Modular Control Design Research Articles

Subsystem-Based Control With Modularity for Strict-Feedback Form Nonlinear Systems

This study proposes an adaptive <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">subsystem-based control</i> (SBC) for systematic and straightforward nonlinear control of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> th-order strict-feedback form (SFF) systems. By decomposing the SFF system to subsystems, a generic term (namely <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">stability connector</i> ) can be created to address dynamic interactions between the subsystems. This 1) enables modular control design with global asymptotic stability, 2) such that the control design and its stability analysis can be performed locally at a subsystem level, 3) while avoiding an excessive growth of the control design complexity when the system order <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> increases. The above properties make the proposed method suitable especially for high-order systems. We also design a smooth projection function for the system parametric uncertainties. The efficiency of the method is demonstrated in simulations with a nonlinear 5th-order system.

Fractional Order Control of Power Electronic Converters in Industrial Drives and Renewable Energy Systems: A Review

The power electronics industry is undergoing a revolution driven by an industry 4.0 perspective, with smart and green/hybrid energy management systems being the requirement of the future. There is a need to highlight the potential of fractional order control in power electronics for the highly efficient systems of tomorrow. This paper reviews the developments in fractional order control in power electronics ranging from stand-alone power converters, industrial drives and electric vehicles to renewable energy systems and management in smart grids and microgrids. Various controllers used in power electronics such as the fractional order PI/PID (FOPI/FOPID) and fractional-order sliding mode controllers have been discussed in detail. This review indicates that the plug-and-play type of intelligent fractional order systems needs to be developed for our sustainable future. The review also points out that there is tremendous scope for the design of modular fractional-order intelligent controllers. Such controllers can be embedded into power converters, resulting in smart power electronic systems that contribute to the faster and greener implementation of industry 4.0 standards.

Control and fault analysis of multiport converters for low voltage DC distribution systems

The recent evolution of distribution systems has shed light on innovative solutions aimed at enhancing the performance of such systems. In this paper, the authors focus their attention on two modular, non-isolated multiport DC/DC converters and their application to low voltage DC distribution systems. The first topology is based on a capacitive internal link, while the second one is based on a less usual inductive link. Unconventional control strategies based on a lower-level pseudo-sliding mode control algorithm and a higher-level control based on inverse dynamics are proposed for both topologies by means of a general, fully modular control design. A six-port application is discussed in detail and its operation is analyzed in steady state, under abrupt load/generation changes and in case of pole-to-pole faults. Finally, a systematic comparison between the two topologies is performed.

Agile maneuvering with intelligent articulated vehicles: a control perspective

Articulated vehicles are the popular means of freight and public transportation. Current trends and development forecasts indicate an increase of their use in the near future, mainly for economic and environmental reasons. Modular High Capacity Vehicles and articulated urban buses are the examples of modern transportation solutions that require agile maneuvering in cluttered spaces. Since maneuvering with articulated vehicles is a highly non-intuitive and burdening process for human-drivers, it seems reasonable to equip this kind of vehicles with systems which provide (semi-) autonomous maneuvering capabilities. In this paper, we consider a modular cascade-like control design methodology that is applicable to intelligent articulated vehicles enabling them to perform complex maneuvers either through a driver-assistance system or in an autonomous control mode. First, we discuss key properties of the so-called N-trailer kinematics, and the correspondence between practical motion problems defined for articulated vehicles and their formulation in the control engineering language. Next, the modular cascadelike control system structure is presented which allows solving various control tasks in a unified manner for multi-body vehicles of different kinematic structures and any number of segments. Solutions to selected control problems are illustrated by numerical and experimental results.

