Mahmoud Moghavvemi

Modelling and PID controller design for a quadrotor unmanned air vehicle

This paper presents the modelling of a four rotor vertical take-off and landing (VTOL) unmanned air vehicle known as the quadrotor aircraft. The paper presents a new model design method for the flight control of an autonomous quad rotor. The paper describes the controller architecture for the quadrotor as well. The dynamic model of the quad-rotor, which is an under actuated aircraft with fixed four pitch angle rotors, will be described. The Modeling of a quadrotor vehicle is not an easy task because of its complex structure. The aim is to develop a model of the vehicle as realistic as possible. The model is used to design a stable and accurate controller. This paper explains the developments of a PID (proportionalintegral-derivative) control method to obtain stability in flying the Quad-rotor flying object. The model has four input forces which are basically the thrust provided by each propeller connected to each rotor with fixed angle. Forward (backward) motion is maintained by increasing (decreasing) speed of front (rear) rotor speed while decreasing (increasing) rear (front) rotor speed simultaneously which means changing the pitch angle. Left and right motion is accomplished by changing roll angle by the same way. The front and rear motors rotate counter-clockwise while other motors rotate clockwise so that the yaw command is derived by increasing (decreasing) counter-clockwise motors speed while decreasing (increasing) clockwise motor speeds.

Artificial neural network approach to network reconfiguration for loss minimization in distribution networks

Abstract Network reconfiguration of distribution systems is an operation in configuration management that determines the switching operations for a minimum loss condition. An artificial neural network (ANN)-based network reconfiguration method is developed to solve the network reconfiguration problem to reduce the real power loss in distribution networks. Training-sets for the ANN are generated by varying the constant P-Q load models and carrying out the off-line network reconfiguration simulations. The developed ANN model is based on the multilayer perceptron network and training is done by the back propagation algorithm. The trained ANN models determine the optimum switching status of the dynamic switches along the feeders of the network, which thereby reduce real power loss by network reconfiguration. The proposed ANN method is applied to the 16-bus test system. Test results indicate that the developed ANN models can provide accurate and fast prediction of optimum switching decisions for minimum loss configuration. The proposed ANN method is compared with Kims method [IEEE Transactions on Power Delivery 8, 1356–1366 (1993)] and a comparative study is presented. The proposed method can achieve minimum loss configuration with drastic reductions in the number of ANNs and less computational time.

Power system security and voltage collapse: a line outage based indicator for prediction

With the increased loading and exploitation of the power transmission system, the problem of voltage stability and voltage collapse is attracting more and more attention. Continuous monitoring of the system status is therefore a necessary requirement. This article is concerned with power system security and investigates a proposed voltage collapse proximity indicator. For each line of the system, a line stability index is calculated based on the power flow through that line. The value of the line stability index is then used for predicting contingency outage of the lines and hence study the voltage collapse of the system. The described technique does not involve computational complexities and therefore can be easily implemented. The performance of the proposed indicator was tested on the IEEE 24 bus Reliability Test System and was found to be accurate and computationally feasible.

Geometrical approach of planar hyper-redundant manipulators: Inverse kinematics, path planning and workspace

A new method for inverse kinematics for hyper-redundant manipulators is proposed in this paper to plan the path of the end-effector. The basic idea is that for a given smooth path consisting of points close enough to each other; computing the inverse kinematics for these points is carried out geometrically using the proposed method. In this method, the angles between the adjacent links are set to be the same, which makes lining up of two or more joint axes impossible; therefore, avoiding singularities. The manipulability index has been used to show how far the manipulator from the singularity configuration is. The determination of the workspace of the manipulator using the proposed method has been presented in this paper. The simulation results have been carried out on a planar and a three dimensional manipulators. The effectiveness of the proposed method is clearly demonstrated by comparing its result with results calculated by the well-known method of measuring manipulability which is used for singularity avoidance for the last two decades.

EAMTR: energy aware multi-tree routing for wireless sensor networks

IEEE 802.15.4 is the prevailing standard for low-rate wireless personal area networks. It specifies the physical layer and medium access control sub-layer. Some emerging standards such as ZigBee define the network layer on top of these lower levels to support routing and multi-hop communication. Tree routing is a favourable basis for ZigBee routing because of its simplicity and limited use of resources. However, in data collection systems that are based on spanning trees rooted at a sink node, non-optimal route selection, congestion and uneven distribution of traffic in tree routing can adversely contribute to network performance and lifetime. The imbalance in workload can result in hotspot problems and early energy depletion of specific nodes that are normally the crucial routers of the network. The authors propose a novel light-weight routing protocol, energy aware multi-tree routing (EAMTR) protocol, to balance the workload of data gathering and alleviate the hotspot and single points of failure problems for high-density sink-type networks. In this scheme, multiple trees are formed in the initialisation phase and according to network traffic, each node selects the least congested route to the root node. The results of simulation and performance evaluation of EAMTR show significant improvement in network lifetime and traffic distribution.

