Engineers explain measurement and control system simulation and measurement and control equipment software technology

1. Equipment-level simulation technology of measurement and control system

1. Technical characteristics of device-level simulation of measurement and control systems

The equipment-level simulation of the measurement and control system mainly uses computer software simulation technology to test the real system or the imagined system with the system model with the help of computers. The equipment-level computer software simulation of the measurement and control system has the following characteristics:

(1) Using software simulation technology to conduct tests can greatly reduce costs, especially for large-scale measurement, control and communication systems, which can reduce expensive hardware investment. At the same time, simulation equipment can be reused, and its test environment and test plan can be easily changed, which can shorten the test cycle;

(2) It is conducive to the rapid absorption of the continuously developing advanced measurement, control and communication technologies and the continuous improvement of measurement, control or communication modules;

(3) Facilitate optimization design. For the measurement, control and communication system in the scheme stage, the system model can be designed first, and repeated experiments can be carried out through simulation to find the optimal system structure and parameters, so as to optimize the system design and improve the design level;

(4) It can be very close to the actual system, providing an accurate evaluation method for engineering design and avoiding the limitation of hardware simulation on the number of test equipment and the level of simulation devices;

(5) Computer software simulation makes it easy to process simulation results and data accurately, quickly and conveniently, and facilitates data storage and subsequent analysis.

2. Main tasks of device-level simulation of measurement and control system

The main task of the device-level simulation of the measurement and control system is to conduct conceptual modeling of the real or imagined system, and to establish mathematical models and simulation models for distance measurement and speed measurement accuracy analysis, and mathematical models and simulation models for telemetry, remote control, voice, and data transmission bit error rate analysis on the basis of the clear system model. Through the operation of the simulation model, the simulation analysis of the system's distance measurement, speed measurement accuracy index and bit error rate index is obtained, the system operation status is qualitatively analyzed from the functional principle, and the system operation status is quantitatively analyzed from the scheme and technical indicators, and the consistency with the actual measurement and control station system operation results is obtained.

On the other hand, in the design of subsystems and components, by establishing mathematical models of each subsystem and component in the ground equipment of the measurement and control system, simulating data flow, control flow and working status, analyzing the dynamic characteristics and steady-state characteristics of the system, and verifying and evaluating the overall and subsystem solutions. First, establish mathematical models of each subsystem and component. The mathematical model of each subsystem adopts a single module design, and the components inside each subsystem module also adopt functional module design. Each functional module is stored in the runtime library in the form of a library module. By selecting different functional modules, subsystems with different functions can be formed. Then, according to the data flow, control flow and working status of each subsystem, organize the independent simulation of the subsystem, and then simulate the whole system through the overall measurement and control communication plan . When the subsystem is independently simulated, the influence of other subsystems on it is taken as the external input of the subsystem, and the external environment simulation module is used to generate equivalent external input. From the subsystem to the overall simulation, the combination principle should be met.

3. Development direction of measurement and control simulation technology

At present, system simulation technology has become a key national technology and national defense technology that developed countries focus on. The rapid development of information technology in the 21st century will make simulation technology and aerospace technology closely integrated into a whole at all levels.

The simulation technology of measurement and control system can provide optimization solutions and key technology designs for future space-based measurement and control, small satellite measurement and control, deep space measurement and control and other systems. In the field of aerospace simulation, we will focus on the development of constellation simulation technology to realize distributed interactive simulation of satellite in-orbit operation and multi-satellite management. Through the participation of the satellite itself and the ground station, each satellite can coordinate operation to maintain accurate position and posture and connection of working status. For various satellite systems from development to operation, system models and simulation systems including ground application systems and satellites should be established according to the situation in order to analyze, optimize and support the long-term operation of satellites and training of management personnel. 2. Software technology of measurement and control equipment

