Reconfigurable Flight Control Design for Combat Flying Wing with Multiple Control Surfaces

With control using redundant multiple control surface arrangement and large-deflection drag rudders,a combat flying wing has a higher probability for control surface failures.Therefore,its flight control system must be able to reconfigure after such failures.Considering three types of typical control surface failures（lock-in-place（LIP）,loss-of-effectiveness（LOE） and float）,flight control reconfiguration characteristic and capability of such aircraft types are analyzed.Because of the control surface redundancy,the aircraft using the dynamic inversion flight control law already has a control allocation block.In this paper,its flight control configuration during the above failures is achieved by modifying this block.It is shown that such a reconfigurable flight control design is valid,through numerical simulations of flight attitude control task.Results indicate that,in the circumstances of control surface failures with limited degree and the degradation of the flying quality level,a combat flying wing adopting this flight control reconfiguration approach based on control allocation could guarantee its flight safety and perform some flight combat missions.

Adaptive leader follower control for multiple quadrotors via multiple surfaces control

Based on the multiple surface and fixed undirected communication topology, the adaptive leader follower contrul for multiple quadrotors is discussed. Our approach is based on leader follower architecture. Multiple surface control （MSC） is used to design consensus controller to make multiple quadrotors construct a formation during flying with the presence of uncertainty item caused by the ground effect during landing or taking off. Simulation results are presented to validate the effectiveness of the proposed controller.

Disturbance Observer-Based Safe Tracking Control for Unmanned Helicopters With Partial State Constraints and Disturbances

In this paper, a disturbance observer-based safe tracking control scheme is proposed for a medium-scale unmanned helicopter with rotor flapping dynamics in the presence of partial state constraints and unknown external disturbances. A safety protection algorithm is proposed to keep the constrained states within the given safe-set. A second-order disturbance observer technique is utilized to estimate the external disturbances. It is shown that the desired tracking performance of the controlled unmanned helicopter can be achieved with the application of the backstepping approach, dynamic surface control technique, and Lyapunov method. Finally, the availability of the proposed control scheme has been shown by simulation results.

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 naturally existing time scale separation. Secondly, the controller based on DSC is designed after obtaining the linear dynamics characteristics of the slow and fast subsystems. An extended state observer is used to detect the uncertainty of the system state variables and aerodynamic parameters to achieve the compensation of the control law. The closed-loop stability of the controller is derived and rigorously analyzed. Finally, the effectiveness and robustness of the design is verified by Monte Carlo simulation considering different initial conditions and parameter uptake. Simulation results illustrate that the missile autopilot based DSC controller achieves better performance and robustness than the other two well-known autopilots.The method proposed in this paper is applied to the design of a missile autopilot, and the results show that the acceleration tracking autopilot based on the DSC controller can ensure accurate tracking of the required commands and has better performance.

Shallow Tunneling Method and Control Measure for Ground Surface Settlement

In order to ensure that the tunnel deformation and surface settlement are controlled within the allowable range during the construction process,the design unit has compiled technical measures and monitoring schemes for ground settlement control of this project.Based on the example of a shallow tunneling project on Subway line 8,this paper analyzes and discusses the shallow tunneling method in detail and puts forward corresponding technical measures for ground settlement control.

Robust adaptive dynamic surface control for nonlinear uncertain systems

We propose a new method for robust adaptive backstepping control of nonlinear systems with parametric uncertainties and disturbances in the strict feedback form. The method is called dynamic surface control. Traditional backstepping algorithms require repeated differentiations of the modelled nonlinearities. The addition of n first order low pass filters allows the algorithm to be implemented without differentiating any model nonlinearities, thus ending the complexity arising due to the 'explosion of terms' that makes other methods difficult to implement in practice. The combined robust adaptive backstepping/first order filter system is proved to be semiglobally asymptotically stable for sufficiently fast filters by a singular perturbation approach. The simulation results demonstrate the feasibility and effectiveness of the controller designed by the method.

