive robust controller with trajectory planning is designed to deal with large parametric uncertainties and uncertain nonlinearities of the system.A theoretic performance result is given and proved.The designed adaptive robust controller and other two traditional controllers are tested in the comparative simulations under three different situations.The simulation results show the tracking and stable validity of the proposed controller.     

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.     

Trajectory tracking theory of quantum systems

The orbit tracking problem of a free-evolutionary target system in closed quantum systems is solved by changing it into the state transferring problem with the help of unitary transformation.The control law designed by the Lyapunov stability theorem employs a carefully constructed virtual mechanical quantity P to ensure the system convergence.The virtual mechanical quantity P is chosen by two approaches according to the forms of limit set,where P = —pf is suitable for regular limit set and a new different P is constructed for irregular one.The proposed tracking control theory is demonstrated on a four-level quantum system by means of numerical simulation experiments.     

Distributed tracking for networked Euler-Lagrange systems without velocity measurements

The problem of distributed coordinated tracking control for networked Euler-Lagrange systems without velocity measurements is investigated. Under the condition that only a portion of the followers have access to the leader, sliding mode estimators are developed to estimate the states of the dynamic leader in finite time. To cope with the absence of velocity measurements, the distributed observers which only use position information are designed. Based on the outputs of the estimators and observers, distributed tracking control laws are proposed such that all the fol- lowers with parameter uncertainties can track the dynamic leader under a directed graph containing a spanning tree. It is shown that the distributed observer-controller guarantees asymptotical stability of the closed-loop system. Numerical simulations are worked out to illustrate the effectiveness of the control laws.     

Design and application of single-antenna GPS/accelerometers attitude determination system

In view of the problem that the current single-antenna GPS attitude determination system can only determine the body attitude when the sideslip angle is zero and the multiantenna GPS/SINS integrated navigation system is of large volume, high cost, and complex structure, this approach is presented to determine the attitude based on vector space with single-antenna GPS and accelerometers in the micro inertial measurement unit （MIMU）. It can provide real-time and accurate attitude information. Subsequently, the single-antenna GPS/SINS integrated navigation system is designed based on the combination of position, velocity, and attitude. Finally the semi- physical simulations of single-antenna GPS attitude determination system and single-antenna GPS/SINS integrated navigation system are carried out. The simulation results, based on measured data, show that the single-antenna GPS/SINS system can provide more accurate navigation information compared to the GPS/SINS system, based on the combination of position and velocity. Furthermore, the single-antenna GPS/SINS system is characteristic of lower cost and simpler structure. It provides the basis for the application of a single-antenna GPS/SINS integrated navigation system in a micro aerial vehicle （MAV）.     

Trajectory linearization control of an aerospace vehicle based on RBF neural network

An enhanced trajectory linearization control （TLC） structure based on radial basis function neural network （RBFNN） and its application on an aerospace vehicle （ASV） flight control system are presensted. The influence of unknown disturbances and uncertainties is reduced by RBFNN thanks to its approaching ability, and a robustifying itera is used to overcome the approximate error of RBFNN. The parameters adaptive adjusting laws are designed on the Lyapunov theory. The uniform ultimate boundedness of all signals of the composite closed-loop system is proved based on Lyapunov theory. Finally, the flight control system of an ASV is designed based on the proposed method. Simulation results demonstrate the effectiveness and robustness of the designed approach.     

Chaotic Behavior of a Generalized Hamiltonian System and Its Circuit Implementation北大核心CSCD

A kind of generalized Hamiltonian systems with dissipative structure and external input is proposed. By configuring its structure matrix and external input, a simpler three-dimensional dynamical system with only one fixed point is designed to illustrate the existence of chaos. Useful tools, including phase portrait, Poincaré section, Lyapunov exponents, bifurcation diagram and power spectrum, are used for detecting chaotic behavior of the proposed system with the enhancement of DC input. Compared with the known three-dimensional chaotic systems, the proposed system has the following two characteristics: Its dissipativity is related to system state variables and its Lyapunov dimension is closer to 3. Finally, a circuit implementation of the new system is presented and the results recorded on an analogue oscilloscope further verify the existence of chaotic behavior. © 2017, The Journal of Agency of Complex Systems and Complexity Science. All right reserved.     

Reference tracking control for flexible air-breathing hypersonic vehicle with actuator delay and uncertainty

This paper considers the problem of reference tracking control for the flexible air-breathing hypersonic flight vehicle with actuator delay and uncertainty.By constructing the Lyapunov functional including the lower and upper bounds of the time-varying delay,the non-fragile controller is designed such that the resulting closed-loop system is asymptotically stable and satisfies a prescribed performance cost index.The simulation results are given to show the effectiveness of the proposed control method,which is validated by excellent output reference altitude and velocity tracking performance.     

QFT control based on zero phase error compensation for flight simulator

To improve the robustness of high-precision servo systems, quantitative feedback theory (QFT) which aims to achieve a desired robust design over a specified region of plant uncertainty is proposed. The robust design problem can be solved using QFT but it fails to guarantee a high precision tracking. This problem is solved by a robust digital QFT control scheme based on zero phase error (ZPE) feed forward compensation. This scheme consists of two parts: a QFT controller in the closed-loop system and a ZPE feed-forward compensator. Digital QFT controller is designed to overcome the uncertainties in the system. Digital ZPE feed forward controller is used to improve the tracking precision. Simulation and real-time examples for flight simulator servo system indicate that this control scheme can guarantee both high robust performance and high position tracking precision.     

