## 20 May 2017

### Mechanism and structure

Mechanism :

Linkage is obtained if one of the links of kinematic chain is fixed to the ground. If the motion of any of these movable ink results in definite motion of the other, the linkage is known as the mechanism.
However, this distance between a mechanism and linkage is hardly followed and it can be referred in place of others.

In a mechanism, links are connected with temporary fasteners. The links can move relative to each other.

This is facilitated by the presence of joints between the links. So a degree of freedom is >=1

Structure :

If one of the links of the redundant chain is fix it is known as a structure.

It is also known as a locked system.
To obtain constrain or definite motion of some of the links of linkage, it is necessary to know how many inputs are needed. In some mechanism, only one input is necessary that determine the motion of other links and it is said to have one degree of freedom. While other mechanisms, two inputs necessary to determine to constrain motion of the other links so we said they have two degrees of freedom.

In a structure again a combination of links connected to each other but no relative motion exists between them. So a degree of freedom is zero.

A structure who have a negative degree of freedom is known as a superstructure.

A mechanism is a force manipulating device, while the structure is a load bearing device.