Abstract: This paper briefly introduces the development of cotton spinning combing machines and programmable logic controllers (PLCs), reviews the application of Omron PLCs in the electrical control systems of the company's products over the years, and focuses on introducing a solution example and application experience of using the Omron CP1H mini PLC in the electrical control of cotton spinning combing machines.
Keywords: combing machine; PLC; control scheme; synchronous development
Abstract: This paper introduces the development of combing machine & PLC, reviews the application of OMRON PLC in the control system of our products, focusing on the specific solution and experiences of the combing machine control system with OMRON sysmac CP1H.
Key words Combing Machine PLC Control Solution Synchronized Development
introduction
Shanghai Yifang Machinery Co., Ltd. (formerly Shanghai No. 1 Textile Machinery Factory and Shanghai Textile Machinery General Factory) has a history of over 80 years and has been specializing in the production of textile machinery for nearly half a century. The company is committed to the development, production, and sales of textile machinery covering a wide range of fields including cotton, wool, linen, silk, and chemical fibers, as well as pre-spinning equipment.
In the rapid development of science and technology, the automation level of the company's textile machinery electrical control system has also undergone significant changes. The control system has evolved from the earliest dozen or so relay controls to various control methods such as single-board computers, programmable logic controllers (PLCs), programmable computer controllers (PCCs), and industrial controllers. Each of these control methods has its own characteristics. For example, pure relay circuits can be used in textile equipment with very simple control, as they are inexpensive and easy to maintain, but their functions are not easily modified. Single-chip microcomputers offer a certain degree of programming flexibility and are cheaper than general PLCs, but their control points and programming capabilities are somewhat limited. PLCs are popular among engineers due to their easy-to-learn programming instructions, expandable input/output modules, and mature anti-interference technology. PCCs offer high reliability, rich programming languages, powerful functions, and good resistance to harsh environments, but their price makes them difficult to widely apply in ordinary textile machinery. Industrial controllers offer excellent performance but are also accompanied by high prices, so they are only used in a few large-scale textile machines. Therefore, PLCs are currently the most common controller in general textile machinery. This article will only review and introduce the application of PLCs in the company's "four generations" of combing machines and other products.
1. Introduction to Cotton Combing Machines
Our company's main product is the combing machine used in cotton mills (its main function is to remove short fibers, impurities, neps, and defects from the cotton web produced by the carding machine, while also improving the straightness of the cotton fibers, so that the combed sliver can be spun into high-count yarn of 60 or higher through subsequent processes, thereby meeting people's needs for comfortable clothing or some special needs). Our company has grown and developed alongside the continuous upgrading of combing machines. More than a decade ago, our company's combing machines had a market share of over 90% in cotton mills nationwide—a truly proud and enviable figure! Even during the era of spindle reduction in the national cotton textile industry, the demand for cotton combing equipment never diminished due to the continuous improvement of people's living standards. Of course, in a market economy, no one can monopolize any product. With the large-scale entry of cotton combing machines manufactured in developed European countries and the multi-pronged attack from domestic competitors, market competition in the cotton combing equipment manufacturing industry has become increasingly fierce, strongly impacting our company's market share. Forced by this situation, we can only continue to survive by continuously developing new textile machinery products. It is evident how crucial it is to the survival and development of the nation, its people, and its enterprises to produce and continuously develop new combing equipment.
2. Development and Schools of Programmable Logic Controllers (PLCs)
The English term for programmable controller is Programmable Controller, which was simply referred to as PC in the 1970s and 80s. In the 1990s, due to the development of personal computers, which were also simply referred to as PC, and because the concept of programmable was too broad, AB (Allenstein's Albert) first named the programmable controller Programmable Logic Controller (PLC). For convenience, it is now simply referred to as "PLC".
In 1968, GM (General Motors) of the United States put forward the requirement to replace the relay control device. The following year, Digital Systems developed the first generation of programmable logic controllers, which met the requirements of GM's assembly line.
