Linear Quadratic Gaussian/loop Transfer Recovery Research Articles

Robust optimal-integral sliding mode control for a pressurized water nuclear reactor in load following mode of operation

A nuclear reactor is a complex, nonlinear, and time-varying system. External disturbances and uncertainty due to neutronic and thermal-hydraulics parameters variation contribute to reactor control challenges and safe operations. Thus, this paper presents a hybrid control system for a nuclear reactor core power control in the presence of a matched disturbance and uncertainties. The hybrid controller combines Linear Quadratic Gaussian/Loop Transfer Recovery (LQG/LTR) optimal control and a nonlinear Integral sliding mode control (ISMC). The nonlinear system of the reactor, which is based on point kinetics equations with three delayed neutron group is linearized to design the LQG/LTR. The Lyapunov theory is used to prove the finite-time convergence of the Integral sliding mode control. Furthermore, a comparative analysis of the hybrid control scheme, LQG/LTR, PID, and an ISMC is conducted with the nonlinear model. Simulation experiments reveal that the closed-loop hybrid control system is stable and achieves the best performance specifications in the presence of external disturbance and uncertainties.

Artificial bee colony optimised controller for small-scale unmanned helicopter

ABSTRACTIn this paper, an efficient approach to design and optimize a flight controller of a small-scale unmanned helicopter is proposed. Given the identified helicopter model, the Linear Quadratic Gaussian/Loop Transfer Recovery (LQG/LTR) robust control method is applied for trajectory tracking and attitude control of the helicopter with a two-loop hierarchical control architecture. Since the performance of the controller extremely depends on its weighting matrices, the Artificial Bee Colony (ABC) algorithm is introduced to automatically select the parameters of the matrices. Comparative studies between optimal algorithms are also carried out. A series of flight experiments and simulations are conducted to investigate the effectiveness and robustness of the proposed optimised controller.

Parameter-robust linear quadratic Gaussian technique for multi-agent slung load transportation

This paper copes with parameter-robust controller design for transportation system by multiple unmanned aerial vehicles. The transportation is designed in the form of string connection. Minimal state-space realization of slung-load dynamics is obtained by Newtonian approach with spherical coordinates. Linear quadratic Gaussian / loop transfer recovery (LQG/LTR) is implemented to control the position and attitude of all the vehicles and payloads. The controller's robustness against variation of payload mass is improved using parameter-robust linear quadratic Gaussian (PRLQG) method. Numerical simulations are conducted with several transportation cases. The result verifies that LQG/LTR shows fast performance while PRLQG has its strong point in robustness against system variation.

LQG/LTR procedure using reduced-order Kalman filters

ABSTRACTThis paper discusses a linear-quadratic-Gaussian/loop transfer recovery (LQG/LTR) procedure using reduced-order Kalman filters by extending known exact-recovery result. The state-space realisation commonly used for reduced-order observer design is employed. The zero structure intrinsic to the realisation is revealed. Asymptotic recovery is achieved using a non-singular reduced-order Kalman filter with a parameterised set of covariance matrices. The proposed procedure provides a systematic method for directly designing reduced-order LQG controllers without additional coordinate transformations. A numerical design example for a simple multivariable plant is presented to compare the proposed design with the standard LQG/LTR design using a full-order Kalman filter.

LQG/LTR과 PID 기반의 무인항공기 슬렁-로드 수송 시스템의 제어기 설계

This paper copes with control design for unmanned aerial vehicle transportation system. Moving pendulum dynamics of slung-load system is derived using two methods: Udwadia-Kalaba equation and Newtonian approach. PID controller is applied to Udwadia-Kalaba equation model for structural consistency and linear quadratic Gaussian / Loop Transfer Recovery (LQG/LTR) technique is employed for Newtonian model with minimal state-space realization. Characteristics of PID and LQG/LTR controller are compared, and two controllers are combined to compensate the drawbacks of each other. Numerical simulation is set for two cases and conducted to evaluate performance of designed controllers. The result proves that combination of LQG/LTR and PID control performs stable and robust.

光电着舰引导系统的视轴稳定

To increase line-of-sight (LOS) tracking and pointing accuracy of an Optic-Electro (O-E) landing guidance system, this work explores how to isolate the LOS tracking and pointing of a O-E theodolite from the carrier motion disturbance. A carrier-based O-E theodolite model was established with various disturbance factors introduced. Three kinds of controllers, Lead-lag, LQG/LTR(Linear Quadratic Gaussian/Loop Transfer Recovery) and H were designed to improve the stability and performance of the system. The Kalman filter and H weighting matrix were investigated in detail. Then, the controllers were emulated in Matlab and verified on a swing bench. The compared experiments for the three kinds of controllers on time domain, frequency response and stability were performed. Obtained results show that both LQG/LTR and H controllers can satisfy the design specifications, and their decoupling effects are as deep as 50 dB, which can ensure precise tracking and pointing performance of LOSs in O-E landing guidance systems.

