The assembly robot is the central equipment in the flexible automated assembly system, and it consists of a robotic manipulator, controller, end effector, and sensing system.
The operating machine has four structural types: horizontal joint, rectangular coordinate, multi-joint, and cylindrical coordinate.
The controller typically uses a multi-CPU or multi-tier computer system to execute motion control and programming.
The end effector is adapted to different assembly objects and comes in various claws and wrist designs.
The sensing system collects information about the interaction between the assembly robot, its environment, and the objects it is assembling.
The basic type and structure
PUMA robot
The PUMA robot, developed by Unimation in the United States in 1977, is a computer-controlled multi-joint assembly robot.
It typically has 5 or 6 degrees of freedom, including rotations at the waist, shoulders, and elbow, as well as bend, rotate, and twist at the wrist (as shown in Figure 1).
The control system of the PUMA robot consists of a microcomputer, a servo system, an input and output system, and an external device.
VALII is used as the programming language for the PUMA. For instance, the statement “APPRO PART, 50” indicates that the hand will move to a position 50 mm above the PART.
The position of the PART can be specified through typing or through a teaching process.
VALII also includes functions for continuous trajectory motion and matrix transformation.
SCARA robot
A significant number of assembly processes involve downward movements, necessitating greater flexibility in the horizontal (X, Y) movement of the fingers to accommodate for positional inaccuracies.
The vertical (Z) movement and rotation around the horizontal axis need to be more rigid for precise and effective assembly.
It is also essential to have increased flexibility around the Z-axis for proper engagement of keys or splines.
The SCARA robot was developed by Yamanashi University in Japan and its structure is designed to meet these requirements (as shown in Figure 2).
The control system is relatively uncomplicated. For instance, the SR-3000 robot utilizes a microprocessor to implement semi-closed loop control for the three-axis (θ1, θ2, and Z) using DC servo motors and open-loop control for the s-axis using a stepper motor.
The programming language is based on a SERF similar to BASIC.
The latest version of Level4 includes features such as coordinate transformation, linear and circular interpolation, adjustable speed setting, subroutines labeled with text, and error detection.
SCARA robots are one of the most commonly used types in the industry.
Application
Assembly robots are primarily utilized in the production of various electrical appliances, including household items such as televisions, tape recorders, washing machines, refrigerators, and vacuum cleaners, as well as small motors, automobile components, computers, toys, and mechanical and electrical products.
