−１／ξ軌跡による多入力フィードバック飛行制御系の応答特性に関する一考察

Singular value analysis can give conservative stability margin results. Applying structure to the uncertainty can reduce this conservatism. This paper presents flight-determined stability margins for the X-29A lateral-directional, multiloop control system. These margins are compared with the predicted unscaled singular values and scaled structured singular values. The algorithm was further evaluated with flight data by changing the roll-rate-to-aileron command-feedback gain by +/- 20 percent. Minimum eigenvalues of the return difference matrix which bound the singular values are also presented. Extracting multiloop singular values from flight data and analyzing the feedback gain variations validates this technique as a measure of robustness. This analysis can be used for near-real-time flight monitoring and safety testing.

Modeling multi-loop intelligent pilot control behavior for aircraft-pilot couplings analysis

The applicability of the steady-state Relative Gain Array (RGA) to measure dynamic process interactions in a multiloop control system was investigated. Several transfer function matrices were chosen, and the gains, time constants, and dead times of their elements were varied to represent the systems with dominant dynamic interactions. It was shown that the steady-state RGA method predicted the controller pairing accurately if the pairing elements recommended by RGA had the bigger gains and the same or smaller time constants compared to other elements in the corresponding rows. When these conditions were not met, the RGA would give a wrong result, and dynamic interaction measurements, such as the Average Dynamic Gain Array (ADGA) and the Inverse Nyquist Array (lNA), should be used instead to determine the best controller pairing in a multiloop control system. Keywords: Control pairing, dynamic process interaction, multiloop control systems, Relative Gain Array (RGA), and steady state.

This work is devoted to the technique of solving the problem of structural-parametric synthesis of typical controllers in a multiloop cascade automatic control system, which is developed on the basis of the alternance method of parametric optimization that provides the maximum degree of invariance of local control loops relative to external perturbations with given limitations on the peak of amplitude-frequency characteristics of closed loops of the synthesized automatic control system. The task of optimizing the subsystem for controlling the fuel oil temperature in a multiloop control system of primary oil refining on an atmospheric and vacuum crude distillation unit is considered as an example, which is of independent interest.

Nonlinear adaptive flight control system: Performance enhancement and validation

Purpose – The presented paper aims to describe the general idea, simulations and prototyping process of an assisting flight control system (FCS) for light sport aircraft (LSA). The proposed FCS framework is intended to simplify piloting, reduce pilot workload, and improve system's reliability and handling qualities of manual flying. Design/methodology/approach – Assisting flight control strategy integrates mechanical and digital FCS into a synergic platform, combining the high reliability of mechanical controls with the computation and actuation power introduced through a single line digital FCS. Concepts drawn from classical control theory along with flight envelope protection algorithms have been used throughout the design of the flight control laws. A prototype of the assisting FCS has been subjected to validation trials during series of hardware-in-the-loop simulations. Findings – Despite controversies between the pilots' perception of a modern aircraft and limitations imposed by the legacy airworthiness codes, it has been shown that a pilot assisting and workload reducing control system can be successfully implemented on board of a LSA while satisfying the expectations on a state-of-the-art equipment meeting required level of safety defined by the current legislation. Research limitations/implications – A transition between specific flight modes as well as nonlinearities in the FCS may lead to unfavorable and unpredictable forms of aircraft-pilot interactions. The number of accessible flight control modes should be therefore limited to the most significant ones. Practical implications – Sport aircraft are mostly flown by a single pilot, who could benefit from the pilot assisting FCS as the system has the potential to supervise the aircraft's safe operation in various flight conditions. Originality/value – Introducing an assisting FCS on board of a LSA through an innovative approach which utilizes hidden and unused resources of modern digital automatic FCSs while respecting the limitations imposed through the weight and cost sensitive nature of the LSA market.