An extension of the linear quadratic Gaussian-loop transfer recovery procedure

The linear quadratic Gaussian-loop transfer recovery procedure is a classical method to desensibilise a system in closed loop with respect to disturbances and system uncertainty. Here an extension is discussed, which avoids the usual loss of performance in LTR, and which is also applicable for non-minimum phase systems. It is also shown how the idea can be extended to other control structures. In particular, it is shown how proportional integral derivative controllers can be desensibilised with this new approach. The method is tested on several examples, including in particular the lateral flight control of an F-16 aircraft.

사역대가 포함된 유압 위치 시스템의 LQG/LTR 제어

A LQG/LTR(linear quadratic Gaussian/loop transfer recovery) controller with an integrator is designed to control the electro-hydraulic positioning system. Without considering the nonlinearity in the dead-zone, computer simulations are performed and show good performances and tracking abilities with the feedback controller based on the linear system model. However, the performance of the closed loop hydraulic positioning system shows big steady-state error in real system because of the dead-zone. In this paper, the feedback controller with a nonlinear compensator is introduced to overcome the dead-zone phenomenon in hydraulic systems. The inverse dead-zone as a nonlinear compensator is used to cancel out the dead-zone phenomenon. Experimental tests are performed to verify the performance of the controller.

Transient Temperature Control of the Hydrodealkylation Reactor

The practical application of robust control design to deal with the problem of thermal excursions of a catalytic hydrodealkylation reactor is addressed. The reactor system is a distributed parameter system, and it consists of a set of five nonlinear partial differential equations. Satisfactory control of this system requires that the control scheme be robust; that is, it must remain stable and perform well in the presence of external disturbances and plant modeling inaccuracies. One approach to solve this design problem is to use the LQG/LTR (linear quadratic Gaussian/loop transfer recovery) method, in which the LTR method is a systematic procedure performed to guarantee the robustness of the LQG controller. The utility of the LQG/LTR approach for designing multivariable controllers to achieve specific performance objectives is examined. The flow velocity of the reactant gas and the volumetric flow-rate of the quench gas are chosen as the manipulated variables. Simulation results obtained with the proposed method exhibit satisfactory capability in attenuating the transient temperature peaks, thus preventing deactivation of catalyst solid, initiation of undesired side reactions, and structural damage to the reactor.

Genetic algorithm for LQG/LTR design parameters. a flight control system application

In this paper we propose a method for tuning Linear Quadratic Gaussian/Loop-Transfer Recovery (LQG/LTR) controller based on genetic algorithms. Suitable time responses as well as satisfactory robustness properties are obtained using two optimisation loops, where genetic algorithms are employed to satisfy design specifications for a flight control system.

Optimal control of a swirl-stabilized spray combustor using system identification approach

An optimal controller using the system identification (SI) method was developed for a swirl-stabilized spray combustor operating between 30 and 114 kW. The efficacy of the controller was tested with two different nozzle configurations. The first consisted of a dual-feed nozzle whose primary fuel stream was utilized to sustain combustion, while the secondarystreamwasused for active control. The second configuration used a single-feed nozzle with two different swirling air streams. An LQG-LTR (linear quadratic Gaussian-loop transfer recovery) controller was designed using the SI-based model to determine the active control input, which was in turn used to modulate the secondary fuel stream. Using this controller, the thermoacoustic oscillations, which occurred under lean operating conditions, were reduced to the background noise level. A time-delay controller was also implemented for comparison purposes. The results showed that the LQG-LTR controller yielded an additional pressure reduction of 14 dB compared to the time-delay controller in both configurations. This improvement can be attributed to the added degrees of freedom of the LQG-LTR controller that allow an optimal shaping of the gain and phase of the controlled combustor over a range of frequencies in the neighborhood of the unstable mode. This leads to the extra reduction of the pressure amplitude at the unstable frequency while avoiding generation of secondary peaks.

Multibody dynamics and robust control of flexible spacecraft

The paper focuses on an approach to the study of the dynamics and control of large flexible space structures, comprised of subassemblies, a subject of considerable contemporary interest. To begin with, a relatively general Lagrangian formulation of the problem is presented. The governing equations are nonlinear, nonautonomous, coupled, and extremely lengthy even in matrix notation. Next, an efficient computer code is developed and the versatility of the program illustrated through a dynamical study of the first element launch (FEL) configuration of the Space Station Freedom, now superseded by the International Space Station. Finally, robust control of the rigid body motion of the FEL configuration using both the linear-quadratic-Gaussian/loop transfer recovery (LQG/LTR) and H/sub /spl infin// procedures is demonstrated. The controllers designed using the simplified linear models, prove to be effective in regulating librational disturbances. Such a global approach-formulation numerical code, dynamics, and control-is indeed rare. It can serve as a powerful tool to gain comprehensive understanding of dynamical interactions and thus aid in the development of an effective and efficient control system.

LQG/LTR frequency loop shaping to improve TMR budget

In this paper, we introduce a systematic method of designing a track-following servo system for hard disk (HD) drives using discrete-time linear-quadratic Gaussian/loop-transfer recovery (LQG/LTR) design technique, and some statistical knowledge on disturbances. The newly designed controller was implemented on a commercial HD drive and its performance was compared to the resided compensator. An improvement of 10% in track misregistration (TMR) budget was observed.

