Nordin Saad

Adopting EWMA Filter on a Fast Sampling Wired Link Contention in WirelessHART Control System

The performance of a wireless industrial process plant is affected by wired and wireless links reliability. While recent related works focus mainly on wireless links reliability, this paper focuses on wired links reliability between the controller and the wireless highway addressable remote transducer (WirelessHART) node. In control application for a process plant with fast sampling, when the wired link delay is too short, message transmissions to the node could occur concurrently resulting in packet collision and packet dropout, thus leading to local contention. This can cause process plant with critical control application to be unstable. Therefore, this paper proposes an effective design of exponentially weighted moving average filter to mitigate the contentions effect and improve the process plants performance. In order to make evident and validate the existence of local contention, an experiment is carried out using a WirelessHART device. From the experiment, the controller delay is 0.1475 s and the estimated packet dropout is 12.29%. Simulation results with the designed filter show a significant improvement in process performance in terms of percentage of overshoot compared with performance of the process plant using traditionally optimized PID controller.

Split-parallel in-wheel-motor retrofit hybrid electric vehicle

One configuration of a hybrid electric vehicle (HEV) is the split-axle parallel architecture, which enables existing vehicles to be retrofitted into a hybrid vehicle with minimal modification - achieved by placing electric motors in the hub of the otherwise non-driven wheels. The present work describes different HEV configurations and identifies specific operating modes of the split-parallel architecture. Coupling of the two power sources - internal combustion engine (ICE) and electric motor - and control system configuration for the split-parallel hybrid are also presented. Proper distribution of power between the two sources determines effective operation of the hybrid vehicle. The control problem consists of determining this power split at each instant of time. The target is to achieve minimum consumption of fuel, while ensuring the state-of-charge (SOC) of the battery bank remains at acceptable level. This paper reviews some of the control strategies for the HEV, which can be investigated on the split-parallel configuration. Finally, development of a prototype of the split-parallel hybrid vehicle with in-wheel motors - retrofitted from a conventional vehicle - is described.

Interline Power Flow Controller (IPFC) based damping controllers for damping low frequency oscillations in a power system

The interline power flow controller (IPFC) is a voltage-source-converter (VSC)-based flexible AC transmission system (FACTS) controller which can inject a voltage with controllable magnitude and phase angle at the line-frequency thereby providing compensation among multiple transmission lines. In this paper, the use of the IPFC based controller in damping of low frequency oscillations is investigated. An extended Heffron-Phillips model of a single machine infinite bus (SMIB) system installed with IPFC is established and used to analyze the damping torque contribution of the IPFC damping control to the power system. The potential of various IPFC control signals upon the power system oscillation stability is investigated a using controllability index. Simulation results using Matlab Simulink demonstrate the effectiveness of IPFC damping controllers on damping low frequency oscillations.

Simulation of WirelessHART networked control system with packet dropout

Industrial communication standard like WirelessHART enables wireless control in process plants. This paper presents a study on wired and wireless networked control system. It emphasizes on using packet dropout array for Markov chain simulation of packet dropout process, a key parameter affecting plants performance, in a closed-loop WirelessHART networked control system. Additionally, Bernoulli simulation of the process is covered for comparison purpose. Overshoot was found to be 633.3 % for Bernoulli model, 33.9 % for Markov model and even through it is the major drawback of the system, WirelessHART networked control system is still suitable for control applications when non-time-critical plant has response time longer than sampling period thousands times even with 50 %, 40 % dropout probabilities for Bernoulli, Markov models.

PLC-based fuzzy logic controller for induction-motor drive with constant V/Hz ratio

This paper presents the design and implementation of a PLC-based fuzzy logic controller for an induction motor speed control at constant V/Hz ratio. The PLC has arithmetic and logic operations instructions set that was utilized in the implementation of the fuzzy control of induction motor speed control. Fuzzy logic algorithm applies rules obtained from human expert of a system. The input signals to fuzzy controller are the linguistic variable of speed error and change of speed error, while the output signal is frequency of PWM inverter. The supply voltage to the induction motor is ascertained from frequency output requirement using constant V/Hz ratio. The objective of the controller is to provide stability in responds to disturbance and sudden changes in reference speed. Results of the proposed system show satisfactory performance.

