Multi-input Multi-output Control Research Articles

Design of microcontroller-based decentralized controller board to drive chiller systems using PID and fuzzy logic algorithms

This study deals with designing a decentralized multi-input multi-output controller board based on a low-cost microcontroller, which drives both parts of variable-speed scroll compressor and electronic-type expansion valve simultaneously in a chiller system. This study aims to show the applicability of commercial low-cost microcontroller to increase the efficiency of the chiller system, having variable-speed scroll compressor and electronic-type expansion valve with a new electronic card. Moreover, the refrigerant system proposed in this study provides the compactness, mobility, and flexibility, and also a decrease in the controller unit’s budget. The study was tested on a chiller system that consists of an air-cooled condenser, a variable-speed scroll compressor, and a stepper driven electronic-type expansion valve. The R134a was used as a refrigerant fluid and its flow was controlled by electronic-type expansion valve in this setup. Both variable-speed scroll compressor and electronic-type expansion valve were driven by the proposed hardware using either proportional integral derivative or fuzzy logic controller, which defines four distinct controller modes. The experimental results show that fuzzy logic controlled electronic-type expansion valve and proportional integral derivative controlled variable-speed scroll compressor mode give more robustness by considering the response time.

Analyses of drives power reduction techniques for multi-axis random vibration control tests

Abstract In multi-axis vibration control testing, the power required by the excitation system for replicating the user defined test specifications is a limiting factor which cannot be overlooked. Excessive power, on top of over-stressing the often expensive test equipment, could cause data acquisition overloads which inevitably interrupt the test even before the full level run. An accurate definition of the Multi-Input Multi-Output (MIMO) control target allows to perform the control test minimising the overall power required by the shakers. In this sense, in the recent years advanced procedures have been developed in this research direction. This paper analyses the available drives power reduction techniques, offering a detailed overview of the current state-of-the-art. Furthermore, this paper provides a novel solution to manage the cases where most of the power is required by a single drive of the multiple inputs excitation system. In order to point out the pros and cons of each procedure and to show the capabilities of the novel technique, the MIMO target generation algorithms are firstly theoretically explained and then experimentally compared by using a three-axial electrodynamic shaker.

Regulatory-intervented sustainable generation expansion planning in multi-electricity markets

Nowadays, according to sustainable development targets in modern societies, electricity markets are gradually connecting together. In this way, in this paper, a multi-agent generation expansion planning in a joint multi-electricity market environment is proposed. The GENCO (Generation Company) agents, competing in a deregulated structure, try to obtain the most profitable investment and operation plan regarding the incentives/taxes that the regulatory sector legislates. The multi-area market assumption encourages the GENCOs to offer their energy blocks to adjacent electricity markets whenever the production capacity is higher than the local load. To confront the uncertainties such as wind speed, market price, and load demand, the Markov chain method is employed. The regulatory entity which monitors the market feedbacks such as reliability, pollution, and renewable penetration, announces the smart stimulating signals to the agents. The signals are sent back to the agents based on a MIMO (Multi Input Multi Output) PID (Proportional–Integral–Derivative) controller which has predefined social-welfare-oriented reference values. In order to verify the efficacy of the study, the results are compared with conventional single electricity market planning framework. The findings underline that by linking the markets together and applying the MIMO controller, the social welfare goals including costs, emissions, and reliability of supply could be improved. A typical average 25 and 50 percent reduction in carbon emission and tracking deviation respectively, verifies the effectiveness of the proposed model.

Pole-Zero Cancellation Method for Multi Input Multi Output (MIMO) Temperature Control in Heating Process System

With the rapid development of industrial technology, the multi-point (multi-input multi-output) heating processing systems with integrated temperature control have been increasingly needed to achieve high-quality and high-performance processing. In this paper, in response to the demand for proper transient response and to provide more accurate temperature controls, a novel pole-zero cancelation method is proposed for multi-input multi-output (MIMO) temperature control in heating process systems. In the proposed method, the temperature differences and transient characteristics of all points can be improved by compensating dead time difference and coupling effect together by matrix compensation and pole-zero cancelation with the feedforward reference model. Both simulations and experiments were carried out. The results were compared to the well-tuned conventional PI control system and PI plus decoupling compensation system to evaluate the control efficiency of the proposed method.

