SCIENTIA SINICA Informationis, Volume 49, Issue 5: 520-537(2019) https://doi.org/10.1360/N112018-00318

UAV sense and avoidance: concepts, technologies, and systems

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  • ReceivedNov 30, 2018
  • AcceptedFeb 28, 2019
  • PublishedMay 15, 2019


Unmanned aerial vehicle (UAV) sense and avoidance is one of the core technologies for integrating UAV into airspace, and it is a significant symbol of UAV autonomy and intelligence. Critical technologies and systems have been gradually developed over the past few years. We review studies related to the concept, techniques, and systems on UAV sense and avoidance, which is based on policies, regulations, and techniques. Moreover, we review the environment sensing technology related to collision avoidance path planning and maneuver control. We also propose two different systematic levels of sense-and-avoid (SAA) considering the differences in platform properties, application scenarios, and operational manners of the large/middle-sized and small/micro-sized UAVs. Furthermore, two different system paradigms, i.e., the hierarchical paradigm and reactive paradigm, are proposed to guide the system design of SAA. Finally, our study provides the prospect of sense and avoidance based on policies and regulations, technologies, and system design.

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  • Figure 1

    (Color online) SAA function flow

  • Figure 2

    UAV SAA environment sensing technology

  • Figure 3

    (Color online) The hierarchical SAA paradigm for large & middle size UAV

  • Figure 4

    (Color online) The reactive SAA paradigm for small & micro size UAV

  • Table 1   UAV SAA sensor configuration
    Platform T-CAS ADS-B Ground radar Airborne radar Lidar Man eye EO IR IRST Ultra-Sonic Stereo MWR
    HALE √* √* √*
    MALE √* √* √*
    TUAV √*
    SUAV √*
    MAV √* √*

    a) represents the sensor applicable to the UAV; * represents the sensors that should be mounted according to the policies and regulations in the future application of UAV.

  • Table 2   Global path planning & reactive collision avoidance
    Global path planning Reactive collision avoidance
    Platform HALE & MALE UAV Small & micro UAV
    Operation space Sparse mid-air scenario Complex low-altitude scenario
    Sensing information Global, wide range target status Local, limited range target measurements
    Control output Global way-points Local control command
    Sensing & control Almost decoupled Coupled
    Loop frequency Low High
  • Table 3   Large & middle size UAV safety capacity level
    Safety level Description
    0 Does not have any security assurance capability and technical means
    Local flight safety support under specific mission functions include:
    (a) limited perceptionability and partial communication ability in VMC environment;
    (b) decision rules and operation methodsin simple task environment;
    (c) and simple flight control operation method and command realization.
    Wide range and long endurance flight safety support in a simple and sparse flightenvironment:
    (a) wide range sensing and multi-link communication capabilities in a VMC condition;
    (b) situation assessment and decision making in a wide range of mission environments;
    (c) and fully controllable task execution.
    Safety flight insurance in complex meteorological conditions and flight environment:
    (a) perception ability and communication link under VMC and IMC;
    (b) environmental situation analysis and fault diagnosis under complex flight conditions;
    (c) and controllable task instruction execution under man's supervision function.
    All-weather flight safety support under complex air traffic control system:
    (a) large-scale perception and cooperative air traffic information under VMC and IMC;
    (b) multi-information support for flight situation analysis and platform health management functions;
    (c) and access to ATC system, complete flight status acquisition and flight command execution.
    Equivalent safe flight in shared airspace with man-machine:
    (a) large-scale perception andhighly reliable information interaction under VMC and IMC;
    (b) highly reliable situationanalysis and decision-making punder the support of multiple information
    sources (more thanpeople in the loop);
    (c) and seamless access to the ATM (air traffic management) system to achieve the mission flight
    under the ATCoperating rules.
  • Table 4   Small & micro UAV safety capacity level
    Safety level Description
    0 Visual line of sight flight with man in the loop remote control (100% man in the loop).
    Partial perception and auxiliary control functions:
    (a) auxiliary navigation andenvironment perception in sparse environment;
    (b) low level auxiliary judgment and warning ability;
    (c) and people in the loop control, with auxiliary functions of the automatic driving system.
    Man in the loop decision making (partial man in the loop):
    (a) auxiliary navigation, environment and target modeling in dense environment;
    (b) auxiliary decision-making function and safety warning ability;
    (c) man in the loop path planning and maneuver control.
    Automatic mission execution with man in the loop supervision:
    (a) reliable navigation and data processing in the task environment;
    (b) supervised online data analysis and decision-making function;
    (c) online path planning and control.
    Autonomous task execution:
    (a) intelligent information processing and environmental perception;
    (b) autonomous analysis and decision-making function;
    (c) optimal online path planning and maneuver control.
    Collaborative task execution ability with multiple platforms:
    (a) multi-platform collaborative perceptionand data analysis;
    (b) collaborative situational awareness and decision-making;
    (c) distributed multi-platform path planning and control.

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