Mehran Mahboubkhah | University of Tabriz (original) (raw)

Papers by Mehran Mahboubkhah

Parallel mechanisms are more utilized, because of their extra precision and stiffness in comparis... more Parallel mechanisms are more utilized, because of their extra precision and stiffness in comparison with serial mechanisms. Measuring position and orientation (pose) of parallel robot end effector and performing kinematic calibration, is a guaranty for, moving precision of these robots. Through different measurement devices, machine vision has advantages such as low cost, simplicity in use and rather appropriate precision. In this research, in order to measure pose of end effector of a 4-DOF (degree of freedom) parallel robot, a vision-based measurement system, is designed and implemented in Matlab software. The laboratory device is a stereo camera. Camera calibration is carried out in Matlab. A triangular shape is used as feature on the robot end effector. By processing the images acquired from pose of end effector, in designed measurement system, rotation matrix and translation vector are obtained and the exact position of the end effector is revealed. For investigating precision and accuracy of proposed measurement system, a conventional measurement method with the help of gauge block and indicator, is used. According to the nature of machine vision, the results achieved in this examination, are acceptable; although better precision can be attained by improving devices used in this research.

European Journal of Science and Technology, 2022

Öz Bu çalışmada, 5 serbestlik derecesine sahip yeni bir 3 boyutlu (3B) yazıcının matematiksel ana... more Öz Bu çalışmada, 5 serbestlik derecesine sahip yeni bir 3 boyutlu (3B) yazıcının matematiksel analizi ve tasarımı gerçekleştirilmiştir. Tasarlanan sistem sayesinde, çok eksenli 3B yazıcı mekanizmalarına yeni bir konsept kazandırılmış ve böylece eklemeli imalat (AM) süreçlerinde parça kalitesini iyileştirilmesi hedeflenmiştir. Öncelikle sistemin kinematik analizi vektör cebri kullanılarak elde edilmiş ve sistem kısıtlamalarını dikkate alınarak yazıcının çalışma uzayı belirlenmiştir. Ardından tasarlanan sistemin mekanik ve elektriksel bileşenleri hakkında detaylı bilgiler verilerek tüm sistemin çalışma prensibi sunulmuştur. Tasarım çalışmalarında elde edilen bulgulara göre önerilen sistem için gerçekleştirilen kinematik analizlerin doğru olduğu kanıtlanmış ve özellikle eklemeli imalat teknolojileri için yeni bir sistem önerilmiştir.

2011 IEEE International Conference on Mechatronics, 2011

This research presents an improved solution to the inverse kinematics and dynamics of the general... more This research presents an improved solution to the inverse kinematics and dynamics of the general Stewart platform. The dynamic equations are generated through Newton­ Euler approach. There have been a number of previous researches on this subject, but most of them consisted of some simplifying approximations which facilitate the formulation. Considering the creativity of the Newton-Euler method in the previous

The International Journal of Advanced Manufacturing Technology, 2007

Parallel mechanisms have found new applications in machine tool's as the end effector carrying th... more Parallel mechanisms have found new applications in machine tool's as the end effector carrying the spindle or used as the table of the machine. Investigations on the dynamics and especially the vibration behavior of these mechanisms are in the initial stage. The authors developed a vibration model for the hexapod table of milling machines and machining centers and derived the relevant explicit equations. The eigenvalue problem of the upper platform of hexapod was solved to obtain the natural frequencies of the platform. The results have been verified with FEM simulation. The distinguishing features of the hexapod tables from the view point of dynamic behavior have also been concluded.

Elektronika ir Elektrotechnika

In this study, the mathematical analysis and design of a new 3D printer with 5 degrees of freedom... more In this study, the mathematical analysis and design of a new 3D printer with 5 degrees of freedom were carried out. Thanks to the developed system, a new concept has been brought to the multi-axis 3D printer mechanisms, and thus, it is aimed to improve the part quality in additive manufacturing (AM) processes. As a result of adding the 4th and 5th axes to the moving platform of the system, the production time of the part was accelerated. It is also possible to print more complex and curved shapes with less support. To design a system with these features, first of all, the kinematic analysis of the system was obtained using vector algebra, and the workspace of the current printer was determined by considering the system constraints in this article. By giving detailed information about the mechanical and electrical components of the designed system, the working principle of the whole system is presented. According to the findings obtained in the studies, the kinematic analyses perform...