Output feedback Cross-Coupled Nonlinear PID based MIMO control scheme for Pressurized Heavy Water Reactor

The dynamics of Pressurized Heavy Water Reactor (PHWR) are complex and open-loop unstable in nature. In such systems, parametric and input disturbances may cause instability if the control system fails to reject these disturbances. For such a large, unstable and uncertain process, designing a control scheme with the ability to reject disturbances along with good reference tracking capabilities is a challenging problem. The control scheme should not only be robust but also deterministic and easier to implement. In order to fulfill all these control scheme requirements for nuclear industries, in this work, a Cross-Coupled Nonlinear Proportional Integral Derivative (CCN-PID) scheme is suggested for a 70th order Multi-Input Multi-Output (MIMO) PHWR. It is also shown in this work that the proposed CCN-PID is a simple Cross-Coupled Proportional, Nonlinear Integrator and Derivative (CC-PNID) sliding surface based Sliding Mode Control (SMC). Furthermore, for the output feedback design, a High Gain Observer (HGO) is constructed for the PHWR process. In order to assure robust stability of the closed loop system, a Lyapunov based analysis of the state feedback CCN-PID control scheme is firstly presented. Then, in a similar way, robust stability analysis of HGO is carried out and finally, the stability analysis of the HGO and CCN-PID based output feedback control scheme is evaluated. In order to investigate the performance of the designed HGO based output feedback CCN-PID control scheme, four different scenarios are simulated. The results of these simulations show that the suggested control scheme efficiently rejects parametric uncertainties and input disturbances and corrects the power tilts while keeping the reactor stable and within safe limits of operation. The results also show that the scheme controls the reactor in an effective manner such that the reactor power closely follows the reference signal. The results of the control scheme presented in this work are also compared with earlier works.

A general vibration control methodology for human‐induced vibrations

This paper proposes a general methodology for the design of vibration control of human-induced vibrations. This uses a feedback loop for the design of control parameters and accounts for the nature of human excitation and how humans feel the vibration. The methodology developed considers not only single-input single-output control systems but also multi-input multi-output control systems, especially useful to cancel vibrations coming from modes with closely spaced natural frequencies. The strategy finds simultaneously the optimal placements of a set of inertial mass dampers and the design parameters (control gain matrix for active vibration control, damping ratios and tuning frequencies of tuned mass dampers for passive vibration control). To make this strategy implementable and suitable to human-induced vibrations, elements such as input-output frequency weighting, output time weighting, band-pass filters, actuator dynamics, and nonlinearities are considered within the design. The proposed methodology is illustrated in an application example on a realistic open-layout floor by designing single-input single-output and multi-input multi-output active and passive strategies with one and two dampers. Simulation tests are carried out to evaluate the performance of the controllers in terms of their vibration reduction capacity using a performance index indicator.

Fractional order MIMO controllers for robust performance of airplane longitudinal motion

This paper presents fractional order multi-input multi-output (MIMO) controllers for the robust performance of airplane longitudinal motion. A novel necessary and sufficient criterion is offered by using the value set concept to analyze the robust performance of fractional order MIMO uncertain systems based on the location of the characteristic equation roots. The criterion is applicable to all linear time-invariant systems of commensurate and incommensurate orders with complex coefficients. The obtained results are applied to an uncertain linear model of a business airplane to improve the robust performance of its longitudinal motion by decentralized MIMO output feedback and MIMO state feedback controllers. Numerical simulations are conducted to confirm the effectiveness of the presented criterion and controllers.