1. New features of the development of measurement and control equipment technology

The aerospace measurement and control system is a complex system, which involves different modulation systems, working modes, information transmission and data modulation and demodulation processing. In the past, China's satellite measurement and control station construction model was basically to develop a new measurement and control station for each satellite (the main new development content was reflected in the terminal equipment). In order to meet the requirements of different measurement and control tasks, the equipment was often huge and it was necessary to repeatedly build hardware equipment with similar functions. With the rapid development of computer technology and digital signal processing technology, measurement and control equipment has gradually developed in the direction of integration, digitization, modularization and standardization. By adopting high-speed A/D, DSP, FP-GA, MPU, DDS, digital-analog hybrid integrated circuits, high-speed large-capacity storage computers and network technology, bus technology, high-speed digital signal processing and data processing are completed, and speed measurement, distance measurement, telemetry, remote control, data transmission and monitoring are integrated into one, and integrated and integrated design is carried out. The main contents of modularization and standardization of measurement and control equipment include unit modularization, function, technical indicator serialization, interface standardization and normalization.

The new features of the development of measurement and control equipment technology have promoted the application of software radio technology in the field of measurement and control communication. Digitalization is the basis for the softwareization of measurement and control equipment, and softwareization is a good technical approach to achieve integration, standardization and normalization of measurement and control equipment.

2. Technical foundation of software-based measurement and control equipment

The technical theory of software-based measurement and control equipment is software radio. Software radio technology breaks through the design limitations of traditional radio equipment with single-function and poorly scalable hardware as the core, and emphasizes the new design idea of ​​using open and simple hardware as a universal platform and using programmable, upgradeable, and reconfigurable application software to realize various radio functions as much as possible. Users can choose different application software to meet the needs of different functions in different periods and different usage environments on a universal and scalable hardware platform, and can adapt to the continuous development of technological progress, save a lot of hardware investment, greatly shorten the research and development cycle of new products, and adapt to market changes in a timely manner.

The basis of software-based measurement and control equipment is digitization, and its core is the ultra-high-speed time response and ultra-large-scale high integration of digital devices and chips. At present, microelectronics technology is developing rapidly, and the number of transistors on a single integrated chip doubles every 18 months. In 2001, integrated chips with 1 billion transistors were launched, and in the next 20 years, integrated chips with 1 trillion transistors will appear. The high degree of integration of digital circuits provides a strong guarantee for the development of software-based measurement and control equipment technology.

3. Characteristics of software technology for measurement and control equipment

The softwareization of measurement and control equipment utilizes programmable technology to load different software to achieve multiple uses of one machine and one station, thereby completing measurement and control tasks with multiple functions and multiple technical states. The main technical features of the softwareization of measurement and control equipment are:

(1) Software is highly flexible. New functions can be easily added by adding software modules. Software modules can be changed or updated by wireless loading. The software modules can be selected based on the strength of the required functions.

(2) Software is highly open. It adopts a modular and standardized structure. The hardware can be updated or expanded as devices and technologies develop, and the software can be continuously upgraded as needed.

(3) Software can easily apply a variety of software algorithms to perform data smoothing, system error correction, modeling and prediction analysis, linear or nonlinear compensation, and fuzzy control under specific conditions, thereby effectively improving measurement and control accuracy;

(4) Software can greatly reduce the types and quantity of equipment hardware, improve the level of equipment miniaturization and system reliability, and greatly reduce the development cost and cost of the measurement and control system;

(5) Softwareization facilitates the modularization and standardization of measurement and control equipment.

4. Contents of measurement and control equipment software technology

The software technology of measurement and control equipment mainly includes:

(1) Measurement and control video data processing software technology, including data processing module, reconfigurable monitoring software module, post-event data processing module, etc.;

(2) Modularization and reconfiguration of channels and software extension from intermediate frequency to radio frequency;

(3) Programmable, reconfigurable, modular, and standardized technologies for terminal equipment;

(4) Antenna pointing programming control technology.

