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In this paper, kinematic and dynamic model of planar cable-driven parallel robots are introduced in general form which are verified for a constrained cable-driven parallel robot in Sim-mechanics. Path planning based on artificial potential field approach is considered to prevent collision between dynamic obstacle, end-effector and cables in order to achieve collision-free path. As well as to reduce energy consumption, cable tension constraints have been involved in optimization of path planning. This method is proposed to control a cable robot. Therefore, obstacles are distributed randomly in order to have a complex environment. By this way, cable tension constraint is studied as one of the most crucial challenges for cable driven robots. Moreover, Fmincon function of Matlab is applied in order to take into account the required constraints and maintain the limits for cables tension. The latter leads to solve the redundancy resolution which is a definite asset in controlling a cable-driven parallel robot. Finally, a four-cables driven parallel robot is controlled by using the so-called computed torque method for tracking the desired and optimized path. The method is explained and obtained results indicate the efficiency of the proposed approach.

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Parallel manipulators are mechanisms with closed kinematic chains which have been developed in different forms, but these manipulators have several drawbacks such as small workspace, existence of singular points in their workspace, and complex kinematics and dynamics equations that lead to increase of difficulty in their control. In spite of this, this mechanism has been being conventionally used in many different industrial applications such as machining, motion simulators, medical robots, etc. To overcome these drawbacks, design and manufacturing of a manipulator with three translational degrees of freedom are provided. Design of this manipulator was based on the possibility of three translational motions for its end-effector. The manipulator degrees of freedom are obtained via screw theory. Basic features, consisting of forward and inverse kinematics, workspace and singularity analyzes and also velocity analysis, are considered in this paper. A numerical algorithm is implemented to determine the workspace regarding applied joint limitations and the design parameters were extracted based on to achieving to the desired workspace. The robot motion is created by using of pneumatic actuators which receive their command from a pneumatic servo valve. After design steps, the required elements were provided and assembled in a robotic lab. Finally, the simulation results have transparently approved the improved robots.

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In this study, the effects of geometrical parameters of 6-DOF Hexa parallel robot on kinematic, and dynamic performance indices are investigated and its structure is optimized using the intelligent multi-objective Bees Algorithm. In this way, after describing the structure and specifying the geometrical parameters of the robot, inverse kinematic relations of the robot are obtained. Jacobian matrix that maps velocity from joint space to Cartesian space is developed. Mass matrix is obtained from calculating the total kinetic energy of the manipulator in terms of the actuated joints vector. Inverse of the homogen jacobian based condition number is considered as a index to evaluate the kinematic dexterity. based on mass matrix as relation between acceleration vector of the end effecter and torque vector of actuated joints, dynamic dexterity index is presented. Using the multi-objective Bees Algorithm and considering dynamic and kinematic performance indices in a pre-determined workspace as the objective functions, structure of Hexa parallel robot is optimized. In this way, the proper geometrical constraints such as limitation of universal and spherical joins, and the constraints to singularity avoidance are considered. Pareto front of the multi objective optimization of the robot is drawn. Diagrams of the kinematic and dynamic performance indices variation in the workspace and the effects of geometrical parameters variation on them are presented.

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Accumulation of plastic strain during cyclic loading is one of the main reasons for fatigue failure. In order to predict the fatigue life of plates, it is necessary to calculate the accumulated plastic strain and the affecting parameters carefully. In this study, a combination of nonlinear isotropic and nonlinear kinematic hardening model (modified Choboche) was implemented in the commercial finite element code of ABAQUS, by using a FORTRAN subroutine to calculate the accumulation of strain in samples made from thin plates of aluminum. In this regard experimental, strain controlled and stress controlled cyclic tests were carried out, and the required coefficients for simulating the hardening behavior of aluminum alloy 2024-T3 were obtained and the accumulation of plastic strain was simulated at different uniaxial loading condition. The comparison of the experimental and the predicted results shows that, the determination of optimal coefficients for combined nonlinear isotropic and nonlinear kinematic hardening model (modified Choboche), has an adequate ability to predict the experimental results. The obtained results also show that, increasing stress amplitude and mean stress increase the strain accumulation. The results from 4 types of cyclic loading indicate that the stress ratio has a direct influence on the strain rate when the maximum applied cyclic load is kept the same, and an increase in stress ratio increases the accumulation of plastic strain. Moreover, the rate of strain accumulation at the first cycles is high while it is reduced by increasing the number of cycles.