1 Department of Mechanical Engineering, University of Tabriz, Tabriz, Iran. 2 School of Engineeri... more 1 Department of Mechanical Engineering, University of Tabriz, Tabriz, Iran. 2 School of Engineering Emerging Technologies, Mechatronics Laboratory, University of Tabriz, Tabriz, Iran. Corresponding author Email: ara_rahmani@gmail.com Abstract: In the design of parallel manipulators, usually mean value of a dexterity measure over the workspace volume is considered as the objective function to be used in optimization algorithms. The mentioned indexes in a hybrid parallel manipulator (HPM) are quite complicated to solve thanks to infinite solutions for every point within the workspace of the redundant manipulators. In this paper, spatial isotropic design axioms are extended as a well-known method for optimum design of manipulators. An upper limit for the isotropy measure of HPM is calculated and instead of computing and minimizing isotropy measure, minimizing the obtained limit is considered. To this end, two different objective functions are suggested which are obtained from objective...

Parallel kinematic machines, are closed loop structures which have more accuracy, stiffness and a... more Parallel kinematic machines, are closed loop structures which have more accuracy, stiffness and ability to withstand high loads. In this paper the vibration equations of the new parallel mechanism, that has higher stiffness because of parallelogram system and fixed length pods, have been derived by analytical approach. Whereas the proposed mechanism is applied as a machine tools, its vibrational behavior investigation has key impact factor. All the kinematic chains of the mechanism have been taken into consideration to achieve the coupled system of equations. To extract mechanism natural frequencies, modal analysis is carried out using three methods including analytical, finite element (FEM) and experimental method on parallel mechanism which has four degrees of freedom including three linear motion along the x, y and z axes and a rotary motion about x axis. Finally the natural frequencies and mode shapes obtained from analytical, experimental and FEM were compared. It is worth noti...

This contribution addresses forward kinematic solution of modular hybrid manipulator which includ... more This contribution addresses forward kinematic solution of modular hybrid manipulator which includes two same Stewart mechanism in serial form known as 2-(6UPS) manipulator. First, using geometrical and vectorial analysis, mathematical model of kinematic analysis for 2-(6UPS) is extracted. As mapping the length of pods to location (orientation and position) of moving mid and upper platforms (forward kinematic) in this specific mechanism is so difficult to solve, which it is related to complicated configuration of 2-(6UPS) and highly nonlinear characteristic of extracted mathematical model. Therefore, we proposed artificial neural network (ANN) based wavelet analysis to resolve forward kinematics of 2-(6UPS). Also, we used wavelet neural network (WNN) to approximate specific trajectory in circle path with oscillating amplitude in z direction and spiral path with elliptical base paths for mid and upper platforms movement respectively. Comparison between the results of proposed network ...

international journal of advanced design and manufacturing technology, 2017

Parallel kinematic machines, are closed loop structures which have more accuracy, stiffness and a... more Parallel kinematic machines, are closed loop structures which have more accuracy, stiffness and ability to withstand high loads. Kinematic of these mechanisms is complicated due to their closed–loop structure, parallel pods, joint constraints and movement constraints. This paper proposes a new parallel mechanism that has four degrees of freedom. In workspace analysis algorithm, conversion of inverse kinematics after providing the moving platform position (position and orientation) from search algorithm, provides basis position for testing the physical limitations of machine. Workspace of the mechanism is obtained by extracting analytical relations and consequently computational programs are written in MATLAB software. Sweep operations is started by dividing the workspace into x – y planes or horizontal sections with fixed spaces of z, then after sweeping all points of the plane, sweep operations of the next plane begins. Constraints and physical limitations considered in this mechan...

International Journal of Computer Integrated Manufacturing, 2021

2018 6th RSI International Conference on Robotics and Mechatronics (IcRoM), 2018

this research presents a novel asymmetrical four degree of freedom parallel kinematic machine too... more this research presents a novel asymmetrical four degree of freedom parallel kinematic machine tool with rotational capability around one of its horizontal axis, developed for milling processes. Mobility analysis is carried out via screw theory and kinematic analyses for position and velocity are done. Form obtained kinematic relationships, the Jacobian matrix is introduced and singularity analysis is carried out and global condition index indicating the dexterity of mechanism is obtained. Finally, the workspace is simulated considering the physical and kinematical constraints. Results, demonstrated the high capability of the proposed mechanism in dexterity and non-singular workspace, which makes the novel mechanism a fitting candidate for milling processes.