5. The development direction of software technology

The software technology of measurement and control equipment is dominated by software. All its working processes and parameter processing can be defined and controlled by software. Its development direction can be explained from the following aspects:

(1) RF front-end sampling digitization technology. The purpose of software radio is to simplify the RF analog front end as much as possible, so that the A/D conversion can be as close to the antenna as possible to complete the digitization of the analog signal, and the digitized signal should be processed by software as much as possible to achieve various functions and indicators. With the rapid increase in the frequency response rate of digital chips and devices, the rate of several gigahertz has reached the stage of engineering application. It can be imagined that in the near future, there will be a major breakthrough in the digitization of RF direct bandpass sampling;

(2) Baseband space transmission. In wireless transmission, the sine wave with strict regular characteristics has always been the main form of carrier signal. Baseband space transmission is to abandon the sine wave carrier modulation and directly realize space transmission in digital form. Its propagation medium is a very narrow time domain pulse, and the pulse width is generally less than 1 ns. Its signal energy is distributed in the range from direct current (DC) to several gigahertz, and can be radiated and received with low distortion using ultra-wideband antennas;

(3) Software testing and identification technology. Since software plays a leading role in software-based measurement and control equipment, the correctness and reliability testing and identification of software will become a specialized technology .

At present, several popular communication simulation design platforms such as COSSAP, SPW, SystemView, etc. can meet the design and simulation requirements at different levels, from digital signal processing, filter design to complex communication systems. In these systems, complex analog, digital, hybrid and multi-rate systems can be constructed in DSP, communication and control systems. The system has a large number of optional libraries, allowing users to selectively add communication, logic, DSP and RF/analog functional modules, and can perform various system time domain/frequency domain analysis, and can perform theoretical analysis and distortion analysis on RF/analog and its hybrid systems. Of course, the simulation platform of the general communication system cannot meet the application simulation requirements of the measurement and control communication system to a large extent. The simulation of the measurement and control system on the general platform (the simulation platform can be developed independently) focuses on solving special problems in the measurement and control field. It not only has qualitative simulation analysis on the system principle, but more importantly, it needs to consider the performance of the actual components of the subsystem and component design indicators. Quantitative simulation analysis guides the actual design of the system and subsystem, and even directly generates practical code for DSP, FPGA or VHDL.

Since softwareization is based on digitization, at the current level of device technology development, the current softwareization of measurement and control equipment is mainly reflected in the softwareization of measurement and control system terminals (i.e. baseband equipment below 70 MHz intermediate frequency). The softwareization of terminal equipment conveniently realizes the reconfiguration of terminal equipment. The requirements of this reconfigurable terminal for digital computing are mainly real-time and accuracy, including computing speed, computing power, data storage capacity, data throughput, etc. There are two ways to realize the softwareization of terminal equipment. One is to use DSP to implement it. With the emergence of new DSP devices, the amount of computing that DSP can provide has been greatly improved, and many algorithms implemented by ASIC may be gradually transferred to DSP implementation to achieve higher flexibility. However, at the current level of technology, this solution has the disadvantages of high power consumption and slow processing speed. The second is to use DSP and FPGA to implement it. In the past, FPGA was a rapid prototyping method for ASIC design and an intermediate process. Now, using FPGA directly for system design can reduce the number of ASIC chips required, improve flexibility, and also significantly shorten the development time. The benefit it brings is that a single or relatively small number of chips can support more standard combinations.

Therefore, the components, subsystems and overall system plan of the measurement and control system can be evaluated through simulation operation and analysis. Since the simulation module is modularized and standardized in function, the terminal module in the overall plan can realize the software of the measurement and control equipment through a dedicated interface, closely combining system simulation and software technology to form a new model for the development of future measurement and control systems.

IV. Conclusion

At present, in the development of measurement and control system equipment, there are only a few examples of special research using simulation technology, and there is still a long way to go before integrated and comprehensive simulation applications. Relatively speaking, the software technology of measurement and control equipment is more mature, but the efficiency in actual engineering applications is still not high, and we need to make a good summary. The organic combination of measurement and control system simulation technology and equipment software technology will be an important direction for us to focus on practical research for a long time in the future.