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In recent years, knee diseases are spread especially in elderly people. Since performing daily activities such as walking and running, the knee supports the weight of the body, there is more likely to be injured. This issue is more important for elderly people who have weak muscles and almost all elderly people suffer from knee pain. One way to help this people in order to move normally is to use a wearable device to aid the knee. In this article, a passive wearable robot will be designed to improve the strength of the elderly who suffers from the knee pain. The robot uses the compliance elements to increase the power of the knee joint in parts of a cycle. This robot will be developed based on a Stephenson II six-bar mechanism. Using this mechanism has the advantage of producing the similar motion to a knee. In other words, this mechanism produces the linear and rotational motions simultaneously. Additionally, more compliance elements can be added to improve the performance of the wearable robot. The optimal dimensions of the robot will be Through the kinematics analysis and also the derivation of the dynamics equations and the numerical validations of these equations, the performance of the robot will be considered. The performance of the robot mounted on the leg is compared with the human. Obtained results show that the less power is required when a wearable robot is used. This proves the merits of the designed robot to be used for the elderly.

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In this paper, the forward kinematics of a parallel manipulator with three revolute-prismatic-spherical (3RPS), is analyzed using a combination of a numerical method with semi-analytical Homotopy Continuation Method (HCM) that due to its fast convergence, permits to solve forward kinematics of robots in real-time applications. The revolute joints of the proposed robot are actuated and direct kinematics equations of the manipulator leads to a system of three nonlinear equations with three unknowns that need to be solved. In this paper a fast and efficient Method, called the Ostrowski-HCM has been used to solve the direct kinematics equations of this parallel manipulator. This method has some advantages over conventional numerical iteration methods. Firstly, it is the independency in choosing the initial values and secondly, it can find all solutions of equations without divergence just by changing auxiliary Homotopy functions. Numerical example and simulation that has been done to solve the direct kinematic equations of the 3-RPS parallel manipulator leads to 7 real solutions. Results indicate that this method is more effective than other conventional Homotopy Continuation Methods such as Newton-HCM and reduces computation time by 77-97 % with more accuracy in solution in comparison with the Newton-HCM. Thus, it is appropriate for real-time applications.

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This paper investigated the imitation of human motions by a NAO humanoid robot which can be regarded as a human-robot interaction research. In this research, first, human motion is captured by a Kinect 3-dimentional camera through a Robot Operating System (ROS) package. Captured motion is then mapped into the robot’s dimension due to the differences between human and humanoid robot dimensions. After performing the mapping procedure, the solution of both forward and inverse kinematic problem of the robot are solved. To this end, a “Distal” form of forward kinematics solution of the NAO humanoid robot is computed and based on the latter form an analytical inverse kinematics solution for the whole-body imitation purpose is used. The foregoing issue, as one of the contributions of this paper, can be regarded as one of the main reason for obtaining a smooth imitation. In order to keep the robot’s stability during the imitation, an ankle strategy based on a Linear Inverted Pendulum Model (LIPM) and the Ground projection of the Center of Mass (GCoM) criteria is introduced. Moreover, the latter LIPM is controlled by a Proportional-Integral-Derivative (PID) controller for two cases, namely, double and single support phases. Considering the limitation on the motion capture device, from experimental and simulation results obtained by implementing the proposed method on a NAO-H25 Version4 it can be inferred that the robot exhibits an accurate, smooth and fast whole-body motion imitation.

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This paper presents a novel formulation for controlling the task space of the robot with the Remote Center of Motion (RCM) constraint in Minimally Invasive Surgery (MIS). In MIS it is usually required to prevent any lateral motion at the point at which the robot enters the body, called the incision point or the trocar. Therefore, the surgical tool is only allowed to penetrate inside the body or rotate around its axis to avoid more injuries to the patient’s body. The proposed control law considers the RCM constraint at the kinematic level and the convergence of the task space error and regulation of RCM constraint are satisfied, simultaneously. Moreover, the null space of the robot is also exploited effectively within the framework to perform two additional tasks which can limit the RCM movement and optimize the manipulability measure of the robot. A comparative study is finally performed between the proposed approach and a well-known approach used in the literature. To evaluate the efficiency of the approach, a planar robot with 5 degrees of freedom with the trocar constraint is simulated and the results is verified successfully.