LMI-Based Design of Distributed Controllers to Achieve Component Swapping Modularity

Component swapping modularity (CSM) refers to distributed modular control design in networks of swappable smart components. CSM reduces control design effort and complexity in platform-based systems. Existing CSM methods achieve promising results for low order multi-input-multi-output systems. However, the lack of generalization, heavy computational burden, and to a lower extent, designer’s involvement limit the applications of the existing CSM methods. Thus, this brief utilizes linear matrix inequalities (LMIs) to present an almost automatic CSM algorithm which converges rapidly and is easy to generalize to an arbitrary linear system. The LMI-based CSM is designed to maintain both disturbance attenuation and quadratic stability. Also, it is desired to satisfy specific time response criteria. Thus, the proposed algorithm combines $\mathcal {H}_{2}$ optimization and robust $\mathcal {H}_\infty $ optimization to obtain a distributed control composed of parts with prescribed orders and partially tunable parameters. The designer’s involvement is dramatically reduced to the iterative tuning of two scalar parameters to optimize the fixed part of the controller. The proposed algorithm incorporates reference tracking. Also, stability measures and design criteria are checked numerically at each step. The LMI-based CSM algorithm has been numerically verified using an engine idle speed control example.

A modular adaptive control design with ISS analysis for nonminimum phase hypersonic vehicle models

SummaryAir‐breathing hypersonic vehicles typically exhibit a nonminimum phase behavior when altitude is controlled via lift generation. This phenomenon prohibits the use of classical inversion‐based control techniques. Dynamic models of these vehicles are also subject to parametric uncertainties and unmodeled dynamics related to flexible effects of the fuselage. In this paper, we present a modular adaptive control method that achieves asymptotic setpoint tracking in both airspeed and altitude using thrust and elevator deflection as the only control inputs for a generic longitudinal model of a hypersonic cruise. The nonminimum phase problem is overcome through output redefinition, with altitude controlled by pitching moment. The internal dynamics, flight path angle, and altitude are then stabilized by saturating the interconnections and exploiting local stability properties. A new technique for the use of saturation functions in error coordinate is presented. The adaptive controller for altitude uses a pitch rate observer combined with projection. This control augmentation decouples the parameter estimation errors from internal dynamics, allowing for the use of small‐gain arguments. Simulation results from a vehicle model with flexible effects and parametric uncertainty are included to demonstrate control effectiveness.

Stabilizing plug-and-play regulators and secondary coordinated control for AC islanded microgrids with bus-connected topology

This paper presents a distributed hierarchical control architecture for voltage and frequency stabilization and reactive power sharing in AC islanded microgrids. In the primary control layer, each generation unit is equipped with a local regulator for voltage and frequency stability acting on the corresponding voltage-source converter. Following the plug-and-play design approach previously proposed by some of the authors, whenever the addition/removal of a distributed generation unit is required, feasibility of the operation is automatically checked by designing local controllers through convex optimization. The update of the voltage-control layer, when units plug-in/-out, is therefore automatized and stability of the microgrid is always preserved. Moreover, local control design is based only on the knowledge of parameters of power lines and it does not require to store a global microgrid model. In this work, we focus on islanded microgrids with bus-connected topology and enhance the primary plug-and-play layer with local virtual impedance loops and secondary coordinated controllers ensuring bus voltage tracking and reactive power sharing. In particular, the secondary control architecture is distributed, hence mirroring the modularity of the primary control layer. We validate primary and secondary controllers by performing experiments with both linear and nonlinear loads, on a setup composed of three bus-connected distributed generation units. Most importantly, the stability of the microgrid after the addition/removal of distributed generation units is assessed. Overall, the experimental results show the feasibility of the proposed modular control design framework, where generation units can be added/removed on the fly, thus enabling the deployment of virtual power plants that can be resized over time.

Modular Control Design and Stability Analysis of Isolated PV-Source/Battery-Storage Distributed Generation Systems

A distributed generation (DG) system with a photovoltaic (PV) source supported by energy storage devices and feeding dc- and ac-loads in islanded-mode operation, is considered and analyzed. As all the DG parts are interfaced through power electronic dc/dc or dc/ac converters, a control strategy is introduced which is applied directly on each individual duty-ratio converter input. The aim of the control design is to drive the PV-array energy production at the maximum power and to ensure instantaneous power balance in the limits of the storage capacity. In this scheme, critical quality demands are fulfilled, such as operation with constant ac- and dc-voltages at the load sides, independently from the power consumed. The particular controllers are implemented by applying the standard local cascaded structure with the inner-loops being fast nonlinear proportional-integral current-mode controllers. To avoid adverse impacts on the system performance, caused by contradictory actions between the individual controllers, the complete accurate DG model is considered as an isolated microgrid with the fast inner-loop controllers incorporated. Adopting a common modular inner-loop nonlinear controller form, a rigorous novel stability analysis is developed by constructing the appropriate Lyapunov function in a new sequential manner. Finally, the stability and convergence to the equilibrium are verified by simulation and experimental results.

