Juncheng Li | Jason Li
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3-RRR Manipulator
Inverse Kinematics determines the joint angles of end-effector at certain positions. The IK of 3-RRR parallel robot arm is derived by geometric methods.
The 3D model of 3-RRR robot arm was established in Solidworks, the render view is shown in Figure.2. The Robot has three active links and three passive links, and the active links were drove by servos. In the middle, we designed a structure to hold the pen and used stand-off to stabilize. There are several physical parameters required to be determined.
Inverse Kinematics determines the joint angles of end-effector at certain positions. The IK of 3-RRR parallel robot arm is derived by geometric methods.
Description
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Abstract
Robot manipulators could be subdivided into two main categories: serial and parallel. In parallel robots, the position of the end effector is determined by multiple arms working at the same time. 3-RRR Robot is a type of parallel robot which consists of three kinematic chains with three revolute joints in each chain. This paper studied the kinematic model of the 3-RRR robot including the FK and IK and compile the mathematical expression into MATLAB program to conduct the simulation. The workspace and singularity of 3-RRR manipulator were analyzed via simulation. The physical construction of the robot was done by laser cut and then using Arduino toolbox in MATLAB to realize the control of the robot. After debugging both the hardware and software, the 3-RRR robot arm could finally realize the function of writing simple words and drawing geometries.
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Construction of the 3-RRR Robot
The 3D model of 3-RRR robot arm was established in Solidworks, the render view is shown in Figure.2. The Robot has three active links and three passive links, and the active links were drove by servos. In the middle, we designed a structure to hold the pen and used stand-off to stabilize. There are several physical parameters required to be determined. According to the trials in program and to get relatively larger workspace. Then, we used the laser cut in RPL to construct the robot, the material we chose to make the base is MDF 1/4 and the links were made of Acrylic 1/4 and 1/8. The servo we choose is FITEC-FS5106B of which the torque is 6kg.cm, big enough to drive the robot.
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Control of the 3-RRR Robot
We used Arduino Uno as the processor and utilized MATLAB Arduino toolbox to control the robot. The chip was powered by the USB Port of PC, the three servos were powered by 4 AA batteries (6V). To control the movement of the end-effector, we first determined the path we want to realize and converted it to the coordinates, then using IK to generate the joint angles along the path line. It should be noticed that the joint angles we get by using the method could not be applied to servo directly. Due to the actual assembly of the robot, the three servos have different zero position, thus the joint angles are different and needed modification.Then, we save these joint angles as matrices and use MATLAB Arduino toolbox to send these values to the servo via Arduino Uno.
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