With the development of integrated circuit and computer technologies, fifth-generation PLC products have now emerged. In the development of the manufacturing industry, besides feedback control primarily based on continuous quantities, there is a large amount of open-loop sequential control primarily based on switching quantities, which performs sequential actions according to logical conditions or timing sequences. Additionally, there are controls that perform interlocking protection actions based on logical relationships, independent of sequence or timing; and there is also data acquisition and monitoring of discrete quantities, primarily state quantities such as switching quantities, pulse quantities, timers, counters, and analog quantity over-limit alarms. Due to these control and monitoring requirements, PLCs have evolved to replace relay circuits and are primarily used for sequential control.
To enable users to create ladder diagrams for control systems similar to relay circuits, a set of control algorithm function blocks (or subroutines) is developed, called the instruction set, which is stored in ROM and can be called by users when developing application programs. The instruction set can be broadly divided into two categories: basic instructions and extended instructions. A more detailed breakdown of the instruction set for a typical PLC includes: basic instructions, timer/counter instructions, shift instructions, transfer instructions, comparison instructions, conversion instructions, BCD arithmetic instructions, binary arithmetic instructions, increment/decrement instructions, logical operation instructions, and special arithmetic instructions. In addition, PLCs provide ample internal resources such as timers, counters, internal relays, registers, and storage areas, greatly facilitating programming.
PLC products worldwide can be categorized into three main types based on region: American, European, and Japanese. American and European PLC technologies were independently researched and developed in isolation, resulting in significant differences between their products. Japanese PLC technology, however, was introduced from the US and inherits some aspects of American products, but Japan primarily focuses on small PLCs. Japanese small PLCs are highly distinctive and renowned in the miniature PLC market. They can achieve certain control functions that require medium or large-scale PLCs from Europe and America. They are significantly superior to European and American small PLCs in developing complex control systems, making them particularly popular with users. Japan has many PLC manufacturers, such as Mitsubishi, Omron, Panasonic, Fuji, Hitachi, and Toshiba, and Japanese products hold approximately 70% of the global small PLC market share.
3. Review of the synchronous development of our company's products with PLC technology
3.1 The C60P is used for the "first generation" (starting from the use of PLC, the same below) FA252 cotton combing machine
In our company's more than 30-year history of developing combing machines before 1990, the electrical control system was entirely controlled by relays. While inexpensive, relays were not easily modified. As control requirements have increased, pure relay control circuits have become increasingly inadequate. Moreover, the excessive number of relays has made the electrical control cabinet increasingly large, with complex and intricate wiring, causing problems for design, manufacturing, and maintenance.
In the early 1990s, when we were developing the new cotton combing machines FA252 and FA253, PLCs had just entered the domestic automation field. We carefully compared several world-renowned brands at the time and determined that small PLCs could meet our control needs. Since Japanese PLCs were more suited to the logical thinking of Easterners in terms of programming languages, we chose Japanese PLCs as our first choice.
Among the many PLC manufacturers in Japan, Omron Automation Group's PLCs stand out as leading products in industrial automation and advanced application technologies. They entered the Chinese market early, boasted stable performance, were easy to program, and convenient to debug (although the software was initially based on the DOS platform "LSS," it already possessed rich functionality, and its field monitoring capabilities were particularly outstanding compared to other Japanese PLC software), making it a leader in the automation field at the time. In China, Omron has a nationwide logistics, sales, and technical support network, enabling it to provide customers with timely and direct service.
Based on the above reasons, when using a PLC as the main controller in the "first generation" of cotton combing machines, we chose the product of Japan's Omron Corporation - the "C60P PLC" from the early 1990s.
The "C60P" programmable controller, by today's standards, is quite large. However, at the time, its size was significantly smaller than our original plan to install dozens of relays in the electrical box. Moreover, the control logic could be modified at any time, and the control function could be changed without moving a single wire or any electrical component. These advancements in technology and components were revolutionary for us in the field of automation design!
After the successful development of our first cotton combing prototype, we participated in the International Textile Machinery Exhibition in Osaka, Japan in 1993. At that time, cotton combing machines both domestically and internationally were still controlled by relays. Because we used PLCs earlier, our combing equipment was at the forefront of the world in terms of control technology.
Following that, the company's combing equipment—the FA355 series sliver winding machine—also adopted the C60P PLC.
