Application analysis of FANUC welding robot control system
Welding is a very important processing method in industrial production, but due to the presence of welding fumes, arcs and metal splashes, the working environment of welding is very harsh. With the gradual increase in labor costs and the improvement of welding quality, welding robots have become more and more widely used.
Features of robot application
Welding robots play an extremely important role in high-quality and efficient welding production, and its main features are as follows:
1. Stable performance and stable welding quality to ensure its uniformity
Welding parameters (such as welding current, voltage, welding speed and welding dry elongation, etc.) play a decisive role in welding results. During manual welding, the welding speed, dry elongation, etc. all change, and it is difficult to achieve uniformity of quality; using robot welding, the welding parameters of each weld are constant, and the quality of the weld is less affected by human factors , Reduced the technical requirements for workers, welding quality is very stable.
2. Improved working conditions for workers
Using robot welding, workers only need to load and unload workpieces, away from welding arcs, smoke, and spatter; when spot welding, workers no longer need to carry bulky manual welding tongs, freed from the intensive manual labor.
3. Improve labor productivity
The robot can be continuously produced 24 hours a day. With the application of high-speed and high-efficiency welding technology, the efficiency of the robot welding is more obvious.
4. Clear product cycle, easy to control product output
The production cycle of the robot is fixed, so the production plan is very clear.
5. Shorten the cycle of product modification and replacement, reduce the corresponding equipment investment
The biggest difference between robot and special plane is that it can adapt to the production of different workpieces by modifying the program, and can realize the welding automation of small batch products. .
FANUC robot control system
1. Overview
FANUC robots are mainly used in the welding workshops of Chery's No. 1 passenger car plant and No. 3 passenger car plant. They are the earliest welding robots introduced by Chery and the first welding robots with additional axes. The application of M-10iA robot arc welding is shown in Figure 1. The control system adopts 32-bit CPU control to increase the operation speed of robot motion interpolation calculation and coordinate transformation; adopts 64-bit digital servo drive unit to control 6-axis motion synchronously, the motion accuracy is greatly improved, and up to 21 axes can be controlled to further improve The robot's dynamic characteristics are supported; offline programming technology is supported, and technicians can set parameters through offline programming software to optimize the robot's motion program; the internal structure of the controller is relatively integrated. This integrated method has a simple structure, the whole machine is cheap, and easy to maintain. Features.
2. Internal structure analysis
The controller is the core part of the robot, which realizes the functions of the robot's operation, signal communication and status monitoring. Take FANUC F-200iB as an example to analyze the internal structure of the control system and the functions of each part:
(1) Power supply unit The transformer inputs 230V AC power to the power distribution unit. The system power distribution function of the unit outputs 210V AC and ± 15V and + 24V DC to each working board inside the control box.
(2) Safety protection circuit The transformer directly supplies power to the emergency stop unit, and connects to the internal control boards to form a protection circuit to protect the entire system.
(3) Servo amplifier not only provides servo motor drive and brake power supply, but also realizes real-time data conversion with absolute value encoder, and uses optical fiber to transmit data with the host computer for real-time signal loop feedback.
(4) Input / output module The standard configuration is ModuleA / B. In addition, it can also communicate with PLC and peripheral devices by installing Profibus board and process control board in the expansion slot.
(5) Main control unit The central part of the entire control system, including the main board, CPU, FROM / SRAM components and servo card, is responsible for the signal processing and exchange of the controller and peripheral devices.
(6) Emergency stop circuit board Used to control the emergency stop system, the electromagnetic contactor of the servo amplifier and the pre-charging.
(7) Teach pendant All operations including robot programming can be completed by the device, and the controller status and data are displayed on the display of the teach pendant.
Failure case analysis
After the FANUC robot controller is powered off and overhauled, power is supplied to the controller and the robot reports a servo failure. The failure code is SERVO-062. Reset this fault: press MENUS → SYSTEM → F1, [TYPE] → find master / cal → F3, RES_PCA → F4, YES, the robot still reports servo failure.
1. Failure analysis and inspection
The interpretation of the fault code SERVO-062 is SERVO2 BZAL alarm (Group:% d Axis:% d). The possible causes of the fault are as follows:
(1) The battery of the data storage on the robot encoder is empty or damaged. Remove the battery installation box of the encoder pulse data storage. The battery box is equipped with 4 ordinary 1.5V No. 1 dry batteries. The voltage of each battery is measured. Both are below 1.4V, the battery voltage is obviously low, so replace the new battery, reset the fault again, the robot still reports SERVO-062 fault.
(2) The control board of the servo amplifier in the controller is damaged. Check the two DC link voltage detection screws above the servo amplifier LED "D7" to confirm the DC link voltage. If the detected DC link voltage is higher than 50V, it can be judged that the servo amplifier control board is in an abnormal state. The actual test found that the DC link voltage was lower than 50V, so it was preliminarily judged that the servo amplifier control board was in a normal state. Further observe the LED colors of P5V, P3.3V, SVEMG, and OPEN on the servo amplifier control board to confirm that the power supply voltage output is normal, there is no external emergency stop signal input, and the communication with the robot motherboard is normal, eliminating the damage to the servo amplifier control board.
(3) The line is damaged. Check the external cable connections RM1 and RP1 of the robot controller and the robot body. RM1 is the robot servo motor power and brake control line. RP1 is the robot servo motor encoder signal and control power line. Circuit and battery circuit for data storage on the encoder. Pull out the plug RP1, and measure the + 5V and + 24V control power supply of terminals 5, 6 and 18 with a multimeter; then check the battery circuit of the data storage on the encoder. The servo motor pulse encoder control terminal of each axis of the robot is composed of 1 to 10 terminals, terminals 8, 9 and 10 are + 5V power supply, terminals 4, 7 are data holding battery power supply, terminals 5, 6 are feedback signal, terminal 3 For grounding, terminals 1 and 2 are empty. Unplug the pulse control plug M1P of the M1 motor, the multimeter measures the terminals 4, 7 and the voltage is 0; the same method checks that the M2 ~ M7 motors are all 0, which can judge the battery line of the data storage on the encoder is damaged. Along the line, it was found that the plug of one end of the positive and negative power supply twisted pair was buried in the standing water for a long time, and the line was severely corroded.
2. Troubleshooting
Reset after replacing the line, perform a full-axis zero point reset on the robot, "ZERO POSITION MASTER", restore normal after importing the backup program, and troubleshoot
Conclusion
As one of the main brands of Japanese robots, FANUC has the same control principle as other brands of robots, but its control structure has its own style, which reflects the habits of Asians and is more suitable for domestic use.
Although the research and application of welding robot technology in China is relatively late, it draws on mature foreign technology and develops very quickly. In 2009, the Qiha robot jointly developed by our company and Harbin Institute of Technology was born. We saw the power of cooperation between enterprises and scientific research units, and believed that it is a good decision for application-oriented enterprises to participate in the research of equipment. Of course, the welding robot is a high-tech product with electromechanical integration. The company's own capabilities are not enough. It is necessary for the government to provide certain policy and financial support for robot manufacturers and enterprises using domestic robot systems to accelerate the development of domestic robots in China. .