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A Review on SCARA Robotic Arm Supervisor: Dr. Rahbari Asr Presented By: Farid, Alidoust 1 Mojtaba, Alizadeh 2 info@alidoost.ir 1- info@alidoost.ir m.alizadeeh@gmail.com 2- m.alizadeeh@gmail.com Mechatronic Department Islamic Azad University, Tabriz Branch

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Topics Introduction Kinematic of Operation Applications Manipulators (End Effectors) Top Brands Conclusion References

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Introduction

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Why Industrial Robotic Arms ? A general-purpose, programmable machine possessing certain anthropomorphic characteristics Used in: Hazardous work environments Repetitive work cycle Consistency and accuracy needed! Difficult handling task for humans Multi-shift operations for industries Reprogrammable, flexible Interfaced to other computer systems

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Introduction In 1981, Sankyo Seiki, Pentel and NEC presented a completely new concept for assembly robots. The robot was developed under the guidance of Hiroshi Makino, a professor at the University of Yamanashi. Its arm was rigid in the Z-axis and pliable in the XY-axes, which allowed it to adapt to holes in the XY-axes.

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Introduction Notation VRO. SCARA stands for Selectively Compliant Assembly Robot Arm. Similar to jointed-arm robot except that vertical axes are used for shoulder and elbow joints to be compliant in horizontal direction for vertical insertion tasks.

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The Scara Properties Developed to meet the needs of modern assembly. Fast movement with light payloads Rapid placements of electronic components on PCB’s Combination of two horizontal rotational axes and one linear joint.

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Kinematic of Operation

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Denavit–Hartenberg co-ordinates Jaques Denavit and Richard S. Hartenberg presented the first minimal representation for a line which is now widely used. Engineers use the Denavit–Hartenberg convention (D–H) to help them describe the positions of links and joints unambiguously.

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Denavit–Hartenberg Line co-ordinates Every link gets its own coordinate system. There are a few rules to consider in choosing the coordinate system: 1.the z-axis is in the direction of the joint axis 2.the x-axis is parallel to the common normal: If there is no unique common normal (parallel z axes), then d (below) is a free parameter. 3.the y-axis follows from the x- and z-axis by choosing it to be a right-handed coordinate system.

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Denavit–Hartenberg Line co-ordinates Once the coordinate frames are determined, inter- link transformations are uniquely described by the following four parameters: : angle about previous z, from old x to new x : offset along previous z to the common normal : length of the common normal (aka a, but if using this notation, do not confuse with α). Assuming a revolute joint, this is the radius about previous z. : angle about common normal, from old z axis to new z axis

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Use the DH Algorithm to assign the frames and kinematic parameters SCARA – Forward Kinematics

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Number the joints 1 to n starting with the base and ending with the tool yaw, pitch and roll in that order. no tool pitch or yaw Note: There is no tool pitch or yaw in this case 1 2 3 4-Tool Roll

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z0z0 y0y0 z1z1 x1x1 y1y1 z2z2 x2x2 y2y2 z3z3 x3x3 z4z4 y3y3 y4y4 x4x4 x0x0 d4d4 d3d3 a2a2 d1d1 a1a1 11 44 22 From this drawing of D-H parameters can be compiled Full DH-Algorithm presentation attached to appendix in final of presentation

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z0z0 y0y0 z1z1 x1x1 y1y1 z2z2 x2x2 y2y2 z3z3 x3x3 z4z4 y3y3 y4y4 x4x4 x0x0 d4d4 d3d3 a2a2 d1d1 a1a1 11 44 22 Joint da Home q 1 1 d 1 a 1 180º 0º 2 2 0 a2 a2 0º 3 d 3 0 0º d max 4 4 d 4 0 0º 9 0º

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Applications

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Applications Useful in Semiconductor Fabrication Industries. mostly adopted wafer handling robot in semi- conductor industry A radius layout, for wafer carriers and aligner

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Applications Useful in Soldering PCB’s

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Applications Finished product inspection, touch-panel type evaluation machine Finished product function test. Developed software evaluation. Push button type quality check. POINT: Supports a variety of systems in a product line Space saving. Using SCARA, judgment is made through image processing by pushing each button.

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Applications Pharmaceutical Industries

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Applications Part Sortation

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Applications Tall work pieces conveying and stacking machine >> Tall work pieces stacked by utilizing long Z axis. POINT: Use of SCARA can cope with the Z axis long stroke as quasi standard. Advantages of use of SCARA: speed of XY axis and space saving installation.

