A study of decoupling with skeleton matrix in two‐degree‐of‐freedom generalized minimum variance control

There are many multi‐input multi‐output (MIMO) systems in chemical plants, and they have multiple time delays of different length in each input and output pair. This paper explains a two‐degree‐of‐freedom (2DOF) control system based on generalized minimum variance control (GMVC) for MIMO systems. It can improve the tracking performance with respect to the reference signals and the response properties for the disturbance. The states between the sampling period can be expressed by using the modified z transform to take account of multiple time delays. Additionally, a tracking controller is designed to decouple the plant. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 176(1): 28–36, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21046     

Adaptive estimation and rejection of unknown sinusoidal disturbances through measurement feedback for a class of non‐minimum phase non‐linear MIMO systems

This paper develops an adaptive estimation method to estimate unknown disturbances in a class of non‐minimum phase non‐linear MIMO systems. The unknown disturbances are generated by an unknown linear exosystem. The frequencies, phases and amplitudes of the disturbances are unknown, the only available information of the disturbances is the number of distinctive frequencies. The system considered in this paper is a class of MIMO non‐linear systems in the output feedback form which can be non‐minimum phase. The proposed estimation algorithm provides exponentially convergent estimates of system states, unknown disturbances in the system and frequencies of the disturbances characterized by the eigenvalues of the exosystem. Moreover, based on the stabilization controller for the disturbance free system, the estimates of the disturbances are used to solve the disturbance rejection problem. The unknown disturbances are compensated completely with the stability of the whole closed‐loop system. Copyright © 2006 John Wiley & Sons, Ltd.     

MIMO multi‐periodic repetitive control system: universal adaptive control schemes

This paper presents a simple adaptive multi‐periodic repetitive control scheme when the MIMO LTI plant is not necessarily positive real (PR), however it is strictly minimum‐phase, the spectrum of high‐frequency gain matrix CB is symmetric and lies in the open right/left half complex plane(sign/spectrum definite). The non‐identifier‐based direct adaptive control technique, which does not need plant parameter information, is used to construct adaptive schemes and the system stability is analysed by Lyapunov second method. The extension to plant under certain non‐linear perturbations and an exponential stability scheme are also discussed. Finally, an adaptive proportional plus multi‐periodic repetitive control scheme is proposed. The theoretical findings are supported with simulations. Copyright © 2006 John Wiley & Sons, Ltd.     

Decoupling control with a limiting form of linear optimal regulator for a non‐minimum phase system

In this paper, a decoupling control for a non‐minimum phase system is considered in terms of the limiting form of linear optimal regulator problems, and an explicit relationship between the limiting properties and the decoupling control is shown. Moreover, using an appropriate performance index, this paper deals with a new method of decoupling control to exclude the effect of the fixed poles by pole‐zero cancellation. Stability and sensitivity are improved by this method. This paper also gives numerical examples to illustrate the effectiveness of decoupling control with the limiting form. © 2000 Scripta Technica, Electr Eng Jpn, 132(2): 49–57, 2000     

Passivity‐based control for stabilization,regulation and tracking purposes of a class of nonlinear systems

In this paper, a new passivity‐based control (PBC) scheme based on state feedback is proposed in order to solve tracking, regulation and stabilization problems for a class of multi‐input multi‐output (MIMO) nonlinear systems expressed in the normal form, with time‐invariant parameters and locally bounded reference weakly minimum phase. For the proposed control scheme two new different state feedbacks, one non‐adaptive for the case when the system parameters are assumed to be known and the other adaptive for the case of unknown parameters, are developed. For the adaptive case it is assumed that the unknown parameters appear linearly in the equations. Analysis of the transient behaviour of the proposed control schemes is presented through the simulation of two examples. Copyright © 2006 John Wiley & Sons, Ltd.     

