Classification of assembly robots
Commonly used assembly robots mainly include two types: PUMA (Programmable Component Assembly Manipulator) robots (first appeared in 1978, the ancestor of industrial robots) and SCARA (Screen Joint Robots). Compared with general industrial robots, assembly robots have the characteristics of high precision, good compliance, small working range, and ability to be used in conjunction with other systems. They are mainly used in the manufacturing industry of various electrical appliances.
1. PUMA Robot
PUMA, developed by Unimation in 1977, is a computer-controlled multi-joint assembly robot. It typically has 5 or 6 degrees of freedom, including rotation of the waist, shoulder, and elbow, as well as flexion, rotation, and twisting of the wrist (Figure 1). Its control system consists of a microcomputer, servo system, input/output system, and external devices. It uses VALII as its programming language; for example, the statement "APPRO PART, 50" indicates that the hand moves to a position 50mm above the PART. The PART's position can be entered or taught. VALII has the capabilities for continuous trajectory motion and matrix transformation.
2. SCARA Robot
A large portion of assembly work is vertically downward, requiring high compliance in the horizontal (X, Y) movement of the gripper to compensate for positional errors. Vertical (Z) movement and rotation around the horizontal axis require high rigidity for accurate and forceful assembly. Additionally, high compliance in rotation around the Z-axis is necessary for keyed or splined fits. The control system is relatively simple; for example, the SR-3000 robot uses a microprocessor to achieve semi-closed-loop control of the θ1, θ2, and Z axes (DC servo motors), and open-loop control of the S-axis (stepper motor). The programming language used is SERF, similar to BASIC. The latest version, Level4, features coordinate transformation, linear and circular interpolation, arbitrary speed setting, named subroutines, and error detection. SCARA robots are one of the most widely used types currently.
Application of assembly robots
Assembly robots are mainly used in the manufacturing of various electrical appliances (including household appliances such as televisions, tape recorders, washing machines, refrigerators, and vacuum cleaners), small motors, automobiles and their parts, computers, toys, electromechanical products and their components, etc.
