Digital Redesign Research Articles

Sampled-data control of underwater gliders: digital redesign approach

This paper discusses a sampled-data control problem for a nonlinear underwater glider based on the digital redesign (DR) technique. An analog controller is pre-designed based on the fully feedback-linearised model. The condition for the DR problem is proposed in terms of linear matrix inequality, using the delta-operator discrete-time models. We show that the DRed sampled-data controller guarantees the semiglobal practical asymptotic stability of the nonlinear steady gliding motion in the sampling period. The numerical simulations demonstrate the advantage of the developed methodology in terms of the larger sampling period and the better preservation of the original analog control performance than the conventional emulation technique.

Linear Matrix Inequalities for Digital Redesign Under Delay Suitable for PI Controllers with Application to PMSMs

This paper investigates the digital redesign of proportional integral (PI) controllers implemented under a delay of one sampling period. The usual digital redesign based on state matching cannot be directly applied here. The digital control gains are obtained by means of linear matrix inequalities that minimize the $${\mathcal {H}}_{\infty }$$ norm associated with an error signal defined as the difference between the closed-loop system with continuous-time controller and the closed-loop system with the discrete-time controller implemented under the delay. Three synthesis conditions are given, exploring extra matrix variables and suitable matrix structures to provide more efficient redesigns that can deal even with large control delays in the implementation of the redesigned controller. As a contribution, the proposed conditions provide a theoretical guarantee that digital PIs, operating under delay, will perform very close to originally designed continuous-time PIs. A numerical example illustrates the efficiency of the proposed conditions, and a practical application for permanent magnet synchronous motor speed regulation shows good experimental results, illustrating the viability of the proposal.

Digital fuzzy control based on ANFIS for boost converter: Digital redesign

Digital fuzzy control based on ANFIS for boost converter: Digital redesign

The impact of a combinatorial digital and organisational intervention on the management of long-term conditions in UK primary care: a non-randomised evaluation

BackgroundBetter management of long-term conditions remains a policy priority, with a focus on improving outcomes and reducing use of expensive hospital services. A number of interventions have been tested, but many have failed to show benefit in rigorous comparative research. In 2016, the NHS Test Beds scheme was launched to implement and test interventions combining digital technologies and pathway redesign in routine health care settings, with each intervention comprising multiple innovations to better realise benefit from their ‘combinatorial’ effect. We present the evaluation of one of the NHS Test Beds, which combined risk stratification algorithms, practice-based quality improvement and health monitoring and coaching to improve management of long-term conditions in a single health economy in the north-west of England.MethodsThe NHS Test Bed was implemented in one clinical commissioning group in the north-west of England (patient population 235,800 served by 36 general practices). Routine administrative data on hospital use (the primary outcome) and a selection of secondary outcomes (data from both hospital and primary care) were collected in the intervention site, and from a comparator area in the same region. We used difference-in-differences analysis to compare outcomes in the NHS Test Bed area and the comparator after initiation of the combinatorial intervention.ResultsTests confirmed the existence of parallel trends in the intervention and comparator sites for hospital outcomes for the period April 2016 to March 2017, and for some of the planned primary care outcomes. Based on 10 months of post-intervention secondary care data and 13 months post-intervention primary care data, we found no significant impact on primary outcomes between the intervention and comparator site, and a significant impact on only one secondary outcome.ConclusionA combinatorial digital and organisational intervention to improve the management of long-term conditions was implemented across a whole health economy, but we found no evidence of a positive impact on health care utilisation outcomes in hospital and primary care.

Digital redesign in teaching training – Connected learning

Digital redesign in teaching training – Connected learning

Intelligent digital redesign for T–S fuzzy systems: sampled‐data filter approach

This study proposes an intelligent digital redesign (IDR) technique for sampled-data fuzzy filters of non-linear systems. The technique constructs a closed-loop system with predesigned continuous-time and sampled-data filters based on the Takagi–Sugeno (T–S) fuzzy model. The closed-loop systems ensure asymptotic stability and state-matching condition in the IDR problem. Unlike previous techniques, the proposed method solves the IDR problem without a discretization process which degrades the IDR performance. Sufficient conditions for solving the IDR problem are proposed and derived in terms of linear matrix inequalities. In addition, the performance recovery of the sampled-data fuzzy filter is shown. Finally, the feasibility of the proposed technique is demonstrated in two simulation examples.