INVESTIGATION OF ACTIVE CONTROL FOR DYNAMIC STABILITY OF HELICOPTER ROTOR－BODY COUPLING

A study is conducted on the feasibility of helicopter ground and air resonanceby using actively controlled tabs mounted at the trailing edge of an aerofoil. A method isdeveloped to obtain the optimal feedback control law through constructing a referencemodel according to requirements of stability levels in the modal space. The effects of rotorspeed and length and location of tabs on the control law are analyzed, and it is found possible that a controller can be designed into constant feedback gain against rotor speed andto feed back only to the dominant system states to eliminate the unstable range of rotorspeed.

Electrochemically Deposited CZTSSe Thin Films for Monolithic Perovskite Tandem Solar Cells with Efficiencies Over 17%

In spite of the high potential economic feasibility of the tandem solar cells consisting of the halide perovskite and the kesterite Cu2ZnSn(S,Se)4(CZTSSe),they have rarely been demonstrated due to the difficulty in implementing solution-processed perovskite top cell on the rough surface of the bottom cells.Here,we firstly demonstrate an efficient monolithic two-terminal perovskite/CZTSSe tandem solar cell by significantly reducing the surface roughness of the electrochemically deposited CZTSSe bottom cell.The surface roughness(R_(rms))of the CZTSSe thin film could be reduced from 424 to 86 nm by using the potentiostatic mode rather than using the conventional galvanostatic mode,which can be further reduced to 22 nm after the subsequent ion-milling process.The perovskite top cell with a bandgap of 1.65 eV could be prepared using a solution process on the flattened CZTSSe bottom cell,resulting in the efficient perovskite/CZTSSe tandem solar cells.After the current matching between two subcells involving the thickness control of the perovskite layer,the best performing tandem device exhibited a high conversion efficiency of 17.5%without the hysteresis effect.

Adaptive Dynamic Surface Control for Integrated Missile Guidance and Autopilot

Integrated guidance and control for homing missiles utilizing adaptive dynamic surface control approach is considered based on the three channels independence design idea. A time-varying integrated guidance and control model with unmatched uncertainties is first formulated for the pitch channel, and an adaptive dynamic surface control algorithm is further developed to deal with these unmatched uncertainties. It is proved that the proposed feedback controller can ensure not only the accuracy of target interception, but also the stability of the missile dynamics. Then, the same control approach is further applied to the control design of the yaw and roll channels. The 6-degree-of-freedom （6-DOF） nonlinear missile simulation results demonstrate the feasibility and advantage of the proposed integrated guidance and control design scheme.

Innovative backfilling longwall panel layout for better subsidence control effect-separating adjacent subcritical panels with pillars

In recent years,field trials of non-pillar longwall mining using complete backfill have been implemented successively in the Chinese coal mining industry.The objective of this paper is to get a scientific understanding of surface subsidence control effect using such techniques.It begins with a brief overview on complete backfill methods primarily used in China,followed by an analysis of collected subsidence factors under mining with complete backfill.It is concluded that non-pillar longwall panel layout cannot protect surface structures against damages at a relatively large mining height,even though complete backfill is conducted.In such cases,separated longwall panel layout should be applied,i.e.,panel width should be subcritical and stable coal pillars should be left between the adjacent panels.The proposed method takes the principles of subcritical extraction and partial extraction;in conjunction with gob backfilling,surface subsidence can be effectively mitigated,thus protecting surface buildings against mining-induced damage.A general design principle and method of separated panel layout have also been proposed.

Adaptive dynamic surface control for air-breathing hypersonic vehicle

This paper describes an adaptive control approach for an air-breathing hypersonic vehicle. The control objective is to provide robust altitudes and velocity tracking in the presence of model uncertainties and varying disturbances. A fuzzy-neural disturbance observer is developed to estimate uncertainties and disturbances, and the adaptive controller is synthesized by the dynamic surface approach combing with the observer. The tracking error at the steady state can be guaranteed to converge to inside of a small residue set which the size of the set can be an arbitrary small value. Simulation results demonstrate the effectiveness of the presented approach.