3.2 CQM1 is used in the "second generation" PX2 cotton combing machine
In the late 1990s, we used Omron's CQM1 PLC in our "second-generation" PX2 cotton combing machine and the matching SR80 sliver lap machine. Within a few years of successful development, sales reached several thousand units. However, since the CQM1 PLC can be roughly classified as a medium-sized PLC, and its price remains relatively high even today, and it has since been replaced by the CP1H small PLC mentioned below, it will not be discussed further in this article.
3.3 CPM1A is used in the "third generation" CJ25 cotton combing machine
With the development of the times, our combing equipment, like other industries, also needs to be constantly updated. First, we need to enhance its functions without expanding the electrical box space, which requires the support of advancements in PLC technology.
In the late 1990s, with the launch of Omron's new CPM1A PLC, its size was almost half that of the original C60P. Moreover, it represented a significant leap forward in key performance indicators compared to the C60P, including instruction types (over 90), instruction execution time (LD instruction 1.72μm), data storage, number of timers/counters (128-bit), interrupt and pulse inputs, high-speed counters, analog setting, and communication distance (50M). It fully met our control requirements. Therefore, we again adopted the Omron CPM1A and MPT002 display combination as the control and display unit for our "third-generation" cotton combing machine (a mid-range combing machine produced and sold concurrently with the "second-generation" combing machine). The successfully developed "third-generation" CJ25 cotton combing machine has been used reliably and received positive feedback from numerous user factories for many years.
3.4 CPM2A is used in other products of the company.
The CPM2A series PLC is an upgraded product launched by OMRON based on the CPM1A. Compared with the CPM1A, it has significant improvements in program capacity, instruction types, instruction execution time, data storage, and the number of timers/counters. It also adds an RS232 communication port, supporting various protocol-free communication methods. In particular, the addition of pulse output and synchronization functions greatly facilitates the automated control of equipment. When we were responsible for the commissioning of the "High-Energy Focused Ultrasound Therapy Instrument," an outsourced product for our subsidiary, we made full use of the CPM2A's pulse output and synchronization functions. This allowed us to effectively control the quality of the equipment during the manufacturing and commissioning process, meeting the customer's order requirements, given the high precision requirements of this therapy instrument.
4. The latest CP1H model is used in the "fourth generation" CJ60 cotton combing machine.
In recent years, the continuous advancement of PLC technology has provided a guarantee for the automatic control of our new product development. Omron's new CP1H mini PLC, launched in 2006, represents a significant improvement over the CPM2A in terms of I/O expansion capabilities, program capacity (20K), instruction types, instruction execution time (LD instruction 0.1μm), DM data area (32K), number of timers/counters (quite numerous), function blocks, complex function operations, floating-point operations (ST), built-in analog input/output functions, serial PLC connectivity, simple Modbus-RTU master station functionality, and three communication ports. These specifications are roughly equivalent to those of mid-sized PLCs in the industry, while the CP1H's size and price are similar to other mini PLCs. Therefore, the CP1H's cost-effectiveness is indeed very attractive. Furthermore, the CP1H introduces a standard USB interface for connecting to personal computers, increasing the device's versatility (however, this function sometimes experiences disconnections during on-site commissioning due to interference from the frequency converter; in such cases, monitoring can be achieved through the CP1H's built-in RS232 serial port).
In terms of software, the CX-One, launched simultaneously with the CP1H, is more user-friendly than previous Omron software versions. It provides users with a high-level application platform in areas such as instruction writing, address searching, code commenting, software protection, function block creation, multiple programming languages, and debugging monitoring. In particular, the flexibility of function block invocation and multiple programming languages greatly facilitates solution design. It's worth mentioning that Omron allows the CX-One software to easily read or upgrade historical programs created nearly 20 years ago using "LSS" software in the DOS operating environment, "SSS" software in the Win 98 environment, and all programs created in the Windows environment. This demonstrates its advantage compared to some large European multinational companies, whose different levels of PLCs are even developed by different teams in different countries, thus using two completely different software development systems. It's difficult for them to maintain the continuity of software development like Omron, ensuring that each new software release takes into account good compatibility with historical products. This is one of the reasons why we have long been willing to use Omron PLC products.
