Actuator failures can cause control system performance deterioration and even lead to instability and catastrophic accidents and incidents. Therefore, the adaptive control of damaged aircraft in designing flight control systems to enhance safety level has recently become the subject of research. Damage causes structural changes and parametric uncertainties which need a new modeling and control approach. In this paper, firstly, a nominal control design based on linear quadratic regulator design is used and shown that the linear quadratic regulator design is not capable of coping with the unknown actuator failure and cannot achieve satisfactory performance. Then, a feedback adaptive signal is designed based on direct approach to handle uncertain actuator failures in linearized system. The adaptive control scheme is applied to the linearized model of a large transport aircraft in which the longitudinal and lateral motions are coupled as the result of using engine differential thrusts. The type of damage which is considered for actuators in this paper is lock-in-place which means control surfaces are fixed in an uncertain value after damage. Analytical stability analysis and simulation results are presented to demonstrate the effectiveness of the proposed approach.

Recently the distributive equations involving various classes of aggregation operators have aroused widespread attention because of their importance in the theoretic and applied communities of fuzzy set theory. 2-uninorms and semi-t-operators are two special classes of aggregation operators and have been proved to be useful in many areas such as fuzzy decision making, approximate reasoning and so on. Therefore, the aim of this paper is to investigate the left (right) distributivity of semi-t-operators over 2-uninorms. We consider five subclasses of 2-uninorms and characterize the corresponding left (right) distributive equations of semi-t-operators over 2-uninorms.

In this paper, a new definition of numerical radius for adjointable operators in Hilbert-module space will be introduced. We also give a new proof of numerical radius inequalities for Hilbert space operators.

Hybrid simulation which combines experimental and numerical modeling is a powerful and relatively new test method for evaluating the seismic performance of structural systems. In this method only critical components of structure are tested experimentally while the rest of the structure is numerically modeled in the computer. In this method the response of the structure is achieved by numerically integrating the equation of motion of the whole system. Among numerical integration methods, operator splitting (OS) method is of great interest for hybrid simulation, since not only its results are more accurate and stable in comparison with explicit methods but also its application for hybrid simulation is much more easier than implicit methods; the reason is that in OS method it is not required to conduct iteration on experimental element or estimate its tangent stiffness matrix during the simulation, the tasks which limit the application of implicit methods for hybrid simulation. But OS method suffers from the shortcoming that the use of initial stiffness matrix in its corrector step decreases the accuracy of results in nonlinear range. This paper presents a modified form of OS method which is termed MOS integration method in which by proposing a new procedure in the predictor step, the accuracy of this step is increased. When the accuracy of the predictor step increases, the difference between predictor and corrector displacements decreases and as a result the effect of initial stiffness approximation becomes less important. This would finally result in the improved accuracy of the whole simulation, as is shown in the paper.The performance, accuracy and stability characteristics of the proposed integration method were studied through numerical simulations, where it was assumed that the restoring force of the system is achieved experimentally and no information about the experimental stiffness is available. The results showed that for the wide range of considered systems including various natural periods, various ductility ratios and various degrees of freedom, MOS results are more accurate than OS method. This shows that the employed method of the predictor step of MOS method has successfully decreased the length of the corrector step with initial stiffness assumption. All the employed error indices also verified that not only the results of MOS are in great harmony with the reference solution but also its accuracy is improved over regular OS method, especially in simulations involving severe nonlinearity. Furthermore results of multi degree of freedom systems with high frequency modes show that MOS results are quite stable as long as the accuracy of important modes of the system is maintained, which is usually the case.As in a real hybrid simulation, experimental errors also affect the accuracy and stability of integration methods, in this paper a hybrid simulation algorithm is numerically modeled and the effect of actuator time delay on the performance of MOS method is investigated. It was observed that in the presence of actuator delay, which is known to be one of the most important sources of experimental errors in hybrid simulation, MOS integration method has solved the equation of motion in an accurate and stable manner with very small level of errors in comparison with the reference solution.

This paper addresses the asymptotic stability, position and force tracking problem in the nonlinear bilateral teleoperation system in the presence of non-passive interaction forces, varying time-delay in communication channel and actuators fault occurrence. For this aim, a passive Fault Tolerant Control (FTC) law is presented which uses the joint positions and velocities of local and remote manipulators to reach control ends. Using the Lyapunov-Krasovskii theorem, sufficient conditions for asymptotic stability and position tracking are derived in terms of Linear Matrix Inequalities (LMIs), to tune controller parameters. The main contribution of the proposed method is that can compensate the bias fault and loss of effectiveness of actuators in nonlinear teleoperation system. Also the asymptotic stability of positions errors in the system with non-passive interaction forces is assured using the integral control. Simulation results of teleoperation system with 2 and 3 degree of freedom manipulators with proposed method and comparison to some rival method show the effectiveness and advantages of the proposed method.

Autonomous mobile actors are under attention of researchers for having numeral applications. The way of placement and movement of actors in environment is very important for appropriate service of events. Two approaches, named settlement in center and settlement in place are introduced in this paper for evaluating placement location and movement method of actors in environment. Probability mass function of traversed distance for servicing events of environment by an actor for two approaches are mathematically proved step by step. Diagrams of simulations’ results and functions are drawn simultaneously and show that results of both methods completely confirms. Simulations’ results show that average displacement of actor in settlement in center approach in comparison with settlement in place approach is more; instead, average distance of events from center of area is less than average distance from location of previous event. In remaining, service of the events by a mobile actor is presented as a queuing theory problem and required relations for determining average length of waiting queue, average turnaround time, required minimum movement speed of actor and maximum dimension of surveillance area are extracted. At last, proposed approaches are extended by defining regions and assigning an actor for each region. Simulations results show that in place settlement approach, if nearest actor to each event is sent for servicing it, average displacement distance is less than the state that only assigned actor of each region has permission to be sent for servicing.