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Parallel mechanisms are widely being used in industrial applications such as machine tool, metrology, earthquake simulator, fly simulator, medical equipment and etc. These mechanisms have some limitations like having erratic workspace, singular points in the workspace and complexity of control systems. These limitations should be studied for suitable usage of parallel mechanisms. In this article, a four degree of freedom parallel mechanism (three linear and one rotation degrees of freedoms) is proposed as machine tool and being studied and its workspace and singularity analysis are done by solving the kinematic relations and using Matlab software. So, at first the inverse and direct kinematic equations of mechanism were solved and then an algorithm is used to determine the workspace and singular points of proposed parallel mechanism. Finally, to investigate the results of workspace analysis the structure has been modeled in Solidworks software and the inverse kinematic relation and the obtained workspace have been validated using the simulation. At the last, to investigate the quality of robot performance and its dexterity in workspace, global condition index of mechanism using Jacobean matrix is calculated for different orientations of moving platform.

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The chewing simulator is designed to perform fatigue tests and durability on a variety of dental specimens. This device, by considering the material (hard or soft) and the type of dental sample (human or animal or artificial) and by applying a specific cyclic and even static force, changes the shape of the sample microscopically and finally this periodic loading and shape change, uses the data to evaluate the fatigue and strength of the sample in the durability test. The testing process of this device will continue until the sample fails or the loading cycle is completed. At design of this device, two movement mechanisms are considered vertically and horizontally, which are responsible for chewing simulation operations, so that in both mechanisms, the movement is reciprocating, the amount and number of this movement is cyclical that is adjustable and controllable, and at the same time, considering the force measuring sensor in this device, the amount of applied force is specified and adjustable at each stage. Two specimens of teeth were placed in the machine for testing. The first priority of testing this device for the samples was their durability under the static force that was applied to the sample step by step. Also, to evaluate the function of the device in the fatigue test, dental specimens were loaded under a certain force and were affected by cyclic motion in both vertical and horizontal directions. According to studies, the refractive force of the specimens varies from 100 N to 800 N, the dental specimens, one artificial and the other natural, failed under the static force, which was in the range of 200 N, that the artificial sample was completely broken, but the natural sample was worn out and part of it was damaged. And this was a good comparison to show the strength and durability of natural teeth compared to artificial ones.
 

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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.