HOW MUCH FREEDOM YOU HAVE JUST TO MOVE ABOUT?

A body can move in three directions, x,y,and z. Also the body can rotate around three axes (x,y,z). Hence we say, the body has "six degrees of freedom". A helicopter or a bird has six degrees of freedom. In aerodynamics language, the three rotations are called, pitch, roll and yaw.

Take a plank of wood. In this three dimensional world, it has six degrees of freedom. Fix the plank as a door in a building. It can now do only one rotational motion about the joint. The six degrees of freedom has come down to one. We understand that the joints restrict the freedom.

There is a formula to calculate the degrees of freedom.

M = 6*n-SUM (6-fi)
for i = 1 to k

M - Degrees of freedom
n - Number of moving parts.
k - number of joints.
fi - number of degrees of freedom of each joint.

That is, (6-fi) should be found for each joint and summed up. Then the total sum is subtracted from 6n to get no. of degrees of freedom.

For example, take our arm. At the shoulder joint, we have 3 DOF (degrees of freedom). At the elbow, only 2 DOF. At the wrist 3. The fingers have only one DOF. Then, what is the total number of freedom for the entire arm. Explore using the above formula.

The DOF of a robotic arm is calculated and designed using the above formula.

Note: A gas molecule(example O2) is free to move (No joints). Hence it has all the six degrees of freedom and vibration freedom also. The molecule executes all the motions due to thermal energy. The energy is equally shared by all the degrees of freedom.

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