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Capability requirements, structure composition and key technology analysis of UAV autonomous control system 1

July 12, 2021

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Thanks to advances in related technologies such as machinery, materials, control, communications, optics, software, and algorithms, the capabilities and key technology maturity of UAV systems have been continuously improved in recent years. And under the dual effects of technology promotion and market pull, UAV systems are gradually entering a virtuous cycle of iterative development mode: On the one hand, UAV systems are becoming more and more proficient in various traditional classic mission scenarios. And excellent, gradually realized the leap from "flying to usable"; on the other hand, the improvement of UAV system capabilities has expanded its application fields, and more new and potential application scenarios have continuously emerged in addition to the original requirements. , And the traction from new demands has in turn promoted the development of related technologies.


In the above development process, the autonomous control system for autonomy/autonomous capability requirements is one of the most important subsystems of UAVs. Its research and application is undoubtedly an important driving force for the continuous maturity and practical application of UAV systems. Its understanding and knowledge are constantly deepening and improving. Fully autonomous control is the inevitable direction and typical feature of the future development of UAVs. Its primary goal is to support the ability of UAVs to achieve autonomous flight and complete specific tasks autonomously. Moreover, the development and progress of artificial intelligence technology in recent years has also provided new ideas and motivation for the realization of intelligent "cognition" and "decision-making" capabilities of autonomous control systems.


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1 Understanding of autonomous control system


Generally speaking, the control process used to realize autonomy or autonomy can be called autonomous control. Autonomous control essentially belongs to the category of intelligent control, and the strength of system autonomy depends on the level of intelligence. As an important means for the realization of autonomy, the discipline of intelligent control has made considerable progress in basic theories, and its application fields have been continuously expanded. But to this day, objectively speaking, intelligent control is still immature. This is largely due to the research on "intelligence" itself. The challenging field of intelligent science has not yet made a fundamental breakthrough, and there are still A large number of key issues need to be explored and studied.


Unmanned systems are the most important application carrier and research direction of intelligent control technology. With the development of electronic technology, computer technology and control technology, unmanned systems represented by drones have exploded since the 1990s. development of. Unmanned systems' inherent autonomy requirements, combined with the development of advanced control technologies such as intelligent control, have given birth to the emergence of autonomous control related concepts. Since then, research on autonomous control of unmanned systems has gradually gained attention in developed countries such as the United Kingdom and the United States, and autonomous control systems and related technologies have become the most important support for the realization of unmanned systems' autonomy. Entering the 21st century, China has also carried out continuous, extensive and in-depth discussions and research on autonomous control technology, and carried out flight demonstration and verification of related technologies for autonomous control of UAV platforms in engineering practice.


Regarding the intelligentization and autonomous control of UAVs, many academicians in the domestic industry have important relevant discussions on this. Academician Wu Hongxin once clearly pointed out: "Autonomous operation is the goal, and intelligent control and various other control methods are the means to achieve autonomous operation." Academician Fan Bangkui also pointed out that advanced UAVs need to be intelligent at three levels: " Single-plane flight intelligence, multi-aircraft collaboration intelligence, and task autonomous intelligence." Academician Bao Weimin once pointed out: "The intelligent autonomous control of unmanned systems is the deep integration of unmanned system platforms, artificial intelligence and intelligent control. Its control theory and technology are cutting-edge, basic and comprehensive, and will support the future of unmanned systems. One of the core areas of development.” Academician Zhao Xu also clearly pointed out: “To further break through the autonomous control technology of UAVs, it is necessary to improve the level of intelligence of UAV systems. The intelligence of autonomous control of UAVs is mainly reflected in 3 Three aspects, namely flight intelligence, decision-making intelligence, and cluster intelligence. The intelligence of drone flight is the basis for the realization of drone decision-making intelligence and cluster intelligence. The intelligence of cluster collaboration is to realize the full autonomy of drones. An important approach to the ultimate goal.” It can be seen that the UAV system expects to have “autonomous intelligence”, that is, intelligence is essentially to better realize task-oriented autonomy, and the main technical means is autonomous control.


Autonomous control of UAV can be understood as "high" automatic control under various uncertain conditions such as unstructured environment, unpredetermined situation, unprogrammed tasks, etc. Its most important feature is: without human intervention , Faced with uncertainty, solve complex optimization control problems in real-time or near real-time. In other words, autonomous control of drones means that without manual/external intervention, drones can independently generate optimized control and management strategies through online environment/situation perception and information processing to avoid various obstacles and threats. Complete various specific tasks, and have fast and effective dynamic task adaptability. The challenges faced by the autonomous control of UAVs mainly come from the complexity, uncertainty and dynamics of the operating environment, tasks and the UAV system itself.


