Bearing and Degrees Of Freedom (DOF). If a farmer goes to milk her cows in the morning carrying a stool under one hand and a pail under another the other hand, how many legs does the stool have?. Degrees of Freedom.
Most mechanisms are holonomic, and with holonomic systems the number of DOF is also the number of coordinates required to specify completely the position of the mechanism. An example of a non-holonomic system is a car with front wheel steering. There are two variables that define the velocity; the rear wheel speed and the angle of the front wheel. However, it requires three variables to define the position of the car (x, y, and orientation). In these notes we will restrict ourselves to holonomic systems. Thus we can identify the DOF by the minimum number of variables required to define the position or body or system.