A DES approach for the contextual load modelling of supply chain system for instability analysis

Abstract In this paper, a modelling and simulation approach for the analysis of a supply chain system taking into account the relations of the system to its contextual components is presented. The purpose is to address several issues particularly on whether decision policies would provide stability in the presence of disturbances, as well as evaluating the effect of disturbances on the system. The task of developing a contextual load model requires the identification of the possible sources of disturbances that exist in the system, the modelling of these disturbances and the particular parameters in the model that are to be changed to simulate such disturbances. Results revealed the effectiveness of the various decision policies to provide stability under the different types of disturbances. The findings demonstrate the ability of the approach to provide a wealth of potential solutions, and confirm the qualitative behaviour of a supply chain in response to the different policies.

Development of fuzzy-logic-based self tuning PI controller for servomotor

Direct Current (DC) servomotors are widely used in robot manipulator applications. Servomotors use feedback controller to control either the speed or the position or both, and the basic continuous feedback control is PID controller. This paper discusses the modeling and simulation of DC servomotor control built using MATLAB/Simulink, and the analysis of controller performance, namely a PID controller, PI controller, fuzzy-scheduled PID controler, and a fuzzy-logic-based self tuning PI controller on the system. The singleton fuzzification is used as a fuzzifier. The center average is used as a defuzzifier. Two control modes are applied in sequential to the plant: speed control, and then position control. Simulation results show that fuzzy-logic-based self tuning PI controller has the best performance compared to conventional PID controller and fuzzy-scheduled PID controler.

Damping of inter area oscillations using Interline Power Flow Controller based damping controllers

This paper investigates the effect of interline power flow controller (IPFC), an advanced flexible AC transmission system (FACTS) controller, in damping low frequency oscillations via supplementary control. For this purpose, a modified linearised Phillips-Heffron model for a single machine infinite bus (SMIB) system installed with IPFC is established, and the power oscillation damping controller is designed. The effect of this damping controller on the system, subjected to wide variations in loading conditions and system parameters, is investigated. Results of simulation investigations in Matlab are presented to validate the proposed approach.

Condition monitoring of induction motors via instantaneous power analysis

Condition monitoring is an important factor in assuring the well-being of motors. Existing approaches of condition monitoring require access to the motor for sensor installation. This paper reviews various forms of existing condition monitoring methods and highlights the need for an economical intelligent fault diagnosis system. In this study, the methodology taken in developing a condition monitoring system for motor bearing fault identification, utilizing the commonly available motor stator current and voltage is demonstrated. This unique diagnostic condition monitoring system provides continuous real time tracking of the various bearing defects and determines the fault severity which can be adopted for fast decision making. The study on different bearing faults under no-load and full-load conditions was carried out experimentally and then analyzed. The results on the real hardware implementation have confirmed the effectiveness of the proposed approach.

Control of induction motor drives using modified-fuzzy logic methods

An investigation into the implementation of a PLC-based modified-fuzzy logic controller for an induction motor drive is presented. The controller consists of two control strategies i.e. a PID-type fuzzy logic controller and an incremental PID action. At the early stage of control action, the task is handled by PID-type fuzzy controller. When the absolute of error is less than a threshold value, the input of integrator at the output side is no longer given by fuzzy action but fed by incremental PID action. In other words, the controller output is no longer PI type + PD type fuzzy control but conventional PID + PD type fuzzy control. In terms of the control action, this can be seen as increasing the proportional and derivative action when the actual value is closed to reference. The controller is simulated under several conditions i.e. sudden changes in reference, sudden changes in load, and both simultaneously. The results revealed the robustness of the controller to the different type of disturbances.