Term - Four-Bar Linkage
From VEX Wiki
A Four-Bar linkage or simply a four-bar, is a simple movable linkage. It consists of four rigid bodies (called bars or links), each attached to two others by single joints or pivots to form a closed loop. Four-bars are simple mechanisms common in mechanical engineering machine design and fall under the study of kinematics.
An example of a four-bar linkage in which opposing links are parallel and of equal length is shown here:
In the above example of a four-bar linkage, the link on the left side is the fixed link. This fixed link is typically attached to the robot structure. One of the diagonal links is the driven link. The output link is the link at the far right. Some sort of object manipulator is mounted on the output link. When the linkage travels through its motion, the output link remains parallel to the fixed link as shown.
This type of motion is useful for any application in which you want the object manipulator to stay in the same orientation as the robot arm moves.
By modifying the lengths of the links in the four-bar linkage, it is possible to create very different motions. This is extremely useful for robot design. Imagine needing a robot that can pick up a cup of water, lift it up without spilling, and then pour it out once it reaches over the height of a bucket. This motion is possible by using a modified four-bar linkage.
Try playing with linkage lengths and experiment to find the optimal motion for your application.
