Hanafy M. Omar

Gain Scheduling Feedback Control for Tower Cranes

The objective of crane control is to build an algorithm to move a load from point to point in the shortest time without inducing large swings. We assume that this objective cannot be accomplished in less than a single oscillation cycle of the load. Therefore, the controller is built to move the load such that it completes only one oscillation cycle at the end of the motion. Consequently, the settling time of the system should be equal to the period of oscillation of the load. This criterion enables the calculation of the controller feedback gains for varying load weight and cable length. The controller is built first for overhead cranes and then modified for tower cranes. Two controllers are used, one for the rotational motion of the tower and the other for the translational motion of the trolley. Numerical simulations show that the controller is effective in reducing the load oscillations and transferring the load in a reasonable time compared with that of optimal control.

Gain Scheduling Feedback Control of Tower Cranes with Friction Compensation

We have designed a controller based on gain-scheduling feedback to move a load from point to point within one oscillation cycle and without inducing large swings. The settling time of the system is taken to be equal to the period of oscillation of the load. This criterion enables us to calculate the controller feedback gains for varying load weight and cable length. First, we designed the controller for gantry cranes and then extended it to tower cranes by considering the coupling between the translational and rotational motions. Numerical simulations show that the controller is effective for reducing load oscillations and transferring the load in a reasonable time compared with that of optimal control. To experimentally validate the theory, we had to compensate for friction. To this end, we estimated the friction, then applied an opposite control action to cancel it. To estimate the friction force, we assumed a mathematical model, then we estimated the model coefficients using an off-line identification technique, the least-squares method. First, the process of identification was applied to a theoretical model of a dc motor with known friction coefficients. From this example, some guidelines and rules were deduced for the choice of the least-squares parameters. Then, the friction coefficients of the gantry crane model were estimated and validated.

New fuzzy-based anti-swing controller for helicopter slung-load system near hover

In this paper, a new fuzzy based anti-swing controller for helicopter slung load system near hover flight is proposed. The output from this controller is additional displacements that are added to the helicopter trajectory in the longitudinal and lateral directions. Hence, its implementation is simple and it just needs small modification to the software of helicopter position controller. The rules of the anti-swing controller are derived based on the time-delayed feedback of the load swing angles. The simulation results show the effectiveness of the proposed controller in suppressing the swing of the suspended load and stabilizing the system.

Genetic -Based Fuzzy Logic Controller for Satellites Stabilized by Reaction Wheels and Gravity Gradient

In this paper, a systematic technique is proposed to design an optimal distributed fuzzy logic controller (FLC) for the attitude control of satellites stabilized by reaction wheels and gravity gradient. A single FLC with two inputs and one output is used for the pitch motion while a distributed controller with fou r FLCs is proposed for the roll and yaw motions to take into consideration the dynamic coupling between roll and yaw. The control action for yaw is determined by the yaw dynamics as well as the roll dynamics and similarly for the roll. The rules, the distr ibution of membership function of the FLC, and the linking parameters of the distributed controller are determined based on solving a constraint optimization problem using the genetic algorithms. To get accurate pointing, long -life time, and fast response for the satellite, the deviation of the satellite from its nominal position, the consumed power, and the time of deviation are included in the optimization objective function. With the use of multiple initial conditions in determining the objective functio n, the designed controller is shown to be stable with a satisfactory performance in a broad range of the operating conditions. Nomenclature

Developments of vapor-compression systems for vehicle air-conditioning: A review:

Vapor-compression systems are still the most widely used type of automotive cooling systems despite their high energy consumption and negative environmental effects. This article gives a review of the carried out developments and the future trends for this type of automotive air-conditioning systems which have served vehicle occupants for more than 50 years. After going over a brief historical progression of the system, the circulating refrigerant developments were presented. Only few refrigerants meet the imposed attributes (e.g. zero ozone depletion potential, low global warming potential), and CO2 as well as R1234yf have a big potential to be the future refrigerants. Then, the developments related to the other major system components were outlined. In this context, the future trends show that the scroll compressor besides the evaporator and the condenser having parallel flow and micro-channels are the most promising for the next generation of (air-conditioning) systems. Concerning the control of the compressor and the expansion device, the advanced electronic control is the most attractive for the future systems. This is due to its provision to better improvement for the air-conditioning system performance. The present vapor-compression air-conditioning systems still have some weaknesses despite their eminent achieved improvements. Models developed for air-conditioning systems still have some shortcomings (e.g. low accuracy). Also, the test procedures for air-conditioning extra fuel consumption are still not worldwide in all aspects. Therefore, more efforts should be made to solve these problems.

