To comprehend robot calibration, view this presentation. For additional information, go to the official website of Dynalog, Inc.

1. A B R I E F E X P L A N A T I O N
O F R O B O T
C A L I B R A T I O N
D Y N A L O G , I N C

2. Robots have historically been taught
manually, i.e. using the robot’s ‘teach
pendant’ to manually drive the robot’s
TCP to the desired point along the part
to be operated on, while visually
verifying – as much as feasible – the
achieved accuracy.
This is obviously a time-consuming
process, to be painstakingly repeated
for each (relevant) point along the
robot’s path in space; furthermore, this
process clearly doesn’t provide a high
level of positional accuracy.

3. Robot Simulation software,
commercialized nowadays by various
companies, offers the ability to model
an entire robot-cell on computer prior
to dealing with it on the actual plant
floor: a desired robot model is chosen,
the end-effector and the fixture can be
modeled, the part can be imported from
some other CAD software – all that
allowing the final robot program (with all
required speeds and including any other
desired commands) to be entirely
created upfront through Simulation.
The created robot program is – theoretically – ready to be executed on the actual robot: this process is referred to as Off-Line
Programming (OLP). More specifically, ‘Downloading’ is the process of transferring robot programs created through Simulation
software in a ‘nominal’ environment, to the ‘actual’ robot-cell on the plant floor;

4. In reality, the differences between the ‘nominal’
world in Simulation and the ‘actual’ environment on
the plant floor prevent from directly executing on
the robot controller a robot program created
through Simulation: each robot unit is built with
certain manufacturing tolerances; the end-effector
and its TCP deviate from their design intent; the
fixture holding the part is not located relative to the
robot coordinate frame as desired; etc. As a result,
the robot programs downloaded from Simulation
will not follow the intended path on the plant floor.
This doesn’t just affect the positioning of the
robot’s TCP, but it can also cause collisions
between the robot and other peripherals within the
robot-cell.

5. A robot program generated through Off-Line Programming is accurate enough if the resulting positioning accuracy of
the robot’s TCP is within the acceptable limits for the intended application. For example, Off-Line Programming
resulting in good enough robot programs for a paint job might not be so for an engine component assembly
application. To maximize the success of Off-Line Programming (minimum manual robot program touchup and collision
avoidance), it is generally imperative to perform ‘Robot-Cell Calibration’, and to correct accordingly (i.e. ‘Filter’) the
robot programs to be downloaded.

6. A robot is generally capable of repeating the
same move towards a specific point in space,
over and over, within a high level of tolerance
(referred to as ‘unidirectional Repeatability’),
generally well below 0.1mm. But this does not
mean that that particular point in space is well
known relative some global coordinate frame
(such as the robot base frame):
The level of ‘Absolute Accuracy’ achieved by an
‘off-the-shelf’ industrial robot is generally in the
several millimeters and more. This is generally
due to manufacturing tolerances for every robot
unit, incorrect joint zero-mastering, mechanical
flexibility, gear backlash, etc.

7. THANK YOU