• Title/Summary/Keyword: Time-to-go Polynomial Guidance Law

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Time-to-go Polynomial Guidance Law for Target Observability Enhancement (표적 가관측성 향상을 위한 Time-to-go 다항식 유도법칙)

  • Kim, Tae-Hun;Lee, Chang-Hun;Tahk, Min-Jea
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.39 no.1
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    • pp.16-24
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    • 2011
  • In this paper, we propose a new guidance law for target observability enhancement, which can control both terminal impact angle and acceleration. The proposed guidance law is simple form, combined conventional time-to-go polynomial guidance and a additional bias term which consists of relative position and proportional gain. The guidance law provides oscillatory flight trajectory and it maintains the conventional time-to-go polynomial guidance performance. To investigate the characteristics of the guidance law, we derive the closed-form solution, and various simulations are performed for proving the validity of the proposed guidance.

Generalized Guidance Law with Control Time Constraint for Exoatmospheric Target Interception (외기권 표적 요격을 위한 제어시간 구속조건을 가지는 일반화된 유도법칙)

  • Park, Bong-Gyun;Kim, Tae-Hun
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.46 no.10
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    • pp.814-822
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    • 2018
  • This paper proposes a guidance law for missiles with control time constraint. Because the proposed guidance law is based on a time-to-go polynomial, it has a generalized form. Also, acceleration of the proposed law converges to zero at the end of the control time, which reduces the sensitivity to the time-to-go estimation error and can increase the flight stability when the separation of the missile appears. A prediction method of the time-to-go is proposed for implementing the proposed law, and the possibility of application to the midcourse and terminal guidance phases is dealt with for exoatmospheric interception. The characteristics and performance of the proposed law are analyzed throughout various simulations.

Target Observability Analysis of Time-to-go Polynomial Guidance Law (Time-to-go 다항식 유도 법칙의 표적 가관측성 분석)

  • Lee, Chang-Hun;Kim, Tae-Hun;Tahk, Min-Jea
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.38 no.7
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    • pp.664-672
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    • 2010
  • This paper provides the target observability analysis of time-to-go polynomial guidance law with bearing-only measurement. In this study, a direct approach is used to analyze the target observability. Since the observability condition of a constant-velocity target is given by the function of LOS angle only, the target observability characteristic is determined by substituting the closed form solution of LOS angle to the observability condition directly. The analysis results show that the target observability is depended on the choice of guidance gain, initial intercept condition and guidance command shape. After that this mathematical analysis result is evaluated and demonstrated by number of simulation.

Study of Time-to-go Polynomial Guidance Law with Considering Acceleration Limit (가속도 제한을 고려한 Time-to-go 다항식 유도 법칙 연구)

  • Lee, Chang-Hun;Kim, Tae-Hun;Tahk, Min-Jea
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.38 no.8
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    • pp.774-780
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    • 2010
  • This paper deals with the choice of guidance gain for the time-to-go polynomial (POLY) guidance law when the acceleration limit is existed. POLY is derived based on the assumption that guidance commands are formed by a time-to-go polynomial function. The main characteristic of POLY is that any positive values can be used for its guidance gain. For this reason, it is ambiguous to choose a proper guidance gain. To relieve this difficulty, we firstly derive the closed-form solution of acceleration command and figure out the relationship between the maximum acceleration and guidance gain. From this analysis, we provide a guideline for choosing a guidance gain which satisfies the desired acceleration limit. Finally, the proposed method is demonstrated by simulation study.

Guidance Law for Vision-Based Automatic Landing of UAV

  • Min, Byoung-Mun;Tahk, Min-Jea;Shim, Hyun-Chul David;Bang, Hyo-Choong
    • International Journal of Aeronautical and Space Sciences
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    • v.8 no.1
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    • pp.46-53
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    • 2007
  • In this paper, a guidance law for vision-based automatic landing of unmanned aerial vehicles (UAVs) is proposed. Automatic landing is a challenging but crucial capability for UAVs to achieve a fully autonomous flight. In an autonomous landing maneuver of UAVs, the decision of where to landing and the generation of guidance command to achieve a successful landing are very significant problem. This paper is focused on the design of guidance law applicable to automatic landing problem of fixed-wing UAV and rotary-wing UAV, simultaneously. The proposed guidance law generates acceleration command as a control input which derived from a specified time-to-go ($t_go$) polynomial function. The coefficient of $t_go$-polynomial function are determined to satisfy some terminal constraints. Nonlinear simulation results using a fixed-wing and rotary-wing UAV models are presented.

Characteristic of ZEM Based Guidance Law with Time-to-go Estimation Methods (잔여시간 추정에 따른 ZEM 기반 유도법칙의 특징)

  • Kim, Tae-Hun;Park, Bong-Gyun
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.47 no.6
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    • pp.429-437
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    • 2019
  • This paper deals with a ZEM (Zero-Effort-Miss) based guidance law for the interception of moving targets and characteristics of the guidance law according to time-to-go estimation methods. To derive the ZEM vector feedback guidance command, we introduce a polynomial function with unknown coefficient, and then we determine the coefficient to satisfy initial and terminal constraints. Since the directions of the guidance command and ZEM vectors are adjusted by the time-to-go, general time-to-go estimation methods are proposed, which can generate the vertical and horizontal guidance commands with respect to an arbitrary reference frame. By performing various numerical simulations, the performance and characteristics of the proposed methods are investigated.

Impact Angle Control Guidance Synthesis for Evasive Maneuver against Intercept Missile

  • Yogaswara, Y.H.;Hong, Seong-Min;Tahk, Min-Jea;Shin, Hyo-Sang
    • International Journal of Aeronautical and Space Sciences
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    • v.18 no.4
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    • pp.719-728
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    • 2017
  • This paper proposes a synthesis of new guidance law to generate an evasive maneuver against enemy's missile interception while considering its impact angle, acceleration, and field-of-view constraints. The first component of the synthesis is a new function of repulsive Artificial Potential Field to generate the evasive maneuver as a real-time dynamic obstacle avoidance. The terminal impact angle and terminal acceleration constraints compliance are based on Time-to-Go Polynomial Guidance as the second component. The last component is the Logarithmic Barrier Function to satisfy the field-of-view limitation constraint by compensating the excessive total acceleration command. These three components are synthesized into a new guidance law, which involves three design parameter gains. Parameter study and numerical simulations are delivered to demonstrate the performance of the proposed repulsive function and guidance law. Finally, the guidance law simulations effectively achieve the zero terminal miss distance, while satisfying an evasive maneuver against intercept missile, considering impact angle, acceleration, and field-of-view limitation constraints simultaneously.