Loss Of Control Effectiveness Research Articles

A Novel Scalable and Reliable Control for DC Microgrids With Varying Number of Agents.

Existing scalable control methods mainly rely on a fixed block-diagonal structure for the Lyapunov matrix, potentially resulting in numerical infeasibility issues. To overcome this limitation, this article proposes a novel scalable and reliable control scheme for dc microgrids. Initially, a general model for dc microgrids is established to enhance reliability, considering scenarios involving loss of control effectiveness (LoCE) and offset faults. Subsequently, a structured free-weight matrix technique is introduced to mitigate negative coupling effects of power lines, and to address numerical infeasibility by avoiding the assumption about the Lyapunov matrix. Furthermore, the stability of the entire dc microgrid is guaranteed by checking local agent conditions, independently of power line couplings. Therefore, the proposed control scheme ensures plug-and-play scalability with varying number of agents. Finally, theoretical results are validated through numerical simulations using the MATLAB/SimPowerSystems toolbox.

Fault-Tolerant Cooperative Control for Multiple Vehicle Systems Based on Topology Reconfiguration.

In this article, the fault-tolerant synchronization and time-varying tracking control problem is investigated for nonlinear multivehicle systems (MVSs) in the presence of partial loss-of-control-effectiveness (LoCE) faults. Based on the graph theory, a two-level fault-tolerant cooperative control framework is proposed, namely, the low-level distributed nominal control scheme and the high-level topology reconfiguration protocols. The low-level scheme is developed to guarantee system performances in the fault-free scenario. With the low-level scheme, the high-level topology reconfiguration protocols, each of which corresponds to one partial LoCE fault scenario, are then proposed to mitigate the fault impact by adjusting the underlying topology. Accordingly, without modifying the structure or the design parameter of the low-level control scheme, the proposed framework can guarantee the synchronization and tracking errors of the MVS asymptotically convergent to zero in both fault-free and fault scenarios. Finally, the effectiveness of the proposed control method is verified via a simulation study of three degree-of-freedom helicopters.

Fault tolerant control with disturbance estimator for a class of linear parameter varying systems subject to time-varying fault

This paper proposes a sliding-mode control (SMC) scheme for a class of linear parameter varying (LPV) systems subject to a loss of control effectiveness and external disturbance. The LPV model is transformed into the non-LPV model representation. The updating law for unknown time-varying fault and the disturbance estimator are designed. The novel sliding-mode fault tolerant control (FTC) law is presented by using estimated fault and estimated disturbance to compensate the effects of faults in both cases: the known and the partial known system matrices. The stability analysis of closed-loop system is performed on the Lyapunov theory. The main advantage of the proposed method is to circumvent solving on-line parameter-dependent nonlinear matrix inequalities, also to adapt to the changes of unknown parameter. The feasibility of the approach is illustrated by means of the simulation examples.

Actuator and Sensor Fault Detection and Diagnosis for Unmanned Quadrotor Helicopters

In this paper, the problem of actuator and sensor fault detection and diagnosis (FDD) for unmanned quadrotor helicopters (UQHs) is addressed by utilizing the interacting multiple model (IMM) approach. The mathematical model of UQHs, including actuator and sensor faults, is firstly introduced. Actuator faults are modelled as the loss of control effectiveness in motors and sensor faults are assumed to be bias fault. In order to reduce the intensive computational load due to the large fault model set, a state augmentation (SA) strategy is applied. This strategy can not only reduce the number of elemental filter, but also identify the magnitude of faults. Through combining the IMM algorithm and the SA strategy, the proposed FDD scheme can effectively detect and diagnose multiple actuator and sensor faults. Finally, the effectiveness of the FDD scheme is validated by two simulation scenarios, and the obtained results prove that the proposed scheme is an effective tool to deal with actuator and sensor faults.

Simple Adaptive Delta Operator Aircraft Flight Control for Accommodation of Loss of Control Effectiveness

A new proof for stability of delta operator simple adaptive control is presented in terms of a set of Linear Matrix Inequalities (LMIs). The paper shows how to design a feedforward gain to satisfy the LMIs over a polytope of loss of control effectiveness failures. The MATLAB Robust Control Toolbox is used to find the feedforward gain with the smallest norm that satisfies the LMIs. Examples are presented of the F/A-18 aircraft and the Innovative Control Effectors (ICE) tailless aircraft that show the design of a feedforward gain for a loss of control effectiveness in any one control effector. The designs use a fixed eigenstructure assignment controller for an inner loop augmented with the simple adaptive controller. Simulations of both aircraft include simultaneous loss of control effectiveness failure and lateral wind gust. Simulation results for the F/A-18 aircraft show that the adaptive controller achieves almost perfect tracking whereas the nonadaptive controller cannot achieve a coordinated turn when an aileron failure occurs. The ICE tailless aircraft uses sideslip, washed-out stability axis yaw rate, and stability axis roll rate feedback for both the inner loop eigenstructure assignment controller and the simple adaptive controller. However, the adaptive controller also uses bank angle feedback. Simulation results for the ICE tailless aircraft show that the adaptive controller achieves almost perfect tracking whereas the nonadaptive controller diverges when an all moving tip failure occurs.