Stability of self‐tuning control based on Lyapunov function

The overall stability of a self‐tuning controller for discrete‐time systems is proved by using the Lyapunov function in this paper, for minimum and a class of non‐minimum phase systems. The self‐tuning controller utilizes a recursive estimate algorithm for the controller parameters based on the generalized minimum variance criterion. Previously, the stability had been proved in the case of minimum phase systems. A new type of self‐tuning controller for the discrete‐time system with delay in control input is also studied which is named the generalized minimum variance criterion‐β equivalent control, and its stability is proved. The simulation is done to evaluate the performance of the proposed self‐tuning controller. Copyright © 2008 John Wiley & Sons, Ltd.     

Recursive Gauss–Seidel algorithm for direct self‐tuning control

A recursive algorithm based on the use of Gauss–Seidel iterations is introduced to adjust the parameters of a self‐tuning controller for minimum phase and a class of nonminimum phase discrete‐time systems. The proposed algorithm is called the Recursive Gauss–Seidel (RGS) algorithm and is used to update the controller parameters directly. The use of the RGS algorithm with a generalized minimum variance control law is also given for nonminimum phase systems, and a forgetting factor is used to track the time‐varying parameters. Furthermore, the overall stability of the closed‐loop system is proven by using the Lyapunov stability theory. Using computer simulations, the performance of the RGS algorithm is examined and compared with the widely used recursive least squares algorithm.Copyright © 2011 John Wiley & Sons, Ltd.     

Application specific integrated circuit solution for multi‐input multi‐output piecewise‐affine functions

This paper presents a fully digital architecture and its application specific integrated circuit implementation for computing multi‐input multi‐output (MIMO) piecewise‐affine (PWA) functions. The work considers both PWA functions defined over regular hyperrectangular and simplicial partitions of the input domains and also lattice PWA representations. The proposed architecture is able to implement PWA functions following different realization strategies, using a common structure with a minimized number of blocks, thus reducing power consumption and hardware resources. Experimental results obtained with application specific integrated circuit (ASIC) integrated in a 90‐nm complementary metal‐oxide semiconductor standard technology are provided. The proposed architecture is compared with other digital architectures in the state of the art habitually used to implement model predictive control applications. The proposal is superior in power consumption (saving up to 86%) and economy of hardware resources (saving up to 40% in comparison with a mere replication of the three representations) to other proposals described in literature, being ready to be used in applications where high‐performance and minimum unitary cost are required. Copyright © 2015 John Wiley & Sons, Ltd.     

Circuit implementation and model of a new multi‐scroll chaotic system

In this paper, a multi‐scroll chaotic system from the improved Chua's system is proposed. Moreover, non‐linear dynamics are analyzed including phase‐space trajectories, bifurcation diagrams, Poincaré maps and so on. The most important thing is that we discovered phase‐space trajectories, bifurcation diagrams and Poincaré maps are unified and closely related, which can describe different aspects of the multi‐scroll chaotic system. Furthermore, the corresponding improved module‐based circuits are designed for realizing two to four‐scroll chaotic attractors, and the experimental results are also obtained, which are consistent with the numerical simulations. Copyright © 2012 John Wiley & Sons, Ltd.     

Fault accommodation for multi‐input linear sampled‐data systems

A novel observer‐based fault accommodation technique for linear multi‐input multi‐output sampled‐data systems affected by a general class of actuator faults in the presence of quantization errors is addressed in the paper. Only the output signal has been assumed to be available for direct measurement. A simulation study on a three‐tank system supports theoretical developments. Copyright © 2014 John Wiley & Sons, Ltd.     

Non‐minimum phase switched systems: HOSM‐based fault detection and fault identification via Volterra integral equation

In this paper, the problem of continuous and discrete state estimation for a class of linear switched systems with additive faults is studied. The class of systems under study can contain non‐minimum phase zeroes in some of their ‘operating modes’. The conditions for exact reconstruction of the discrete state are given using structural properties of the switched system. The state space is decomposed into the strongly observable part, the non‐strongly observable part, and the unobservable part, to analyze the effect of the unknown inputs. State observers based on high‐order sliding mode to exactly estimate the strongly observable part and Luenberger‐like observers to estimate the remaining parts are proposed. For the case when the exact estimation of the state cannot be achieved, the ultimate bounds on the estimation errors are provided. The proposed strategy includes a high‐order sliding‐mode‐based fault detection and a fault identification scheme via the solution of a Volterra integral equation. The feasibility of the proposed method is illustrated by simulations. Copyright © 2013 John Wiley & Sons, Ltd.     

