Afzal Khan

Aerodynamic analysis and dynamic modeling of small horizontal axis wind turbine

In wind turbine the output torque and power depends on the incoming wind speed. Due to the rapid changes in the incoming wind speed the quality of output power becomes a serious problem. Many controls are introduced in wind turbines in order to get a constant output rated power. In this research work we have focused on dynamic analysis and Pitch control of horizontal axis wind turbine. Pitch control is one of the most useful and important control that is present in all of the current wind turbine models. For dynamic analysis and pitch control, simulation techniques and experimental works were done side by side. Simulations were carried out in ADAMS software in which a wind turbine model was imported from Pro/E. The Matlab functions calculated the wind turbine blade parameters and aerodynamic forces. The aerodynamic forces were applied on wind turbine blades in ADAMS environment. Various changes were made in wind turbine blade parameters and similarly output graphs were obtained from ADAMS post-processor. On the other side a wood model of wind turbine was made and tested by applying wind on its blades. The input wind speed was sensed by the sensors and when this speed data was given to the controller it rotated the stepper motors connected with each blade of the turbine. It showed that by introducing the pitch control the power output was successfully controlled in high and low speed conditions, and as a result the overloading and outage of the wind turbine was prevented. By modeling the wind turbine in virtual environment it became very easy to design and test various wind turbine models prior to manufacture.

Performance analysis of a semiactive suspension system with particle swarm optimization and fuzzy logic control.

This paper uses a quarter model of an automobile having passive and semiactive suspension systems to develop a scheme for an optimal suspension controller. Semi-active suspension is preferred over passive and active suspensions with regard to optimum performance within the constraints of weight and operational cost. A fuzzy logic controller is incorporated into the semi-active suspension system. It is able to handle nonlinearities through the use of heuristic rules. Particle swarm optimization (PSO) is applied to determine the optimal gain parameters for the fuzzy logic controller, while maintaining within the normalized ranges of the controller inputs and output. The performance of resulting optimized system is compared with different systems that use various control algorithms, including a conventional passive system, choice options of feedback signals, and damping coefficient limits. Also, the optimized semi-active suspension system is evaluated for its performance in relation to variation in payload. Furthermore, the systems are compared with respect to the attributes of road handling and ride comfort. In all the simulation studies it is found that the optimized fuzzy logic controller surpasses the other types of control.

Experimental and numerical analysis of nanoindentation of Ti-6246 alloy

ABSTRACT Titanium and its alloys exhibit a very desirable set of mechanical properties like high strength-to-density ratio, high corrosion resistance, and the ability to work safely in extreme temperature conditions. In this work, nanoindentation technique was used to evaluate the mechanical properties of Ti-6246 alloy. The response of material to the indentation load was checked with light microscopy, and scanning electron microscopy (SEM) imaging was done to study the area around the indents for any sinks-in or piles-up. The light microscopy and SEM images are presented in this work and discussed in detail. In this work it was found that nanoindentation can be successfully used to evaluate the mechanical properties of high-strength material like Ti-6246. The hardness values and Young’s modulus values obtained in this work were found to be in close agreement to that reported in literature. A finite-element model was developed for the nanoindentation processes of the studied alloy using commercially available finite-element software DEFORM 3D. The model was used for parametric analysis of the nanoindentation process, and results obtained from FEA model were in good agreement with the experimental results.

A NOVEL APPLICATION OF PARTICLE SWARM OPTIMIZATION TECHNIQUE IN SEMI-ACTIVE SUSPENSION SYSTEM CONTROL

This paper is based on the quarter car semi-active suspension system. Semi-active suspension system proves to be a better choice in comparison with the passive and active systems keeping in view the inherent benefits of better performance, light weight and cost effective design. The semi-active system is driven by a fuzzy logic controller that is based on the feedback of relative displacement of the suspension with respect to the road disturbance and relative velocity across the damper. Fuzzy logic control can cope with the non-linearities of system using heuristic rules. Three gains are incorporated in the system corresponding to the inputs and output of the controller. Particle swarm optimization method is utilized for its better convergence and precision. The technique results in evaluation of appropriate gains that result in superior performance of the designed system. The models are compared on the basis of suspension displacement and tire displacement for ascertaining ride comfort and road handling attributes respectively.

PARAMETRIC ANALYSIS OF VARIOUS CONTROL ALGORITHMS FOR SEMI-ACTIVE SUSPENSION SYSTEM

The research paper involves modeling of passive and semi-active suspension systems using quarter car model. Different systems incorporating control strategies of groundhook, skyhook and hybrid are modeled on the basis of fuzzy logic control. A novel optimized control system is also developed that utilizes relative displacement and relative velocity across the masses as inputs to the fuzzy logic controller resulting in the output of modulating damping coefficient. A comparison of all the designed systems is carried out with the passive system for ascertaining ride comfort and road handling characteristics. The optimized system outperforms all other systems in both the parameters based on the rapid stabilizing time and minimum percentage overshoot. The optimized system comprises three membership functions for each of the inputs resulting in only nine rules thus enabling faster processing of the controller besides improved performance. The results manifest successful designing of an optimized fuzzy logic based control strategy for semi-active suspensions.

AUCTION-BASED FAULT-TOLERANT MULTI-ROBOT COOPERATION

This paper presents a market driven approach for robust multi-robot cooperation. The example task that is considered is object transportation from an original location to a goal location. The developed methodology relies on market-based decision making, which uses auction as a process of assigning a task to a robot by offering it up for a bid. In the event of robot failure during the execution of a task, the task is re-allocated to another suitable robot using the same auctioning process. This paper addresses two possible robot malfunctions—partial and full failures, which can happen any time during the execution of a task. The practicability of the developed methodology is demonstrated by implementing an auction-based approach on a team of simulated robots that cooperatively execute a task.

CASTING ANALYSIS AND QUALITY IMPROVEMENT OF STEEL GRADES WR-67 AND WR-62

Two steel grades WR-67 and WR-62 cast at Pakistan Steel were analysed for variation in properties of the same grade and heat. Homogenization status of liquid steel and macro segregation aspect during solidification with different continuous casting parameters were focused and it was found that non-homogenization of liquid steel in ladle leads the steel grades to exhibit non-uniform properties of the same grade and was no axial ( centreline ) segregation bot in billet and bloom. Increasing trend of porosity from surface to centre was observed. Increased purging time and installation of electromagnetic stirrer at mould were recommended for elimination of segregation, achieving good cast structure of bloom and billet and having uniform properties.