Unpower aerocraft augmented state feedback tracking guaranteed cost control

Aimed at designing the unpower aerocraft attitude control system in a simple and practical way, the guaranteed cost control is adopted. To eliminate the steady-error, a novel tracking control approach--augmented state feedback tracking guaranteed cost control is proposed. Firstly, the unpower aerocraft is modeled as a linear system with norm bounded parameter uncertain, then the linear matrix inequality based state feedback guaranteed cost control law is combined with the augmented state feedback tracking control from a new point of view. The sufficient condition of the existence of the augmented state feedback tracking guaranteed cost control is derived and converted to the feasible problem of the linear matrix inequality. Finally, the proposed approach is applied to a specified unpower aerocraft. The six dimensions of freedom simulation results show that the proposed approach is effective and feasible.     

Adaptive Robust Dead-Zone Compensation Control of Electro-Hydraulic Servo Systems with Load Disturbance Rejection

A backstepping method based adaptive robust dead-zone compensation controller is proposed for the electro-hydraulic servo systems(EHSSs) with unknown dead-zone and uncertain system parameters.Variable load is seen as a sum of a constant and a variable part.The constant part is regarded as a parameter of the system to be estimated real time.The variable part together with the friction are seen as disturbance so that a robust term in the controller can be adopted to reject them.Compared with the traditional dead-zone compensation method,a dead-zone compensator is incorporated in the EHSS without constructing a dead-zone inverse.Combining backstepping method,an adaptive robust controller(ARC) with dead-zone compensation is formed.An easy-to-use ARC tuning method is also proposed after a further analysis of the ARC structure.Simulations show that the proposed method has a splendid tracking performance,all the uncertain parameters can be estimated,and the disturbance has been rejected while the dead-zone term is well estimated and compensated.     

Nonlinear differential geometric guidance for maneuvering target

Based on the idea of zeroing the line of sight rate(LOSR),a novel nonlinear differential geometric(DG) law for intercepting the agile target is proposed.In the first part,the DG formulations are utilized to describe the relatively kinematics model of missile and target,and the nonlinear DG guidance(DGG) law is proposed based on the nonlinear control theory to eliminate the influence brought by target.Further,the missile guidance commands are derived to overcome the information loss caused by decoupling condition,the new necessary initial condition is developed to guarantee capture the agile target.Then,the designed nonlinear DGG commands are transformed from an arc-length system to the time domain.A desirable aspect of the designed guidance law is that it does not require rigorous information about target acceleration.Representative numerical results show that the designed guidance law obtain a better performance than the traditional DGG law for agile target.     

Multi-dimensional scattering properties diagnosis system of scale aircraft model in an anechoic chamber

Aiming at the concept of ＂diagnosis＂, a simple and effective broadband radar cross section （RCS） measurement system is constructed, and some multi-dimensional scattering properties diagnosis techniques are presented based on the system. Firstly, a stepped-frequency signal is employed to achieve high range resolution, combining with a variety of signal processing tech- niques. Secondly, cross-range resolution is gained with a rotating table, and the high-resolution two-dimensional （2-D） imaging of the scale model is obtained by the microwave imaging theory. Finally, two receiving antennas with a small distance in altitude are used, and the three-dimensional （3-D） height distribution of scattering points on the scale model is extracted from the phase of images. Some typical bodies and a scale aircraft model are diagnosed in an anechoic chamber. The experimental results show that, after scaling with a metal sphere, the accurate one- dimensional （l-D） RCS pattern of the model is obtained, and it has a large dynamic range. When the bandwidth of the transmitting signal is 4 GHz, the resolution of the 2-D image can reach to 0.037 5 m. The 3-D height distribution of scattering points is given by interferometric measurement. This paper provides a feasible way to obtain high-precision scattering properties parameters of the scale aircraft model in a conventional rectangular anechoic chamber.     

Study on the Generation of Ultra-Wideband (UWB) High Power Microwave

The experimental study of ultra-wideband (UWB) technology, its generation and on-line measurement are presented. An experimental repetitive UWB system is designed, manufactured, and tested. High-pressure spark gap switch and its components, as well as oil spark gap switch are studied experimentally on the system. Experimental results indicate that the system operates at a 200 pps repetitive rate with a stable performance. 100 MW peak power UWB pulses are obtained on the system. Fast-time response capacitive divider is designed and fabricated, allowing for an accurate measurement of the high power UWB signal. The main issues related to the design of the switch and the UWB signal online measurement are discussed.     

Structure-Preserving Recurrent Neural Networks for a Class of Birkhoffian Systems

In this paper, the authors propose a neural network architecture designed specifically for a class of Birkhoffian systems — The Newtonian system. The proposed model utilizes recurrent neural networks(RNNs) and is based on a mathematical framework that ensures the preservation of the Birkhoffian structure. The authors demonstrate the effectiveness of the proposed model on a variety of problems for which preserving the Birkhoffian structure is important, including the linear damped oscillator, the...     

Sliding mode control of three-phase AC/DC converters using exponential rate reaching law

Sliding mode control(SMC) becomes a common tool in designing robust nonlinear control systems, due to its inherent characteristics such as insensitivity to system uncertainties and fast dynamic response.Two modes are involved in the SMC operation, namely reaching mode and sliding mode.In the reaching mode, the system state is forced to reach the sliding surface in a finite time.The major drawback of the SMC approach is the occurrence of chattering in the sliding mode, which is undesirable in most applications.Generally, the trade-off between chattering reduction and fast reaching time must be considered in the conventional SMC design.This paper proposes SMC design with a novel reaching law called the exponential rate reaching law(ERRL) to reduce chattering, and the control structure of the converter is designed based on the multiinput SMC that is applied to a three-phase AC/DC power converter.The simulation and experimental results show the effectiveness of the proposed technique.