Robust modular control system design using an inner‐loop reference model and μ synthesis techniques

SUMMARYFor complex dynamic systems, a modular control design process is often employed, wherein the overall design is partitioned into smaller modules. This paper considers a particular inner‐loop/outer‐loop modular control strategy in which the designer of the outer‐loop module does not know the specifics of the inner loop but instead possesses a reference model that captures the ideal inner‐loop input–output behavior. In the first part of this paper, we establish analytical properties of the modular reference‐model‐based design. In the second part, we introduce a novel mechanism, referred to as the modular control error compensation, which mitigates the performance loss that arises when the inner‐loop reference model is not matched. We propose an iterative algorithm, using μ synthesis, to design this compensator to reduce performance loss on the basis of two concrete worst‐case performance metrics. The effectiveness of the modular control strategy with the modular control error compensation is demonstrated through experimental results on an automotive system. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Evolutionary Computing Based Modular Control Design for Aircraft with Redundant Effectors

In this paper, we present a genetic algorithm based modular reconfigurable control strategy for an over-actuated ADMIRE nonlinear aircraft system. The control law was based on multi-input multi-output (MIMO) linear quadratic regulator (LQR) strategy to produce virtual command signals. A pseudo-inverse based allocation method was used for effective distribution of commands produced by controller to redundant control surfaces in normal and fault condition. Actuator position limits can be considered for reconfiguration of virtual command signals. Simulation results show that satisfactory and improved performance even in fault scenario can be achieved quickly by using natural evolution based optimization technique in modular control design.

Optimized Reconfigurable Modular Flight Control Design using Swarm Intelligence

This paper presents an optimized reconfigurable control design methodology by separating control commands distribution task from flight controller for different types of fault handling. The proposed strategy improves the flight control performance in normal and fault situations. The particle swarm optimization (PSO) based multi-input multi-output (MIMO) linear quadratic regulator (LQR) is used to produce virtual command signals. A modified weighted pseudo-inverse (WPI) based cascaded re- allocation technique is employed for effective implementation of commands to redundant control surfaces in a realistic nonlinear aircraft benchmark model. Control surface fault modelling is performed for the evaluation of optimized reconfiguration based modular flight control strategy. Simulation results show that acceptable fault tolerant control (FTC) performance can be achieved by using swarm intelligence based optimization technique for modular control design.

Verification of Fault Tolerance of Discrete-Event Object-Oriented Models using Model Checking

Abstract The Object-Oriented (O-O) approach has been recently used in the industrial automation to design logic control systems, thanks to the features of specification languages (e.g. UML) that can help to describe event-based behavioral requirements. In this paper, we aim to formalise an O-O framework for the design of modular logic controllers, in which faults occurring in the plant can alter the behavior of closed-loop system. Given the formal model of the system in terms of Kripke structures, it is possible to verify with model checking that even in case of faults the system do not violate given safety and liveness properties. Moreover, we will consider the case in which an O-O logic controller is refined applying the so-called “design-by-extension” mechanism, in which case it is important to verify that the fault tolerance property is inherited by the refined system.

A modular control design method for a flexible manufacturing cell including error handling

This paper introduces a new modular control design method for a cell controller with integrated error handling. To make the complexity of the cell controller manageable, its control logic is separated into two parts: resource allocation control and operation control. To create the operation control not only quickly but correctly, modular operation blocks integrated with error handling are developed. An algorithm automatically generates the operation control. The operation control created by the proposed method is proved to have desired control behaviors. The method is applied to an example system.

