Papers by Keyword: System Identification

Abstract: The availability of electrical energy is essential for human progress and economic development. Renewable energy solutions, including waste-to-energy (WtE) systems, present sustainable alternatives but require advanced control strategies for optimal performance. This research aims to enhance the control of drum level, temperature, and pressure in WtE steam boilers at Ethiopia's Reppie power plant. The existing Programmable Logic Controller (PLC) system is limited in its ability to predict future states and handle nonlinear system behaviors. To overcome these challenges, a Radial Basis Function Autoregressive with Exogenous input (RBF-ARX) model was developed and integrated with a Model Predictive Controller (MPC). The results demonstrate that the MPC approach significantly surpasses the performance of the Linear Quadratic Regulator (LQR) in terms of control efficiency. For temperature control, the MPC achieves a settling time of 0.3955 seconds and a rise time of 0.0195 seconds, compared to LQR's 5.99 seconds. Similarly, for pressure control, the MPC achieves a settling time of 0.6678 seconds, outperforming the LQR's 12.507 seconds. Drum level regulation further showcases the superiority of MPC, with a settling time of 0.5223 seconds versus the LQR's 8.302 seconds. This proposed RBF-ARX-based MPC framework not only optimizes control efficiency at Reppie but also demonstrates scalability and applicability to other WtE plants, enhancing operational performance under varying conditions. MATLAB/Simulink was used for the modeling and simulation, confirming the robustness of this approach for global adoption in WtE systems.

Abstract: As it stands, in terms of environmental impact and efficiency, photovoltaic (PV) energy has appeared to be a potential renewable power source that notably contends with the traditional power generation schemes. More so, a noteworthy factor that contrariwise influences the PV module efficiency is the PV module temperature. Therefore, the more the PV module temperature increases, the lesser the PV module efficiency. More importantly, the impact of undesired spectrum wavelengths on the PV module temperature is further reduced by passive optical filters, nonetheless, active optical filters which is more superior to the passive type, based on the PV module temperature and output power during the day, dynamically change the cut-off wavelength. Consequently, the efficiency as well as the lifecycle is both enhanced by controlling the active optical filter so as to attain optimal output power. Therefore, in this paper, a wavelength-based thermo-electrical model of a PV module was designed and simulated, the essence of this model is mainly to predict the impact of each module wavelength on both the temperature and the output power of the PV module. In view of this, since the output power is affluence by the module temperature, it is expedient to design a controller that locates the optimal cut-off spectral wavelength to lessen the module temperature whereas getting the most out of the output power over a period of time. In this vein, we designed a Model Predictive Controller whose objective is to maximize the output power by simply controlling the input power through filtering the spectrum wavelength for a photovoltaic (PV) system. The design and simulation of the plant model as well as the MPC controller were carried-out on MATLAB/Simulink environment.

Abstract: This paper addresses the modal and structural identification of the historical masonry bell tower of Ficarolo, in Italy. After the seismic sequence of May 2012, the tower reported a serious damage pattern. Retrofitting interventions were designed and they mainly consisted in the rebuilding of cracked zones and the strengthening of masonry walls with carbon bars embedded in the masonry with epoxy resin. Afterwards, a continuous dynamic monitoring system has been installed on the tower. From the recorded structural response under ambient excitation, the dynamic characteristics of the tower are identified using Operational Modal Analysis techniques. Results of the first months of continuous monitoring are presented in this paper. Moreover, in order to analyse the evolution of the structural behaviour, the effect of changing temperature on the identified natural frequencies is investigated. The experimental modal parameters are also used to identify the elastic modulus of the reinforced masonry through the calibration of a Finite Element (FE) model of the tower. In addition, the influence of the soil-foundation system on the structural behaviour is evaluated. The calibration procedure is performed adopting an improved surrogate-assisted evolutionary strategy. The calibrated FE model can be adopted to simulate the structural response to far-field earthquakes. Moreover, the monitoring system can give valuable information on the structural behaviour and the structural health in the case of seismic events.

Abstract: This study describes a practical and systematic procedure for identifying and modeling nonlinear systems based on the input-output analysis. Frequency domain data is used to obtain a reduced linear models of nonlinear systems. A coherence function is introduced to specify the identification accuracy. The procedure is applied to a small vertical take-off and landing air vehicle. Control compensators are then designed based on the identified models and autonomous hovering is successfully achieved. Simulation results demonstrate the effectiveness and superiority of this method in comparison with other classical approaches.

