Frames: Difference between revisions
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Frames are what allow us to use mathematical expressions to define motion and positions in the real world. They utilize the two main coordinate systems, Cartesian and Joint to define a position, configuration, or orientation as numbers.▼
[[File:55e490a8e9af5b3c4f3fe220 Fanuc robot white.jpg|thumb|500x500px]]▼
▲Frames are what allow us to use mathematical expressions to define motion and positions in the real world. They utilize the two main coordinate systems, Cartesian and Joint.
== Coordinate Systems ==
[[File:Joint Coordinate System.png|thumb|Joint Coordinate System - Each joint has a value based on degrees from a designated zero position.]]Coordinate systems are the methods we use to measure positions and orientations of physical objects. The robot doesn't know anything about the real world or what is in it, as it's driven by a processor that can only work with numbers.
We live in a 3 dimensional universe, meaning a position in space can be referenced by 3 values, each a measurement from an origin point. The robot is a series of joints, so it can reference positions related to the angle of each joint, and the distance between each of the joints, using trigonometry.
'''Examples:'''
You have a quarter on a table. It is 10mm from the front edge of the table, 14.5mm from the left edge of the table, and is 1.75mm high. This means we can express the location we'd need to reach to pick it up in X,Y,Z format as (10, 14.5, 1.75). This is the WORLD frame. We are referencing it's position relative to a point we've chosen in the real world.
However, the human body (specifically your brain) does not operate in a WORLD frame. Your arm is a series of joints that must work together to reach positions, even if we fully understand and measure that position with a ruler. For example, for you to reach that quarter your brain will tell your elbow to extend to 78°, your shoulder to 93.75° and your wrist to turn to 12°. This would be expressed in a JOINT reference system as (78, 93.75, 12).
If you give someone a map that told them the location of something in degrees, they would have no idea what you were talking about. The human brain likes systems that reference things in the real world instead. Thankfully, industrial robots always include a variation on the WORLD reference system.
=== Joint Coordinate System ===
▲[[File:55e490a8e9af5b3c4f3fe220 Fanuc robot white.jpg|thumb|500x500px]]
The joint coordinate system is the simplest from the point of design and control. Each joint has a specific range of motion it is capable of, expressed in degrees. A joint coordinate is simply a list of each joint's angular position.
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