Optimal control of multi‐hop control networks based on the MLD framework

A multi‐hop control network (MHCN) is a control system in which plants and controllers are connected through a multi‐hop wireless network modeled by a directed graph. In this paper, based on the MLD (mixed logical dynamical) framework, which is one of the powerful methods in hybrid systems control, we propose a modeling method and an optimal control method of MHCNs. First, a directed graph in MHCNs and a switch of the control input are modeled by a pair of a linear state equation and a linear inequality with binary variables. Thus, the MLD model expressing a given MHCN is derived. Next, using the MLD model, the optimal control problem is transformed into a mixed integer quadratic programming problem. Finally, numerical examples are presented. The proposed method provides us a basic result for control of MHCNs. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

On constructing complex grid multi‐wing hyperchaotic system: Theoretical design and circuit implementation

This paper further investigates some novel methods for generating complex grid multi‐wing hyperchaotic attractors from four‐dimensional (4D) quadratic hyperchaotic systems, based on our previous works. First, a modified double‐wing hyperchaotic Lü system by using non‐uniform variable scaling transformation is obtained, and n‐wing hyperchaotic system equipped with a duality‐symmetric multi‐segment quadratic function is also constructed. Then, by switching control in the z direction, mirror symmetry conversion and rotation transformation, three classes of n × m‐wing hyperchaotic systems are respectively realized. Finally, two types of improved module‐based circuits are designed for generating various grid multi‐wing hyperchaotic attractors. One characteristic of the proposed approaches lies in their generality, which is also suitable for constructing 4D grid multi‐wing hyperchaotic Lorenz and Chen systems. Both numerical simulation and circuit implementation have demonstrated the feasibility and effectiveness of the proposed approaches. Copyright © 2010 John Wiley & Sons, Ltd.     

Carrier‐envelope phase‐stabilized chirped‐pulse amplification system

We demonstrated a carrier‐envelope phase (CEP) stabilized chirped‐pulse amplifier system. This amplifier system is composed of grating based pulse‐stretcher and compressor, a regenerative amplifier and a multi‐pass amplifier. We employed a new pulse‐pick‐up method to select CEP stabilized seed pulses. This pulse selection method is different from established practice which is based on pulse train timing, but is based on CEP of seed pulse. We measured amplitude‐to‐phase noise conversion coefficient of microstructure fiber and evaluated the additional out‐of‐loop error of carrier‐envelope offset (CEO) control. We also investigated the effect of beam pointing of the measured fringe shift in self‐referencing spectral interference method. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(3): 35–42, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20334 Copyright © 2006 Wiley Periodicals, Inc.     

Excitation and steam‐valving coordinated robust controller design for multi‐machine power systems based on the multi‐index nonlinear robust control approach

This paper proposes a novel multi‐index nonlinear robust control (MNRC) approach for multi‐machine power systems. The MNRC approach combines multi‐index nonlinear control with the control theory. With the multi‐index nonlinear control, which selects the output functions as arithmetic combination of state variables, multiple performance indices of the controlled system can be achieved simultaneously in the nonlinear control framework. The control is able to ensure that the system possess the desired robust performance during disturbance. Then, excitation and steam‐valving coordinated robust controllers are developed based on the MNRC approach for multi‐machine power systems. The effectiveness of the proposed robust controller is evaluated by a six‐machine power system simulation. Simulation results show that the expected dynamic and steady‐state performances of power system can be achieved with the MNRC approach. Meanwhile, it is able to achieve the prescribed system performance despite the presence of disturbances. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Robust self‐tuning PI decoupling control of uncertain multivariable systems

In this paper, for a class of multivariable systems with strong couplings, a robust self‐tuning PI decoupling controller is developed by combining a self‐tuning PI controller with a feedforward decoupling compensator and a filter. To determine the gains and other parameters of the PI decoupling controller, we first introduced a reduced order model. The parameters of the reduced order model are identified by using a normalized projection algorithm with dead zone. The gains of the PI controller together with other parameters are tuned online according to the certainty equivalent principle. By resorting to time‐varying operation, we presented the bounded‐input bounded‐output stability conditions and convergence conditions of the closed‐loop system. Simulation results on a synthetic system and a twin‐tank level system show the effectiveness of the proposed method. Copyright © 2011 John Wiley & Sons, Ltd.     

