In the automotive and parts manufacturing industry, the use of industrial robots can reduce scrap rates and product costs, improve equipment utilization, and lower the risk of defective parts caused by worker errors, resulting in significant benefits. Robots have the capability to perform high-risk tasks, with an average failure interval exceeding 60,000 hours, making them more advanced than traditional automation processes.Industrial robots integrate advanced technologies from multiple disciplines, including mechanics, electronics, control, computing, sensors, and artificial intelligence, and are important automation equipment in modern manufacturing. Since the first industrial robot was developed in the United States in 1962, robot technology and its products have rapidly evolved, becoming essential tools in flexible manufacturing systems (FMS), automated factories (FA), and computer-integrated manufacturing systems (CIMS).At Chery’s production site, welding robots, painting robots, handling robots, and assembly robots are used, with a significant number being from brands such as FANUC, KUKA, and COMAU. Below, we will discuss the application of welding robots as an example in Chery’s automobile production line.Application of FANUC Robots in Welding LinesFANUC industrial robots are primarily used for welding in Chery’s A-series platform models, with the following technical characteristics:In terms of the mechanical body, a joint-type 6-degree-of-freedom serial structure is adopted, with motors + RV reducers driving joints 1, 2, and 3, all having the same motor power; joints 4, 5, and 6 also have the same motor power and are arranged in an L-shape. The drive chain for the 4th axis consists of a motor + long transmission shaft + straight gear + RV reducer; the 5th axis drive chain consists of a motor + long transmission shaft + straight gear + transmission shaft + bevel gear + RV reducer; the 6th axis drive chain consists of a motor + long transmission shaft + straight gear + transmission shaft + bevel gear + straight gear + bevel gear + RV reducer. Except for the 5th axis, which has a specially customized RV reducer to reduce size, the other axes use standard series RV reducers; the robot’s 2nd axis is equipped with a dual-spring balancing cylinder; the main body is made of a strip-style casting (simple structure, lightweight).In terms of the electrical control system, the FANUC control system adopts a typical master-slave two-level control structure, with the upper computer including the mainboard, CPU, and FROM/SRAM components, responsible for signal processing and exchange within the controller and peripheral devices. The lower computer—servo card and servo amplifier—not only provides drive and brake signals for the servo motor but also achieves real-time data conversion with absolute encoders, using fiber optics for data transmission to the main control unit for real-time signal feedback. The servo amplifier of this robot integrates the motors of all 6 axes onto a single circuit board, meaning that if one amplifier fails, the entire circuit board must be replaced. The FANUC robot has only one power supply unit supplying power to all boards in the control box, with the safety protection circuit powered directly by the transformer to the emergency stop unit, connecting to various internal control boards to form a protection circuit for the entire system.The human-machine interaction of the FANUC industrial robot system is achieved through a teach pendant, with software designed based on a LINUX operating system, and the code is fully open. An embedded expert can trim the kernel appropriately to obtain the required functional system, and then use LINUX structured language to write the necessary application programs to be ported to the embedded chip. However, its application program’s graphical functionality is weak, the interface is not user-friendly, and it is difficult for operators to master, making development and upgrades challenging. In operation, when using the FANUC teach pendant, it is necessary to press and hold the “DEADMAN” switch and the “SHIFT” key simultaneously before clicking on various function keys to operate. Programs can be written directly on the teach pendant or on other computers and read in via the CF card interface.Application of KUKA Robots in Welding LinesKUKA robots are mainly used for welding in Chery’s B, T, and S series platform models, with the following technical characteristics:In terms of the mechanical body, a joint-type 6-degree-of-freedom serial structure is adopted, with motors + RV reducers driving joints 1, 2, and 3, all having the same motor power; joints 4, 5, and 6 also have the same motor power and are arranged in an L-shape. The drive chain for the 4th axis consists of a motor + long transmission shaft + straight gear + RV reducer; the 5th axis drive chain consists of a motor + long transmission shaft + belt drive + transmission shaft + belt drive + RV reducer; the 6th axis drive chain consists of a motor + long transmission shaft + belt drive + transmission shaft + belt drive + bevel gear + reducer; the 5th and 6th axis drive chains include belt drives, and the 6th axis does not use an RV reducer, while the other axes use standard series RV reducers. The robot’s 2nd axis is equipped with a dual-spring balancing cylinder, and the main body is made of a closed casting.In terms of the electrical system, the KUKA control system adopts a distributed control structure, with the industrial computer being the central part of the entire control system, responsible for signal processing and exchange with the main power supply, safety circuit, RDC, and peripheral devices. In addition to standard configurations, it also includes MFC cards (controlling safety circuits, non-maskable interrupts) and DSE-IBS cards (communicating with RDC serial ports, outputting to KSD for three-loop control). KUKA servo drives (KSD) communicate with the industrial computer using INTERBUS bus, with a standard configuration of 6 independent drives controlling the 6-axis motion in real-time, expandable to 8 axes within the cabinet. The KUKA ESC safety system provides 27 V DC