Mohammed Zaheeruddin

Design of decentralized robust controllers for multizone space heating systems

Temperature control of multizone environmental spaces is studied. A bilinear model of a multizone space heating (MZSH) system is developed. The MZSH system is acted upon by constant unknown disturbances and step changes in the desired set-points. Robust decentralized controllers are designed with linear and nonlinear models, using two different methods based on optimization of quadratic performance criteria. In each case, the output responses of the resulting closed-loop bilinear system are examined. Simulation results showing the regulation properties of the decentralized and centralized controllers are presented. The results show that the system performance with decentralized control is very close to the performance of the system with centralized control. A decentralized controller is also designed for the bilinear model based on minimizing not only the output error and energy input, but also a measure of sensitivity to parameter variations. Simulation results for the corresponding bilinear closed-loop system are presented. >

Robust decentralized control of HVAC systems using H∞-performance measures

Abstract In this paper, we present the results of a study on the use of H ∞ constraints in an optimization technique for the design of robust decentralized output feedback control of a heating, ventilation and air conditioning (HVAC) system. Robust stability and performance specifications are used to achieve temperature control in multi-zone HVAC system in the presence of disturbances and model uncertainties and under constraints on control input energy. The resulting fixed-gain decentralized output feedback controller, which is based on a linear model, is then implemented via simulation on a full bilinear model of the HVAC system. Comparison of these results with those based on “constrained” linear-quadratic optimal regulator design show significantly superior performance of the H ∞ -based design.

Decentralized preview control for multiple disturbance rejection in HVAC systems

Abstract A decentralized preview controller is designed for temperature control of multizone indoor environmental spaces. A two-zone space heating system is considered. The physical system consists of a boiler, heat pumps, distribution network and two environmental zones. By assuming that the outdoor temperature variations are “previewable”, a decentralized preview controller is designed by using a parameter optimization method. The output responses of the resulting decentralized closed-loop bilinear system acted upon by single and multiple disturbances with and without preview action are compared. Also, results showing the robustness property of the controller, and the 24-hour building operation with unoccupied and occupied setpoint tracking using preview control are given.

Temperature and humidity control of indoor environmental spaces

Abstract The temperature and humidity control of indoor environmental spaces is studied. A constant volume heating and humidification system consisting of a boiler, a heating coil, ductwork and a fan, and a two-zone building is considered. The temperature and humidity control models are developed and multivariable controllers are designed. The closed loop system responses subject to step disturbances in outdoor temperatures and relative humidity are given. Also, results showing a typical-day operating performance of the closed loop system are given.

Inter-model comparisons between three PC programs and blast

Abstract Inter-model comparisons between three PC programs and a reference program (BLAST) were made. In the methodology adopted, first, the differences in the input data and the modelling techniques used by these programs were recorded. Predictions of energy budgets and the sensitivity results to changes in loads, systems and plants parameters were then compared. Although the results show an acceptable range of variations, the relative differences between the monthly averages are larger than the annual averages. An attempt was made to explore if there existed a trend between the user-friendly attributes of PC programs and their predictions. Under certain cases it appears that the programs with low run times, which also happen to be most user-friendly, show somewhat large differences in their predictions.

Temperature Control of Multi-Zone Space Heating Systems Using Decentralized Robust Controllers

Abstract In this paper, temperature control of multi-zone environmental spaces is studied. Decentralized and centralized controllers are designed based on solving constrained servomechanism problems for a bilinear system. Simulation results are presented which show the regulation properties of the decentralized and centralized controller designed for the bilinear model. A decentralized controller is also designed for the bilinear model based on minimizing not only the output error and input energy but also a measure of sensitivity to parameter variations. Simulation results for the corresponding bilinear closed-loop system are presented.

