Design and Implementation of DDC Control System for Intelligent Welding Network Device
Abstract
Smart welding network devices are developed to reduce welding and fabrication costs, increase production efficiency and improve product quality. With the development of welding automation technology, the DDC control system has become a necessary link in the welding network device. The DDC control system of the intelligent welding network device uses fuzzy PID temperature control algorithm to control the temperature and realize semi-automatic and automatic welding.
Keywords: Intelligent welding; Network device; DDC control system; Fuzzy PID temperature control algorithm.
I. Introduction
Subsequently, the traditional manual welding process has been replaced by intelligent welding and fabrication, as the advent of computers and programmable logic controllers (PLCs) has revolutionized the welding industry. At present, in order to improve the safety and efficiency of welding, the development of intelligent welding technology has become a direction. The biggest feature of intelligent control technology is that it can make decisions based on the actual situation to achieve the best control effect.
In recent years, welding automation technology has made rapid development and breakthroughs, especially the development of various intelligent welding network devices. With the development of numerical control technology, various welding network devices with both welding and reproducing functions have been developed. It is mainly used for semi-automatic or automatic welding of medium and large objects, such as aeronautical welds or small parts.
In order to make these welding network devices smarter, a control system is needed to effectively control and manage the welding process. The Direct Digital Control (DDC) control system has been widely used in intelligent welding network devices. DDC is a technology used for the direct control of the production process without manual intervention, and it is based on digital logic circuits and can be programmed by a computer. The DDC control system can take advantage of the object’s relevant parameters, so that the welding process can be more accurate and flexible, which greatly improves the quality of the welding products and meets the modern production requirements.
II. Design of DDC Control System
The design of the DDC control system mainly includes two aspects: hardware and software. The hardware circuit system mainly consists of I/O interface, frequency conversion control system, communication interface and other control circuits. The software system mainly consists of temperature control module, motion control module, logic control module and secondary development module.
1. Hardware circuit system
The hardware circuit system mainly consists of I/O interface, frequency converter system, communication interface and other control circuits. The I/O interface is composed of various input signals, such as temperature and current. The frequency conversion system is used to control the speed and acceleration of the welding network device. The communication interface is mainly used for communication between the DDC control system and the host computer and peripheral equipment. The other control circuits mainly include power supply control and power output circuit, etc.
2. Software system
The software system mainly includes four modules: temperature control module, motion control module, logic control module and secondary development module. The temperature control module is used to adjust the welding temperature according to the temperature requirements of the welding specimen. The motion control module can control various motions of the welding network device with precise control. The logic control module can monitor the operation of the welding network device in real time and make logical judgments to ensure the normal operation of the welding network device. The secondary development module is used for secondary development of the welding network device and can be used for other applications..
III. Fuzzy PID Temperature Control Algorithm
In order to realize precise temperature control, a fuzzy PID temperature control algorithm is used in the DDC control system. This algorithm is based on a linear combination of fuzzy logic and PID (Proportional Integral Derivative) control. Fuzzy logic is used to approximate nonlinear characteristics, and PID control is used for precise and stable temperature control.
The fuzzy PID temperature control algorithm can be divided into four parts: fuzzification of input signals, PID controller, fuzzy inference system and defuzzification of output signals. The input signals of the fuzzy PID temperature control algorithm are the actual temperature and the set temperature, and the output signal is the control signal.
The fuzzification of the input signals is the first step.
The input signals are fuzzified into five linguistic variables: very low, low, medium, high and very high. The variable membership functions of each fuzzy variable can be determined according to the specific requirements of the system.
The second step of the algorithm is to use linear combination method to construct the PID controller. This method is used to combine the proportional, integral and derivative control functions into one equation and realize the adjustment of parameters.
The third step is fuzzy inference system. In this step, the membership functions of the input linguistic variables are connected with the membership functions of the output variables through a set of fuzzy rules.
The fourth step is defuzzification of the output signals. In this step, the output of the fuzzy inference system is converted into a numerical value, which is used to control the welding temperature. The Centre of the Area (COA) method is used to calculate the output signals of the system.
IV. Implementation of DDC Control System
The DDC control system is implemented on a Freescale S08 MCU platform. The system real-time operating system (RTOS) is used to optimize the multitasking time and space. In the hardware circuit system, various I/O interfaces are used to sense the actual temperature and control the power output. The frequency converter is used to control the speed and acceleration of the welding network device. The communication interface is used to communicate with the host computer and other peripheral equipment.
In the software system, the temperature control module is used to monitor the actual temperature and adjust the parameters of the PID controller to realize the accuracy and stability of the temperature control. The motion control module is used to control the motion of the welding network device and realize the accuracy and positioning of the movement. The logic control module is used for real-time monitoring and control of the welding network device and fault detection and alarm. The secondary development module is used for secondary development of the welding control system to meet the application requirements.
V. Conclusion
This paper introduces the design and implementation of the DDC control system for the intelligent welding network device. The hardware circuit system and software system of the DDC control system are designed, in which the fuzzy PID temperature control algorithm is used to ensure the accuracy and stability of the temperature control. Finally, the system is implemented on a MCU platform, and the various modules are tested to ensure the normal operation of the system. This control system has been successfully applied in intelligent welding network devices, which has effectively improved the welding quality, safety and efficiency.