INVERSE DYNAMICS OF HEXAPOD MACHINE TOOL TABLE AND COMPARATIVE INVESTIGATION ON THE EFFECTIVE LOA... more INVERSE DYNAMICS OF HEXAPOD MACHINE TOOL TABLE AND COMPARATIVE INVESTIGATION ON THE EFFECTIVE LOADS MAHBOUBKHAH M.,NATEGH MJ*,KHADEM SE * TARBIAT MODARRES UNIVERSITY, TEHRAN, IRAN ...

In this research, a new parallel robot with four degrees of freedom is studied. The key important... more In this research, a new parallel robot with four degrees of freedom is studied. The key important design stages of a parallel ro bot are obtaining its workspace and singularities. At first, the positions of the robot components were calculated using the inverse kinematic relations. Then, the workspace of the parallel mechanism has been obtained considering the limitations such as singularities. In this paper, various configurations have been analyzed to minimize these points in the workspace. Analysis of Jacobian matrix was used to assess the quality of the workspace. Also, by separating the workspace to some regions using a program that was written in Matlab, all of them are classified as areas with different coefficients of the local Dexterity. As a result, it was seen that asymmetry of the components can improve the performance of robot and reduce the singular points at the proposed robot configuration. Despite of asymmetry of the workspace, the structure of mechanism has been de...

The International Journal of Advanced Manufacturing Technology

Application of nanofluids in minimum quantity lubrication (MQL) system in grinding has been prove... more Application of nanofluids in minimum quantity lubrication (MQL) system in grinding has been proven as an effective approach to counter the negative effects of high temperature evolution in grinding process. However, the cooling and tribological properties of nanolubricants are physical synergetic as the morphology, atomic structure, and physical properties of nanoparticles are determining factors on their performance in MQL systems. Graphite and CuO nanoparticles are representatives of nanoparticles with different atomic structures and physical properties. In this study, a finite difference model based on exponential distribution of moving heat source in wheel-workpiece contact area has been developed to determine the energy partition and temperature distribution of workpiece in nanofluid MQL grinding process using graphite and CuO nanofluids as lubricants. In order to study the effects of atomic structures of nanoparticles on the tribological properties of nanofluids, surface roughness and SEM images of ground surfaces have been evaluated. The results showed that CuO nanofluids with rolling action of nanoparticles in the contact area provide lower energy partition and better surface quality of workpiece in comparison with that of graphite nanofluids with sliding mechanism of atomic planes of nanoparticles at the wheel-workpiece interface during grinding process.

Scientia Iranica

Nowadays, researchers are very interested to investigate the dynamic behavior of the thin-walled ... more Nowadays, researchers are very interested to investigate the dynamic behavior of the thin-walled structures during the machining process due to their broad application in aerospace, automotive industries and etc. One of the main problems in machining of thin-walled structures is unstable chatter vibrations, which causes the poor machined surface quality and decreases the system life span. In this regard, the main aim of this paper is to propose a practical method to solve the chatter instability problem during the milling process of thin-walled components. To this end, first the effects of geometrical parameters like workpiece height, thickness, and tool overhang, diameter and their ratios on the chatter stability are investigated. Then three dimensional stability lobe diagrams (SLDs) base on the mentioned parameters are presented for the first time. In which one can implement the mentioned diagrams to switch the unstable machining process to stable one by changing the value of the system parameters. Finally, the results obtained by the experimental test show that the presented three dimensional diagrams can be utilized to avoid chatter instability in the milling process.

Indian Journal of Science and Technology

This contribution addresses forward kinematic solution of modular hybrid manipulator which includ... more This contribution addresses forward kinematic solution of modular hybrid manipulator which includes two same Stewart mechanism in serial form known as 2-(6UPS) manipulator. First, using geometrical and vectorial analysis, mathematical model of kinematic analysis for 2-(6UPS) is extracted. Mapping the length of pods to location (orientation and position) of moving mid and upper platforms (forward kinematic) in this specific mechanism is difficult to solve, as it is related to complicated configuration of 2-(6UPS) and highly nonlinear characteristic of extracted mathematical model. Therefore, we propose artificial neural network (ANN) based wavelet analysis to resolve forward kinematics of 2-(6UPS). Also, we used wavelet neural network (WNN) to approximate specific trajectory in smooth circle and semi-cardioid paths for mid and upper platforms movement respectively. Comparison between the results of proposed network and closed form solution (CFS) of kinematics for 2-(6UPS) shows proper performance of proposed network in less than 1% error.