Unscented Kalman Filter (UKF) and frequency analysis (FA) techniques used for fault detection, diagnosis and isolation (FDDI) in Heating Ventilation Air Conditioning systems (HVAC)-comparison results

Monitoring and controlling the modern and sophisticated Heating Ventilation Air Conditioning (HVAC) building systems under a wide variety of occupancy and load related operating conditions represents a difficult and challenging task. Their complexity drastically increases and the control becomes more difficult task due to the several control loops that interact between them. The main objective of this study is to compare the performance of the automated strategies for fault detection, diagnosis and isolation (FDDI) based on frequency and spectral analysis (FA) of the system response, and an interactive multiple model (IMM), based on the Unscented Kalman Filter (UKF) estimation technique to the problem of fault detection diagnosis and isolation (FDDI) of the valve actuator failures in Discharge air temperature (DAT) loop of the HVAC systems. The both techniques are HVAC model-driven based and the simulations results reveal the superiority of the Interactive Multiple Model based on Unscented Kalman Filter estimation algorithm (IMM_UKF) concerning its accuracy and robustness to the changes in the system structure parameters. These algorithms are implemented in a simulation environment, and the fault diagnosis results are presented for a several fault scenarios in terms of mode probabilities and active fault index. From the preliminaries simulations, for different scenarios we found that the IMM_UKF algorithm is robust to the choice of the matrix probability and to the small changes in process and measurement noise level, result that is confirmed in the literature.

Decentralized control of a variable air volume system

Decentralized and partially decentralized control of a multizone variable air volume (VAV) system is studied. The VAV system consists of two environmental zones and an air distribution system. By assuming that the temperature of supply air is perfectly controlled and therefore remains constant, an eighth-order nonlinear model of the VAV system is developed. The control problem is to regulate the zone temperatures and air flow rates in response to step changes in cooling loads acting on the system. Decentralized controllers are designed by minimizing a quadratic performance index subject to constraints on the input energy and the eigenvalues of the slow and fast modes of the linearized model to preserve the two time scale property of the system. The designed controllers are implemented on the nonlinear system. The resulting closed-loop system responses show that good regulation of the zone temperatures can be achieved while maintaining sufficient air flow rates in the system with the designed decentralized controllers.

An Adaptive Observer State-of-Charge Estimator of Hybrid Electric Vehicle Li-Ion Battery - A Case Study

In this research paper we investigate the procedure design and the implementation in a real time MATLAB SIMULINK R2017a simulation environment of an accurate adaptive observer state estimator. The effectiveness of the observer state estimator design is proved through intensive simulations performed to estimate the state-of-charge of a lithium-ion rechargeable battery integrated in a hybrid electric vehicle Battery Management System structure for a particular Honda Insight Japanese car. The state-of-charge is an essential internal parameter of the lithium-ion battery, but not directly measurable, thus an accurate estimation of battery state-of-charge becomes a vital operation for the Battery Management System. This is the main reason that motivates us to find the most suitable state-of-charge estimator in terms of estimation accuracy, fast convergence and robustness to the possible changes in the state-of-charge initial value, to the temperature effects on the battery, changes in the battery internal resistance and nominal capacity.

Characterization, analysis, and noise control measures of a mechanical room

The acoustic environment of a mechanical room in buildings has received little attention because the space is occasionally occupied by building maintenance staff. However, the room typically includes the loudest noise sources in buildings. It is necessary to investigate noise exposure in the mechanical room for the staff. The aim of this study is, thus, to assess noise levels in the room by examining acoustic characteristics of the noise sources and mapping noise levels produced by the sources. This study also aims to provide optimal solutions to decrease the noise levels being produced. The framework consists of (1) identifying the major locations at which noise is being produced; (2) measurement of noise levels; and (3) performing noise level analysis of each activity. These findings will provide useful information to establish effective noise management plans for mechanical rooms in buildings.The acoustic environment of a mechanical room in buildings has received little attention because the space is occasionally occupied by building maintenance staff. However, the room typically includes the loudest noise sources in buildings. It is necessary to investigate noise exposure in the mechanical room for the staff. The aim of this study is, thus, to assess noise levels in the room by examining acoustic characteristics of the noise sources and mapping noise levels produced by the sources. This study also aims to provide optimal solutions to decrease the noise levels being produced. The framework consists of (1) identifying the major locations at which noise is being produced; (2) measurement of noise levels; and (3) performing noise level analysis of each activity. These findings will provide useful information to establish effective noise management plans for mechanical rooms in buildings.