Controlling an unmanned quad-rotor aerial vehicle with model parameter uncertainty and actuator failure

It is challenging to stabilise an unmanned quad-rotor aerial vehicle when a dynamic change in its model parameters or failure of its actuator occurs. In this paper, a quad-rotor unmanned aerial vehicle UAV is controlled based on model reference adaptive control MRAC and a linear quadratic regulator LQR. The kinematics and dynamics of the quad-rotor are calculated, and Lyapunov's direct stability method is used to design the MRAC. In order to evaluate the performance of the adaptive control algorithms in the presence of thrust loss that may occur due to component failure or physical damage, a real quad-rotor is built from scratch using commercial components. Both controllers are designed, implemented and tested using AVR microcontrollers. Comparison is made between the controllers under normal and faulty situations and the effectiveness of the proposed control strategy is verified. Simulation and experimental results show that both controllers have satisfactory performance under normal conditions and even in the presence of the partial loss of thrust that may occur due to the loss of control effectiveness in one of the rotors or the damage of one propeller, superior system performance is observed using the proposed MRAC controller.

A Reconfiguration Scheme for Quadrotor Helicopter via Simple Adaptive Control and Quantum Logic

A reconfiguration control scheme is proposed for a quadrotor helicopter with loss of control effectiveness via simple adaptive control and quantum logic. Some good control performances of the helicopter can be achieved by applying quadratic optimal control with scheduled stability degree when the system is in normal operation. A parallel feedforward compensator is introduced to fulfill the condition of positive realness, and thus, the simple adaptive controller can be utilized for the helicopter. Quantum logic is also applied to the quadrotor control system, which achieves the quantization of the disturbances patterns. A mathematical model of the quadrotor helicopter for application is obtained from its dynamic equations with pitch, roll, and yaw axes, which includes the parameter perturbation and outer disturbances. Several simulation and experimental results for the faulty helicopter validate the robustness and reconfiguration control capability of the proposed scheme.

Neural network-based adaptive consensus tracking control for multi-agent systems under actuator faults

In this paper, a distributed output feedback consensus tracking control scheme is proposed for second-order multi-agent systems in the presence of uncertain nonlinear dynamics, external disturbances, input constraints, and partial loss of control effectiveness. The proposed controllers incorporate reduced-order filters to account for the unmeasured states, and the neural networks technique is implemented to approximate the uncertain nonlinear dynamics in the synthesis of control algorithms. In order to compensate the partial loss of actuator effectiveness faults, fault-tolerant parts are included in controllers. Using the Lyapunov approach and graph theory, it is proved that the controllers guarantee a group of agents that simultaneously track a common time-varying state of leader, even when the state of leader is available only to a subset of the members of a group. Simulation results are provided to demonstrate the effectiveness of the proposed consensus tracking method.

Experimental Test of a Two-Stage Kalman Filter for Actuator Fault Detection and Diagnosis of an Unmanned Quadrotor Helicopter

This paper addresses the problem of Faut Detection and Diagnosis (FDD) of a quadrotor helicopter system in the presence of actuator faults. To this end a Two-Stage Kalman Filter (TSKF) is used to simultaneously estimate and isolate possible faults in each actuator. The faults are modelled as losses in control effectiveness of rotors. Three fault scenarios are investigated: loss of control effectiveness in one single actuator, simultaneous loss of control effectiveness in all motors, and loss of control effectiveness in three motors with different magnitudes. The developed FDD algorithm is evaluated through experimental application to an unmanned quadrotor helicopter testbed available at the Department of Mechanical and Industrial Engineering of Concordia University, called Qball-X4. The obtained results show the effectiveness of the proposed FDD method.

Fault-Tolerant Fuzzy Gain-Scheduled PID for a Quadrotor Helicopter Testbed in the Presence of Actuator Faults

In the current study, an adaptive PID controller is proposed for fault-tolerant control of a quadrotor helicopter system in the presence of actuator faults. A fuzzy inference scheme is used to tune in real-time the controller gains. Tracking errors and change in tracking errors are used in this fuzzy scheduler to make the system act faster and more effectively in the event of fault occurrence. Two fault scenarios are investigated: the loss of control effectiveness in all actuators and the loss of control effectiveness in one single actuator. The proposed adaptive PID controller is compared with the conventional one through an experimental application to a quadrotor helicopter testbed at the Department of Mechanical and Industrial Engineering of Concordia University. The obtained results show the effectiveness of the proposed method.

