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| What types of joints are there? |
| Prismatic Joint |
| Revolute Joint |
| Screw Joint |
| Joint Motion Examples |
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| What types of joints are there? |
| To properly understand the motions of robotic systems, mathematicians and engineers had to develop a new system of kinematics. For this new system of kinematics, they had to develop ideal joints that served as the focal points for relative motion between links. Three distinct types of joints are necessary: prismatic (linear motion), revolute (rotational motion), and screw (linear and rotational).
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| Prismatic Joint |
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Prismatic joints, often called sliders, constitute purely linear motion along the joint axis. As shown in the first animation to the left, the joint slides in one of two directions along a singular axis. This type of motion can most often be visualized a link getting longer or shorter through the motion of the prismatic joint. This type of motion is common in hydraulic or pneumatic cylinders.
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| Revolute Joint |
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Revolute joints constitute purely rotational motion along the joint axis. Revolute joints are the most commonly found joint in industrial and research robots.
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| Screw Joint |
| Screw joints are really just a combination of the first two types of joints. They constitute a simultaneous rotation and linear motion along a joint axis. Some mathematicians claim that this is the only joint necessary to understand the kinematics of robots. True screw joints have very few applications. Screws are more often used in tools for a robot end effector rather than a joint of motion for a robot.
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The robot above uses purely revolute joints to impart motion. The red lines denote the interfaces between rotating parts.
This motion may be hard to imagine. To better visualize you may wish to see how this robot moves.
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| Joint Motion Examples |
Joint Motion Example
World Motion Example |
Individually the different joints are very simple. Their motions are easy to understand and visualize. In the Joint Motion Example on the left a prismatic and revolute joint are used to move a simple robot end effector.
Only one joint moves at a time so that you can easily see the individual movements provided by the prismatic joint (linear motion of the yellow member along the red member) and the revolute joint (rotational motion of the red member about the base).
These two simple joints can create much more complex motions when they work in concert, as shown in the World Motion Example on the left.
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