The International Journal of Advanced Manufacturing Technology, 2014

Manipulator kinematics refers the analytical study of the motion of manipulator, such as position... more Manipulator kinematics refers the analytical study of the motion of manipulator, such as positions, velocities, and accelerations of the links of a manipulator. As formulating the suitable kinematics models for a manipulator is very crucial for analyzing the behavior of manipulators and light weight design of manipulators, many researches have been focused on it in recent decades with a result of many valuable contributions. However, current researches always focus on rigid manipulator, while the manipulator is always a rigid-flexible coupling multibody system, which can affect the accuracy of kinematics analysis and numerical simulation. This paper proposed a model of kinematics analysis of manipulator based on rigid-flexible coupling virtual prototyping. After a model of manipulator kinematics based on the D-H method was proposed, rigid-flexible coupling virtual prototyping-based kinematics simulation and numerical simulation was then put forward. The kinematical experiment is carried out based on manipulator physical prototyping, which demonstrates that the accuracy of the kinematics calculation and the rationality of design based on rigid-flexible coupling virtual prototyping. The design of a five-degrees-of-freedom manipulator is given as an example, which demonstrates that the methodology is obviously helpful to manipulator design.

One of drawbacks of parallel robot is its unsuitable form and limitation of workspace. This probl... more One of drawbacks of parallel robot is its unsuitable form and limitation of workspace. This problem can be solved through establishing of the complementary axis for it. In this paper, a manual and semiautomatic table with capability of movement in Z axis, as the complementary degree of freedom of robot for adjusting the table and work piece in robot workspace has been designed and manufactured. Firstly, design with drawing the schematic plan of table set such as upper part, its frame, guide ways, chassis and etc. was implemented, then the parts was modeled in CATIA software. Also, all of the mechanical parts such as electro motors, gears and etc., considering machining forces and weight of parts has been computed and selected. After that, to stiffness, the table set was modeled in ANSYS software and deformations of components were determined. After improving the weakness points of design and reanalyzing of table set, the construction of table has been implemented. To approve and inv...

Parallel mechanisms are more utilized, because of their extra precision and stiffness in comparis... more Parallel mechanisms are more utilized, because of their extra precision and stiffness in comparison with serial mechanisms. Measuring position and orientation (pose) of parallel robot end effector and performing kinematic calibration, is a guaranty for, moving precision of these robots. Through different measurement devices, machine vision has advantages such as low cost, simplicity in use and rather appropriate precision. In this research, in order to measure pose of end effector of a 4-DOF (degree of freedom) parallel robot, a vision-based measurement system, is designed and implemented in Matlab software. The laboratory device is a stereo camera. Camera calibration is carried out in Matlab. A triangular shape is used as feature on the robot end effector. By processing the images acquired from pose of end effector, in designed measurement system, rotation matrix and translation vector are obtained and the exact position of the end effector is revealed. For investigating precision and accuracy of proposed measurement system, a conventional measurement method with the help of gauge block and indicator, is used. According to the nature of machine vision, the results achieved in this examination, are acceptable; although better precision can be attained by improving devices used in this research.

European Journal of Science and Technology, 2022

Öz Bu çalışmada, 5 serbestlik derecesine sahip yeni bir 3 boyutlu (3B) yazıcının matematiksel ana... more Öz Bu çalışmada, 5 serbestlik derecesine sahip yeni bir 3 boyutlu (3B) yazıcının matematiksel analizi ve tasarımı gerçekleştirilmiştir. Tasarlanan sistem sayesinde, çok eksenli 3B yazıcı mekanizmalarına yeni bir konsept kazandırılmış ve böylece eklemeli imalat (AM) süreçlerinde parça kalitesini iyileştirilmesi hedeflenmiştir. Öncelikle sistemin kinematik analizi vektör cebri kullanılarak elde edilmiş ve sistem kısıtlamalarını dikkate alınarak yazıcının çalışma uzayı belirlenmiştir. Ardından tasarlanan sistemin mekanik ve elektriksel bileşenleri hakkında detaylı bilgiler verilerek tüm sistemin çalışma prensibi sunulmuştur. Tasarım çalışmalarında elde edilen bulgulara göre önerilen sistem için gerçekleştirilen kinematik analizlerin doğru olduğu kanıtlanmış ve özellikle eklemeli imalat teknolojileri için yeni bir sistem önerilmiştir.

