Kutzbach Criterion
DOF of a mechanism in space can be determined as follows:
In mechanism one link should be fixed. Therefore total no. of movable links are in mechanism is (N-1)
Any pair having 1 DOF will impose 5 restraints on the mechanism, which reduces its total degree of freedom by 5P1.
Any pair having 2 DOF will impose 4 restraints on the mechanism, which reduces its total degree of freedom by 4P2
Similarly, the other pairs having 3, 4 and 5 degrees of freedom reduce the degrees of freedom of mechanism. Thus,
Thus,
Hence,
F = 6 (N-1) – 5 P1 – 4 P2 – 3 P3 – 2 P4 – 1P5 – 0P6
Hence,
F = 6 (N-1) – 5 P1 – 4 P2 – 3 P3 – 2 P4 – 1P5
The above equation is the general form of Kutzbach criterion. This is applicable to any type of mechanism including a spatial mechanism.