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In this paper, position control is addressed for a pneumatically actuated 6-DoF Gough-Stewart parallel robot. At first, dynamic model of the pneumatic system of each link of the robot which comprises a pneumatic actuator and a proportional electrical control valve is extracted. Unknown parameters of the obtained dynamic model consisting friction force, viscous coefficient and the parameters of the valve are identified by employing an evolutionary algorithm. Then, position control of the robot’s pneumatic actuator is performed based on designing Backstepping-Sliding Mode controller according to the nonlinear dynamic model of the pneumatic system. Moreover, kinematic equations of the 6-DoF parallel robot are achieved and a novel method is proposed, the so-called Geometry-based Quasi-Forward Kinematic, to the end of calculating the position of the end-effector of the robot without using expensive position sensors. Accordingly, kinematic closed-loop control of the parallel robot, which is based on simultaneous joint space and task space control, is investigated for trajectory tracking using potentiometers, a rotation sensor, and based on the computed position of the end-effector by the proposed method. Desired sinusoidal trajectories with pure motions and also complicated trajectories are tracked in which error of positions and rotations are lower than 2 (cm) and 3 (deg), respectively. The results reveal that the trajectory tracking control of the pneumatic 6-DoF Gough-Stewart parallel robot is performed properly based on the proposed control strategies and the novel method for calculating the position of the end-effector.

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Recently, robotic systems are widely used in surgery, due to their characteristics such as having high precision, being tireless and making no mistakes. They are especially suitable for operation on hard tissue, as the bone is stationary and does not change shape and therefore preoperative planning of the system is much more straightforward. Nevertheless, proposed robotic systems for surgery on skull bone are still in the research stage. In this study, by considering the requirements of craniotomy surgery, a Remote Center of Motion spherical mechanism is used in design and prototyping of a surgical system. The kinematic equations and Jacobian of the mechanism are calculated analytically and later verified through software simulation. Detailed design and force analysis helped selection and use of appropriate AC servo motors for actuation. An aluminum prototype is fabricated out of CNC machined parts. Performance of different connection methods between PC and the robot were tested and a combination of them is proposed for higher reliability and speed. Finally, a software library is generated in LabVIEW environment to simplify the connection with servo motors and utilization and control of the robotic system.

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Among the pieces are ceramic balls that are special because of the physical and mechanical properties that have been the industry's attention. Ceramic balls are produced by powder metallurgy way. Finally, by grinding, lapping and polishing processes is reached to surface smoothness, roundness and diameter of the desired. Since the required finishing process to ceramic finishing for surface quality and geometry accuracy of the desired is Time consuming and expensive, creating an economical finishing way is an important issue in the application of ceramic balls. In this article, a mechanism for ceramic balls lapping is proposed. Proposed mechanism consist of two lap plates. Lower lap plate has an eccentric v-shaped groove and placed on out of upper lap plate rotation center. Kinematic analysis of proposed mechanism has been done and lapping trajectory has been investigated on the ball surface. The results of kinematic analysis and lapping trajectory show that the proposed mechanism increases removal rate and roundness of the ball. In general, efficiency and productivity of balls lapping process will improve to achieve the desired surface smoothness and roundness. It can increase the speed of operation and reduce the process time by increasing removal rate.