2011 IEEE International Conference on Mechatronics, 2011

This research presents an improved solution to the inverse kinematics and dynamics of the general... more This research presents an improved solution to the inverse kinematics and dynamics of the general Stewart platform. The dynamic equations are generated through Newton­ Euler approach. There have been a number of previous researches on this subject, but most of them consisted of some simplifying approximations which facilitate the formulation. Considering the creativity of the Newton-Euler method in the previous

The International Journal of Advanced Manufacturing Technology, 2007

Parallel mechanisms have found new applications in machine tool's as the end effector carrying th... more Parallel mechanisms have found new applications in machine tool's as the end effector carrying the spindle or used as the table of the machine. Investigations on the dynamics and especially the vibration behavior of these mechanisms are in the initial stage. The authors developed a vibration model for the hexapod table of milling machines and machining centers and derived the relevant explicit equations. The eigenvalue problem of the upper platform of hexapod was solved to obtain the natural frequencies of the platform. The results have been verified with FEM simulation. The distinguishing features of the hexapod tables from the view point of dynamic behavior have also been concluded.

Elektronika ir Elektrotechnika

In this study, the mathematical analysis and design of a new 3D printer with 5 degrees of freedom... more In this study, the mathematical analysis and design of a new 3D printer with 5 degrees of freedom were carried out. Thanks to the developed system, a new concept has been brought to the multi-axis 3D printer mechanisms, and thus, it is aimed to improve the part quality in additive manufacturing (AM) processes. As a result of adding the 4th and 5th axes to the moving platform of the system, the production time of the part was accelerated. It is also possible to print more complex and curved shapes with less support. To design a system with these features, first of all, the kinematic analysis of the system was obtained using vector algebra, and the workspace of the current printer was determined by considering the system constraints in this article. By giving detailed information about the mechanical and electrical components of the designed system, the working principle of the whole system is presented. According to the findings obtained in the studies, the kinematic analyses perform...

1 Department of Mechanical Engineering, University of Tabriz, Tabriz, Iran. 2 School of Engineeri... more 1 Department of Mechanical Engineering, University of Tabriz, Tabriz, Iran. 2 School of Engineering Emerging Technologies, Mechatronics Laboratory, University of Tabriz, Tabriz, Iran. Corresponding author Email: ara_rahmani@gmail.com Abstract: In the design of parallel manipulators, usually mean value of a dexterity measure over the workspace volume is considered as the objective function to be used in optimization algorithms. The mentioned indexes in a hybrid parallel manipulator (HPM) are quite complicated to solve thanks to infinite solutions for every point within the workspace of the redundant manipulators. In this paper, spatial isotropic design axioms are extended as a well-known method for optimum design of manipulators. An upper limit for the isotropy measure of HPM is calculated and instead of computing and minimizing isotropy measure, minimizing the obtained limit is considered. To this end, two different objective functions are suggested which are obtained from objective...

Parallel kinematic machines, are closed loop structures which have more accuracy, stiffness and a... more Parallel kinematic machines, are closed loop structures which have more accuracy, stiffness and ability to withstand high loads. In this paper the vibration equations of the new parallel mechanism, that has higher stiffness because of parallelogram system and fixed length pods, have been derived by analytical approach. Whereas the proposed mechanism is applied as a machine tools, its vibrational behavior investigation has key impact factor. All the kinematic chains of the mechanism have been taken into consideration to achieve the coupled system of equations. To extract mechanism natural frequencies, modal analysis is carried out using three methods including analytical, finite element (FEM) and experimental method on parallel mechanism which has four degrees of freedom including three linear motion along the x, y and z axes and a rotary motion about x axis. Finally the natural frequencies and mode shapes obtained from analytical, experimental and FEM were compared. It is worth noti...