Adaptive Control Allocation in the Presence of Actuator Failures

This paper proposes a control allocation framework where a feedback adaptive signal is designed for a group of redundant actuators and then it is adaptively allocated among all group members. In the adaptive control allocation structure, cooperative actuators are grouped and treated as an equivalent control effector. A state feedback adaptive control signal is designed for the equivalent effector and adaptively allocated to the member actuators. Two adaptive control allocation algorithms, guaranteeing closed-loop stability and asymptotic state tracking when partial and total loss of control effectiveness occur, are developed. Proper grouping of the actuators reduces the controller complexity without reducing their efficacy. The implementation and effectiveness of the strategies proposed is demonstrated in detail using several examples.

Fault-Tolerant Attitude Control for Flexible Spacecraft Without Angular Velocity Magnitude Measurement

S INCE some catastrophic faults or failures may be induced due to the aging or damage of actuators and sensors during the mission of a spacecraft, those faults would lead to performance degradation of the spacecraft attitude control system or even result in the specified aerospacemission failure. Therefore, fault tolerance of the spacecraft attitude control system is one of the key issues that needs to be addressed. With a view to tackle such a challenge, fault-tolerant control (FTC) has received considerable attention in order to enhance the spacecraft reliability and to guarantee the attitude control performance [1–5]. In [5], an adaptive FTC is developed for the flexible spacecraft attitude tracking system where the persistent bounded disturbances, unknown inertia parameter, and even two types of reaction wheel faults are successfully accommodated. Indeed, the aforementioned approaches offer many attractive conceptual features, but at the same time they are derived based on the availability of direct and exact measurements of both the angular velocity and the attitude orientation. It is important to note, however, that when it comes to practical implementation, the angular velocity measurements are not always available because of either cost limitations or implementation constraints. Motivated from such a practical consideration, it is therefore highly desirable to develop partial state feedback attitude control strategies with spacecraft angular velocity measurements eliminated. The issue has been addressed in the literature by using observer-based control [6,7], Lyapunov-based control [8,9], and variable structure control [10] under normal operation of spacecraft. In this work, we provide solutions to two different problems of the flexible spacecraft attitude control system. The first problem consists of developing a control law to perform a attitude stabilization maneuver without angular velocity magnitude. In contrast with the velocity-free control schemes available in the literature, the presented approach can guarantee the attitude control performance be greatly robust to external disturbances and unknown inertia parameters. The second problem solved is the casewhere both loss of control effectiveness and additive fault occur in actuators simultaneously, but the attitude still requires stabilization with high resolution. To the best knowledge of the authors, this study is the first attempt to deal with fault-tolerant attitude stabilization control for flexible spacecraft with the angular velocity magnitude eliminated. The Note is organized as follows. Section II presents the mathematical model and attitude control problems formation of a flexible spacecraft under normal and faulty actuator conditions. Section III presents the proposed fault-tolerant attitude stabilization controller without velocity magnitude in the presence of two types of actuator faults. Simulation results to demonstrate various features of the proposed scheme are given in Sec. IV followed by conclusions in Sec. V.

Robust structural control with system constraints

SUMMARY Physical limits of real control systems, such as force saturations and state variable constraints, if attained during the motion, may cause actuator damages, loss of control effectiveness or even a dynamic instability. In order to overcome these drawbacks and improve the overall reliability of the control policy without turning to uneconomic designs, it might be convenient to account for physical limitations directly in the control law. This philosophy is embraced in this paper, where a general approach is presented based on the tool of the state-dependent Riccati equation, in the general framework of nonlinear regulation. The proposed formulation is meant to be feasible to handle limitations on both state variables and control forces. This general control strategy is then specialized to the case of a seismically excited multi-storey frame structure equipped with an active mass damper subjected to actuator saturation and stroke limitation. In-depth numerical simulations are also performed in order to investigate the effectiveness of the proposed approach, for different levels of constraint severities, and its robustness against unknown random variations of structural parameters, also in the case of incomplete number of sensors, measurements affected by noise and the presence of process disturbances. Copyright © 2011 John Wiley & Sons, Ltd.

