• 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.

• 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.

• 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.

• 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.