Controlling the optimal combustion phasing in an HCCI engine based on load demand and minimum emissions

Despite the potential benefits of the Homogenous Charge Compression Ignition (HCCI) engines, controlling the combustion phasing and emissions are the main obstacles in its development but, in conventional engines the load demand is simply controlled by accelerator. The aim of present work is developing a HCCI engine controller which controls its main parameter similar to conventional engine: controlling the combustion phasing based on load demand. In the present study, A Multi-Input Multi-Output (MIMO) controller has been designed and validated which is used to control HCCI engine main parameters such as: optimum combustion phasing, engine load and minimum emissions. Similar to conventional IC engine the controller is capable of tracking all desired set-points solely by means of load demand as the only reference trajectory. A physic-based control model together with application of Artificial Neural Networks (ANN) is developed to predict the optimum combustion phasing with minimum emissions based on load demand. The results of proposed model are validated with the experimental data for steady state and transient cases. The optimal CA50 is selected based on minimizing the emissions using a multi-zone kinetic coupled with a genetic algorithm. The developed controller performance has been tested thoroughly to evaluate the tracking and disturbance rejection capabilities. Results show that it is capable of rejecting the disturbances for fix engine loads. The controller is quick to reject the disturbances within 3–5 engine cycles, while deviations within 0.04 bar, 0.5CAD and 0.03 for IMEP, CA50 and emissions respectively.

An energy management strategy for supplying combined heat and power by the fuel cell thermoelectric hybrid system

Although integrating the thermoelectric device (TED) to fuel cells (FC) is a promising way to improve the overall system’s output efficiency, its application to the micro-combined heat and power (μCHP) application requires an effective energy management strategy. Therefore, this paper aims to develop a real time energy management strategy (EMS) that intelligently allows the FC and TED to cooperatively minimize primary energy consumption and startup time while properly balancing energy in the energy storage components. This EMS is unique in that it includes TED’s mode of operation and FC and TED’s operating powers as controller parameters for a multi-input multi-output (MIMO) controller. As such, it regulates FC and water tank temperatures and the electric battery’s state of charge. The proposed overall system is tested under 3 dynamic simulations that include startup from ambient and satisfying the energy demands during a winter and summer day. Results demonstrate that adding the TED has reduced startup times by up to 4.45 and 1.77 times for the 1 kW FC stack and 50 kg water tank respectively. Primary energy consumption efficiencies also improved by up to 3.4% in winter and 5.6% in summer when the TED is included into the system.

A Two-Level Hierarchical Controller to Enhance Stability and Dynamic Performance of Islanded Inverter-Based Microgrids With Static and Dynamic Loads

This paper proposes phasor measurement unit (PMU) supported two-level hierarchical controller to enhance stability and dynamic performance of islanded inverter-based microgrids with static and dynamic loads. The proposed hierarchical controller consists of a local decentralized controller for each inverter-interfaced distributed generation (IIDG) unit at the primary level helped by a multi-input multioutput centralized controller at the secondary level. The primary-level decentralized controller incorporates the addition of auxiliary control terms to the conventional droop controller. The auxiliary control terms are based on the total real and reactive power generation information acquired from wide area measurement system through PMUs and the desired power sharing of each IIDG unit. The secondary-level centralized controller, on the other hand, enhances the performance of each local decentralized controller by compensating the voltage and frequency deviations caused by the load disturbances. The performance of the proposed hierarchical controller has been demonstrated through eigenvalue analysis and time-domain simulation results carried out in MATLAB/SIMULINK environment. Further, in order to have a fair comparison, the performance of the proposed hierarchical controller, based on modal-based extended linear quadratic Gaussian (LQG) approach, has been compared with that of hierarchical controller based on state-based extended LQG approach. Simulation results revealed the capability of the proposed hierarchical controller to mitigate the unstable oscillations as well as to settle quickly at different operating points under the application of small-signal disturbances.

The Behavior Analysis of Magnetoresistive Tunnel Junction Devices in State Space

The behavior of magnetoresistive tunnel junction (MTJ) devices in the electronic (digital) circuits is governed by several differential equations. The LLG equation determines the dynamic of the magnetic polarization vector which ultimately affects the (anti)parallel resistance of MTJs. This vector differential equation is decomposed into two scalar differential equations. In the proposed method, the differential equations are expressed in the state space and the corresponding well-developed theories are applied. In fact, the device is considered as a multi-input multi-output control system and the qualitative solutions are presented. The state diagram gives an insight into the device behavior. It can provide additional information about the device performance and can be considered as a complementary technique of other available analysis approaches. With this ability, the designer can engineer the MTJ devices for their optimum performance in the circuit. Using this theory, we also suggested a power and performance improving approach for the spin transfer torque MTJ-based logic circuits. To show the efficiencies offered by the proposed method, a STT-MRAM cell and an array are designed and it is shown that better specifications can be achieved in terms of switching time and power dissipation. The reliability issues are also investigated and we show that the proposed power/performance improvement approach can effectively consider the reliability concerns.

