People often ask, "What should I do if I want to learn how to operate an industrial robot but don't know how to use a PLC?"
For beginners, encountering these kinds of questions is quite common. After reading the following easy-to-understand article, you will probably understand the absolute relationship between industrial robots and PLCs .
Let's first understand the basic structure and principle of industrial robots. Simply put, the hardware structure of an industrial robot is generally composed of 3-6 servo drive systems working together to complete various actions. Controlling an industrial robot is essentially controlling those motors to rotate forward, reverse, faster, or slower. I believe everyone can understand this.
Anyone who has studied electrical control understands that to control these motors to move as you intend, you naturally need a device similar to a PLC as a control platform to write programs for them, and a human-machine interface similar to a touchscreen to issue commands. Here, "PLC" refers to the robot's integrated controller, and "touchscreen" refers to the teach pendant.
In fact, in the entire industrial robot industry, the value of the robot itself accounts for roughly one-third. So where does the other two-thirds go?
This two-thirds is mainly comprised of integrated equipment and industrial software surrounding the robot. As we all know, industrial robots are increasingly becoming standardized components. To flexibly utilize industrial robots according to actual field conditions, the cooperation of peripheral equipment and industrial software is required. Industrial robots do not work in isolation. A robot workstation often requires the cooperation of peripheral equipment, such as tooling fixtures, conveyor belts, welding positioners, and moving guides. How these components cooperate with each other requires coordination by the PLC.
A production line requires the collaboration of multiple industrial robot workstations, and it also includes other relatively independent automated equipment, such as AGVs, automated storage and retrieval systems, painting equipment, assembly equipment, and so on. In this case, a higher-level PLC is needed to coordinate the workstations.
To give a very simple example:
A conveyor production line has three industrial robot workstations at positions A, B, and C, representing three different processes. The PLC first controls the conveyor belt. When a workpiece arrives at workstation A, its position sensor detects the workpiece's arrival and sends a signal to the PLC. The PLC receives this input signal and, along with other external signals, determines that the robot at workstation A is ready to begin work. It then outputs a signal to robot A: "You can start working now, hurry up!" After robot A finishes its work, it sends a completion signal back to the PLC: "My job is done, you can continue." The PLC then continues to operate the motor, controlling the conveyor belt to transport the workpiece to workstation B, repeating the above logic.
Dear readers, after reading the above, I believe at least half of your questions have been answered. Now it's time to draw a conclusion: the application of industrial robots cannot be separated from the participation of PLCs, and the area where the industrial robot industry will truly make a difference in the future is customized industrial robot solutions. Therefore, learning industrial robot technology but only knowing how to operate it will only make you an operator technician, not an application engineer! For newcomers or those entering the industrial robot field from other industries, it is best to have a basic understanding of electrical automation theory. If you don't have an electrical background, you must start by learning basic electrical circuits and PLC programming.
How does the robot communicate and connect with the PLC?
The real application of industrial robots is on production lines (such as automobile assembly lines, semiconductor silicon wafer handling, etc.). After the robot's various handling motion trajectories are debugged, it also needs to cooperate with the action requirements of the production line, which means it also needs to connect and communicate with the PLC. The two parties exchange signals, and the PLC tells the robot when to carry out the work and the robot notifies the PLC when it has completed the work. Through such interactive communication, the robot can act as a "member" of the entire production line and complete the entire production task with other mechanisms on the production line.
>>>Communication connection between industrial robots and PLCs
If we master both industrial robot programming and PLC control technology, then controlling a robot via PLC becomes very simple. It simply requires effectively connecting the industrial robot and the PLC and transmitting signals between them. There are two communication methods between industrial robots and PLCs: I/O connection and communication cable connection. The following section describes the control method using the most common method: the I/O connection.
▲Figure 1: Composition of PLC and Robot System
The PLC shown in the diagram above is a Siemens brand, with the S7-300 serving as the host computer and the S7-200 connected to the machine tool via I/O signals. The S7-300 and S7-200 are connected via a Profibus bus. The S7-300 is connected to the industrial robot via I/O signals. The industrial robot body and the controller are connected using a built-in communication cable (direct plug-in).
▲Figure 2: S7-300 (CPU-313) Input/Output Signals
▲Figure 3: S7-200 input/output signals (controlling the lathe)
▲Figure 4: S7-200 input/output signals (controlling the washing machine)
