Industrial Parallel Robot:
Industrial Parallel Robot:
CAD software used: Autodesk Inventor 2014.
Download Scope: 3D CAD model (Autodesk Inventor files), STEP. Price: 5$
An industrial parallel robot “ARMO”, with (5) degrees of freedom (DOF). The parallel robots differs from the series ones mainly in on point; in parallel robots, all arms are connected directly with the actuator head, while in series robots, the robots consist of one single arm which made up from many sequential joints starting from robot base and ending with actuator head with one joint directly connected. This robot, in terms of mechanical design, seems to be simple, and the equipments needed to build it do so. But the difficulty remains in the kinematic and dynamic analyses. The actuator head of this robot can move toward the three axes (X,Y,Z) with the limited ability to rotate around (X,Y) axes, and thus, the robot has (5 DOF) according to the six points theory.
According to the Kinematic Analysis; for the aim of reaching to the purpose point, I depended on the arms linked to each other by two bases; the first on is fixed and it represents the robot body, and the second one has the ability to move and it represents the actuator head base. The number of the arms is (4) where each two arms are located in one plan. And so, the two resulted plans are perpendicular to each other since the angle between two adjacent arms is (90 degrees). In fact, each arm is divided to two successive joints for purpose of giving more flexibility in motion to the robot. The two joints have in total (5 DOF), and they are all rotational. By putting the arms to result a (90 degrees) angle between each adjacent arm and connecting the arms to the actuator head bas, we get an actuator head with (5 DOF); three are linear and two are rotational. And by putting some limiting conditions regarding to the design and dimensions issues, I was able to reach to the full kinematic diagram, which represents the Work Space of the robot. By this diagram we can know the value of each arm rotation according to the purpose point parameters, and so, I was able to reach to (4) kinematic equations determine the purpose point movement. Each two arms in the same plan have two equations linked to each other, and these equations are linked the two equations resulted from the other plan. According the Dynamic Analysis, the inertia forces and torques were studied, and so the the velocity required to move the actuator head. Consequently, stepper motors were chosen, the number of them is like the number of leader joints form the four arms joints, these motors rotate (1.8 degree) by each pulse they get, these motors characterized with a good accuracy, the value of rotation will surely taken in consideration to determine the robot accuracy, the load torque for each motor is (4.4 Kg.cm). According to the Design Issue, the four arms have (5 DOF) by each; rotational for the first joint, rotational for the second joint around the first joint axis and the additional (3 DOF) earned by using Ball and Sockets Joints. The ball and socket joints play an important effective role in giving the flexibility in robot motion. For the purpose of the four leader joints calibration, four micro switches are used with suitable mechanism for them. According to the Actuator Head, it’s, for example, a gripper with three jaws. The gripper works pneumatically using compressed air and directed using 4/2 single solenoid valve. The robot is provided by a vision system for monitoring targets by installing an industrial camera can mono color photos or full colored ones with resolution of (656×490 pixels). Return to the Robot Work Space, I set the full kinematic diagram by studying all possible odds which the four leader joints can rotate in. approximately, I increased the value that each stepper motor can rotate by each pulse by five times for decreasing the time needed to conclude the work space purpose. As a result I reached to the diagram shows all possible odds for the actuator head location (the green lines). And by taking in mind that the limiting value for each stepper motor rotation is (55 degrees) up toward and (75 degrees) low toward, the number of these odds is (523). By connecting between the limiting green line centers we can find the work space which represented by the closed red curve. This red curve is somehow like the armor, and thus, I named this robot “ARMO”. It’s worth mentioning that this diagram express the motion for two arms in the same plane. Consequently, there is another diagram will be perpendicular to this diagram regarding the other two arms. So, the robot work space is changed from being “Armor” plan to vacuity one. From the work space we can fetch up the dimensions of this space which located under the robot body in a specific distance. The actuator head can move in vertical direction by (35 cm) as a maximum value, and can draw a circle with (55 cm) diameter as maximum value according to the actuator head location. |
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