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Applications Assembling (such as Cosmetic Handling and Packaging)

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Applications Assembly cell (independent cell) >> Base machine of independent type assembly cell. POINT: Optimum for multi type variable quantity production. Setting up reception places forms a construction of multiple number of cells.

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Applications Assembly cell (independent cell) >>

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Applications Assembly cell (line cell) >> Base machine of line type assembly cell. POINT: Utilization of advantages of SCARA with a wide operation range. Form a line to any length by coupling these cells together.

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Applications Assembly cell (line cell) >>

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Applications Assembly cell (line cell) >>

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Manipulators

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End Effectors The special tooling for a robot that enables it to perform a specific task Two types: Grippers – to grasp and manipulate objects (e.g., parts) during work cycle Tools – to perform a process, e.g., spot welding, spray painting End Effector

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Grippers: mechanical, magnetic and pneumatic. Mechanical: Two finger most common, also multi-fingered available. Applies force that causes enough friction between object to allow for it to be lifted. Not suitable for some objects which may be delicate / brittle End Effectors

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Magnetic: Ferrous materials required Electro and permanent magnets used Pneumatic: Suction cups from plastic or rubber Smooth even surface required Weight & size of object determines size and number of cups End Effectors

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Ladle Ladling hot materials such as molten metal is a hot and hazardous job for which industrial robots are well suited. In piston casting permanent mold, die casting and related applications, the robot can be programmed to scoop up and transfer the molten metal from the pot to the mold, and then do the pouring.

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Spray gun Ability of the industrial robot to do multipass spraying with controlled velocity fits it for automated application of primers, paints, and ceramic or glass frits, as well as application of masking agents used before plating. For short or medium ‑ length production runs, the industrial robot would often be a better choice than a special purpose setup requiring a lengthy change ‑ over procedure for each different part. Also the robot can spray parts with compound curvatures and multiple surfaces.

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Tool changing A single industrial robot can also handle several tools sequentially, with an automatic tool changing operation programmed into the robot's memory. The tools can be of different types or sizes, permitting multiple operations on the same workpiece.

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Servo motors Acts as Actuator Contain motor, gearbox, driver controller and potentiometer Three wires - 0v, 5v and signal Potentiometer connected to gearbox – monitors movement Provides feedback If position is distorted - automatic correction + 5V

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Servo motors Operation Pulse Width Modulation (0.75ms to 2.25ms) Pulse Width takes servo from 0° to 180° rotation Continuous stream of Pulses, every 20ms On Control block, pulse width and output pin must be set.

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Top Brands for SCARA robots:

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Fastest SCARA robot in World

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Conclusion on SCARA Robots Advantages: - 1 linear axis, 2 rotating axes - Height axis is rigid - Large work area floor space - Can reach around obstacles - Two ways to reach a point Disadvantages: - Difficult to program off ‑ line - Highly complex arm

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References: 1. Westerland, Lars (2000). The Extended Arm of Man, A History of the Industrial Robot. ISBN 91-7736-467-8. 2. “Ivax SCARA Robot”, “Feedback Instruments Ltd”, 2001, Crow borough, England. 3. “SCARA – Forward Kinematics”, Richard Kavanagh,UCC,2004 4. Nof, Shimon Y. (editor) (1999). Handbook of Industrial Robotics, 2nd ed. John Wiley & Sons. 1378 pp. ISBN 0-471-17783-0. 5. ISO Standard 8373:1994, Manipulating Industrial Robots

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Any Questions ?!

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Thank for Audience

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Appendix Full DH Algorithm Represent

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Assign a right-handed orthonormal frame L 0 to the robot base, making sure that z 0 aligns with the axis of joint. Set k=1 z0z0 x0x0 y0y0 k=0

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z0z0 x0x0 y0y0 z1z1 22 Align z k with the axis of joint k+1. Locate the origin of L k at the intersection of the z k and z k-1 axes If they do not intersect use the the intersection of z k with a common normal between z k and z k-1.(can point up or down in this case) Common Normal k=1

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z0z0 x0x0 y0y0 z1z1 Select x k to be orthogonal to both z k and z k-1. If z k and z k-1 are parallel, point x k away from z k-1. Select y k to form a right handed orthonormal co-ordinate frame L k x1x1 y1y1 k=1

