1. ROBOTICS (VII Semester, B.Tech. Mechatronics)
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ROBOTICS (VII Semester, B.Tech. Mechatronics)
Prepared By:
Nehul J. Thakkar
Asst. Professor
U.V.Patel College of Engineering
Ganpat University
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2. Chapter 2: Fundamentals of Robot Technology
Robot Anatomy
Robot Motions
Work Volume
Degree of Freedom (DOF)
Robot Drive Systems
Speed of Motions
Load-carrying Capacity
Control Systems
Dynamic Performance
Compliance
End Effectors
Sensors
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3. Robot Anatomy
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The physical construction of the body, arm and wrist of the machine
The wrist is oriented in a variety of positions
Relative movements between various components of body, arm and wrist are provided by a series of joints
Joints provide either sliding or rotating motions
The assembly of body, arm and wrist is called “Manipulator”
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4. Robot Anatomy..
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Attached to the robot’s wrist is a hand which is called “end effector”
The body and arm joints position the end effector and wrist joints orient the end effector
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5. Robot Anatomy.. Robot Configurations
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Robot Configurations
Variety of sizes, shapes and physical configuration
Cartesian Coordinates Configuration
Cylindrical Configuration
Polar or Spherical Configuration
Articulated or Jointed-arm Configuration
Selective Compliance Assembly Robot Arm (SCARA) Configuration
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6. Robot Anatomy.. Cartesian Coordinate Configuration
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Cartesian Coordinate Configuration
Uses three perpendicular slides to construct x , y and z axes
X-axis represents right and left motions, Y- axis represents forward-backward motions and Z-axis represents up-down motions
Kinematic designation is PPP/LLL
Other names are xyz robot or Rectilinear robot or Gantry robot
Operate within a rectangular work volume
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7. Robot Anatomy.. Cartesian Coordinate Configuration.. 25 April 2017
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8. Robot Anatomy.. Cartesian Coordinate Configuration.. Advantages
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Cartesian Coordinate Configuration..
Advantages
Linear motion in three dimension
Simple kinematic model
Rigid structure
Higher repeatability and accuracy
High lift-carrying capacity as it doesn’t vary at different locations in work volume
Easily visualize
Can increase work volume easily
Inexpensive pneumatic drive can be used for P&P operation
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9. Robot Anatomy.. Cartesian Coordinate Configuration.. Disadvantages
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Cartesian Coordinate Configuration..
Disadvantages
requires a large volume to operate in
work space is smaller than robot volume
unable to reach areas under objects
must be covered from dust
Applications
Assembly
Palletizing and loading-unloading machine tools,
Handling
Welding
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10. Robot Anatomy.. Cylindrical Configuration
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Cylindrical Configuration
Use vertical column which rotates and a slide that can be moved up or down along the column
Arm is attached to slide which can be moved in and out
Kinematic designation is RPP
Operate within a cylinder work volume
Work volume may be restricted at the back side
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11. Robot Anatomy.. Cylindrical Configuration.. 25 April 201711
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12. Robot Anatomy.. Cylindrical Configuration.. Advantages Disadvantages
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Cylindrical Configuration..
Advantages
Simple kinematic model
Rigid structure & high lift-carrying capacity
Easily visualize
Very powerful when hydraulic drives used
Disadvantages
Restricted work space
Lower repeatability and accuracy
Require more sophisticated control
Applications
Palletizing, Loading and unloading
Material transfer, foundry and forging
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13. Robot Anatomy.. Polar or Spherical Configuration
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Polar or Spherical Configuration
Earliest machine configuration
Has one linear motion and two rotary motions
First motion is a base rotation, Second motion correspond to an elbow rotation and Third motion is radial or in-out motion
Kinematic designation is RRP
Capability to move its arm within a spherical space, hence known as ‘Spherical’ robot
Elbow rotation and arm reach limit the design of full spherical motion
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14. Robot Anatomy.. Polar or Spherical Configuration.. 25 April 201714
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15. Robot Anatomy.. Polar or Spherical Configuration.. Advantages
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Polar or Spherical Configuration..
Advantages
Covers a large volume
Can bend down to pick objects up off the floor
Higher reach ability
Disadvantages
Complex kinematic model
Difficult to visualize
Applications
Palletizing
Handling of heavy loads e.g. casting, forging
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16. Robot Anatomy.. Jointed Arm Configuration Similar to human arm
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Jointed Arm Configuration
Similar to human arm
Consists of two straight components like human forearm and upper arm, mounted o a vertical pedestal
Components are connected by two rotary joints corresponding to the shoulder and elbow
Kinematic designation is RRR
Work volume is spherical
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17. Robot Anatomy.. Jointed Arm Configuration.. 25 April 2017
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18. Robot Anatomy.. Jointed Arm Configuration.. 25 April 201718
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19. Robot Anatomy.. Jointed Arm Configuration.. Advantages Disadvantages
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Jointed Arm Configuration..
