It is usually used as a technical indicator of the robot to reflect the flexibility of the robot's movement, which can be expressed by the number of straight-line movements, swings,or rotation of the axis. The number of joints that the robot mechanism can move independently is called the Degree of Freedom of the robot mechanism, which is expressed by the DOF abbreviation. At present, the control method adopted by industrial robots is to treat each joint on the mechanical arm as a separate servo mechanism, that is, each axis corresponds to a servo, and each servo is controlled by the bus, and the controller uniformly controls and coordinates the work.
IS08373 explains industrial robots: "The robot has automatic control and reprogrammable, multi-purpose functions. The robot manipulator has three or more programmable axes. In industrial automation applications, the base of the robot can be fixed or mobile". It can be seen that the axis number of industrial robots is an important technical index.
The number of axes determines the degree of freedom of robots with different degrees of freedom in industrial applications. Are the more degrees of freedom the better?
The more degrees of freedom, the more close to the action function of human hands, the better the versatility; However, the more degrees of freedom and the more complex the structure, the higher the overall requirements of the robot, which is a contradiction in the robot design. As the number of axes increases, so does the robot's flexibility. However, in the current industrial applications, the most commonly used industrial robots are three-axis, four-axis, five-axis with two arms, and six-axis, and the selection of axis number usually depends on the specific application. This is because, in some applications, high flexibility is not required, and three-axis and four-axis robots are more cost-effective, and three-axis and four-axis robots also have a great speed advantage. For simple applications, such as picking and placing parts between conveyor belts, a four-axis robot is sufficient. If the robot needs to work in a tight space and the arm needs to twist and reverse, a six - or seven-axis robot is the best choice.
At present, six-axis robots are widely used in the industrial field. The six-jointed industrial robot closely resembles a human arm, with the equivalent of a shoulder, elbow, and wrist. Its "shoulder" is usually mounted on a fixed base structure. The role of the human arm is to move the hand to different positions, while the role of the six-axis robot is to move the end-effector. The end of the robot arm is fitted with a variety of actuators suitable for specific application scenarios, such as claws, blowtorch, drill, and paint sprayer, to accomplish different tasks.
Recently, robot manufacturers have released the latest human-machine collaboration robots, almost all of them using 7-axis redundant DOF industrial robots. International well-known robot manufacturers have made efforts to launch new products of seven-axis robots, in order to seize the high-end new market, but compared with the traditional four-axis and six-axis industrial robots, the gap between product types and sales is very obvious.