Sampled-data Control of Fuzzy Systems Based on the Intelligent Digital Redesign Technique: An Input-delay Approach

In this paper, a novel intelligent digital redesign (IDR) method for a Takagi-Sugeno fuzzy system is proposed based on the guaranteed cost method. The objective of the IDR is to determine a sample-data data gain that achieves the same performance as a given continuous-time controller. Unlike previous works, we use the state-matching error cost function and develop an IDR technique without the use of any discretization methods. To this end, a sufficient condition guaranteeing both the asymptotic stabilization of the error dynamics model and the minimization of the upper bound of the error cost function is formulated in terms of linear matrix inequalities based on the input-delay approach. Finally, a simulation example validates the superiority of the proposed method.

Intelligent Digital Redesign for Sampled-data Fuzzy Control Systems Based on State-matching Error Cost Function Approach

This paper presents a novel intelligent digital redesign (IDR) technique for a sampled-data fuzzy controller of fuzzy systems which can be modeled in Takagi-Sugeno (T-S) fuzzy systems. The IDR technique, which is one of sampled-data fuzzy controller design techniques, is to effectively convert a well-designed analog fuzzy controller into a sampled-data fuzzy controller in the state-matching sense. In this paper, unlike previous IDR techniques, the state-matching error is minimized by defining the state-matching error cost function. Also, to improve the state-matching condition, the exact discretized model is used for the proposed IDR technique. The sufficient condition of the proposed IDR technique is developed and derived in terms of linear matrix inequalities (LMIs). Finally, some numerical examples are provided to verify the effectiveness of the proposed techniques.

Sampled‐data control of fuzzy systems based on the intelligent digital redesign method via an improved fuzzy Lyapunov functional approach

This study presents a linear matrix inequality (LMI) approach to the sampled-data control of Takagi-Sugeno fuzzy systems, based on the intelligent digital redesign (IDR) technique. The objective of the IDR is to design a digital control system whose trajectory closely matches that of a given well-constructed analogue control system by minimising the state-matching error. In this study, state-matching performance is enhanced by using a continuous-time state-matching criterion, which guarantees that the state-matching error is minimised through the entire time interval. Unlike previous studies, mismatched information of membership functions for both analogue and digital control systems is directly manipulated. Moreover, the authors introduce an improved fuzzy Lyapunov functional that consists of both membership functions for analogue and digital control systems, which relaxes the conservativeness of LMI conditions. Finally, two examples demonstrating the effectiveness of the authors' method are provided.

Digital redesign of analogue dynamic output-feedback controllers for polytopic systems

ABSTRACTThis paper is devoted to the problem known as digital redesign, i.e. given a previously designed stabilising continuous-time controller for a continuous-time plant, synthesise a digital controller that provides the hybrid closed-loop system with output trajectories as similar as possible to the continuous-time ones. To accomplish this goal, two distinct optimisation criteria are investigated: (i) the Euclidean norm of the difference between the dynamic matrix of the discretised closed-loop continuous-time system and the dynamic matrix that represents the discretised open-loop system fed back by the designed digital controller; (ii) the norm of the transfer function from the noise input to the error between the outputs of the two systems. As main novelties with respect to the existing results on digital redesign, the proposed conditions can deal with polytopic systems, and can synthesise reduced-order dynamic output-feedback digital controllers as well.

Historic watermills digital survey and sustainable re-design in Cilento and Vallo di Diano National Park (Italy)