As for the autonomous control system of UAVs, there is no clear definition so far, and the connotation and understanding of the autonomous control system are also different with the application occasions, technological development and the passage of time. However, from the perspective of functional decomposition and system implementation, it is generally believed that the autonomous control system of drones is generally composed of the drone task management system, flight management system, control execution system, and perception and communication system. The decision-making, management and control functions of the machine can complete complex tasks in a dynamic and uncertain environment. The functional configuration and task application configuration of different UAV autonomous control systems make UAVs have different autonomous control capabilities to adapt to different autonomy requirements and complete different tasks. Its main function is to organically combine the various modules of the system such as perception, planning, decision-making and action. Its functions include: connecting the various subsystems into a whole, including the interface specifications, communication protocols and data processes of each component; unified management and scheduling of each subsystem, controlling their functions, and coordinating the work according to the overall working model. Each subsystem completes the overall task in unison; provides an intelligent processing mechanism for uncertainty, and realizes independent decision-making, management and control within the scope of authorization and without external manual intervention.


2 Capability requirements of UAV autonomous control system


For UAV systems, due to the different requirements for autonomy on different platforms and different task scenarios for different users, the requirements for the realization of autonomous control systems are also different. However, it is still possible to study and analyze the capability requirements of UAV autonomous control systems from a macro perspective, so as to provide an important reference and reference for technical research and guide the development and design of UAV autonomous control systems in engineering practice.


Up to now, many domestic experts and scholars have conducted in-depth research on the capabilities of autonomous control systems for UAVs, and have formed a number of relatively complete viewpoints. Researcher Wang Yingxun of Beijing University of Aeronautics and Astronautics believes that autonomous drones should have four basic capabilities: security capabilities, perception capabilities, decision-making capabilities, and coordination capabilities; Professor Zhu Huayong of the National University of Defense Technology [15] believes that the future technical requirements for autonomous control of UAV systems It is mainly reflected in the realization of the following four capabilities: comprehensive environmental awareness and intelligent battlefield situation awareness, autonomous navigation, planning and control capabilities under complex conditions, human-computer intelligent integration and learning adaptability, and multi-platform distributed collaboration Ability; Researcher Fan Yanming of Shenyang Institute of Aviation Industry believes that the system must have three main capabilities: independent information acquisition capability, independent independent information processing and decision-making capability, and independent behavior execution capability based on the autonomous behavior of drones. Researcher Ma Weihua and Liu Jiarun of Beijing Aerospace Automatic Control Institute believe that the capabilities of aerospace intelligent control systems can be summarized into five aspects: perception and understanding capabilities, movement and control capabilities, learning and adaptation capabilities, planning and decision-making capabilities, communication and collaboration ability. Regarding the intelligent control system, Academician Wu Hongxin clearly pointed out that it should have the following abilities: perception and cognition, online planning and learning, reasoning and decision-making, and coordinated control of multiple actuators.


Summarizing the above-mentioned various points of view, it is not difficult to find that the capability requirements of the UAV autonomous control system and the embodiment of UAV autonomy are highly unified, and a brief analysis can be made from the following perspectives.


First of all, if it is implemented based on the OODA cycle, since "no one is on board" and "people are on the loop", for the autonomous control system of UAVs, it is natural to expect that all links can best be derived from the UAV system. The master completes and forms a closed loop of control. In this way, in order to realize an autonomous OODA cycle, it is necessary to have the corresponding perception and cognition ability, evaluation and judgment ability, planning and decision-making ability, and control execution ability.


Secondly, considering the actual use of drones, in addition to the drone itself, the main elements of its application scenarios generally include the natural environment, missions, hostile forces, friendly forces, and operations/users. The realization of the UAV autonomous control system must comprehensively consider the influence of the above-mentioned elements, especially the effective resource management, scheduling and control for flight and mission must be realized through the interaction, integration and coordination of one's own forces. Therefore, in addition to the capabilities necessary for the realization of the above-mentioned OODA cycle, the UAV autonomous control system should also have the corresponding human-machine fusion capability and multi-aircraft coordination capability.


In addition, in addition to the basic capabilities required for the realization of autonomous control functions, it is also expected that the UAV autonomous control system will have certain fault-oriented fault-tolerant repair capabilities, as well as more intelligent learning and evolution capabilities.


To sum up, the main capability requirements of the UAV autonomous control system can be summarized into 8 items, namely: perception and cognitive ability, evaluation and judgment ability, planning and decision-making ability, control execution ability, human-machine integration ability, and multi-machine coordination ability. , Fault tolerance, learning and evolution ability.