Technique for assessment of voltage stability in ill-conditioned radial distribution network

A technique is proposed in this letter to study the voltage collapse situation in a radial distribution network. The radial distribution network has been reduced to a single line equivalent circuit and then represented through a /spl pi/ network. A stability index is developed that indicates the severity of the loading situation of the system. The index can have a maximum value of one (1.00) when the system is at the point of collapse and a minimum value of zero (0) when there is no load in the system. Voltage collapse can be assessed based on the value of the developed index. If the system yields a value exceeding its maximum limit of stability index (1.00) it indicates a voltage collapse situation. The proposed technique is tested on a practical system of a 12-bus radial system (main feeders only) and on a 27-bus radial distribution system with laterals. The results obtained are encouraging and indicate that the technique has the potential to be used as a tool for system monitoring and future load planning.

A Coordinated Design of PSSs and UPFC-based Stabilizer Using Genetic Algorithm

This paper details a new coordinated design between power system stabilizers (PSSs) and a unified power flow controller (UPFC) using genetic algorithms (GAs). A GA scheme determines the optimal location for a UPFC while tuning its control parameters, resulting in the optimization of the quantity, parameters, and locations of PSSs under different operating conditions. The problem is formulated as a multiobjective optimization problem in order to maximize the damping ratio(s) of electromechanical modes, matching different numbers of PSSs with a UPFC. The approach is successfully tested on the New England-New York interconnected system (a 16-machine and 68-bus system), proving its effectiveness in damping local and interarea modes of oscillations.

Effects of FACTS devices on static voltage stability

This paper presents a study of FACTS devices mainly static VAr compensator (SVC) and controlled series compensator (CSC). Their steady-state modeling and effects on power system performance have been studied. It also studies static stability improvement of a power system and hence power flow improvement in the network. Standard stability evaluation technique has been used to identify the optimum place for the implementation of flexible AC transmission system (FACTS) devices and the effects of FACTS on system loadability has been studied and presented here. The technique to identify the optimum location for the placement of FACTS devices is based on the concept of maximum power transferring capability of the lines and buses. The study has been carried out on the IEEE 24 and 118 bus test systems. Study reveals that incorporation of FACTS devices significantly enhanced system stability as well as power transfer capability of the system.

A non-invasive PC-based measurement of fetal phonocardiography

A simple, low cost and non-invasive PC-based system that is capable to process real time fetal phonocardiographic signal has been built. The hardware of the system mainly consists of two modules: the front-end module and the data acquisition & control module. The front-end module is mainly used for heart sound signal capturing and conditioning. A new electronic stethoscope with enhanced performance that is non-intrusive, cost friendly and simple to implement has been built. The audio output unit enables the system to provide simultaneous listening and visual representation of the heart sound. The data acquisition & control module offers a four-channel analog multiplexer, a programmable gain amplifier, and a 12-bit resolution ADC. Various sampling rates can be provided through the programmable timer. Window 95-based software, which processes the real time heart sound signal, has been developed. The software written for the PCG allows for both time varying amplitude graph and power spectral plot (based on 512-point fast Fourier transform (FFT)) to be shown simultaneously on a channels view. The simultaneous spectrograms gives a much better insight of the heart sounds characteristics than just the time-amplitude plot alone as in conventional PCG software. Using digital signal processing techniques, the power of the spectral plot is used to extract useful information of the heart sounds characteristics even in a situation where the heart sounds are among considerably loud background noises.

Maximizing radial voltage stability and load balancing via loss minimization in distribution networks

Distribution networks have to be operated under minimized loss conditions due to economic reasons. Besides economic considerations, a reconfigured distribution network operating at a minimum loss condition has some added advantages in the form of increased voltage stability and load balancing. This paper presents the relationship between voltage stability and loss minimization in which it can be shown that voltage stability is maximized when power losses are minimized in the networks. A relationship between load balancing and loss minimization is also presented. A new load balancing index is proposed and applied to a distribution network to investigate the improvement in load balancing after network reconfiguration. Test results indicate that improvement in voltage stability and load balancing can be achieved by network reconfiguration.