The document discusses several measures of a robot's precision of movement: 1. Spatial resolution refers to the smallest increment of movement the robot can make and depends on control resolution and mechanical inaccuracies like elastic deflection. 2. Accuracy refers to the robot's ability to position its wrist at a desired target point within its work volume and is one-half the spatial resolution. 3. Repeatability refers to the robot's ability to return to a previously taught point in space when commanded.

1. P.VETRIVEL
EST-IND

2.  Precision of the robot’s movement is another
measure of performance.
1. Spatial resolution
2. Accuracy
3. Repeatability
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3.  Smallest increment of movement into which the robot
can divide its work volume.
Spatial resolution depends on two factors
1. Control resolution
2. Mechanical inaccuracies
Number of Increments=2n
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4. 1. Control resolution
 Total motion range divided by the number of
increments.
 To obtain the Control resolution of entire
robot, component resolutions for each joint would
have to be summed vectorically.
 The total control resolution would depend on the
wrist motions as well as the arm and body moitons.
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5. 2. Mechanical inaccuracies
 Mechanical inaccuracies in the robot’s links and joint
components and its feedback measurement system
constitute the other factor that contributes to spatial
resolution.
1. Elastic deflection in structural members
2. Gear backlash
3. Stretching of pulley cords
4. Leakage of hydraulic fluids
5. Load handled
6. Speed of arm movement
7. Maintenance
Spatial resolution can be improved by increasing the bit
capacity of control memory. 2013 4/5/2013 6:08:32 AM
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6.  Robot’s ability to position its wrist end at a desired
target point within the work volume.
 Robot’s accuracy to be one-half of its spatial resolution
 Accuracy varies with work volume, worse when target
in outer range of its work volume and better when
closer to the base.
 Accuracy is improved if the motion cycle is restricted
to a limited work range
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8.  Robot’s ability to position its wrist or an end effector
attached to its wrist at a point in space that had
previously been taught to the robot.
 Repeatability refers to the robot’s ability to return to
the programmed point when commanded to do so.
 In three dimensional space, Repeatability of
manipulator is the radius of the idealized sphere.
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