The present work is part of a multidisciplinary research carried out within the Benecon Competence Center Demonstration Project and related to Cilento and Vallo di Diano National Park area, one of the UNESCO World Heritage Sites and included in the Biosphere Reserve network. Cilento and Vallo di Diano landscape is an organic unit generated by the complex combination of physical and natural phenomena, firmly tied each other by mutually reciprocal relationships. The research for a dialogue between man and this heterogeneous set of elements, processes and interrelations has characterized the antrophized and natural heritage that has formed the landscape of these places characterized by great water wealth, dense slopes and lush Mediterranean vegetation. The Geographical Information System platform of the territory of Cilento and Vallo di Diano National Park synthesizes the integrated work of knowledge of the area and of all its forms of production either cultural or material, including through the actions of the peoples who have inhabited these sites. The GIS of Cilento and Vallo di Diano National Park has been developed to create a georeferred and dynamic database that would gather and integrate the cognitive activities carried out on the area through an innovative equipment. The GIS has been dynamically structured in thematic layers always implementable that at different scale contain the results and the elaborations of survey and data acquisition. Information, cataloged according to the ‘data warehouse’ methodology, has been structured to make easy the access by the user and to support decision-making. The layers, integrating the information with the aforementioned data, are organized, also in reference to the various scales and main time variations. In particular, the census of the territorial resources of the territory concerned the more than two hundred watermills surveyed within the perimeter of the National Park and subsequently surveyed through 3D digital laser sensors, cataloged on the basis of cadastral data and then inserted into the GIS platform on a georeferred map as a starting point for further documentation actions. The aforementioned analysis has been developed before a subsequent step of the research on technological and environmental issues. On some watermills have been developed a surveys to check the relationship between the water system, soil quality and its uses with to define a reference framework for the use of appropriate environmental technology for water cycle optimization systems. This study concerned the ‘Auso’ Valley water system, in the territory of Ottati, a municipality located in the north-eastern part of Cilento and Vallo di Diano National Park and has been structured in three phases. An initial phase of analysis took into account the hydraulic characteristics of the ‘Auso’ Valley, with particular reference to the nature of the water stream, the vegetation, geological and lithological conditions of the site, the hydrological and ecological environment. The second phase of the work concerned the check on the presence of hydraulic conditions suitable for the reactivation of the historic mills as examples of the hydro-mechanical technology used in the past. The last phase finally allowed an analysis on the quality characteristics of the waters of the ‘Auso’ Torrent. It has been possible to hypothesize the creation of a “filter system” with river phytodepuration techniques in order to safeguard the water course from induced pollution. DOI: http://dx.doi.org/10.5755/j01.sace.20.3.19174

Digital redesign of analog smith predictor for systems with long input time delays

The discretization of the analog Smith predictor by using the prediction-based state-matching digital redesign method for systems with various input time delays was recently investigated in the literature. This paper presents an alternative Chebyshev quadrature state-matching digital redesign method for discretization of the analog Smith predictor for systems with a long input time delay. In order to implement the digitally redesigned Smith predictor by utilizing the output-feedback of the plant, an ideal state reconstructor for the long input-delayed plant is established. The long dead time of interest is an integer plus a fractional input delay. An illustrative example is given to demonstrate the effective of the proposed approach.

H2 and H∞ digital redesign of analog controllers for continuous-time polytopic systems

The aim of this paper is to investigate the problems of designing H∞ and H2 discrete-time stabilizing controllers for polytopic continuous-time systems through the digital redesign methodology. This technique consists of determining a stabilizing digital gain starting from a predetermined continuous-time controller, such that a performance criterion, associated to the difference between the continuous-time and discrete-time state trajectories, is minimized. In this paper, synthesis conditions are proposed in terms of parameter-dependent matrix inequalities with polynomial variables and a given scalar parameter. Differently from other approaches that minimize the Euclidean norm and can only handle precisely known systems, the proposed method minimizes a bound to the H2 or H∞ norm of a system that represents the dynamics of the error between the polytopic continuous-time plant and the discrete-time representation. Numerical examples are presented to show the advantages of the proposed methodology when compared with other conditions from the literature in the precisely known case, and to illustrate the applicability of the technique for uncertain systems.

An improved digital redesign for sampled-data fuzzy control systems: Fuzzy Lyapunov function approach

This paper proposes an improved digital redesign (DR) technique for sampled-data fuzzy controllers in nonlinear systems, based on a Takagi–Sugeno (T–S) fuzzy model. To improve the performance of the DR technique, two methodologies are used: a state-matching error cost function, and a continuous-time fuzzy Lyapunov function. Using these two methodologies, a novel DR technique is proposed to guarantee both the stability and state-matching conditions of the sampled-data fuzzy control system. Further, the proposed DR technique is represented as an optimal problem using the linear matrix inequality (LMI) format. Finally, some simulation examples are provided to verify the effectiveness of the proposed technique in comparison with previous techniques.

