Robotics Technology – Arms

The robot arm comes in all shapes and sizes and is the single most important part in robotic architecture. The arm is the part of the robot that positions the End Effector and Sensors to do their pre-programmed business. Many (but not all) resemble human arms, and have shoulders, elbows, wrists, even fingers. This gives the robot a lot of ways to position itself in its environment.

Many robots resemble human arms, and have shoulders, elbows, wrists, even fingers. This gives a robot lots of options for moving, and helps it do things in place of a human arm. In order to reach any possible point in space within its work envelope, a robot uses a total of 7 degrees of freedom. Each direction a joint can go gives an arm 1 degree. So, a simple robot arm with 3 degrees of freedom could move in 3 ways: up and down, left and right, forward and backward. Many robots of today are designed to move with these 7 degrees of freedom.

The human arm is an amazing design. It allows us to place our all-purpose end effector, the hand, where it is needed. Jointed arm robots mimic the ability of human arms to be flexible, precise, and ready for a wide variety of tasks. The jointed-arm robot has six degrees of freedom, which enable it to perform jobs that require versatility and dexterity. The design of a jointed-arm robot is similar to a human arm, but not exactly the same. 

Seven Degrees of Freedom

    The robotic arm is very similar to the human arm in that it has the capability of having 7 and not 6 degrees of movement, as previously thought. Out of the 7 degrees of movement, your shoulder has 3 of the arm’s 7 degrees of freedom. The easiest way to explain the movement of the robotic arm is to use your own arm as an example. Hold out your arm and follow along . . . 

First Degree: Shoulder Pitch

    To find your arm's first degree of freedom:
Point your entire arm straight out in front of you. Move your shoulder up and down. The up and down movement of the shoulder is called the shoulder pitch. 

Second Degree: Arm Yaw

    To find your arm's second degree of freedom:
Point your entire arm straight out in front of you. Move your entire arm from side to side. This side to side movement is called the arm yaw. 

Third Degree: Shoulder roll

    To find your arm's third degree of freedom:
Point your entire arm straight out in front of you. Now, roll your entire arm from the shoulder, as if you were screwing in a light bulb. This rotating movement is called a shoulder roll. 

Fourth Degree: Elbow Pitch

    To find your arm's fourth degree of freedom:
Point your entire arm straight out in front of you. Hold your arm still, then bend only your elbow. Your elbow can move up and down. This up and down movement of the shoulder is called the shoulder pitch. 

Fifth Degree: Wrist Pitch

    To find your arm's fifth degree of freedom:
Point your entire arm straight out in front of you. Without moving your shoulder or elbow, flex your wrist up and down. This up and down movement of the wrist is called the wrist pitch. 

Sixth Degree: Wrist Yaw

    To find your arm's sixth degree of freedom:
Point your entire arm straight out in front of you. Without moving your shoulder or elbow, flex your wrist from side to side. The side to side movement is called the wrist yaw. 

Seventh Degree: Wrist Roll

    To find your arm's seventh degree of freedom:
Point your entire arm straight out in front of you. Without moving your shoulder or elbow, rotate your wrist, as if you were turning a doorknob. The rotation of the wrist is called the wrist roll.

Source : www.electronicsteacher.com