Degrees of freedom of motion refer to the number of variables required for a robot manipulator to move in space. They are parameters used to represent the flexibility of a robot's movements and are generally expressed as the number of independent movements along an axis and rotation around an axis.
A free object in space has six degrees of freedom (three rotational degrees of freedom and three translational degrees of freedom). Industrial robots are often open linkage systems, with each joint having only one degree of freedom; therefore, the number of degrees of freedom of a robot is usually equal to its number of joints. The more degrees of freedom a robot has, the more powerful its capabilities. Currently, industrial robots typically have 4-6 degrees of freedom. When the number of joints (degrees of freedom) of a robot increases to the point that it no longer functions for the orientation and positioning of the end effector, redundant degrees of freedom emerge. Redundancy increases the robot's flexibility but also makes control more complex.
Industrial robots can generally be categorized into two types of motion: linear motion (abbreviated as P) and rotational motion (abbreviated as R). The abbreviations P and R can be used to represent the characteristics of the manipulator's degrees of freedom. For example, RPRR indicates that the robot manipulator has four degrees of freedom, with the joint movements from the base to the arm end in the sequence of rotation-linear-rotation-rotation. Furthermore, the degrees of freedom of industrial robots are also limited by their range of motion.
The precision of a robot's mechanical system mainly involves pose precision, repeatability of pose precision, trajectory precision, and repeatability of trajectory precision.
Pose accuracy refers to the deviation between the commanded pose and the actual pose center when approaching the commanded pose from the same direction. Repeatable pose accuracy refers to the degree of inconsistency between the actual pose and the actual pose after responding to the same commanded pose n times from the same direction.
Track accuracy refers to the degree to which a robot's mechanical interface closely follows a commanded trajectory when following it n times in the same direction. Track repeatability accuracy refers to the degree of inconsistency between the actual trajectories after following a given trajectory n times in the same direction.
