1. Degrees of freedom
The number of joints that a robot mechanism can move independently is called the robot mechanism's degrees of freedom, or simply DOF. Currently, the control method used in industrial robots treats each joint on the robotic arm as an individual servo mechanism; that is, each axis corresponds to one servo, and each servo is controlled via a bus, with a controller unifying and coordinating their work.
In current industrial applications, the most commonly used are three-axis, four-axis, five-axis dual-arm, and six-axis industrial robots. The choice of the number of axes usually depends on the specific application; in the industrial field, six-axis robots are the most widely used.
2. Joints
A kinematic pair, also known as a kinetic pair, is a mechanism that allows relative movement between the various parts of a robot arm. A precision reducer is the core component of this motion; it uses a gear-based speed converter to reduce the motor's rotational speed to the desired speed while obtaining a larger torque, thereby reducing the rotational speed and increasing the torque.
3. Scope of Work
The working range of an industrial robot refers to the spatial area that can be reached by the robot's arm or hand attachment point. Because the size and shape of the end effector vary widely, to accurately reflect the robot's characteristic parameters, this refers to the working area without the end effector.
The shape and size of a robot's working area are very important. A robot may be unable to complete its work tasks due to dead zones that its hand cannot reach.
The number of degrees of freedom a robot possesses determines its motion pattern; while the change in degrees of freedom (i.e., the distance of linear motion and the size of the rotation angle) determines the size of the motion pattern.
The working range of a robot can generally be represented using two methods: graphical method and analytical method.
4. Speed
The distance or angle that the center of the mechanical interface or the center point of the tool moves per unit time when the robot is under load and moving at a constant speed during operation.
Currently, small-load industrial robots can achieve speeds of 1.0m/s to 1.5m/s, while small robots launched by companies such as ABB, KUKA, and FANUC can generally reach 5-6m/s.
5. Workload
This refers to the maximum weight that a robot's wrist can withstand at any position within its working range when a load is mounted on its forearm. It is generally expressed as mass, torque, or moment of inertia. It is also related to parameters such as operating speed and acceleration. The workload is generally measured by the weight of the workpiece the robot can grasp at high speeds. The load capacity of a handling robot must take into account the combined weight of the gripper and the workpiece.
Taking the ABB IRB6700-235/2.65 robot as an example, this robot has a payload of 235 kg and a working radius of 2.65 meters.
6. Resolution
It refers to the minimum distance a robot can move or the minimum angle of rotation, and is divided into programming resolution and control resolution.
7. Accuracy
Positioning accuracy refers to the difference in how often a robot repeatedly reaches a target position. The two accuracy indicators for industrial robots are repeatability and absolute positioning accuracy. Absolute positioning accuracy indicates the deviation between the preset value and the actual value; repeatability refers to the positional deviation of the robot when it repeatedly reaches a point.
Because of the embargo on high-precision sensor technologies such as encoders and grating rulers to China, the use of foreign CPUs and FPGAs, and the import of precision reducers from Japan, the precision of domestically produced robots is generally inferior to that of international robot brands.