This contribution addresses forward kinematic solution of modular hybrid manipulator which includ... more This contribution addresses forward kinematic solution of modular hybrid manipulator which includes two same Stewart mechanism in serial form known as 2-(6UPS) manipulator. First, using geometrical and vectorial analysis, mathematical model of kinematic analysis for 2-(6UPS) is extracted. As mapping the length of pods to location (orientation and position) of moving mid and upper platforms (forward kinematic) in this specific mechanism is so difficult to solve, which it is related to complicated configuration of 2-(6UPS) and highly nonlinear characteristic of extracted mathematical model. Therefore, we proposed artificial neural network (ANN) based wavelet analysis to resolve forward kinematics of 2-(6UPS). Also, we used wavelet neural network (WNN) to approximate specific trajectory in circle path with oscillating amplitude in z direction and spiral path with elliptical base paths for mid and upper platforms movement respectively. Comparison between the results of proposed network ...

international journal of advanced design and manufacturing technology, 2017

Parallel kinematic machines, are closed loop structures which have more accuracy, stiffness and a... more Parallel kinematic machines, are closed loop structures which have more accuracy, stiffness and ability to withstand high loads. Kinematic of these mechanisms is complicated due to their closed–loop structure, parallel pods, joint constraints and movement constraints. This paper proposes a new parallel mechanism that has four degrees of freedom. In workspace analysis algorithm, conversion of inverse kinematics after providing the moving platform position (position and orientation) from search algorithm, provides basis position for testing the physical limitations of machine. Workspace of the mechanism is obtained by extracting analytical relations and consequently computational programs are written in MATLAB software. Sweep operations is started by dividing the workspace into x – y planes or horizontal sections with fixed spaces of z, then after sweeping all points of the plane, sweep operations of the next plane begins. Constraints and physical limitations considered in this mechan...

International Journal of Computer Integrated Manufacturing, 2021

2018 6th RSI International Conference on Robotics and Mechatronics (IcRoM), 2018

this research presents a novel asymmetrical four degree of freedom parallel kinematic machine too... more this research presents a novel asymmetrical four degree of freedom parallel kinematic machine tool with rotational capability around one of its horizontal axis, developed for milling processes. Mobility analysis is carried out via screw theory and kinematic analyses for position and velocity are done. Form obtained kinematic relationships, the Jacobian matrix is introduced and singularity analysis is carried out and global condition index indicating the dexterity of mechanism is obtained. Finally, the workspace is simulated considering the physical and kinematical constraints. Results, demonstrated the high capability of the proposed mechanism in dexterity and non-singular workspace, which makes the novel mechanism a fitting candidate for milling processes.

INVERSE DYNAMICS OF HEXAPOD MACHINE TOOL TABLE AND COMPARATIVE INVESTIGATION ON THE EFFECTIVE LOA... more INVERSE DYNAMICS OF HEXAPOD MACHINE TOOL TABLE AND COMPARATIVE INVESTIGATION ON THE EFFECTIVE LOADS MAHBOUBKHAH M.,NATEGH MJ*,KHADEM SE * TARBIAT MODARRES UNIVERSITY, TEHRAN, IRAN ...

In this research, a new parallel robot with four degrees of freedom is studied. The key important... more In this research, a new parallel robot with four degrees of freedom is studied. The key important design stages of a parallel ro bot are obtaining its workspace and singularities. At first, the positions of the robot components were calculated using the inverse kinematic relations. Then, the workspace of the parallel mechanism has been obtained considering the limitations such as singularities. In this paper, various configurations have been analyzed to minimize these points in the workspace. Analysis of Jacobian matrix was used to assess the quality of the workspace. Also, by separating the workspace to some regions using a program that was written in Matlab, all of them are classified as areas with different coefficients of the local Dexterity. As a result, it was seen that asymmetry of the components can improve the performance of robot and reduce the singular points at the proposed robot configuration. Despite of asymmetry of the workspace, the structure of mechanism has been de...

The International Journal of Advanced Manufacturing Technology

Application of nanofluids in minimum quantity lubrication (MQL) system in grinding has been prove... more Application of nanofluids in minimum quantity lubrication (MQL) system in grinding has been proven as an effective approach to counter the negative effects of high temperature evolution in grinding process. However, the cooling and tribological properties of nanolubricants are physical synergetic as the morphology, atomic structure, and physical properties of nanoparticles are determining factors on their performance in MQL systems. Graphite and CuO nanoparticles are representatives of nanoparticles with different atomic structures and physical properties. In this study, a finite difference model based on exponential distribution of moving heat source in wheel-workpiece contact area has been developed to determine the energy partition and temperature distribution of workpiece in nanofluid MQL grinding process using graphite and CuO nanofluids as lubricants. In order to study the effects of atomic structures of nanoparticles on the tribological properties of nanofluids, surface roughness and SEM images of ground surfaces have been evaluated. The results showed that CuO nanofluids with rolling action of nanoparticles in the contact area provide lower energy partition and better surface quality of workpiece in comparison with that of graphite nanofluids with sliding mechanism of atomic planes of nanoparticles at the wheel-workpiece interface during grinding process.