Abstract: To respond to challenges created by an increase of product variants, multi-variant lines are used as today’s assembly systems. In these multi-variant lines different product variants with diverse lot sizes can be efficiently assembled. These assembly systems are characterized by modular structures that allow assembly system adaptation by reconfiguration.The variety of parameters to be considered from the product’s perspective and the correct allocation of different assembly modules increases the complexity when planning these systems. This complexity makes it difficult to successfully plan and implement production processes. Therefore, digital planning tools and models have to be used to schedule new product variants and to verify that the assembly is possible, given by the modules in the assembly line.Due to its ability to reconfigure, the actual assembly system is adaptable to different product variants. But these modifications are performed by the operator on the shop floor and are often neither properly documented nor communicated to the assembly planer. Thus, the configuration status in reality and the virtual model differ from each other. Using the outdated model for planning without taking into account the changes can result in an unrealizable assembly plan.To overcome this problem, the presented paper introduces a method and technical system to identify the actual assembly system configuration before the assembly planning is done. Due to the subsequent update of the virtual model depending on the actual configuration, the assembly planner is supported with the latest version of the assembly system configuration. Furthermore, the assembly planning process is improved, because possible failures are detected in advance in the virtual planning environment.

Abstract: The aim of this paper is to present a method of nonparametric and parametric secondary path model identification for adaptive active noise control systems with low-power non-Gaussian excitations of the form of a higher-order discrete-time multisine random process and data processing based on cross-higher-order spectra. Properties of the discussed method are illustrated by simulation experiments devoted to secondary path identification for feedforward and feedback active noise control systems. Its robustness to nonlinear distortions implied by data acquisition system and adaptation procedure is proved.

Abstract: The paper is devoted to structural health monitoring using a non-destructive method based on the method of direct stiffness determination combined with the model updating method. The primary aim of the paper is to determine the change in bending and torsional stiffnesses. In the first part of the work it was necessary to prepare a simple experimental scale model of the bridge which was made from two materials – wood and plaster boards. The same bridge model was created in the finite element commercial codes RFEM5 - Dlubal (a more detailed 3D analysis) and ANSYS (a 2D analysis). The last numerical model consists of beam elements with lumped mass elements. The modal analysis was made and these results were used as a comparative base for measurements. In either case data for the original and the damaged models were acquired. Analysis of the measurement data led to the identification of vertical and torsional mode shapes. Last part of the paper is devoted to identification of the damage by application of the direct stiffness calculation method.

Abstract: A thin-disc ultrasonic actuator using a piezoelectric buzzer is proposed as the actuating component for the shaft-driving type ultrasonic actuator. By placed the screw constraints on the metal sheet of a buzzer, a 3-phase reflected wave was constituted and propagated based on the purpose locations of constraints. This wave configuration could convert electrical energy to actuate the kinematical power for rotating the rotor. The input and output signals were acquisition according to the single-frequency exciting of system resonant frequency. The dynamic transfer function of a stator was obtained via the system identification technique, and, therefore, one model of a 3^th-order equivalent circuit was built in which the dynamic features and electromechanical characteristics were considered based on material oscillating behaviors. Because of the admittance transfer function derived from measured method, it is more representative than that of past issues through the theoretical deduction in materials, physics, and mechanics.

Abstract: This work proposes a simple and efficient approach to locating the storeys whose stiffness change in the life cycle of a structure. The storeys that may be damaged are determined by comparing the unitary stiffness matrix in different stages in the life cycle of a building. An appropriate ARX (autoregressive with exogenous input) model of structure in established from the structural dynamic responses in terms of acceleration or velocity. The parameters in an ARX model are identified through the short time Fourier transform, and the natural frequency and damping ratio of structure are estimated directly through these identified parameters. The effectiveness of the proposed procedure is verified using the numerically simulated earthquake acceleration responses of a six-storey structure that is damaged at one or two storeys. The proposed scheme is compared to the DLV approach (flexibility-based damage locating vector approach) in identifying damage storeys.

Abstract: This paper presents the development of the system identification (SI) for the highly nonlinear piezoelectric patch actuator. The transfer function is determined by using the nonlinear least square (NLS) method after the direct measurements of input-output data are taken from the actuator that is installed on a well-equipped platform. The results were validated to ensure that the transfer function derived fits well with the experimental output.