Design and Implementation of Modular FPGA-Based PID Controllers

In this paper, modular design of embedded feedback controllers using field-programmable gate array (FPGA) technology is studied. To this end, a novel distributed-arithmetic (DA)-based proportional-integral-derivative (PID) controller algorithm is proposed and integrated into a digital feedback control system. The DA-based PID controller demonstrates 80% savings in hardware utilization and 40% savings in power consumption compared to the multiplier-based scheme. It also offers good closed-loop performance while using less resources, resulting in cost reduction, high speed, and low power consumption, which is desirable in embedded control applications. The complete digital control system is built using commercial FPGAs to demonstrate the efficiency. The design uses a modular approach, so that some modules can be reused in other applications. These reusable modules can be ported into Matlab/Simulink as Simulink blocks for hardware/software cosimulation or integrated into a larger design in the Matlab/Simulink environment to allow for rapid prototyping applications.

APPLYING MISSILE GUIDANCE CONCEPTS TO MOTION CONTROL OF MARINE CRAFT

This paper considers employing missile guidance concepts to design motion control systems for marine craft. Initially, classical concepts such as line of sight (LOS), pure pursuit (PP), and constant bearing (CB) are reviewed. Subsequently, the relationship of these concepts to motion camouflage strategies in nature is pointed out, as well as their application to robot manipulators. Ultimately, the CB guidance scheme is used to design a motion control system for fully actuated marine surface craft. For this purpose, the notion of asymptotic interception becomes fundamental, as the motion control goal is not to hit a physical target in finite time, but to hit a virtual target asymptotically. A modular control design inspired by backstepping and cascade theory results in a classical inner-outer loop guidance and control structure.

Modular design and testing for anti-lock brake actuation and control using a scaled vehicle system

A unique decoupling feature in frictional disk brake mechanisms, derived through kinematic analysis, enables modularised design of an Anti-lock Braking System (ABS) into a sliding mode system that specifies reference brake torque and a tracking brake actuator controller. Modelling of brake actuation, vehicle dynamics, and control design are described for a scaled vehicle system. The overall control scheme is evaluated by hardware-in-the loop testing of the electromechanical brake system, and experimental results for two braking scenarios illustrate the benefits of the modular control design scheme and its impact on practical hardware-in-the-loop implementation.

외란 관측기를 이용한 견실한 차량 안정성 제어

A disturbance observer-based vehicle stability controller is proposed in this paper. The lumped disturbance to the vehicle yaw rate dynamics caused by the uncertain factors such as uncertain tire forces and parameters is estimated by the disturbance observer, which is utilized by the robust controller to stabilize the lateral dyof the vehicle. The dynamics of the hydraulic actuator is incorporated in the vehicle stability controller design using the model reduction technique. Modular control design methodology is adopted to ettectively deal with the mismatched uncertainty. Simulation results indicate that the proposed disturbance observervehicle stability controller can achieve the desired reference tracking performance as well as sut1icient level of robustness.<br/>

Virtual Decomposition Based Adaptive Control for Robot Manipulators: Theory and Experiments

Virtual decomposition is a modular approach in which only the dynamics of the subsystems instead of the dynamics of the complete system are used in control design. The modular structure allows a variety of control objectives (position control, force control, constraint control, joint flexibility, and optimization) for a variety of robotic systems (single and multiple robot arms, space robots, walking robots, and human robots) without limitation on robot type. In this paper, the proposed approach is applied to adaptive control of an industrial robot manipulator. Both theoretical and experimental results are presented. In the theoretical aspect, modular control design together with modular stability analysis is presented. Lyapunov asymptotic stability is ensured. In the experimental aspect, preliminary results achieved on the industrial robot KUKA 361 demonstrate the advantage of the proposed approach compared to the original KUKA controller, particularly when the robot moves at a high speed.

A language for compositional specification and verification of finite state hardware controllers

The authors consider the state machine language (SML) for describing complex finite state hardware controllers. It provides many of the standard control structures found in modern programming languages. The state tables produced by the SML compiler can be used as input to a temporal logic model checker that can automatically determine whether a specification in the logic CTL is satisfied. The authors describe extensions to SML for the design of modular controllers. These extensions allow a compositional approach to model checking which can substantially reduce its complexity. To demonstrate these methods, the authors discuss the specification and verification of a simple central-processing-unit (CPU) controller. >