An indirect adaptive pole‐placement control for MIMO discrete‐time stochastic systems

In this paper, an indirect adaptive pole‐placement control scheme for multi‐input multi‐output (MIMO) discrete‐time stochastic systems is developed. This control scheme combines a recursive least squares (RLS) estimation algorithm with pole‐placement control design to produce a control law with self‐tuning capability. A parametric model with a priori prediction outputs is adopted for modelling the controlled system. Then, a RLS estimation algorithm which applies the a posteriori prediction errors is employed to identify the parameters of the model. It is shown that the implementation of the estimation algorithm including a time‐varying inverse logarithm step size mechanism has an almost sure convergence. Further, an equivalent stochastic closed‐loop system is used here for constructing near supermartingales, allowing that the proposed control scheme facilitates the establishment of the adaptive pole‐placement control and prevents the closed‐loop control system from occurring unstable pole‐zero cancellation. An analysis is provided that this control scheme guarantees parameter estimation convergence and system stability in the mean squares sense almost surely. Simulation studies are also presented to validate the theoretical findings. Copyright © 2005 John Wiley & Sons, Ltd.     

Intelligent control using multiple models and neural networks

Most adaptive control algorithms for nonlinear discrete time systems become invalid when the controlled systems have non‐minimum phase properties and large uncertainties. In this paper, an intelligent control method using multiple models and neural networks (NN) is developed to deal with those problems. The proposed control method includes a set of fixed controllers, a re‐initialized neural network (NN) adaptive controller and a free‐running NN adaptive controller. The bounded‐input‐bounded‐output (BIBO) stability and performance convergence of the system are guaranteed by the free‐running adaptive controller, while the multiple fixed controllers and the re‐initialized adaptive controller are used to improve the transient response. Simulation results are presented to demonstrate the effectiveness of the proposed method. Copyright © 2007 John Wiley & Sons, Ltd.     

Robust adaptive control of Hammerstein nonlinear systems and its application to typical CSTR problems

This paper considers the robust adaptive control of Hammerstein nonlinear systems with uncertain parameters. The control scheme is derived from a modified criterion function which can overcome non‐minimum phase property of the linear subsystem. The parameter adaptation is performed by using a robust recursive least squares algorithm with a deadzone weighted factor. The control law compensates the model error by incorporating the unmodeled dynamics estimation. An online pole assignment technique is also presented to guarantee that Assumption 2 always holds. Rigorous theoretical analysis indicates that the parameter estimation convergence and the closed‐loop system stability can be guaranteed under mild conditions. Simulation examples including two typical continuous stirred tank reactor problems are studied to verify the effectiveness of the control scheme. Copyright © 2016 John Wiley & Sons, Ltd.     

A study on adaptive noise canceller using linear phase filter

In this paper, we propose a new adaptive noise canceller using a linear phase filter. The linear model in which an arbitrary signal is defined by the output signal of a linear system at the white signal input is used. The noise is suppressed by the estimated linear system and the signal‐to‐noise ratio is improved. At this point, to minimize the distortion of the signal due to the nonlinearity of the phase shift, the linear phase filter has been newly introduced. The transfer function of the linear system is an arbitrary minimum phase rational transfer function that has poles and zeros. It has the feature of not being specified for all pole models. The adaptive algorithm is a gradient‐based algorithm with few computational complexities. The features of the proposed adaptive noise canceller are that the inverse filter of the adaptive filter is stable, the convergence of the algorithm is guaranteed, the distortion of the signal is minimal, and there is no restriction on the transfer function of the linear system. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(1): 50–55, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21116