Advantages
Maximum flexibility
Cover large space relative to work volume objects up off the floor
Suits electric motors
Higher reach ability
Disadvantages
Complex kinematic model
Difficult to visualize
Structure not rigid at full reach
Applications
Spot welding, Arc welding
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20. Robot Anatomy.. SCARA Configuration Most common in assembly robot
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SCARA Configuration
Most common in assembly robot
Arm consists of two horizontal revolute joints at the waist and elbow and a final prismatic joint
Can reach at any point within horizontal planar defined by two concentric circles
Kinematic designation is RRP
Work volume is cylindrical in nature
Most assembly operations involve building up assembly by placing parts on top of a partially complete assembly
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21. Robot Anatomy.. SCARA Configuration.. 25 April 2017 25 April 2017 21
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23. Robot Anatomy.. SCARA Configuration.. Advantages Disadvantages
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SCARA Configuration..
Advantages
Floor area is small compare to work area
Compliance
Disadvantages
Rectilinear motion requires complex control of the revolute joints
Applications
Assembly operations
Inspection and measurements
Transfer or components
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24. Robot Motions Industrial robots perform productive work
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Industrial robots perform productive work
To move body, arm and wrist through a series of motions and positions
End effector is used to perform a specific task
Robot’s movements divided into two categories:
Arm and body motions
Wrist motions
Individual joint motions referred as ‘ DOF ’
Motions are accomplished by powered joints
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25. Robot Motions..
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Three joints are associated with the action of arm and body
Two or three used to actuate the wrist
Rigid members are used to connect manipulator joints are called links
Input link is closest to the base
Output link moves with respect to the input link
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26. Robot Motions..
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Joints involve relative motions of the adjoining links that may be linear or rotational
Linear joints involve a sliding or translational motion which can be achieved by piston, telescopic mechanism
May be called ‘Prismatic’ joint
Represented as L or P joint
Three types of rotating motion:
Rotational (R)
Twisting (T)
Revolving (V)
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27. Robot Motions..
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28. Robot Motions..
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Physical configuration of the robot can be described by a joint notation scheme
Considering the arm and body first
Starting with the joint closest to the base till the joint connected to the wrist
Examples are LLL, TLL, TRL, TRR, VVR
Wrist joints can be included for notation
From joint closest to the arm to the mounting plate for the end effector have either T or R type
Examples are TRL : TRT, TRR : RT
The scheme also provide that robot move on a track or fixed to a platform
Example TRL : TRT, L-TRL : TRT
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29. Robot Motions..
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30. Robot Motions..
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31. Robot Motions..
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32. Robot Work Volume
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The space within which the robot can manipulate its wrist end
different end effector might be attached to wrist but not counted as part of the robot’s work space
Long end effector add to the extension of the robot compared to smaller end effector
End effector may not be capable of reaching certain points within the robot’s normal work volume
Larger volume costs more but can increase capabilities of robot
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33. Robot Work Volume..
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It depends upon following physical characteristics:
Robot’s configuration
Size of the body, arm and wrist components
Limits of the robot’s joint movements
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34. Robot Work Volume..
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35. Robot Work Volume..
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36. Degree of Freedom (DOF)
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Rotate Base of Arm Pivot Base of Arm Bend Elbow Wrist Up and Down Wrist Left and Right Rotate Wrist
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37. Degree of Freedom..
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It is a joint , a place where it can bend or rotate or translate
Can identify by the number of actuators on the arm
Few DOF allowed for an application because each degree requires motor, complicated algorithm and cost
Each configurations discussed before utilizes three DOF in the arm and the body
Three DOF located in the wrist give the end effector all the flexibility
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38. Degree of Freedom..
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A total 6 DOF is needed to locate a robot’s hand at any point in its work space
The arm and body joints move end effector to a desired position within the limits of robot’s size and joint movements
Polar, cylindrical and jointed arm configuration consist 3 DOF with the arm and body motions are:
Rotational traverse: Rotation of the arm about vertical axis such as left-and-right swivel of the robot arm about a base
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39. Degree of Freedom..
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Radial traverse: Involve the extension and retraction (in or out movement) of the arm relative to the base
Vertical traverse: Provide up-and-down motion of the arm
For a Cartesian coordinate robot, 3 DOF are vertical movement (z-axis motion), in-and-out movement (y- axis motion), and right-and-left movement (x-axis motion) which are achieved by slides of the robot arm
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40. Degree of Freedom..
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41. Degree of Freedom..
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Wrist movement enable the robot to orient the end effector properly to perform a task
Provided with up to 3 DOF which are:
Wrist Pitch/Bend: Provide up-and-down rotation to the wrist
Wrist Yaw: Involve right-and-left rotation of the wrist
Wrist Roll/Swivel: Is the rotation of the wrist about the arm axis
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42. Degree of Freedom..
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43. Degree of Freedom..
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44. Drive Systems Capacity to move robot’s body, arm and wrist
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Capacity to move robot’s body, arm and wrist
Determine speed of the arm movements, strength of the robot & dynamic performance
Type of applications that the robot can accomplish
Powered by three types of drive systems:
Hydraulic
Pneumatic
Electric
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45. Drive Systems..