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z0z0 y0y0 z1z1 x1x1 y1y1 Align z k with the axis of joint k+1. Vertical Extension Again z k and z k-1 are parallel the so we use the intersection of z k with a common normal. Common Normal z2z2 x0x0 k=2

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z0z0 y0y0 z1z1 x1x1 y1y1 z2z2 Select x k to be orthogonal to both z k and z k-1. Once again z k and z k-1 are parallel, point x k away from z k-1. x2x2 y2y2 Select y k to complete the right handed orthonormal co-ordinate frame x0x0 k=2

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z0z0 y0y0 z1z1 x1x1 y1y1 z2z2 x2x2 y2y2 Align z k with the axis of joint k+1. 44 Locate the origin of L k at the intersection of the z k and z k-1 axes z3z3 x0x0 k=3

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z0z0 y0y0 z1z1 x1x1 y1y1 z2z2 x2x2 y2y2 z3z3 Select x k to be orthogonal to both z k and z k-1. Again x k can point in either direction. It is chosen to point in the same direction as x k-1 x3x3 Select y k to complete the right handed orthonormal co-ordinate frame y3y3 x0x0 k=3

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z0z0 y0y0 z1z1 x1x1 y1y1 z2z2 x2x2 y2y2 z3z3 x3x3 Set the origin of L n at the tool tip. Align z n with the approach vector of the tool. z4z4 Align y n with the sliding vector of the tool. y3y3 y4y4 Align x n with the normal vector of the tool. x4x4 x0x0 k=4

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z0z0 y0y0 z1z1 x1x1 y1y1 z2z2 x2x2 y2y2 z3z3 x3x3 z4z4 y3y3 y4y4 x4x4 x0x0 With the frames assigned the kinematic parameters can be determined.

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z0z0 y0y0 z1z1 x1x1 y1y1 z2z2 x2x2 y2y2 z3z3 x3x3 z4z4 y3y3 y4y4 x4x4 x0x0 Locate point b k at the intersection of the x k and z k-1 axes. If they do not intersect, use the intersection of x k with a common normal between x k and z k-1 b4b4 k=4

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z0z0 y0y0 z1z1 x1x1 y1y1 z2z2 x2x2 y2y2 z3z3 x3x3 z4z4 y3y3 y4y4 x4x4 x0x0 Compute k as the angle of rotation from x k-1 to x k measured about z k-1 It can be seen here that the angle of rotation from x k-1 to x k about z k-1 is 90 degrees (clockwise +ve) i.e. 4 = 90º But this is only for the soft home position, 4 is the joint variable. 44 k=4

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z0z0 y0y0 z1z1 x1x1 y1y1 z2z2 x2x2 y2y2 z3z3 x3x3 z4z4 y3y3 y4y4 x4x4 x0x0 Compute d k as the distance from the origin of frame L k-1 to point b k along z k-1 b4b4 d4d4 Compute a k as the distance from point b k to the origin of frame L k along x k In this case these are the same point therefore a 4 =0 44 k=1

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z0z0 y0y0 z1z1 x1x1 y1y1 z2z2 x2x2 y2y2 z3z3 x3x3 z4z4 y3y3 y4y4 x4x4 x0x0 b4b4 d4d4 Compute k as the angle of rotation from z k-1 to z k measured about x k It can be seen here that the angle of rotation from z 3 to z 4 about x 4 is zero i.e. 4 = 0º 44 k=4

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z0z0 y0y0 z1z1 x1x1 y1y1 z2z2 x2x2 y2y2 z3z3 x3x3 z4z4 y3y3 y4y4 x4x4 x0x0 b3b3 d4d4 Locate point b k at the intersection of the x k and z k-1 axes. If they do not intersect, use the intersection of x k with a common normal between x k and z k-1 44 k=3

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z0z0 y0y0 z1z1 x1x1 y1y1 z2z2 x2x2 y2y2 z3z3 x3x3 z4z4 y3y3 y4y4 x4x4 x0x0 b3b3 d4d4 Compute k as the angle of rotation from x k-1 to x k measured about z k-1 It can be seen here that the angle of rotation from x k-1 to x k about z k-1 is zero i.e. 3 = 0º 44 k=3