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Earthquakes are one of the most Terrible danger that are likely to cause heavy human losses and destroy entire civilization on scale of minutes. The more recent damaging events in Mexico City (1985 Mexico) in bam (2003 Iran) or Tohoku (2011 Japan) recall that so far little is known about earthquake physics that could prevent people from their deadly effects. To reduce casualties Decades of research involving numerous laboratories worldwide aim at investigating this large scale phenomenon and trying to understand how it triggers, propagates, and stops. A trusty physical modeling of strong ground motion requires to examine three crucial parameters of seismic source specifications, wave propagation path, and seismic site effects. A reliable physical modeling of strong ground motion requires to examine three crucial parameters of seismic source specifications, wave propagation path, and seismic site effects. Among various seismic source specifications, a more physically realistic source model is the specific barrier model or (SBM) for short. The SBM is specifically more suitable for regions with poor seismological data bank and/or ground motions from large earthquakes with large recurrence intervals. In order to simulate seismic ground motions from a specific earthquake source model in an efficient way, the stochastic modeling method has been widely used. An essential part of the seismological model used in this method is the quantitative description of the far-field spectrum of seismic waves emitted from the seismic source. Since shear (S) wave is primarily the main factor of earthquake damages, the application of stochastic approach of the SBM has almost been focused on the far-field S wave spectrum, in which two corner frequencies of observed earthquake are represented. The ‘two-corner-frequency’ shows two considerable length-scales of an earthquake source: a length-scale that quantifies the overall size of the fault that ruptures (e.g., the length L of a strike-slip fault) and another length-scale that measures the size of the subevents. Associated with these length-scales are two corresponding time scales: (1) the overall duration of rupture, and (2) the rise time. The SBM has a few main source parameters which have been calibrated to earthquakes of different tectonic regions. In this paper, it has been tried to simulate source, path and site of entire earthquake and compare the results of simulation with real earthquake. To this end SBM with uniform PDF for arrival time but different types of PDFs of subevent size used to simulate source. To investigate effect of PDFs of subevent size on the source spectra as well as earthquake spectra as result of simulation, uniform and fractal distribution along with classic distribution for subevent size are considered. In order to take into account, the effects of path of propagation, Geometric and inelastic Attenuation Compatible with center of Italy (L’Aquila region) have been used. Finally, to considering effect of the layers of soil (sediments) near surface on amplitude, period, duration and other characteristic of seismic waves, transfer function for linear wave propagation has been computed with the Thomson-Haskell matrix method. Transfer function in this method illustrate how a soil column with different layers attenuates and amplifies seismic waves as a function of frequency.

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This paper discussed nonlinear adaptive control of a 6 DOF biped robot. The studied robot was divided to three part, fix leg, moving leg and a torso and all the joints were considered rotational. Generally, for calculations, robots are considered as a whole which makes the related calculations complex. For balance calculations, the zero moment point (ZMP) was either considered as a fix point on the ground or a moving point on the foot plate. In the presented robot in this study with priority of movements, first, the calculations were carried out on the moving foot, then the effect of the motion on the foot was inspected and a pendulum was used to balance the robot. To check the balance, ZMP in the simulation in MATLAB software was considered as a fix point While in Adams software simulation, ZMP was considered moving along the bottom of the sole. All the charts active with both software met each other. In the presented study the inverse kinematics was calculated by trigonometric method and inverse dynamics of each leg was investigated by Newton-Euler iterative method. All calculations were carried out in MATLAB software and were verified by ADAMS software. By writing the equilibrium equations, the angle of torso at each time was achieved. In the next step, because of uncertainties in manufacturing and some parameters like mass, length, etc. adaptive computed torque control was used on each leg to achieve the maximum torque that each joint needs for stable walking.

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Robotic arms are widely used for 2D desktop applications. In this paper, a new mechanism for a planar robotic arm is presented. In addition to having the benefits of both series of parallel robots, the proposed mechanism also eliminates the disadvantages of both categories. The arm made on the same side as the parallel arms has rigidity, strength and precision, and other positive features of the parallel arms, and on the other hand, like the serial arms, due to the lack of singular points inside the workspace, has a large, symmetrical and also be able to move continuously in the entire workspace. The kinematics relations for the arm are derived, and a controller based on AVR microcontroller & computer for the arm are introduced. The results indicate an improvement in arm performance and the removal of singular points from within the workspace.

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Origami, as a paper folding art and Japanese culture, has been utilized broadly in engineering areas. The exclusive features of origami such as negative Poisson’s ration, lightweight, deployable and so forth, can be considered in the design of deployable space structures, expandable shelters, drug delivery, and robots. In this study, firstly, the continuum robot with six serial modules of origami parallel structure as its skeleton and the helical springs as the compliant backbone is studied, and constant curvature kinematics was implemented in order to simplify and approximate the kinematic model. Accordingly, the kinematic model of one module was derived. Then, the robot kinematics was obtained as a series of mentioned modules. Furthermore, the proposed continuum robot was modeled by an equivalent mechanism, and a comparison was conducted between the methods to obtain a workspace. Based on the results, the modeling of the equivalent mechanism has an advantage in terms of calculation's volume compared to the constant curvature method and the workspace obtained from both methods was the same. The Jacobian matrix was obtained through the constant curvature approximation methods, which can be considered for singularity analysis in specific conditions and the analysis reveals that the singularities occur when the curve and radius are equal and symmetry is created and the other is when the radius is equivalent to zero. The paper concludes a perspective on several of the themes of current research that are shaping the future of origami-inspired robotics.