power directly from the main power supply to the ESC card, connecting with the industrial computer, teach pendant, and peripheral devices to protect the entire system’s circuitry. The KUKA main power supply provides 600 V voltage to each servo drive, while the auxiliary power supply provides 27 V DC to the industrial computer, safety module, servo drives, motor brakes, and battery modules.In terms of human-machine interaction, the KUKA robot system can connect external displays, keyboards, and mice to form a PC, in addition to the teach pendant. The design of the teach pendant resembles that of a handheld PC, and its software system is the VX-Win operating system developed in collaboration with Microsoft, combining Windows and VxWorks into a proprietary paid software. It is similar to Windows, supports VC object-oriented software for application programming, has a user-friendly interface, is easy to master, and is relatively easy to develop and upgrade, but has high usage costs.Application of COMAU Robots in Welding LinesCOMAU industrial robots are mainly used for welding in Chery’s M and S series platform models, with the following technical characteristics:In terms of the mechanical body, a joint-type 6-degree-of-freedom serial structure is adopted, with the motor of the 1st axis fixed together with the base, driven by a reducer and gear transmission, while the 2nd and 3rd axes are driven by motors + RV reducers, with the motors of the 1st, 2nd, and 3rd axes having the same power; the motors of the 4th, 5th, and 6th axes also have the same power and are arranged in a T-shape. The drive chain for the 4th axis consists of a motor + long transmission shaft + straight gear + RV reducer; the 5th axis drive chain consists of a motor + long transmission shaft + straight gear + transmission shaft + bevel gear + RV reducer; the 6th axis drive chain consists of a motor + long transmission shaft + straight gear + transmission shaft + bevel gear + straight gear + bevel gear + RV reducer. The robot’s 2nd axis is equipped with a dual-spring balancing cylinder. The large arm adopts a channel steel reinforced plate structure casting, while the small arm is a welded component.In terms of the electrical system, the COMAU industrial robot control system adopts a distributed control structure, with its RPU process handling system being the main control module of the entire system, including the main processor and motion co-processor, working in a master-slave control manner to complete I/O and field bus management, motion control, and robot program execution. The COMAU DSA digital servo amplifier feeds back encoder signals through the robot interface module, communicating with the motion co-processor via the Internet, providing the servo motor’s drive power and brake power to control robot motion. The COMAU RSM safety protection system communicates safety signals with the process handling system, system communication module, and peripheral devices to ensure the entire system’s safety. The COMAU DPP power distribution system provides the main power supply to the auxiliary power supply and digital servo amplifier. The APS auxiliary power supply provides 24 V DC power to the digital servo amplifier, process handling system, and system communication module, and also supplies 24 V DC power to the safety module through the system communication module.In terms of human-machine interaction, COMAU uses the same operating system as KUKA, with the teach pendant design similar to that of FANUC robots but more comfortable to operate, featuring a graphical user interface that is easy to master. In operation, the COMAU robot’s “DEADMAN” switch has a two-level switch; pressing the first level allows teaching, while pressing the second level is for testing the installation of external devices. If the installation is complete and the second level switch is pressed, an alarm will occur. This system can connect external displays, keyboards, and mice to form a PC, allowing programming, debugging, and settings to be performed.Problems Encountered in Actual ApplicationsIn actual production, the highest proportion of faults occurs in industrial robot welding, with many types of faults causing these issues, including software problems such as lost or ineffective control program instructions, and hardware issues such as encoder position feedback errors, welding gun failures, and servo motor faults. For example, in the case of FANUC, such faults account for about 82%. Servo faults occur occasionally, mostly due to excessive torque alarms, accounting for about 5%. Bus network faults, including errors in network wiring programs, internal PLC faults, and PROFIBUS bus errors, account for about 8%. Industrial robots may also experience no operation due to internal motion function interpolation failures, control program failures, or external signals not being sent to the robot control program, accounting for about 5%.These issues can impact production, and in severe cases, may delay production and cause significant losses. Their detection and resolution may require specialized personnel from the manufacturer, imported parts from abroad, or substantial inventory.To address these issues, equipment maintenance personnel must actively engage in extensive improvement work. To reduce welding faults, maintenance personnel can install protective devices on cables and pipelines; to address signal interference, they can investigate and isolate interference sources, while also rectifying cable routing, which can significantly lower the fault rate.ConclusionAs China transitions from a manufacturing giant to a manufacturing powerhouse, competition in the manufacturing industry, especially in the automotive sector, will become increasingly fierce. Improving product quality and labor productivity will be key factors for companies to succeed in this intense competition. The widespread use of cost-effective industrial robots will not only enhance product quality and labor productivity but also reduce labor and lower production costs, making it an inevitable trend in the development of China’s manufacturing industry.
Source: China Robot Education Network
