Robotic joints

It is obvious that in order to achieve different degrees of freedom, different robotic joints are needed. Unlike human joints where we saw 3 degrees of freedom in the shoulder, the joints in a robot are normally restricted to 1 degree of freedom, to simplify the mechanics and control of the manipulator. There are two types of joints commonly found in robots: rotary joints and prismatic joints.

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The top two linkages in the diagram above are generally used as a waist joint. An example of a waist joint can be seen in the Crust Crawler robot, it is the joint that pivots the entire robot. The Blue section is fixed and the green rotates about it.

The bottom linkages are examples of elbow joints. In the case of the four joints they are only capable of one degree of rotation, the joint variable is the angle that the joint move to. Most rotary joints cannot rotate through 360° degrees as they are mechanically restrained by the arm construction and the servo motor.

Linear Joints

https://i.imgur.com/4nanump.png

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A prismatic joint is a sliding joint. It can be used for merely a simple axial direction. These linear joints are not as common as the rotary joints but are very useful.

The cylindrical robot below has both types of joints evident. The rotary joint allows the grabber to rotate about the axis; while the linear joints Y&Z determine height and reach.