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Parallel robots, which have several advantages over serial robots, have been one of the important industrial developments to increase the efficiency of controllable devices. Parallel structures have more suitable features such as higher rigidity, higher movement speed, non-cumulative errors and flexibility of the end-effecter pose. However, the workspace of parallel robots, compared to serial robots, faces limitations due to the existence of multiple kinematic chains, as well as the complexities related to robot control. Small size of workspace is one of the main challenges of parallel robots. Designing moving platform of a parallel robot is of the factors affecting the workspace of the robot. C4 is a four-dof parallel robot that is developed based on the three-dof Delta robot. In current study, the influence of the moving platform design on the workspace and efficiency of the robot has been investigated. After the initial overall design of the robot, three proposed modes for the moving platform have been investigated by considering the robot's kinematic parameters and robot error analysis. According to the results of the workspace and the robot efficiency analyses, the most efficient design has been selected.
 

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In this article, the kinematic and dynamic analysis of a multi-bar drum mechanism is discussed using Adams software. At first, the modeling of the mechanism is done in the catia engineering software, and then the model is entered in the Adams software. Then, by determining the appropriate joints, the initial speed is given to the mechanism and THE MOTION OF the mechanism is simulated. A kinematic analysis of the mechanism is performed and results of speed and acceleration of the joints are presented. The performed design and simulation show the effectiveness of the mechanism.

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In many wheeled robot applications, in addition to accurate position control, dimensional and weight limitations are also important. The limitation of weight and dimensions means that it is not possible to use arbitrarily large actuators. On the other hand, accurate and fast tracking usually requires high control gains and, as a result, large control inputs. If the control input exceeds the saturation limit of the operator, in addition to increasing the tracking error, it may lead to robot instability in some cases. Therefore, it will be precious to provide a control method that can simultaneously provide high control accuracy and guarantee the robot's stability, taking into account the saturation limit of the actuators (speed and torque) in a predetermined manner. This issue has been addressed in the present study. The proposed control includes two parts: a kinematic controller and a dynamic controller. The kinematic control design is based on the Lyapunov approach, which can adjust the speed saturation limit of the actuators. For dynamic control, the robot velocity components are considered as control reference values ​​and the robot wheel torque is considered as control inputs. In the dynamic control design, the torque saturation limit of the actuators is included in a predetermined way. To evaluate the performance of the proposed nonlinear control, various analyses were performed on the wheeled robot. The results showed that the proposed control algorithm while guaranteeing stability and following the path with high accuracy, has also fully met the requirements of the actuators’ saturation limits

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Rotary forging is an incremental bulk forming process, possessing salient advantages compared with the conventional forging, including reduced force, smoothness of operation, lower investment, apt for near net shaping and producing workpieces with intricate profiles. However, the conventional rotary forging machines suffer serious limitation in their kinematics, which originates from their simple eccentric mechanism of the actuating device. The parallel-kinematics hexapod mechanism with six degrees of freedom can circumvent this limitation. The theory and practice of this concept has been successfully implemented in the present study. The inverse kinematics of hexapod has been adapted to the kinematics of the rotary forging processes. This could yield a proper method to generate the orbitally rocking motion prevailing in the process. In order to investigate the material flow in the lower die, physical modeling was carried out by the use of plasticine and several experiments were conducted in a hexapod machine. The final shapes of the workpieces, the degrees of die filling, and the forging forces were compared with the conventional forging, indicating improved results. It was observed that the motion pattern in the rotary forging influences the time and the force required for forming. The maximum forces required for rotary forging using the circular and planetary motion patterns were 32 N and 38 N respectively. In comparison, conventional forging required a significantly higher force, approximately 200 N. The time required to form a bevel gear using planetary motion was almost half of the time needed for circular motion