A high-stability air temperature control system

Hovering performance of unmanned helicopter is of key importance in flight.This paper presents an autonomous control system to achieve the excellent hovering performance for a miniature unmanned helicopter. First, the response data of system is collected during special flight test and a linear time-invariant model is extracted by frequency identification technique.Then, the control system is designed and implemented on hover control of the helicopter using multi-loop control method.The method has simple structure, straightforward design process and low com-puting load imposed on the flight control system. The proposed multi-loop controller is composed of inner-loop attitude control, mid-loop velocity control and the outer-loop position control.The application results show that the proposed controller can obtain outstanding hovering performance.This control system structure is very feasible in engineering, and can be benefit for control system design of other miniature unmanned helicopters.

The cooperative control of both electrode remelting rate and position was applied in order to obtain optimal electro-slag remelting metallurgy effect and improve melting production efficiency. The nonlinear dynamic model of electro-slag remelting process was linearized. And the lineariztion model was analyzed including its stability, coupling property and variable matching strategy. The multi-loop PID controllers with cascade PID controllers were applied to the linearization model based on matching strategy. The dynamic performance was analyzed to electro-slag remelting control system. Study results show that linearizition model of electro-slag remelting process have characteristic of stability and weakly-coupled property. Multi-loop PID control system can realize stable control both electrode melting rate and electrode position. The control system has faster dynamic response and better anti-interference capability.

The comparison of different multi-loop control structures for a basic triangular system is the focus of the present paper. The idea is originated from game theory, where information is an essential component. Hence, the game-theoretic view of controller design in multi-loop control systems allows the question, how unequally distributed or incomplete information affects the control structure and the selection of the playerspsila strategies. Additionally, if constraints on the control signals are considered, the strategy set of each player is bounded. Thus, the solution of each game provides different Pareto-optimal sets depending on different bounded strategy sets. In the present paper, an asymmetric triangular multi-loop control structure of a reverse osmosis desalination plant was chosen as basis to study and discuss the effects of different information sets, due to the control structure, to the solution of each game.

The objective of the present paper is to evaluate the application of a promising new mathematical technique called interval analysis for reentry flight clearance. Whereas a Monte Carlo approach clears the vehicle only for a finite number of sets of uncertainty parameters, the new approach clears the vehicle within prespecified uncertainty parameter intervals. The new approach is applied to the reentry trajectory of the Delft Aerospace Reentry Test Demonstrator, a hypothetical ballistic reentry vehicle equipped with an attitude-stabilizing flight control system. As the clearance requirement, the stability of the system is chosen, which is evaluated using two different mathematical criteria: worst-case linear eigenvalue analysis and nonlinear Lyapunov analysis. The new approach, based on interval analysis, is applied in an evaluation of both criteria. Subsequently, Monte Carlo analysis was performed to verify the validity of these results. I. Introduction R EENTRY flight is inseparable from the present and future spaceflight missions. During the reentry flight, a vehicle has to follow a predefined trajectory toward a designated landing area. Trajectory tracking, flight stability, and landing precision are important aspects in the reentry flight. The predefined trajectory has to be tracked with a sufficient margin of error. The stability margin has to be fulfilled against the variation and uncertainty in flight parameters such as aerothermodynamic parameters, mass, and inertia.Theaccuracyoflandingisimportantaswelltoensurethatthe vehicle and its contents reach the target ground intact. All of these aspects need to be analyzed and evaluated in a systematic way to ensure the stability and performance of the reentry vehicle. To certify a reentry vehicle as safe to fly, the reentry flight model has to be evaluated before actual flight. This is known as the reentry flight model clearance, or reentry flight clearance for short. One exampleofthe flightmodelclearanceistheevaluationofthestability and performance of the reentry vehicle model in its flight envelope. AsillustratedinFig.1,thereentry flightenvelopeisdefinedalongthe nominal flight trajectory. The flight safety is checked by evaluating the regions in the flight envelope using predefined stability or performance criteria. The region in which the criteria are fulfilled is then “cleared,” which means that, under the defined flight condition, the vehicle can fly safely in this region. The right-hand side of Fig. 1 shows a blown-up view of the envelope with flyable and nonflyable regionsasaresultoftheclearance.The flyableareasareshownbythe shaded rectangles in the flight envelope. Thechallengeforthereentry flightclearanceliesinthefactthatthe mathematical models of reentry vehicles and the environments are generally nonlinear. Moreover, the models may contain uncertainty due to the unknowns and variations in the dynamics or parameters. Therefore, to produce a reliable clearance result, mathematical analysis methods that account for the nonlinearity and uncertainty in the models are needed. To answer this question, this paper contributesasystematic approachtoperform reentry flightclearance using interval analysis. This method can meet the aforementioned challenge,for itcanbeapplied tolinearaswellasnonlinearsystems, and can account for the uncertainty in the system model. To give the reader an overview of the method, the algorithm is described in Sec. V. The strong point of the method is illustrated using an example of clearance for a nonlinear system. In the sequence, we perform clearance on a reentry vehicle model with a flight control system, with stability robustness in the presence of uncertainty as the clearance criteria (see Sec. VI). The mathematical modelofthesystemisnonlinearwithuncertainparameters.Toshow that the method canbe applied tolinear as well as nonlinear systems, both linearized and nonlinear models of the system are evaluated. The clearance is performed inside the vehicle’s reentry flight envelope. For the linearized system, the eigenvalue criteria is applied, whereas for the nonlinear system, the Lyapunov function isevaluated.TheresultsarevalidatedusingMonteCarloanalysis.As literature survey,Secs.IIandIIIprovidethereader withanoverview of the current clearance practice and of the available methods, which leads to the choice of the clearance method in this paper.

