If we want to determine the position of a point in space, we need three parameters: X, Y, Z, but the rigid body has size and shape, not only the position but also the attitude. The angle around the X axis, Y axis and Z axis is used to describe the attitude of the rigid body α，β，γ To express.

Therefore, six parameters are required to describe the position and attitude of rigid bodies in three-dimensional space. The degree of freedom of unconstrained rigid bodies in three-dimensional space is 6. If the end of industrial robot wants to achieve unconstrained movement in three-dimensional space, it needs six degrees of freedom.

Therefore, the end coordinates of the six-joint industrial robot are represented by six parameters (X, Y, Z, A, B, C). The six degrees of freedom are translation in three directions and rotation around three axes. Then the six-joint robot can achieve its position and posture within its range of motion.

In fact, not all industrial robots have six degrees of freedom. For example, Scara and Delta robots have only four degrees of freedom. Most right-angle robots have only 3-4 degrees of freedom.

Generally, the simple and rough way to judge how many degrees of freedom a robot has is to count how many motors it has.