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In this paper, an optimal adaptive fuzzy integral sliding mode control is presented to control the robot manipulator position tracking in the presence of uncertainties and permanent magnet DC motor. In the proposed control, sliding surface of the sliding mode control is defined according to the information of position tracking error, derivatives, and error integral. In order to estimate bounds of the existing structured and unstructured uncertainties in the dynamics of the robot manipulator and the permanent magnet DC motor, a MIMO fuzzy adaptive approximator is designed. This helps to overcome the undesired chattering phenomenon in the control input by using fuzzy logic. Mathematical proof shows that the closed-loop system with the adaptive fuzzy integral sliding mode control in the presence of all the uncertainties has the global asymptotic stability. Furthermore, modified harmony search optimization algorithm is used to define the input coefficients of the proposed control and also to reduce the control input amplitude. In order to validate performance of the proposed controller, a case study on the SCARA robot manipulator is conducted in the presence of permanent magnet DC motor. Results of the Simulation show desired performance of the proposed controller.

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In most of the researches that have been done in the position control of robot manipulator, the assumption is that robot manipulator kinematic or robot Jacobian matrix turns out from the joint-space to the task-space. Despite the fact that none of the existing physical parameters in the equations of the robot manipulator cannot be calculated with high precision. In addition, when the robot manipulator picks up an object, uncertainties occur in length, direction and contact point of the end-effector with it. So, it follows that the robot manipulator kinematic is also has the uncertainty and for the various operations that the robot manipulator is responsible, its kinematics be changed too, certainly. To overcome these uncertainties, in this paper, a simple adaptive fuzzy sliding mode control has been presented for tracking the position of the robot manipulator end-effector, in the presence of uncertainties in dynamics, kinematics and Jacobian matrix of robot manipulator. In the proposed control, bound of existing uncertainties is set online using an adaptive fuzzy approximator and in the end, controller performance happens in a way that the tracking error of the robot manipulator will converge to zero. In the proposed approximator design, unlike conventional methods, single input-single output fuzzy rules have been used. Thus, in the practical implementation of the proposed control, the need for additional sensors is eliminated and calculations volume of control input decreases too. Mathematical proofs show that the proposed control, is global asymptotic stability. To evaluate the performance of the proposed control, in a few steps, simulations are implemented on a two-link elbow robot manipulator. The simulation results show the favorable performance of the proposed control.

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Abstract Nowadays, polymeric materials are used in most industrial and engineering applications. In many of the applications, crack is initiated in mixed mode loading conditions. As a result, investigation of these materials at different loading angles is essential for safe design of structures. In this paper the mixed-mode elastic-plastic fracture behavior of ABS material based on J-integral key parameter was studied and the modified Arcan fixture was employed to investigate fracture behavior of this material under pure mode I (opening mode), pure mode II (shearing mode) and in plane mixed mode loading conditions. This work has been carried out experimentally by J–integral method named multi-specimen and normalization techniques. Finally, by fitting linear and power functions based on ASTM E813-81 and E813-87 test procedures respectively, the fracture toughness of this polymeric material was obtained in plane strain condition. The (J-R) curve comparison showed good agreement between the two methods. The minimum difference between the two methods obtained in a shear mode by ASTM E813-81 was about 1.37% and the maximum difference observed in tensile mode by ASTM E813-87 was about 30.7%.

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In recent decades, the researchers have been attracted in utilizing of the multi-agent systems due to the sophistication in industrial processes, the cost of performing them and increasing the reliability. One of the interesting problems in this field of study is formation control of agents. In this paper, we are going to design a decentralized control strategy for the formation control of a group of quadrotors. To be more specific, we simplify the nonlinear dynamic of a quadrotor by using motion approximation and feedback linearization. Then, we solve the formation control problem of quadrotors by the utilization of leader-follower strategy with a decentralized protocol. In this control strategy, only do a partial number of followers have access to the leader’s information. This matter can reduce noticeably the energy consumption of the leader since it requires to send less amount of information. Thereafter, we will corroborate the convergence of quadrotors to the predefined formation and leader tracking mathematically. Finally, the simulation example will be presented in order to validate the theoretical results.

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In this paper, the single point incremental forming (SPIF) of friction stir welded (FSWed) 5083 aluminum alloy sheets are investigated experimentally and numerically. The aluminum sheets with 2mm thickness are friction stir welded with the same FSW parameters. In order to obtain the effect of FSW on the formability of SPIF, the base sheets and FSWed sheets are formed to conical shapes with different forming angles and then the limiting wall angles are determined for each condition. The experimental results indicate that the limiting forming angle of FSWed sheet is not so much different than the base sheet and FSW does not have a negative effect on the sheet metal formability in SPIF. To study the effect of SPIF and FSW in mechanical and microstructural properties of the formed parts, the effects of these process on the grain size and micro-hardness is investigated. Furthermore, the incremental forming is numerically simulated using the ABAQUS software and the sheet thickness distribution, obtained from the simulation, is compared with the experimental results. After verification of the numerical simulation model, the effect of FSW on the thickness distribution and strain distribution in SPIF is studied. The results indicate that in weld region and base metal region, the distributions of thickness and major strain are uniform while the distribution of minor strain is non-uniform.