Dynamic surface control-backstepping based impedance control for 5-DOF flexible joint robots

A new impedance controller based on the dynamic surface control-backstepping technique to actualize the anticipant dynamic relationship between the motion of end-effector and the external torques was presented. Comparing with the traditional backstepping method that has ＂explosion of terms＂ problem, the new proposed control system is a combination of the dynamic surface control technique and the backstepping. The dynamic surface control （DSC） technique can resolve the ＂explosion of terms＂ problem that is caused by differential coefficient calculation in the model, and the problem can bring a complexity that will cause the backstepping method hardly to be applied to the practical application, especially to the multi-joint robot. Finally, the validity of the method was proved in the laboratory environment that was set up on the 5-DOF （degree of freedom） flexible joint robot. Tracking errors of DSC-backstepping impedance control that were 2.0 and 1.5 mm are better than those of backstepping impedance control which were 3.5 and 2.5 mm in directions X, Y in free space, respectively. And the anticipant Cartesian impedance behavior and compliant behavior were nchieved successfully as depicted theoretically.

A Flexible Hingeless Control Surface Inspired by Aquatic Animals

A flexible hingeless control surface model was proposed for motion control of Underwater Vehicles (UVs),which is inspiredby the flexible bending control surfaces of underwater creatures,such as fish and squid.Computational Fluid Dynamics(CFD) simulation demonstrates that,in comparison with the hinged or rigid control surface,the proposed flexible bendingcontrol surface can suppress the flow separation so as to improve the turning performance.A prototype of the flexible controlsurface was fabricated,in which Shape Memory Alloy (SMA) wires were selected as the actuators.The elastic energy storageand exchange mechanism was incorporated into the actuation of the control surface to improve the efficiency.Thermal analysisof SMA wires was performed to find proper actuating condition.Open-loop bending experiments were carried out.The resultsshow that the proposed control surface can achieve the maximum bending angle of 104°.Moreover,the power and energyconsumption under different pulse conditions were compared.

Adaptive Fuzzy Dynamic Surface Control of Flexible-Joint Robot Systems With Input Saturation

In this paper, we propose an adaptive fuzzy dynamic surface control(DSC) scheme for single-link flexible-joint robotic systems with input saturation. A smooth function is utilized with the mean-value theorem to deal with the difficulties associated with input saturation. An adaptive DSC design with an auxiliary first-order filter is used to solve the "explosion of complexity"problem. It is proved that all the signals in the closed-loop system are semi-globally uniformly ultimately bounded, and the tracking error eventually converges to a small neighborhood around zero. The main advantage of the proposed method is that only one adaptation parameter needs to be updated,which reduces the computational burden significantly. Simulation results demonstrate the feasibility of the proposed scheme and the comparison results show that the improved DSC method can reduce the computational burden by almost two thirds in comparison with the standard DSC method.

Nonlinear aeroelastic analysis of a two-dimensional wing with control surface in supersonic flow

Based on the piston theory of supersonic flow and the energy method, a two dimensional wing with a control surface in supersonic flow is theoretically modeled, in which the cubic stiffness in the torsional direction of the control surface is considered. An approximate method of the cha- otic response analysis of the nonlinear aeroelastic system is studied, the main idea of which is that under the condi- tion of stable limit cycle flutter of the aeroelastic system, the vibrations in the plunging and pitching of the wing can approximately be considered to be simple harmonic excita- tion to the control surface. The motion of the control surface can approximately be modeled by a nonlinear oscillation of one-degree-of-freedom. The range of the chaotic response of the aeroelastic system is approximately determined by means of the chaotic response of the nonlinear oscillator. The rich dynamic behaviors of the control surface are represented as bifurcation diagrams, phase-plane portraits and PS diagrams. The theoretical analysis is verified by the numerical results.

