I. Classification of Industrial Robots
(I) Classification by driving method
1) Pneumatic transmission robot: A robot that uses compressed air as a power source to drive and perform directional movements. It is characterized by its flexible movements, simple structure, and low cost. It is suitable for high-speed, light-load, high-temperature, and dusty environments.
2) Hydraulic transmission robot: Driven by hydraulic components, it features strong load capacity, smooth transmission, compact structure and flexible movement, and is suitable for heavy-duty and low-speed driving applications.
3) Electrically driven robots: Robots driven by AC or DC servo motors do not require base changes. They have simple mechanical structures, fast response speeds, and high control precision, making them a commonly used robot transmission structure in recent years.
(II) Classification by Construction Method
1) Cartesian coordinate robots: The hands of these robots move independently in space along three mutually perpendicular directions: X, Y, and Z. They are simple to control, intuitive to move, and easy to achieve high precision and positioning accuracy. However, they have poor operational flexibility, lower movement speed, smaller operational plans, and occupy relatively large space.
2) Cylindrical coordinate robot: This type of robot has a column mounted on a horizontal turntable. The column is mounted on a rotating base, and the horizontal arm is flexible and can move up and down along the column. It has a large working range and high movement speed, but as the horizontal arm extends in the horizontal direction, its linear displacement resolution decreases.
3) Spherical coordinate robot: Also known as a polar coordinate robot, it consists of a reversing base, a pitch hinge, and a flexible arm, and has two rotational axes and one translational axis. The working arm can not only rotate around the vertical axis, but also pitch around the horizontal axis, and can also move elastically along the arm axis. Its operation is more flexible than that of the cylindrical coordinate robot, and it can expand the robot's working space, but the linear displacement resolution of the rotary joints reflected on the end effector is a variable.
4) Articulated robots: These robots consist of a base, upper arm, forearm, and wrist connected by multiple joints. The upper and lower arms are hinged together to form elbow joints, and the upper arm and column are connected to form shoulder joints. The upper and lower arms can move in a plane perpendicular to the base and can also roll around a vertical axis. They offer the best operational flexibility, high movement speed, and large operational scope, but their accuracy is affected by the arm's posture, making high-precision movements difficult. They can grasp objects close to the base and can also navigate around obstacles between the robot body and the target to grasp objects. With high movement speed and excellent flexibility, they have become the most versatile type of robot.
II. Functional Characteristics of Industrial Robots
The functional characteristics of industrial robots affect their working efficiency and reliability. The following functional objectives should be considered when designing and selecting robots:
(1) Degrees of Freedom Degrees of freedom are the primary indicator for measuring the skill level of a robot. A degree of freedom refers to the independent motion of a moving part relative to a fixed coordinate system. Each degree of freedom requires a servo axis for drive; therefore, the higher the degree of freedom, the more complex the actions the robot can perform, the stronger its versatility, and the wider its application range, but correspondingly, the greater the technical difficulty. Typically, general-purpose industrial robots have 3-6 degrees of freedom.
(2) The workspace refers to the spatial scale in which the robot uses its gripper to perform tasks. The wrist reference point for describing the workspace can be selected at the center of the hand, the center of the wrist, or the fingertips. The size and shape of the workspace will vary depending on the reference point. The robot's workspace depends on the robot's construction method and the range of motion of each joint. The workspace is a primary functional objective of industrial robots and a key objective in designing industrial robot designs.
(3) Load Capacity Load capacity refers to the maximum weight that a robot can bear in any position within its working range. The magnitude of load capacity depends on the mass of the load, the speed of operation, and the magnitude and direction of acceleration. Based on different load capacities, industrial robots are roughly divided into: ① Micro robots - load capacity below 10N; ② Small robots - load capacity 10-50N; ③ Medium robots - load capacity 50-300N; ④ Large robots - load capacity 300-500N; ⑤ Heavy robots - load capacity above 500N.
(4) Motion Speed: Motion speed affects the robot's work efficiency and motion cycle, and is closely related to the robot's gravity and positioning accuracy. Higher motion speeds result in increased dynamic loads on the robot, leading to greater inertial forces during acceleration and deceleration, thus affecting the robot's operational stability and positioning accuracy. Currently, the maximum linear motion speed of most general-purpose robots is below 1000 mm/s, and the maximum reverse rotation speed typically does not exceed 120°/s.
(5) Positioning accuracy is another technical indicator for measuring the quality of robot operation. The positioning accuracy of industrial robots includes positioning accuracy and repeatability. Positioning accuracy depends on the positioning control method and the accuracy and rigidity of the robot's moving parts themselves. In addition, it is closely related to factors such as gravity and motion speed. Repeatability is the accuracy of the robot in repeatedly positioning a certain position. The typical positioning accuracy of industrial robots is usually in the range of ±0.02mm to ±5mm.