Intermittent Redesign of Analog Controllers via the Youla Parameter

The paper studies digital redesign of linear time-invariant analog controllers under intermittent sampling. The sampling pattern is only assumed to be uniformly bounded, but otherwise irregular and unknown a priori . The contribution of the paper is twofold. First, it proposes a constructive algorithm to redesign any analog stabilizing controller so that the closed-loop stability is preserved. Second, it is shown that when applied to (sub) optimal $\boldsymbol{H}^{2}$ and $\boldsymbol{H}^{\infty}$ controllers, the algorithm produces (sub) optimal sampled-data solutions under any a priori unknown sampling pattern. The proposed solutions are analytic, computationally simple, implementable, and transparent. Transparency pays off in showing the optimality, under a fixed sampling density, of uniform sampling for both performance measures studied.

Fuzzy filter for nonlinear sampled-data systems: Intelligent digital redesign approach

This paper presents a fuzzy filter design method for nonlinear sampled-data systems using an intelligent digital redesign (IDR) technique. Based on a Takagi–Sugeno (T–S) fuzzy model, discretized closed-loop systems with pre-designed analog fuzzy and digital fuzzy filters are presented. An IDR problem is given to guarantee both state-matching condition and asymptotic stability. Sufficient conditions for solving the IDR problem are proposed and are derived in terms of linear matrix inequalities (LMIs). Finally, a simulation example is given to show the effectiveness of the proposed method.

An On-Line Tracker for a Stochastic Chaotic System Using Observer/Kalman Filter Identification Combined with Digital Redesign Method

This is the first paper to present such a digital redesign method for the (conventional) OKID system and apply this novel technique for nonlinear system identification. First, the Observer/Kalman filter Identification (OKID) method is used to obtain the lower-order state-space model for a stochastic chaos system. Then, a digital redesign approach with the high-gain property is applied to improve and replace the observer identified by OKID. Therefore, the proposed OKID combined with an observer-based digital redesign novel tracker not only suppresses the uncertainties and the nonlinear perturbations, but also improves more accurate observation parameters of OKID for complex Multi-Input Multi-Output systems. In this research, Chen’s stochastic chaotic system is used as an illustrative example to demonstrate the effectiveness and excellence of the proposed methodology.

State-space Modelling and Digital Controller Design for DC-DC Converter

The recent development in digital technology offers better platform for easy implementation of advance control algorithm in power converter design making digital control a viable alternative to analogue counterpart. Controller design for power converters has been very challenging due to non-linear characteristics of power switches, the supply voltage variability, load current changes and circuit element variation. This paper presents dynamic averaged state-space modelling of non-ideal dc-dc boost converter with parasitic and digital controller design for boost converter using digital redesign and direct digital design methods. The system was simulated in Matlab/Simulink to investigate the dynamic performance of the two controllers’ transient response, control bandwidth and response to variable supply voltage. The results demonstrated fast transient and wide control bandwidth for tight voltage regulation of variable input voltage.

Constrained State Feedback Speed Control of PMSM Based on Model Predictive Approach

This paper presents constrained state feedback speed control of a permanent-magnet synchronous motor (PMSM). Based on classical control theory, nonlinear state-space model of PMSM is developed. A simple linearization procedure is employed to design a linear state feedback controller (SFC). Digital redesign of a SFC is carried out to achieve discrete form suitable for implementation in a DSP. Model predictive approach is used to a posteriori constraint introduction into control system. It overcomes limitations of motion control system with nonconstrained SFC resulting in low dynamic properties. The novel concept utilizes machine voltage equation model to calculate the boundary values of control signals which provide permissible values of the future state variables. Secondary control objectives such as zero $d$ -axis current are included. Simulation and experimental results are presented to validate the proposed constrained state feedback control algorithm in comparison to nonconstrained state feedback control and cascade control structure, respectively.

Intelligent digital redesign of fuzzy controller for non‐linear systems with packet losses

In this study, a novel intelligent digital redesign (IDR) technique is proposed for the sampled-data fuzzy controller of the non-linear system with packet losses. For the IDR development, the non-linear system is represented in the Takagi–Sugeno fuzzy model and the packet loss is assumed to be an independent, identically distributed Bernoulli random process. After introducing the traditional IDR technique, the closed-loop system with state-matching error and the state-matching error cost function are achieved for the development of the novel IDR technique. In the discrete-time Lyapunov sense, the exponential mean-square stability is guaranteed while minimising the state-matching error, and its sufficient condition is derived into linear matrix inequalities. Two examples are provided to verify the effectiveness of the proposed technique by comparison.