MULTI-OBJECTIVE RECONFIGURABLE CONTROLLER DESIGN FOR THREE-TANK SYSTEM USING PARAMETRIC EIGENSTRUCTURE ASSIGNMENT

The reconfigurable controller (RC) design of strongly interacting multi-input multi-output system is a challenging problem for the designer. In this paper, a parametric right eigenstructure assignment based multiobjective dynamic reconfigurable controller through state feedback is proposed against partial actuator failure for a benchmark three-tank system. The practical aspects of controller design require the conflicting objectives of robust stability to parameter perturbation and smaller controller gain to improve the transient response of the system. These design objectives rise to the minimum condition number of closed-loop eigenvector and minimum norm of feedback controller gain of closed-loop system respectively. Fast and elitist multiobjective genetic algorithm known as nondominated sorting genetic algorithm-II is successfully applied to select the pareto-optimal eigenstructure of closed-loop system. Further, RC has been designed to accommodate partial actuator failure which is considered as loss of control effectiveness in actuators. Added value of this work, the controller uses complex-valued chromosomes. The effectiveness of the proposed controller is illustrated for different actuator fault scenarios through simulation and its performance is analysed.

Aerodynamic Analysis of a Jet Transport in Windshear Encounter During Landing

Stability and control characteristics of a nominally controllable jet transport airplane that ran off the runway after touchdown during windshear encounter are evaluated based on the data in the onboard flight data recorder (FDR). To determine these characteristics, the recorded wind profile is first improved, and then the unsteady aerodynamic models for the aircraft in dynamic ground effect are estimated. The recorded wind field is improved through the extended-Kalman-filter (EKF) technique to reconstruct the wind profile along the flight path from the data in the FDR. The windshear guideline is reviewed and compared with the airport weather data. To analyze the windshear effect in more detail, unsteady aerodynamic models for the aircraft are developed based on two artificial intelligent methods, the fuzzy-logic modeling and the feed-forward neural networks, applied to the processed FDR data. The stability and control characteristics are then estimated by using these aerodynamic models. The results indicate that a less favorable dynamic ground effect exists near touchdown in crosswind. In addition, the dynamic motion is shown to exhibit directional instability, unstable yaw damping, and loss of control effectiveness near the ground in a combined crab and sideslip landing in unsteady windshear conditions.

Detection, estimation, and accommodation of loss of control effectiveness

Detection, estimation, and accommodation of loss of control effectiveness

Survey of viscous interactions associated with high Mach number flight

T most severe problems of atmospheric flight at high Mach numbers are associated with viscous-inviscid interactions. Cruise vehicles for Mach numbers above four and lifting re-entry vehicles have highly complex three-dimensional configurations in which exist many regions of high compression that can cause boundary layers to separate. Although separation can result in loss of control effectiveness or flow degradation in an engine inlet, flow reattachment gives rise to heat rates that can far exceed those for an attached boundary layer. A further, and possibly far more severe viscous interaction problem is the impingement of shock waves generated by the forebody and other external components of a vehicle on aft sections resulting in local heat rates that may be many times larger than stagnation point values. Peak heating conditions may be laminar for lifting re-entry configurations, though our knowledge of boundary layertransition is far from adequate so that transitional and turbulent flows cannot be ruled out. However, Reynolds num, bers of potential high Mach number cruise vehicles are high— 10 to 10—so that viscous interactions will be predominately associated with turbulent boundary layers and their attendant higher heat rates. The high local heat rates resulting from viscous interactions cause hot spots that could lead to catastrophic failure. Vivid examples of damage resulting from viscous interactions are given in Figs. 1 and 2. A ventral pylon on the X-15 airplane, shown in Fig. 1, caused high^local heating of the fuselage around its root, and developed large holes near its tip due to the impingement of the shock wave from a dummy ramjet it supported, during a flight at Mach 6.7 in 1967. A study of the flowfield of the pylon-mounted dummy ramjet configuration is reported in Ref. 1. Figure 2 shows considerable damage due to interaction heating to the underside of a sled and its supporting slipper as a result of a run at 7000 fps on the 7-mile test track at Holloman Air Force Base. Unlike stagnation-point heating the location is obvious, the problem with complex configurations is to determine where high heat rates are likely to occur, as well as their magnitude. It is the purpose of this paper to identify some potentially critical areas of viscous interactions associated with high Mach number vehicles and briefly review our state of knowledge in these areas with emphasis on the basic flow phenomena.

Transonic Buffeting on Aerofoils

There are many problems to be solved when it is required to fly an aircraft at speeds approaching the speed of sound. When the speed of the aeroplane exceeds its critical Mach number, regions of supersonic flow appear at points on its surface, where the velocity of the displaced air is greatest. These regions of supersonic flow increase in size with increasing speed until the flow is wholly supersonic. The range of speed in which this mixed flow occurs is called the transonic range. In this range an aircraft will experience a sudden increase in drag, trim changes, loss of control effectiveness and possibly instability, or buffeting.