This paper proposes a new collision avoidance control law for aircraft. RCPA (Range of Closest Point of Approach), representing risk in the future, and TCPA (Time to CPA), representing current risk, are used as risk functions. Furthermore, fuzzy logic is introduced in order to achieve human maneuvering and to settle singular point and chattering problems that are discussed in previous studies. Avoidance strategy consists of four main phases, maintaining course, avoidance, parallel flight and recovery phase, and three transition phases. The parallel flight phase and three transition phases are introduced to achieve moderate avoidance and smooth phase transition, respectively. Simulation results show that the proposed control law settles the past problems and achieves smooth and adequate avoidance. This paper also discusses the fuzzy evaluation method.Key Words: Guidance and Control, Collision Avoidance, Fuzzy Logic Nomenclature x, y, z: inertial coordinate system $, , : relative coordinate system v: aircraft velocity, m/s : direction angle, rad : flight path angle, rad : angle between line of sight and relative velocity, rad !: angular velocity, rad/s R r : relative range between evader and intruder, m R os : offset range from original course, m

: This paper proposes a new collision avoidance control law of aircraft. RCPA (Range of Closest Point of Approach) representing risk in the future and TCPA (CPA time to go) representing current risk are used as risk functions. Also fuzzy logic is introduced to achieve the human maneuvering and to settle singular point and chattering problems that are shown in previous studies. Avoidance strategy consists of four main phases; course keeping, avoidance, parallel flight, and recovery phase; and three intermediate phases. Parallel flight phase and three intermediate phases are introduced to achieve moderate avoidance and smooth phase transition, respectively. Simulation results show that the proposed control law settles the past problems and achieves the smooth and adequate avoidance. This paper also discusses on the fuzzy evaluation method. 1.

This paper describes a collision avoidance problem for aircraft. In a conventional avoidance problem, it is assumed that the target information is certain. However, information may not be always certain, and handling of uncertain information has not been discussed. Therefore, a new control law is proposed to deal with uncertain information and to obtain correct information. The uncertainty depending on position, which is defined in the inertial or relative coordinate system, is dealt with in this paper. To cover each coordinate system, the proposed control law is applied to the 'corner' and 'infog' problems. Several elements are defined to express uncertainty of target information. Simulation results show that severe avoidance caused by conventional law is improved to obtain satisfactory performance by dealing with uncertain information.

: This paper describes a collision avoidance problem of aircraft. In a conventional avoidance problem, there is an assumption that target information is certain. However, information may not be always certain in reality, and handling of uncertain information has not been discussed. Therefore, new control law is proposed to deal with uncertain information and to get correct information. The uncertainty depending on position, which is defined in the inertial or relative coordinate system, is dealt with in this paper. To cover each coordinate system, proposed control law is applied to 'corner problem' and 'in-fog problem', respectively. Several elements are defined in order to express uncertainty of target information. Simulation results show that the severe avoidance by conventional law is improved and to be obtained satisfactory performance by dealing with uncertain information.