Dynamics and control of multibody tethered systems

The equations of motion for a multibody tethered satellite system in a three dimensional Keplerian orbit are derived. The model considers a multi-satellite system connected in series by flexible tethers. Both tethers and subsatellites are free to undergo three dimensional attitude motion, together with longitudinal and transverse vibration for the tether. The elastic deformations of the tethers are discretized using the assumed-mode method. In addition, the tether attachment points to the subsatellites are kept arbitrary and time varying, with deployment and retrieval degrees of freedom. The governing equations of motion are derived using an Order ( N) Lagrangian formulation. Next, two independent controllers, i.e. an attitude and vibration controller, are designed to regulate the rigid and flexible motion present in the system, excited from various maneuvres performed during the course of a mission. The former controller utilizes the thrusters and momentum-wheels located on the rigid satellites with a control algorithm based on the feedback linearization technique. On the other hand, the latter is designed using the robust linear quadratic Gaussian-loop transfer recovery method actuating the variable tether attachment point, or offset position. Both controllers are successful in suppressing unwanted disturbances in the system in a acceptable amount of time.

Recovery Surface on Robust Control

In this work we present a new procedure to analyze dynamic system controllers (Linear Quadratic Gaussian/Loop Transfer Recovery (LQG/LTR) and Loop Transfer Recovery by Output Feedback Control). The stability robustness will be defined considering the singular values, frequency and recovery steps via recovery surfaces. These surfaces provide a better way to analyze the system robustness since the colors carry all the required information. The systems considered here are not necessarily minimum phase and not necessarily right invertible.

OBSERVER DESIGN FOR LOOP TRANSFER RECOVERY

A design technique of loop transfer recovery (LTR) is introduced to design a robust full-order observer that recovers the full-state feedback loop properties for uniformly completely controllable (UCC) and uniformly completely observable (UCO) linear time-varying (LTV) systems. Asymptotic loop transfer recovery is achieved by selecting the observer gains based on the observability Gramian of closed loop system. We study the loop recovery problem at the input of the plant when the loop is broken•t the input When the loop is broken at the output, similar results can be developed for the recovery problem at the output of the plant. For linear time-invariant (LTI) systems the observer gain is computed via solving a simpler algebraic equation compared with the standard.. linear quadratic Gaussian/loop transfer recovery (LQG/LTR). For linear time-varying (LTV) systems the stability of the closed loop system is guaranteed during the recovery process without any additional constrain. Finally, two examples are given to illustrate the effectiveness' of the proposed approach.

LTR design of discrete-time proportional-integral observers

Applies the proportional-integral (PI) observer in connection with loop-transfer recovery (LTR) design for discrete-time systems. Both the prediction and the filtering versions of the PI observer are considered. We show that a PI observer makes it possible to obtain time recovery, i.e., exact recovery for t/spl rarr//spl infin/, under mild conditions. Two systematic LTR design methods, one based on an extension of the linear quadratic Gaussian loop-transfer recovery (LQG/LTR) and the other based on linear matrix inequality (LMI), are derived for the discrete-time PI observer case, Explicit expressions for the recovery error when exact recovery is not achievable for all frequencies are also given.

An auxiliary LQG/LTR robust controller design for cogeneration plants

A robust controller is designed to reduce the sensitivity of the frequency and the extraction steam pressure to the disturbance imposed on a cogeneration plant by using the LQG/LTR (linear quadratic Gaussian/loop transfer recovery) methodology. The natural frequency of the generator swing is analyzed to determine the frequency band of the disturbance due to the variation in load and utilized as a design specification for the LQG/LTR controller. The singular-value Bode diagram of the sensitivity transfer function matrix is shaped to reduce disturbance effects on the power system frequency and steam pressure according to the design specification. The high order LQG/LTR controller is reduced to a low order controller and implemented in a nonlinear cogeneration plant model. Simulation shows the performance of the LQG/LTR controller in disturbance rejection.

Robust control of series parallel resonant converters

A robust controller is designed for the series parallel resonant DC/DC converter based on the linear quadratic Gaussian/loop transfer recovery (LQG/LTR) methodology. The controller structure, comprising a servo-compensator with an internal model, reference state observer, plant and disturbance state observer, ensures tracking of the reference voltage and rejection of system disturbances. The controller performance is insensitive to converter parametric and operational variations. The controller design is based on a converter small-signal model derived using the principles of the describing function and harmonic balance on the nonlinear time-varying converter equations. The controlled converter is shown by computer simulation to perform excellently well, with very good tracking and disturbance capabilities in the presence of changes of load and input voltage.

Robust Controller for Gas Turbines Based Upon LQG/LTR Design With Self-Tuning Features

A feasibility study is described for the design of a self-tuning controller for gas turbines with the multivariable discrete-time robust controller designed using a Linear Quadratic Gaussian/ Loop Transfer Recovery (LQG/LTR) design approach.