In 2006, when developing our latest "fourth-generation" CJ60 high-speed cotton combing machine, we found that the automatic control functions of the equipment were significantly increased compared to the previous three generations. The system included analog control, function operations, Modbus communication, and high-speed data acquisition. Without the CP1H, we could only use a medium-sized PLC to meet the requirements of the control scheme. After comprehensive consideration, we chose the Omron CP1H small PLC.
4.1 Overall Plan
By combining Omron's CP1H programmable controller, Pro-face's touchscreen, and KEB's frequency converter, the company has developed a control solution for its "fourth generation" CJ60 cotton combing machine. Its core technology involves connecting the PLC, touchscreen, and frequency converter via RS232 and Modbus communication, respectively. The PLC's built-in analog input function directly connects to eight analog sensors, enabling intelligent and digital control of key equipment components, memorization of historical fault occurrence and resolution times and frequencies, multi-level password-based hierarchical management, and upward communication via the touchscreen's Ethernet interface. This provides essential support for the modern management of textile mills.
For PLC software programming, program segments with different functions are separated as needed, and each task is completed using the most suitable programming language, such as ladder diagram or high-level language.
4.2 I/O Configuration, Flags, and Variable Declarations
The I/O configuration, flags, and variable declaration tables allow for convenient and flexible access to the type, address, and function comments of each I/O point, flag, and variable. Some declarations are shown below:
The system's logic control is primarily implemented using ladder diagrams. Ladder diagrams provide clear, simple, intuitive, and easy-to-understand signal flow; they are an object-oriented, real-time, graphical programming language. A section is shown below: (see Figure 2)
One of the features of Cx-One software is that it can display the address bar of a variable on the same page below the program segment, which is convenient for observation and debugging.
4.4 Application of ST Language
ST language is particularly convenient for control programs with multiple loops and function operations. Such programming methods are generally found in medium-sized PLCs, but the CP1H small PLC also possesses this feature, which is quite unique. In the CJ60's overall control system, besides the control of logical quantities, other control functions are implemented using the flexible ST language. For example, the control program written using this language for reading and processing signals from N sensors with the same function has achieved excellent results. An excerpt is shown below: (See Figure 3)
4.5 Function Block Development and Invocation
Function block programming is another distinctive feature of the CP1H minicomputer. When programming recurring sequences of identical logic, various function blocks are pre-defined and then called upon as needed by the main program. This simplifies the entire programming language, making the design of the control system more concise, readable, modifiable, and maintainable. Examples are shown below (see Figures 4 and 5).
5. Conclusion
To date, apart from the CJ40S multi-axis drive cotton comber developed by our company using the PCC system in the past two years, the CJ60 cotton comber, which uses Omron's most advanced small-scale CP1H machine as its central controller, boasts the most advanced level of electrical automation control among similar products both domestically and internationally. Nearly 200 CJ60 cotton combers have been sold and are well-received by users. Recently, the CJ60 also successfully passed the new product scientific and technological achievement appraisal by a national authoritative institution and the acceptance of a national special funding project. The appraisal conclusion for the entire machine is: "The CJ60 cotton comber is at a leading level domestically and an advanced level internationally."
Omron's CP1H mini PLC is also used in our CL15 sliver winding machine paired with the CJ60, as well as in the upgraded CJ40 and SR80 pre-spinning equipment. Omron PLCs are stable and reliable, inexpensive, feature-rich, flexible and convenient to use, and easy to operate and maintain—these are the fundamental reasons for their enduring market presence. In today's era of widespread automation, computers, digitalization, and the internet, textile machinery must continuously improve its automation level to maintain a place in the fierce market competition and make its due contribution to improving people's living standards.
For PLC developers, the market potential is enormous. Not only in my country, but even in industrially developed Japan, surveys show that PLC-supported mechatronics products account for about 40%, while relay and contactor control still accounts for over 20%. Therefore, there are still many applications requiring PLCs, especially in my country. We hope that PLC manufacturers will continue to launch increasingly high-performance industrial control products to meet the automation control needs of various fields.
Both PLCs and textile machinery have a bright future.
References
Programming manuals and operation manuals for all generations of Omron PLCs.
