Historical development

The earliest automation control can be traced back to ancient China’s automation timers and leakage guide cars, while the widespread application of automation control technology began during the Industrial Revolution in Europe. Watt, a British inventor, applied the principle of feedback while inventing the steam engine and invented the centrifugal governor in 1788. When the load or steam supply changes, the centrifugal governor can automatically adjust the opening of the intake valve to control the speed of the steam engine. [2]
More than 150 years ago, the first generation of process control systems was based on the pneumatic signal standard of 5-13psi (pneumatic control system PCS), Pneumatic Control System）。 A simple on-site operation mode, control theory has initially formed, and there is no concept of a control room yet.
The second generation process control system (analog or ACS, Analog Control System) is based on current analog signals of 0-10mA or 4-20mA. This significant advancement firmly dominated the entire field of automatic control for a full 25 years. It marks the arrival of the era of electrical automatic control. The control theory has made significant development, and the establishment of the three major control theories has laid the foundation for modern control; The establishment of control rooms and the mode of separating control functions have been used to this day.
The Third Generation Process Control System (CCS) began the application of digital computers in the 1970s, which gave rise to significant technological advantages. People were the first to use it in the fields of measurement, simulation, and logic control, leading to the emergence of the Third Generation Process Control System (CCS), Computer Control System）。 This is known as the third-generation process control system, which is a revolution in the field of automatic control. It fully leverages the strengths of computers, and people generally believe that computers can do everything well. Naturally, a central control computer system called “centralized control” emerged. It should be pointed out that the signal transmission system of the system is still mostly using 4-20mA analog signals. However, soon after, it was discovered that with the concentration and reliability of control, the danger of losing control has also increased, and even a slight mistake can paralyze the entire system. So it quickly developed into Distributed Control Systems (DCS).
The fourth generation process control system (DCS): With the rapid development of semiconductor manufacturing technology, the widespread use of microprocessors, and the significant increase in computer technology reliability, the fourth generation process control system (DCS) is currently widely used. Its main feature is that the entire control system is no longer just a single computer, but a control system composed of several computers, intelligent instruments, and intelligent components. So decentralized control became the most important feature. Another important development is that the signal transmission between them not only relies on 4-20mA analog signals, but also gradually replaces analog signals with digital signals.
The fifth generation process control system (FCS): FCS evolved from DCS, just like DCS evolved from CCS, with a qualitative leap. The development of “decentralized control” to “on-site control”; The transmission of data adopts a “bus” method. But the real difference between FCS and DCS is that FCS has a broader development space. Due to the continuous improvement of traditional DCS technology, the communication network only reaches the level of on-site control station at the lowest end. The connection between on-site control station and on-site detection instruments and actuators still uses one-to-one transmission of 4-20mA analog signals, which is costly, inefficient, and difficult to maintain. It cannot fully realize the potential of on-site instrument intelligence and achieve comprehensive monitoring and deep management of the working status of on-site equipment. The so-called fieldbus is a fully digital, bidirectional transmission, multi node branch structure communication link that connects intelligent measurement and control equipment. Simply put, traditional control is a loop, while FCS technology involves various modules such as controllers, actuators, detectors, etc. hanging on a bus to achieve communication, and of course, transmitting digital signals. The main buses include Profibus, LonWorks, etc.

1. 1940s – early 1960s:
Demand driving force: market competition, resource utilization, reducing labor intensity, improving product quality, and adapting to the needs of mass production. Main features: This stage is mainly a single machine automation stage, characterized by the emergence of various single machine automation processing equipment, and the continuous expansion of applications and development towards depth. Typical achievements and products: CNC machine tools for hardware CNC systems.
2. In the mid-1960s to early 1970s:
Demand driving force: Market competition intensifies, requiring fast product updates, high product quality, and adapting to the needs of large and medium batch production and reducing labor intensity. Main features: This stage is mainly marked by automatic production lines, which are characterized by the emergence of various combination machine tools and combination production lines on the basis of single machine automation. At the same time, software numerical control systems have emerged and been used for machine tools. CAD, CAM and other software have begun to be used in actual engineering design and manufacturing. At this stage, hardware processing equipment is suitable for large and medium batch production and processing. Typical achievements and products: an automatic production line used for drilling, boring, milling and other processing.
3. From the mid-1970s to present: Demand dynamics: Changes in the market environment have made common problems in multi variety, medium and small batch production increasingly severe, requiring automation technology to develop in its breadth and depth, making its related technologies highly integrated and exerting overall optimal efficiency. Main features: Since American scholars first proposed the concept of CIM in the early 1970s, there have been significant changes in the field of automation. Its main characteristics are that CIM has gradually been accepted as a philosophy and method by people; CIM is also a corresponding technology for implementing integration, integrating dispersed and independent unit automation technologies into an optimized whole. The so-called philosophy is that enterprises should analyze and overcome existing “bottlenecks” based on their needs, in order to achieve the ideological strategy of continuously improving their strength and competitiveness; As the corresponding technology for implementing integration, it is generally believed to be: data acquisition, distribution, and sharing; Network and communication; Workshop level equipment controller; The specifications, standards, etc. of computer hardware and software. Meanwhile, parallel engineering, as a business philosophy and work mode, has been applied and active in the field of automation technology since the late 1980s, and will further promote the integration of unit automation technology. Typical achievements and products: CIMS factory, flexible manufacturing system (FMS).
With the introduction of new achievements in modern applied mathematics and the application of electronic computers, in order to adapt to the development of aerospace technology, automatic control theory has entered a new stage – modern control theory. The main research focuses on the optimal control problem of multivariable variable parameters with high performance and precision, using the state space method based on the state. At present, the theory of automatic control is still developing, and intelligent control theory based on control theory, information theory, and bionics is deepening.
In order to achieve various complex control tasks, the controlled object and control device must be connected in a certain way to form an organic whole, which is the automatic control system. In automatic control systems, the output of the controlled object, also known as the controlled quantity, is a physical quantity that requires strict control. It can be required to maintain a constant value, such as temperature, pressure, or flight path; The control device is the overall mechanism that applies control to the controlled object. It can use different principles and methods to control the controlled object, but the most basic one is a feedback control system based on feedback control principles.
In a feedback control system, the control effect exerted by the control device on the controlled device is obtained from the feedback information of the controlled quantity, which is used to continuously correct the deviation between the controlled quantity and the control quantity to achieve the task of controlling the controlled quantity. This is the principle of feedback control.