Reduction of Structural Loads in Wind Turbines Based on an Adapted Control Strategy Concerning Online Fatigue Damage Evaluation Models

In recent years, the rapidly-increasing demand for energy generation from renewable resources has been noticeable. Additional requirements are consequently set on Wind Turbine (WT) systems, primarily reflected in WT size and power rating increases. With the size increase of WT, structural loads/fatigue stress on the wind turbine become larger, simultaneously leading to its accelerated aging and the shortening of its lifetime. The primary goal of this contribution is to establish an approach for structural load reduction while retaining or slightly sacrificing the power production requirements. The approach/control strategy includes knowledge about current fatigue damage and/or damage increments and consists of multi-input multi-output controllers with variable control parameters. By the appropriate selection of the designed Multi-Input Multi-Output (MIMO) controllers, the mitigation of structural loads in accordance with a predefined range of accumulated fatigue damage or damage increments, exactly to the extent required to provide a predefined service lifetime, is obtained. The validation of the aforementioned control strategy is based on the simulation results and the WT model developed by National Renewable Energy Laboratory (NREL). The obtained results prove the efficiency of the proposed control strategy with respect to the reduction of rotor blade bending moments, simultaneously exhibiting no significant impact on the resulting power generation.

Robust control with compensation of adaptive model for dual-stage inertially stabilized platform

To achieve excellent tracking accuracy, a coarse-fine dual-stage control system is chosen for inertially stabilized platform. The coarse stage is a conventional inertially stabilized platform, and the fine stage is a secondary servo mechanism to control lens motion in the imaging optical path. Firstly, the dual-stage dynamics is mathematically modeled as a coupling multi-input multi-output (MIMO) control system. Then, by incorporating compensation of adaptive model to deal with parameter variations and nonlinearity, a systematic robust H∞ control scheme is designed, which can achieve good tracking performance, as well as improve system robustness against model uncertainties. Lyapunov stability analysis confirmed the stability of the overall control system. Finally, simulation and experiment results are provided to demonstrate the feasibility and effectiveness of the proposed control design method.

New Smith predictive fuzzy immune PID control algorithm for MIMO networked control systems

Aiming at the problem of network-induced delays for multi-input multi-output networked control systems (MIMO NCS), a new Smith predictive fuzzy immune PID algorithm is introduced to effectively reduce the adverse effect of network-induced delays about stability in MIMO NCS, firstly, by using the v-norm type to decouple the coupling plant. Based on the generalized plant after decoupling, the new Smith predictor is designed. Then, an modified fuzzy immune feedback control algorithm is used to tune PID controller parameters online. When there is a model mismatch or parameter perturbation, the set-point tracking performance and robustness of output response can be significantly optimized. The proposed algorithm does not contain the network delay prediction model and does not need to measure, estimate, or identify the network delay. It can be used in MIMO NCS where the network bandwidth is constrained and the network-induced delays are large. Numerical examples with Ethernet protocol are built to illustrate the correctness and effectiveness of this new algorithm.

Realization of Nonlinear Time-Delay Input–Output Equations

In this letter the problem of transforming a nonlinear multi-input multi-output time-delay control system, described by a set of higher order functional differential equations relating system inputs and outputs, into a set of first order functional differential equations, is studied. The globally linearized system equations are described in terms of polynomials in a delay operator and derivative operator. The Euclidean left division of polynomials is used to compute the basis of a certain free submodule of differential 1-forms. The integrability of the submodule is proved to be necessary and sufficient for the solvability of the problem.