Multiobjective Evolutionary Algorithm for Designing Fuzzy-Based Missile Guidance Laws

In this paper, a strength Pareto evolutionary algorithm based approach is proposed for designing a multistage fuzzy-based guidance law which consists of three fuzzy controllers. Each of these controllers is activated in a region of the interception. The distribution of the membership functions and the rules are obtained by solving a nonlinear constrained multiobjective optimization problem where final time, energy consumption, and miss distance are treated as competing objectives. A hierarchical clustering technique is implemented to provide the decision maker with a representative and manageable Pareto-optimal set without destroying the characteristics of the trade-off front. Moreover, a fuzzy-based mechanism is employed to extract the best compromise solution over the trade-off curve. The simulation results show that the proposed design technique was able to generate a missile guidance law which has better performance than the classical proportional guidance law.

Designing integrated guidance law for aerodynamic missiles by multi-objectives evolutionary algorithm and Tabu search

In this paper, a Strength Pareto Evolutionary Algorithm (SPEA) based approach is proposed for designing an Integrated Fuzzy Guidance Law which consists of three fuzzy controllers. Each of these controllers is activated in a region of the interception. The distribution of the membership functions and the rules are obtained by solving a nonlinear constrained multiobjectives optimization problem where final time, energy consumption, and miss distance are treated as competing objectives. Tabu search is proposed to get the initial feasible solution for the multi-objective optimization algorithm. Then a hierarchical clustering technique is implemented to provide the decision maker with a representative and manageable Pareto-optimal set without destroying the characteristics of the tradeoff front. Moreover, a fuzzy-based mechanism is employed to extract the best compromise solution over the trade-off curve. The simulation results show that the proposed design technique was able to generate a missile guidance law with satisfactory performance with the existence of noisy measurements.

LQG-based control of unmanned helicopter using OKID-based identification approach

This paper presents the system identification and control of an unmanned helicopter(UH) with ducted fan. The plant is an unstable multi-input-multi-output (MIMO) system. First, four identification methods have been considered in this work. Two of these methods studied the identification of the system as a set of transfer functions relating different inputs and outputs, namely the least square method with QR-factorization (LS-QR) and the recursive least square method (RLS). The other two methods are state-space identification method. Indeed, the classical subspace identification method and the observer-Kalman filter identification (OKID) method have been used to identify the system in state space representation. Analytical formulations of these methods as well as comparison of their performances based on their degree of fitness are presented for the special case of UH system. The results show that OKID out-performs the other methods. Based on this result, an OKID-LQGI-based controller for velocities tracking controller is proposed. The simulation results show excellent tracking performance.

Anti-Swing Nonlinear Path Tracking Controller for Helicopter Slung Load System

Abstract In this paper a tracking controller is designed for a helicopter plus slung load system. The controller designed is nonlinear and is based on the Backstepping method. First we develop a comprehensive nonlinear mathematical model of the helicopter and design the nonlinear Backstepping controller for trajectory tracking for the helicopter alone. Then we model the slung load mathematically as a slung load and integrate it to the helicopter system. In the next step we design the delayed feedback controller for load swing damping which works independent of the nonlinear tracking controller. The anti-swing controller for load is optimized for best performance by the differential evolution (DE). Finally we present the simulation and results to illustrate the effectiveness of the method.

Enhancing automatic control learning through Arduino-based projects

ABSTRACT Systems dynamics and automatic control is classified as one of the toughest courses in the college of engineering at Qassim University according to the statistical analysis of the final grades. This motivated us to think about a new approach to teach this course by extending the design term project to include experimental part beside the theoretical analysis. This approach has become feasible due to the publicity of the low-cost microcontrollers such as the Arduino in the recent years. In this paper, we present our experience in conducting Arduino-based projects and how we used them to support the teaching of all the automatic control subjects in the course such as the mathematical modelling, the stability analysis, the controller design and the implementation of the PID controller. It was found that the new approach improves the attention and the overall performance of the students in the course which was reflected in the students’ marks in the quizzes and exams. Moreover, it motivated the students to be creative by utilising the control theory to design new systems that can be useful for their local community.