Firas B. Ismail

Trajectory Tracking Controller for flexible robot arm

The most important benefits of flexible link manipulator include high payload-to-arm weight ratio. The reduction of weight leads to increase of the link elasticity that significantly complicates the control of the manipulator. The difficulty in control is caused by the fact that the link model is a distributed parameter plant. In this case, several elastic modes are required to achieve sufficiently high accuracy. Plus, the plant has several uncertain parameters (payload mass, hub and structural damping factors, etc.) that influence the systems performance. In this paper, Trajectory Tracking Controller is suggested by utilizing the hybrid controller approach to overcome the problem of vibration of tip position through motion which is a characteristic of the flexible link system. A modified version of the proportional-derivative rigid controller to track the hub position while sliding mode control was used for vibration damping. Also, a second controller (a fuzzy logic based proportional integral plus derivative control scheme was developed for both vibration damping and trajectory tracking. Results are illustrated in the robust performance of the proposed tip position tracking controllers over the payload variation. A good performance is obtained for the trajectory tracking. The stability of these controllers is also proved.

A review on mobile robots motion path planning in unknown environments

Robotics sector have achieved enormous founds in recent years due to its high demands in factories to carry out high-precision jobs like riveting and welding. They are also often applied in special situations that would be hazardous for humans such as disposing toxic wastes or defusing bombs. Mobile robots alone however have gained much focus from researches relating optimization of their motion path planning. In this paper, a brief review on mobile robots motion path planning in unknown environment have been done based on recent founds. The paper categorizes motion path planning into two groups which is the Optimized Classic Approaches and Evolutionary and Hybrid Approaches. The optimized classic approaches represents the recent optimized motion path planning that implies the classic approaches such as A* search algorithm, Rapidly-exploring Random Trees (RRT), D* and D* Lite algorithm. The evolutionary and hybrid approaches are those adapts Artificial Intelligence (AI) such as neural networks (NN), genetic algorithms (GA), fuzzy systems and reinforced learning either acting alone or as hybrids together with other algorithms. Finally a comparison between these two categories are done differentiating their advantages and disadvantages.

Material design consideration for gear component using functional graded materials

Gears have numerous practical applications. It is an essential element for power transmission. It is used to increase or decrease the speed or change the direction of a power resource. When gears are operating, it will develop high stress concentration on the contact tooth surface. In practice most gear teeth fail due to surface contact, which is the most common failure. Selecting the ideal material for a gear tooth is significant for the purpose of operating gear system. This review study will increase additional understanding of ceramic functional graded materials (FGMs) and their applications and how these materials can solve the gear tooth surface problem. This study gives evidence that FGM is able to enhance the microstructure, mechanical properties of the gear and gives better hardness between two tooth surfaces. The conclusion will suggest a solution for the problem of contact surfaces in the gear tooth, by using functional graded materials. In the structure of FGM, the metal phase will provide strength to the gear tooth and the ceramic phase will augment the heat and wear resistance.

Carbon/Epoxy Woven Composite Experimental and Numerical Simulation to Predict Tensile Performance

Currently, there is demand for the utilisation of woven composites in aerospace and industrial applications, mostly due to their superior strength-to-weight ratio and thermal properties, as opposed to conventional materials. However, the mechanical behaviour of woven composites is not on par with traditional materials. The central objective of this study is to develop an understanding of three-dimensional woven composites through the improvement of accurate numerical models that are also validated with experimental results. Five specimens were fabricated using American Society for Testing and Materials (ASTM D3039) guidelines to study the mechanical performance of carbon/epoxy. The experimental tensile tests results and the finite element analysis outcomes for the carbon/epoxy composite agree with each other, with 5.05 percentages of error, which validates the numerical results. KeywordsComposite Materials; Matrix Composite; Numerical Simulation

Numerical Analysis and Improvement of the Heat Exchanger Designed For Co-Generating Units

Abstract Research on the heat exchangers for the co-generating units was carried out to obtain the best design, by comparing the efficiency and the concepts used by different heat exchangers. The system was designed based on three basic parameters optimization: number of coolant tubes, diameter of the coolant tube and inlet velocity of the cold gases. These three variables were manipulated in order to investigate heat transfer performances, as well as, effects of heat transfer fluids and the system’s efficiency. Simulations using Computational Fluid Dynamic (CFD) were carried out, to have a better understanding and distinct visualization of the fluid flow, and to test and compare the results. The outcomes show that, different size of coolant tube diameter has the biggest impact on the system efficiency, compared to the other two variables. Design improvement, based on the contributions of the key parameters to efficiency of the heat exchanger, is recommended, as a final outcome of the project conducted.

The Effect of Thickness and Mesh Spacing on the Impact Resistance of Ferrocement Slab

This paper investigates the effect of the thickness and mesh spacing on the impact of ferrocement for the concrete slab of 300mm x 300mm size reinforced subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.236 kg drop at height of 150 mm, 350mm, and 500mm has been used in this research work. The objective of this research is to study the relationship of impact resistance of ferrocement against slab thickness and mesh reinforcement spacing. There is a good linear correlation between impact resistance of ferrocement against slab thickness and its mesh spacing. The first and ultimate crack impact resistance for 40 mm slab are 2.00 times and 1.84 times respectively against the 20 mm slab with the same mesh spacing. The first and ultimate crack impact resistance for 40 mm slab with 20 mm mesh spacing are 2.24 times and 3.70 times respectively against 50 mm mesh spacing with the same slab thickness. The mesh with higher content of reinforcement provides more contribution to the slab resistance as compare with the thickness.

The Effect of Mortar Grade and Thickness on the Impact Resistance of Ferrocement Slab

This paper investigate the effect of the thickness and mesh spacing on the impact of ferrocement for the concrete slab of 300mm × 300mm size reinforced subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.236 kg drop at height of 150 mm, 350mm, and 500mm has been used in this research work. The objective of this research is to study the relationship of impact resistance of ferrocement against the mortar grade and slab thickness. There is a good linear correlation between impact resistance of ferrocement against the mortar grade and the thickness of ferrocement slab. The first and ultimate crack impact resistance of mortar grade 43 (for 40 mm thick slab with mesh reinforcement) are 1.60 times and 1.53 times respectively against the mortar grade 17 slab (of same thickness with mesh reinforcement). The first and ultimate crack impact resistance for 40 mm thick slab (mortar grade 43 with mesh reinforcement) are 3.55 times and 4.49 times respectively against the 20 mm thick slab (of same mortar grade with mesh reinforcement).

Runtime reduction in optimal multi-query sampling-based motion planning

Sampling-based motion planning algorithms have been successfully applied to various types of high-dimensional planning tasks. Recently an extension of PRM algorithm called PRM* planner has been proposed which guarantees asymptotic optimal solutions in terms of path length. However, the high runtime of sampling-based algorithms is still a serious disadvantage. In this paper, a new extension of PRM planner is proposed which incorporates the variable neighborhood radius feature of PRM* and the sampling radius of low-dispersion sampling in order to improve the cost of the generated solutions in terms of path length and runtime. The performance of the proposed algorithm is tested in different planning environments. Furthermore, the proposed planner is compared to the original PRM and the PRM* approaches and shows significant improvement.