Scientia Iranica

Nowadays, researchers are very interested to investigate the dynamic behavior of the thin-walled ... more Nowadays, researchers are very interested to investigate the dynamic behavior of the thin-walled structures during the machining process due to their broad application in aerospace, automotive industries and etc. One of the main problems in machining of thin-walled structures is unstable chatter vibrations, which causes the poor machined surface quality and decreases the system life span. In this regard, the main aim of this paper is to propose a practical method to solve the chatter instability problem during the milling process of thin-walled components. To this end, first the effects of geometrical parameters like workpiece height, thickness, and tool overhang, diameter and their ratios on the chatter stability are investigated. Then three dimensional stability lobe diagrams (SLDs) base on the mentioned parameters are presented for the first time. In which one can implement the mentioned diagrams to switch the unstable machining process to stable one by changing the value of the system parameters. Finally, the results obtained by the experimental test show that the presented three dimensional diagrams can be utilized to avoid chatter instability in the milling process.

Indian Journal of Science and Technology

This contribution addresses forward kinematic solution of modular hybrid manipulator which includ... more This contribution addresses forward kinematic solution of modular hybrid manipulator which includes two same Stewart mechanism in serial form known as 2-(6UPS) manipulator. First, using geometrical and vectorial analysis, mathematical model of kinematic analysis for 2-(6UPS) is extracted. Mapping the length of pods to location (orientation and position) of moving mid and upper platforms (forward kinematic) in this specific mechanism is difficult to solve, as it is related to complicated configuration of 2-(6UPS) and highly nonlinear characteristic of extracted mathematical model. Therefore, we propose artificial neural network (ANN) based wavelet analysis to resolve forward kinematics of 2-(6UPS). Also, we used wavelet neural network (WNN) to approximate specific trajectory in smooth circle and semi-cardioid paths for mid and upper platforms movement respectively. Comparison between the results of proposed network and closed form solution (CFS) of kinematics for 2-(6UPS) shows proper performance of proposed network in less than 1% error.

The International Journal of Advanced Manufacturing Technology, 2014

Manipulator kinematics refers the analytical study of the motion of manipulator, such as position... more Manipulator kinematics refers the analytical study of the motion of manipulator, such as positions, velocities, and accelerations of the links of a manipulator. As formulating the suitable kinematics models for a manipulator is very crucial for analyzing the behavior of manipulators and light weight design of manipulators, many researches have been focused on it in recent decades with a result of many valuable contributions. However, current researches always focus on rigid manipulator, while the manipulator is always a rigid-flexible coupling multibody system, which can affect the accuracy of kinematics analysis and numerical simulation. This paper proposed a model of kinematics analysis of manipulator based on rigid-flexible coupling virtual prototyping. After a model of manipulator kinematics based on the D-H method was proposed, rigid-flexible coupling virtual prototyping-based kinematics simulation and numerical simulation was then put forward. The kinematical experiment is carried out based on manipulator physical prototyping, which demonstrates that the accuracy of the kinematics calculation and the rationality of design based on rigid-flexible coupling virtual prototyping. The design of a five-degrees-of-freedom manipulator is given as an example, which demonstrates that the methodology is obviously helpful to manipulator design.

One of drawbacks of parallel robot is its unsuitable form and limitation of workspace. This probl... more One of drawbacks of parallel robot is its unsuitable form and limitation of workspace. This problem can be solved through establishing of the complementary axis for it. In this paper, a manual and semiautomatic table with capability of movement in Z axis, as the complementary degree of freedom of robot for adjusting the table and work piece in robot workspace has been designed and manufactured. Firstly, design with drawing the schematic plan of table set such as upper part, its frame, guide ways, chassis and etc. was implemented, then the parts was modeled in CATIA software. Also, all of the mechanical parts such as electro motors, gears and etc., considering machining forces and weight of parts has been computed and selected. After that, to stiffness, the table set was modeled in ANSYS software and deformations of components were determined. After improving the weakness points of design and reanalyzing of table set, the construction of table has been implemented. To approve and inv...