Flight control modal types and key technical issues


Modern flight, whether military or civilian, manned or drone , can change the input/output characteristics of the aircraft itself to have different flight qualities by adding appropriate feedforward and feedback networks to the fly-by-wire system. To accommodate the need to perform different missions at different flight phases, thereby forming a multi-task multi-modal control technique or system in modern flight control.
A broader definition of multimodal control is that the system has a different set of control laws and that the set of control laws allows the controlled aircraft to have predetermined performance specifications under different operating modes. The operating mode of the drone is related to the dynamics of the flight and its operating environment. Generally, the operating modes of the drone can be divided into three categories: mission mode, internal mode and external mode.
(1) Mission mode. The drone undergoes many different operational modes during the mission. For example, in the first draft of the Dong Lei mission, an advanced drone was required to complete takeoff, high altitude cruise, low altitude penetration, target attack, target simulation, air combat maneuver, low altitude launch, and power approach and landing. In general, in these modes, different operating modes require different control laws in order to achieve the desired performance. These expected performances include not only accurate tracking of command signals, but also performance requirements such as optimal navigation, optimal fuel consumption, and maximum beam sea.
(2) Internal mode. The internal mode of the drone itself mainly refers to the dynamics of flight during different mission phases due to the consumption of fuel, the release of mission equipment (infrared, visible light simulation equipment, attack weapons, etc.) and the quality change. The system is placed in a different flight mode. In addition to this, what is more desirable is the failure mode of the system, because failure of the flight-critical subsystem or component will cause a significant reduction in the system's performance. These faults include various types of sensors, actuators (steering gears, throttle motors), and engine faults. For these internal modes, the UAV flight control system is required to have different control strategies. The currently rapidly developing adaptive control method for advanced aircraft fault monitoring and identification, as well as an integrated method that can handle multiple simultaneous faults in a flight critical subsystem, is a control strategy for the tuxedo to accommodate these fault modal control needs.
(3) External mode. When the unmanned environment of the drone changes unpredictably and causes changes in the operating mode of the system (including very large external disturbances, combat operations, and sudden threats), a new working mode needs to be formed. The development of a wide range of autonomous intelligent flight control strategies to ensure that any unexpected operational modes are encountered, the system can still achieve the desired goals.
In the development process of foreign flight control systems, multi-modal control has also developed greatly in the afternoon. Multi-task, tailorable multi-modal control laws are used for both manned and unmanned aerial vehicles. For example, in order to meet the needs of aircraft take-off, cruise and different air combat missions, a normal operating mode (for the entire flight envelope for take-off, cruise to landing, and secondary missions), air-to-air shooting mode, Air-to-ground design modalities and air-to-ground bombing of Du mode, as well as target simulation modalities and so on. In order to improve system reliability and safety, a control rate reconstruction mode and an independent bloody control mode are also designed. The former aims to adopt new control structures and control laws after some sensors and some actuators fail in the system. The latter is switched to the standby control system in the event of a failure of the master system, so that although the performance and flight quality will be degraded, the flight is safe.
The key issues to be solved in designing a multi-modal control system are: 1 how to determine and classify the control mode of the flight control system ; 2 how to implement complex multi-modal control management; 3 how to reduce and suppress the conversion of different modal control laws The transient response of the flight.

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