Journal of Simulation and Analysis of Novel Technologies in Mechanical Engineering
Volume:4 Issue: 2, 2012

Mobile robots that consist of a mobile platform with one or many manipulators mounted on it are of great interest in a number of applications. Combination of platform and manipulator causes robot operates in extended work space. The analysis of these systems includes kinematics redundancy that makes more complicated problem. However, it gives more feasibility to robotic systems because of the existence of multiple solutions in specified workspace. This paper presents a methodology for generating paths and trajectories for both the mobile platform and a 3DOF manipulator mounted on it, in the presence of obstacles. Obstacles add kinematics constraint into optimization problem. The method employs smooth and continuous functions such as polynomials. The proposed method includes obtaining time history of motion of mobile robot. It is supposed obstacles can be enclosed in cylinders. Platform that has been used in this research is a differentially-driven platform. The core of the method is based on mapping the non-holonomic constraint to a space where it can be satisfied trivially. A suitable criterion can be used to solve an optimization problem to find the optimal solution. In this research, the problem of path planning with simultaneous optimization of kinematics and dynamic indices has been accomplished using genetic algorithm in order to find the global optimum solution. The validity of the methodology is demonstrated by using a differential-drive mobile manipulator system, and various simulations of platform with a spatial 3-link manipulator are presented to show the effectiveness of the presented method.

The most prominent feature of sheet material forming process is an elastic recovery phenomenon during unloading which leads to springback and side wall curl. Therefore evaluation of springback and side wall curl is mandatory for production of precise products. In this paper, the effects of some parameters such as friction coefficient, sheet thickness, yield strength of sheet and blank-holder force on the springback and side wall curl in U-bending of DP600 steel alloy sheet has been investigated. The investigations have been done by computer simulation. In the simulations the ABAQUS finite element software has been used and the results compared to experimental ones. The finite element results have been validated from experimental results. After validation of FEM simulation via experimental results a powerful, rapid and efficient tool was introduced for investigating some important aspects and parameters of U-bending process such as blank-holder force, sheet thickness, yield strength of sheet and friction coefficient. MINITAB, a statistical software, was used to analyze finite element results. With the use of MINITAB, equations for prediction of springback and side wall curl radius by friction coefficient, sheet thickness, yield strength and blank-holder force were obtained.

This study experimentally investigates the effect of processing parameters on mechanical properties of injection molded copolymer. This paper presents an experimental study on the effects of processing parameters including melt temperature, injection pressure and amount preliminary materials on tensile strength of injection molded copolymer PP-WGRT. Polypropylene (PP - supplied by T.P.C of Iran) was used as thermoplastic material. Semi-crystalline material, Maleic anhydride-grafted (MA-g) used as agent cross-linked. Also, melt temperature was changed between 180 to 220 (˚C) and injection pressure was changed between 400 to 800 Bars. The tensile properties of produced parts were measured according to ASTM D 638 – 02. Results showed that tensile strength of copolymer decreases if the amount of WGRT increases. Also, the tensile strength increases by increasing the melting temperature and injection pressure.

Determination and analysis of vibration behavior of structures for at least first few natural frequencies and mode shapes needs several sensors to be connected at different non node points and exciting the structure at one point. Other method for determination of first few mode shapes is to excite several points of the structure at once and sensing the response from one point. Both methods need several force or accelerometer sensors. Excitation of the structure can be done by impulse from a hammer, electromagnetic, pneumatic, and acoustic or laser exciters. Other method for determination of mode shapes with only one accelerometer sensor and one force transducer is possible by a moving exciter with predetermined velocity. Force excitation can be from electromagnetic, hydraulic or pneumatic system. Pneumatic type of excitation which is clean and is sensitive to small changes is used to design a moving non touching exciter for structures. This type of exciter is useful for determination of vibration behavior of sensitive and fragile structures which hammer or touching electromagnetic system cannot be used. This paper presents a design and production of a pneumatic moving exciter of a structure. Excitation force can be impulse, step, ramp or harmonic with different speeds of moving excitation point. The system was used to excite a beam and results are verified with theoretical results.

Structural health monitoring and damage detection is one of the most important subjects for mechanic and aerospace engineers. Structural fault can cause uncompensated problems for both human and environment. There are several methods for solving this problem, but the most useful methods are those which focuse on structural change in the vibrational properties. This paper presents a feasibility study on locating damage in circular cylindrical fiber-reinforced composite shells based on mode shape methods and the sensibility of different damage intensity. In view of the fact that damage detections based on shape mode which do not use unprepared data are less reliable, in comparison by other damage detection methods, and highly efficient method mentioned depended on accuracy of modal testing and data extraction. As a whole, this paper shows that among the methods which used damage oriented approach, the first hole with thickness of 4mm in the other stages are more able to detect damage detection.

This paper starts with developing kinematic and dynamic model of a snake shape robot in serpentine locomotion and finishes with actual experimentation. At the beginning the symmetrical and unsymmetrical serpenoid curves are introduced. Kinematics and dynamics of a snake robot on flat and inclined surfaces are obtained for a general n-link robot. SimMechanics toolbox of MATLAB software is employed to simulate the snake robot. Effects of serpenoid curve parameters on joint torques and progression of the snake robot are also investigated. Results indicate that by increasing the inclination angle of the surface, link length and numbers of links, joint torques are increased. NSGA multi optimization method is next utilized to obtain the unsymmetrical curve parameters resulting in minimum joint torques and maximum snake progression. Optimal solutions are presented in the form of Pareto front optimal. The optimization shows that the required range of parameters of snake robot's body curve for higher progression and less torque, is limited. Additionally, it is shown that by employing the unsymmetrical serpenoid curves the efficiency of snake robot can be increased. Finally, FUM-Snake I robot is employed to validate the theoretical results on a flat surface. The experimental results show that the proposed kinematics and dynamics model are reasonable.

Maxwell 3D of Ansoft software were used for this study. Ansoft’s solutions are based on a more general program using Maxwell’s equations. A simple analysis has been done for calculating the magnetic force interacted between two magnets of similar poles facing each other. The modeling in Anosoft has been described.

The purpose of this research is to analyze the forging of bevel gears based on conventional forging method with material number 1.7131 with finite element method by means of SUPER FORGE software and to compare it with experimental cold orbital forging results.After doing simulation of conventional forging and obtaining press tonnage due to orbital forging method with DEFORM software, orbital forging dies are produced. Since bevel gears production based on conventional forging has three pre-form steps, so the forging process should be applied on the basis of hot forge. But in orbital forging process, bevel gear is produced in only one step which is cold forge. Finally, a comparison is done between microstructure of bevel gear which is produced by orbital forging and a bevel gear that is constructed through machining method and dies. Results obtained showed that the method of pieces production just before applying the heat treatment process have a high effectiveness on the microstructure. In orbital forging the tonnage of the levels are lower than conventional forging method and the capability of filling the mold’s cavity of raw materials in orbital forging is more than conventional forging method. The geometry of the billet have more affect on filling the mold’s cavity.