Adaptive Pseudo Inverse Control for a Class of Nonlinear Asymmetric and Saturated Nonlinear Hysteretic Systems

This paper aims at eliminating the asymmetric and saturated hysteresis nonlinearities by designing hysteresis pseudo inverse compensator and robust adaptive dynamic surface control(DSC)scheme.The"pseudo inverse"means that an on-line calculation mechanism of approximate control signal is developed by applying a searching method to the designed temporary control signal where the true control signal is included.The main contributions are summarized as:1)to our best knowledge,it is the first time to compensate the asymmetric and saturated hysteresis by using hysteresis pseudo inverse compensator because the construction of the true saturated-type hysteresis inverse model is very difficult;2)by designing the saturated-type hysteresis pseudo inverse compensator,the construction of true explicit hysteresis inverse and the identifications of its corresponding unknown parameters are not required when dealing with the saturated-type hysteresis;3)by combining DSC technique with the tracking error transformed function,the"explosion of complexity"problem in backstepping method is overcome and the prespecified tracking performance is achieved.Analysis of stability and experimental results on the hardware-inloop platform illustrate the effectiveness of the proposed adaptive pseudo inverse control scheme.

Output-feedback Dynamic Surface Control for a Class of Nonlinear Non-minimum Phase Systems

In this paper, an output-feedback tracking controller is proposed for a class of nonlinear non-minimum phase systems.To keep the unstable internal dynamics bounded, the method of output redefinition is applied to let the stability of the internal dynamics depend on that of redefined output, thus we only need to consider the new external dynamics rather than internal dynamics in the process of designing control law. To overcome the explosion of complexity problem in traditional backstepping design, the dynamic surface control(DSC) method is firstly used to deal with the problem of tracking control for the nonlinear non-minimum phase systems. The proposed outputfeedback DSC controller not only forces the system output to asymptotically track the desired trajectory, but also drives the unstable internal dynamics to follow its corresponding bounded and causal ideal internal dynamics, which is solved via stable system center method. Simulation results illustrate the validity of the proposed output-feedback DSC controller.

Adaptive Neural Network Dynamic Surface Control for Perturbed Nonlinear Time-delay Systems

This paper proposes an adaptive neural network control method for a class of perturbed strict-feedback nonlinear systems with unknown time delays. Radial basis function neural networks are used to approximate unknown intermediate control signals. By constructing appropriate Lyapunov-Krasovskii functionals, the unknown time delay terms have been compensated. Dynamic surface control technique is used to overcome the problem of ＂explosion of complexity＂ in backstepping design procedure. In addition, the semiglobal uniform ultimate boundedness of all the signals in the closed-loop system is proved. A main advantage of the proposed controller is that both problems of ＂curse of dimensionality＂ and ＂explosion of complexity＂ are avoided simultaneously. Finally, simulation results are presented to demonstrate the effectiveness of the approach.

Adaptive Fuzzy Dynamic Surface Control for Uncertain Nonlinear Systems

In this paper, a robust adaptive fuzzy dynamic surface control for a class of uncertain nonlinear systems is proposed. A novel adaptive fuzzy dynamic surface model is built to approximate the uncertain nonlinear functions by only one fuzzy logic system. The approximation capability of this model is proved and the model is implemented to solve the problem that too many approximators are used in the controller design of uncertain nonlinear systems. The shortage of ＂explosion of complexity＂ in backstepping design procedure is overcome by using the proposed dynamic surface control method. It is proved by constructing appropriate Lyapunov candidates that all signals of closed-loop systems are semi-globally uniformly ultimate bounded. Also, this novel controller stabilizes the states of uncertain nonlinear systems faster than the adaptive sliding mode controller （SMC）. Two simulation examples are provided to illustrate the effectiveness of the control approach proposed in this paper.