Multicoordination Control Strategy Performance in Hybrid Power Systems

This paper evaluates a state-space methodology of a multi-input multi-output (MIMO) control strategy using a 2 × 2 tightly coupled scenario applied to a physical gas turbine fuel cell hybrid power system. A centralized MIMO controller was preferred compared to a decentralized control approach because previous simulation studies showed that the coupling effect identified during the simultaneous control of the turbine speed and cathode airflow was better minimized. The MIMO controller was developed using a state-space dynamic model of the system that was derived using first-order transfer functions empirically obtained through experimental tests. The controller performance was evaluated in terms of disturbance rejection through perturbations in the gas turbine operation, and setpoint tracking maneuver through turbine speed and cathode airflow steps. The experimental results illustrate that a multicoordination control strategy was able to mitigate the coupling of each actuator to each output during the simultaneous control of the system, and improved the overall system performance during transient conditions. On the other hand, the controller showed different performance during validation in simulation environment compared to validation in the physical facility, which will require a better dynamic modeling of the system for the implementation of future multivariable control strategies.

A New Design of Wide-Area MIMO Coupling Robust HVDC Supplementary Controller

A new multi-input multi-output (MIMO) robust coordination approach for the controller design of multi-infeed high voltage direct current (HVDC) system is proposed. This design will enhance the damping of certain low frequency oscillation mode. The dominant mode ratio (DMR) is applied to choose the appropriate feedback signals, while time delay of wide-area signals is considered. The Total Least Squares-Estimation on Signal Parameters via Rotational Technique (TLS-ESPRIT) algorithm serves in identifying the MIMO system model. To reach the best control effect and disturbance suppression level, the mixed H2/H∞ robust theory with regional poles placement is introduced to design the controller. The new MIMO design approach avoids system decoupling in complex situation, and it uses the interactions of different control loops to enhance the system's stability when most MIMO HVDC controllers are designed by decoupling strategy. Simulation results of a multi-infeed HVDC system validate the control effect and robustness of the proposed method.

Design of dynamic plant model and model-based controller for a heat recovery system with a swirling flow incinerator

We developed a plant model and model-based controller for a heat recovery system with a swirling flow incinerator located in South Korea. First, a plant model was designed to understand the dynamic characteristics of the system. The system was divided into three parts: incinerator, boiler, and steam drum. Then, each part was modeled with a multi-zone, zero-dimensional modeling scheme. Consequently, we found that the plant model followed the dynamic behavior of the target system, particularly for the seven important variables: boiler inlet temperature, superheater inlet temperature, boiler outlet temperature, oxygen mole fraction, steam production rate, steam pressure, and steam temperature. Then, we designed a multi-input multi-output controller for the system with a nonlinear control model. In the controller design, input variables were selected as air flow rate, fuel supply rate and steam valve opening area; while output variables were oxygen mole fraction of exhaust gas, steam production rate and steam pressure. A nonlinear control model was constructed by reducing the plant model. Then a linear quadratic regulator was applied while evaluating control gain at each time step. Finally, we validated the controller on the plant model, which adequately suppressed the disturbance on fuel composition and adjusted the steam production rate.

Observer design for Boolean control networks with unknown inputs

In this paper, multi-input multi-output Boolean control networks are considered as polynomial discrete-time systems in the Galois field F 2 . Two algorithms are proposed to design observers, able to recognise the state and the input of the system in finite time, without any requirement on the structure of the Boolean control network. It is shown that such procedures can be used, in a wholly probabilistic framework, to estimate the state and the input, even when random noise is superimposed to the available measures. The interest in these methods relies on biological applications, as, for instance, regulatory networks, where the state and the input of the system need to be estimated from scarce and noisy data.

Model extension for model based MIMO control in HVAC systems

The presented work deals with the multi-input multi-output (MIMO) control of Heating Ventilating and Air Conditioning (HVAC) systems. In previous work a model based control strategy consisting of a linear model predictive control (MPC) and the Local Linear Model Tree (LoLiMoT) algorithm was presented by the authors. The underlying modeling approach is based on a detailed representation of each HVAC system component. However, the dry effect due to residual condensation after a dehumidification period was not taken into account. In literature, this effect is also not considered in sufficient detail to the best knowledge of the authors. In this contribution a model extension including a novel approach regarding the above mentioned dry effect is discussed. The obtained improvements with respect to previous work are demonstrated in simulation as well as on a real world system.