A new inverse trigonometric shear deformation theory for isotropic and functionally graded sandwich plates

A new inverse trigonometric shear deformation theory is proposed for the static, buckling and free vibration analyses of isotropic and functionally graded (FG) sandwich plates. It accounts for a inverse trigonometric distribution of transverse shear stress and satisfies the traction free boundary conditions. Equations of motion obtained here are solved for three types of FG plates: FG plates, sandwich plates with FG core and sandwich plates with FG faces. Closed-form solutions are obtained to predict the deflections, stresses, critical buckling loads and natural frequencies of simply supported plates. A good agreement between the obtained predictions and the available solutions of existing shear deformation theories is found to demonstrate the accuracy of the proposed theory

An implementation of rotor speed observer for sensorless induction motor drive in case of machine parameter uncertainty

The paper describes observers using model reference adaptive system for sensorless induction motor drive with the pulse width modulator and the direct torque control under the circumstances of incorrect information of induction motor parameters. An approximation based on the definition of the Laplace transformation is used to obtain initial values of the parameters. These values are utilized to simulate sensorless control structures of the induction motor drive in Matlab-Simulink environment. Performance comparison of two typical observers is carried out at different speed areas and in presence of parameter uncertainty. A laboratory stand with the induction motor drive and load unit is set up to verify the properties of observers. Experimental results confirm the expected dynamic properties of selected observer

Speed estimators using stator resistance adaptation for sensorless induction motor drive

The paper describes speed estimators for a speed sensorless induction motor drive with the direct torque and flux control. However, the accuracy of the direct torque control depends on the correct information of the stator resistance, because its value varies with working conditions of the induction motor. Hence, a stator resistance adaptation is necessary. Two techniques were developed for solving this problem: model reference adaptive system based scheme and artificial neural network based scheme. At first, the sensorless control structures of the induction motor drive were implemented in Matlab-Simulink environment. Then, a comparison is done by evaluating the rotor speed difference. The simulation results confirm that speed estimators and adaptation techniques are simple to simulate and experiment. By comparison of both speed estimators and both adaptation techniques, the current based model reference adaptive system estimator with the artificial neural network based adaptation technique gives higher accuracy of the speed estimation

Utilizing STEM-based practices to enhance mathematics teaching in Vietnam: Developing students' real-world problem solving and 21st century skills

In Vietnam, STEM-based teaching approaches have been recommended for schools since 2018 with the integration of multiple courses in schools. Teachers’ perspectives on integrated STEM education, and how to design a STEM lesson that supports students’ learning are critical for ensuring that an integrated STEM curriculum is to be implemented successfully. This paper aims to describe a study examining STEM education practices in teaching Mathematics, in particular “Trigonometry ratio of an acute angle” in Vietnam. This study utilized mixed methods approaches with three phases: the first stage employed a quantitative phase to examine Vietnamese teachers’ perspectives on STEM education. The second phase was an experiment on teaching while applying STEM education to design and organize a mathematics lesson, and the third, final phase, was to employ a qualitative study to explore the Vietnamese students’ experiences of STEM education connected with real-world problem-solving and 21st-century skills development. A total of 47 teachers and 85 students participated in this study and data was collected from multiple research tools such as questionnaires and semi-structured interviews. Findings showed Vietnamese teachers’ perspectives on the necessity and importance of applying STEM education practices; however, they reported facing numerous challenges. A lesson designed as a STEM education application and the students’ feedback in relation to real-world problems. Learning outcomes connected with 21st-century skills in this study were expected to provide further knowledge for further discussions and practices to enhance teaching and learning STEM and mathematics education in VietnamPeer Reviewe

Pulse-width modulation direct torque control induction motor drive with Kalman filter

The paper deals with application of Kalman filter in induction motor drive using pulse-width modulation direct torque control (PWM-DTC). In the first part, the conventional PWM-DTC drive is described and Kalman filter is utilized to filter components of stator current vector those are assumed to be disturbed by white noise. The second part contains simulation results that are obtained in different cases of load torque, process and measurement noise covariances. The integral time absolute error (ITAE) performance index, undershoot, ripple of important quantities are used to compare the conventional drive structure and proposed drive structure with Kalman filter. The simulation results confirm the expected dynamic response of the proposed structure

Aplikace pozorovatele MRAS v pohonu s asynchronním motorem s přímým řízením momentu

The PhD thesis describes model reference adaptive system speed observers for a speed sensorless induction motor drive with direct torque control methods. A mathematical description of components in control system such as induction motor, frequency converter is given. Theoretical analyses and assumptions of the direct torque control and the model reference adaptive system are presented. Simulations are used to verify the assumptions and choose the suitable direct torque control method and model reference adaptive system speed observer. A description of laboratory workplace is given. Fuzzy logic is applied in the speed controller of control structures. Verification the application of the model reference adaptive system in sensorless induction motor drive with direct torque control is experimentally carried out in various conditions. Advantages and disadvantages of the direct torque control methods and the model reference adaptive system speed observer, and the role of fuzzy logic are concluded.The PhD thesis describes model reference adaptive system speed observers for a speed sensorless induction motor drive with direct torque control methods. A mathematical description of components in control system such as induction motor, frequency converter is given. Theoretical analyses and assumptions of the direct torque control and the model reference adaptive system are presented. Simulations are used to verify the assumptions and choose the suitable direct torque control method and model reference adaptive system speed observer. A description of laboratory workplace is given. Fuzzy logic is applied in the speed controller of control structures. Verification the application of the model reference adaptive system in sensorless induction motor drive with direct torque control is experimentally carried out in various conditions. Advantages and disadvantages of the direct torque control methods and the model reference adaptive system speed observer, and the role of fuzzy logic are concluded.430 - Katedra elektronikyvyhově

Application of fuzzy logic in sensorless induction motor drive with PWM-DTC

The paper deals with the application of fuzzy logic in the current-based model reference adaptive system (CB-MRAS) for sensorless induction motor drives using direct torque control with pulse-width modulation. The stability analysis of the selected observer is described in the first part. Fuzzy logic is used to adjust the parameters of proportional-integral (PI) adaption algorithm of the CB-MRAS observer. The description of a laboratory workplace with an induction motor drive and load system is presented in the third part. Comparisons of conventional PI and fuzzy logic-based adaptation algorithms are shown in the paper. The theoretical assumptions of the sensorless induction motor drive are confirmed by the simulation and experimental results.Web of Science102114012

Application of BEMF-MRAS with Kalman filter in sensorless control of induction motor drive

This paper describes an induction motor speed estimation using the observer with back electromotive force-based model reference adaptive system and Kalman filter. In the first part of the paper, there is a mathematical description of the rotor speed observer. The second part of the paper includes Kalman filter that is used for the filtration of measured stator currents and obtaining their time derivatives. The third part contains a description of the laboratory workplace with the induction motor drive and active load unit that was used for an experimental verification of the rotor speed observer. The last section of the paper shows experimental results that were obtained for different changes in the induction motor speed. The experimental results confirmed expected dynamic properties of the induction motor drive with sensorless control.Web of Science9941160115

Application of Sensorless Sliding Mode Observer in Control of Induction Motor Drive

Induction motors are widely used in an industry and it is necessary to improve control methods for induction motors to increase the efficiency of them. In this paper, sliding mode controllers are proposed instead of traditional PI controllers in vector control of induction motor drives. Moreover, rotor speed is estimated by a sliding mode observer. In addition, the robustness of control and observer algorithms are also proved by Lyapunov’s criterion. The experiments are obtained in different speed changes of an induction motor drive. These experimental results confirm the dynamic properties of a sensorless sliding mode control of an induction motor drive