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46. Drive Systems.. Hydraulic Drive Associated with large robot
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Hydraulic Drive
Associated with large robot
Provide greater speed & strength
Add floor space
Leakage of oil
Provide either rotational or linear motions
Applications such as:
Spray coating robot
Heavy part loading robot
Material handling robot
Translatory motions in cartesian robot
Gripper mechanism
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47. Drive Systems.. Hydraulic Drive.. 25 April 2017 25 April 2017 47 Cont.

48. Drive Systems.. Hydraulic Drive.. 25 April 2017 25 April 2017 48 Cont.

49. Drive Systems.. Pneumatic Drive Reserved for smaller robot
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Pneumatic Drive
Reserved for smaller robot
Limited to “pick-and-place” operations with fast cycles
Drift under load as air is compressible
Provide either rotational or linear motions
Simple and low cost components
Used to open and close gripper
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50. Drive Systems..
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51. Drive Systems.. Electric Drive
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Electric Drive
Rotor, stator, brush and commutator assembly
Rotor has got windings of armature and stator has got magnets
The brush and the commutator assembly switch the current in armature windings
The most commonly used are DC servomotors, AC servomotors and stepper motors
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52. Drive Systems.. Electric Drive.. Servomotor 25 April 201752
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55. Speed of Motion
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Speed determines how quickly the robot can accomplish a given work cycle
Desirable in production to minimize cycle time
Industrial robot speed range up to a maximum of 1.7 m/s
Speed would be measured at wrist
Highest speed can be obtained by large robot with fully extended arm
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56. Speed of Motion.. Most desirable speed depends on factors:
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Most desirable speed depends on factors:
Accuracy
Weight of the object
Distance
Inverse relation between the accuracy and the speed
Heavier objects must be handled more slowly
Capable of traveling one long distance in less time than a sequence short distances whose sum is equal to the long distance
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57. Speed of Motion..
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Short distance may not permit for programmed operating speed
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58. Load-Carrying Capacity
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It depends upon size, configuration, construction and drive system
Robot arm must be in its weakest position to calculate load-carrying capacity
In polar, cylindrical and jointed-arm, the robot arm is at maximum extension
Ranges from less than a pond to several thousand pounds
Gross weight include the weight of the end effector
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59. Control Systems
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Controlling drive system to properly regulate its motions
Four categories according to control systems
Limited-sequence robot
Playback robots with PTP control
Playback robots with continuous path control
Intelligent robot
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60. Speed of Response & Stability
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The speed of response refers to the capability of the robot to move to the next position in a short amount of time
Stability is defined as a measure of the oscillations which occur in the arm during movement from one position to the next
Good stability exhibit little or no oscillation and poor stability indicated by a large amount of stability
Damping control stability but reduces the speed of response
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61. Speed of Response & Stability..
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62. Spatial Resolution
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63. Spatial Resolution..
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Defined as smallest increment of movement into which the robot can divide its work volume
Depends on two factors: system’s control resolution and the robot’s mechanical inaccuracies
Control resolution is determined by robot’s position control system and its feedback measurement system
Ability to divide total range of movement for the particular joint into individual increments that can be addressed in the controller
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64. Spatial Resolution..
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Joint range depends on the bit storage capacity in the control memory
Number of increments for a axis is given by
Number of Increments = 2n
Have a control resolution for each joint in case of several DOF
Resolution for each joint to be summed vectorially
Total control resolution depend on the wrist motions as well as the body and arm motions
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65. Spatial Resolution..
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Mechanical inaccuracies come from elastic deflection in the structure elements, gear backlash, stretching of pulley cords, leakage of hydraulic fluids and other imperfections in the mechanical system
Also affected by load being handled, the speed of arm moving, condition of maintenance of robot
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66. Accuracy
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Ability to position its wrist end at a desired target point within the work volume
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67. Accuracy..
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Depends on spatial resolution means how closely the robot can define the control increments
Lie in the middle between two adjacent control increments
One half of the control resolution
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68. Accuracy..
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Depends on spatial resolution means how closely the robot can define the control increments
Lie in the middle between two adjacent control increments
One half of the control resolution
Same anywhere in work volume
It may be changed in work volume due to mechanical inaccuracies
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69. Accuracy.. Affected by many factors Mechanical inaccuracies Work range
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Affected by many factors
Mechanical inaccuracies
Work range
Weight
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70. Repeatability
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Ability to position its wrist at a point in space that had been taught
Accuracy relates to its capacity to be programmed to achieve a given target point
Programmed point and target point may be different due to limitations of resolution
Repeatability refers to ability to return to the programmed point when commanded to do so
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71. Repeatability..
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72. Compliance
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Displacement of the wrist end in response to a force or a torque exerted against it
High compliance means that wrist is displaced a large amount by small force known as ‘Springy’
Reduce the robot precision of movement under load
Directional feature
Reaction force of the part may cause deflection to the manipulator
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73. Thank You
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