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z0z0 y0y0 z1z1 x1x1 y1y1 z2z2 x2x2 y2y2 z3z3 x3x3 z4z4 y3y3 y4y4 x4x4 x0x0 b3b3 d4d4 Compute d k as the distance from the origin of frame L k-1 to point b k along z k-1 Compute a k as the distance from point b k to the origin of frame L k along x k In this case these are the same point, therefore a k =0 d3d3 Since joint 3 is prismatic d 3 is the joint variable 44 k=3

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z0z0 y0y0 z1z1 x1x1 y1y1 z2z2 x2x2 y2y2 z3z3 x3x3 z4z4 y3y3 y4y4 x4x4 x0x0 b3b3 d4d4 d3d3 Compute k as the angle of rotation from z k-1 to z k measured about x k It can be seen here that the angle of rotation from z 2 to z 3 about x 3 is zero i.e. 3 = 0º 44 k=3

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z0z0 y0y0 z1z1 x1x1 y1y1 z2z2 x2x2 y2y2 z3z3 x3x3 z4z4 y3y3 y4y4 x4x4 x0x0 b2b2 d4d4 d3d3 Once again locate point b k at the intersection of the x k and z k-1 axes If they did not intersect we would use the intersection of x k with a common normal between x k and z k-1 44 k=2

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z0z0 y0y0 z1z1 x1x1 y1y1 z2z2 x2x2 y2y2 z3z3 x3x3 z4z4 y3y3 y4y4 x4x4 x0x0 b2b2 d4d4 d3d3 Compute k as the angle of rotation from x k-1 to x k measured about z k-1 It can be seen here that the angle of rotation from x 1 to x 2 about z 1 is zero i.e. 2 = 0º But this is only for the soft home position, 4 is the joint variable. 44 22 k=2

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z0z0 y0y0 z1z1 x1x1 y1y1 z2z2 x2x2 y2y2 z3z3 x3x3 z4z4 y3y3 y4y4 x4x4 x0x0 b2b2 d4d4 d3d3 Compute d k as the distance from the origin of frame L k-1 to point b k along z k-1 In this case these are the same point therefore d 2 =0 Compute a k as the distance from point b k to the origin of frame L k along x k a2a2 44 22 k=2

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z0z0 y0y0 z1z1 x1x1 y1y1 z2z2 x2x2 y2y2 z3z3 x3x3 z4z4 y3y3 y4y4 x4x4 x0x0 b2b2 d4d4 d3d3 a2a2 Compute k as the angle of rotation from z k-1 to z k measured about x k It can be seen here that the angle of rotation from z 1 to z 2 about x 2 is zero i.e. 2 = 0º 44 22 k=2

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z0z0 y0y0 z1z1 x1x1 y1y1 z2z2 x2x2 y2y2 z3z3 x3x3 z4z4 y3y3 y4y4 x4x4 x0x0 b1b1 d4d4 d3d3 a2a2 For the final time locate point b k at the intersection of the x k and z k-1 axes 44 22 k=1

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z0z0 y0y0 z1z1 x1x1 y1y1 z2z2 x2x2 y2y2 z3z3 x3x3 z4z4 y3y3 y4y4 x4x4 x0x0 bkbk d4d4 d3d3 a2a2 Compute k as the angle of rotation from x k-1 to x k measured about z k-1 It can be seen here that the angle of rotation from x 0 to x 1 about z 0 is zero i.e. 1 = 0º But this is only for the soft home position, 1 is the joint variable. 11 44 22 k=1

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z0z0 y0y0 z1z1 x1x1 y1y1 z2z2 x2x2 y2y2 z3z3 x3x3 z4z4 y3y3 y4y4 x4x4 x0x0 b1b1 d4d4 d3d3 a2a2 Compute d k as the distance from the origin of frame L k-1 to point b k along z k-1 Compute a k as the distance from point b k to the origin of frame L k along x k d1d1 a1a1 11 44 22 k=1

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z0z0 y0y0 z1z1 x1x1 y1y1 z2z2 x2x2 y2y2 z3z3 x3x3 z4z4 y3y3 y4y4 x4x4 x0x0 b1b1 d4d4 d3d3 a2a2 d1d1 a1a1 Compute k as the angle of rotation from z k-1 to z k measured about x k-1 It can be seen here that the angle of rotation from z 0 to z 1 about x 1 is 180 degrees 11 44 22 k=1

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