Age-of-information (AoI) is a metric quantifying information freshness at the receiver. Since AoI combines packet generation frequency, packet loss, and delay into a single metric, it has received a lot of research attention as an interface between communication network and application. In this work, we apply AoI to the problem of wireless scheduling for multi-loop networked control systems (NCS), i.e., feedback control loops closed over a shared wireless network. We model the scheduling problem as a Markov decision process (MDP) with AoI as its observable states and derive a relation of control system error and AoI. We further derive a stationary scheduling policy to minimize control error over an infinite horizon. We show that our scheduler outperforms the state-of-the-art scheduling policies for NCS. To the best of our knowledge, this is the first work proposing an AoI-based wireless scheduling policy that minimizes the control error over an infinite horizon for multi-loop NCS.

The paper presents the algorithm of a simultaneous control of multiple HVDC links and series FACTS devices (such as phase angle regulator) to improve stability of an AC power system. The purpose of the study is to demonstrate that such stabilizing control, optimal from the perspective of the whole AC power system and insensitive to the loading condition and network configuration (robust control) may be clearly determined mathematically. The proposed method of control was derived using the direct Lyapunov method. The control system is a multi-loop control system using state variables as input signal, activated in the transient state and supplementary to the main steady-state control designed for regulating the power flow. Efficiency of the methods was confirmed with computer simulations. The algorithm perfectly damps the inter-area power swings, showing at this very high robustness to changes in network configuration, loading conditions. Moreover, the proposed control produces additive damping i.e. each controlled HVDC line and/or FACTS device contributes to positive damping in AC power system.

A Filter Based Approach for Estimation of PI Achievable Performance

Time delays in a control system are usually considered to degrade system performance. This is true when stability margins (gain and/or phase margins) of the control system are taken as the performance criteria. However, there are many instances when performance criteria other than stability margins are used for control system design and controllers comparison. For example, tracking error is one such performance criterion that is widely used for designing many real control systems. When tracking error is considered as the performance criterion, it is shown that consistent time delays in the feedback path can actually reduce the steady-state tracking error of a control system to polynomial reference inputs (such as ramps).