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회전 행렬과 회전 벡터를 사용한 멀티콥터 3 차원 비행 자세 제어
장종태(Jong Tai Jang),공현철(Hyeon Cheol Gong),유준(Joon Lyou) 제어로봇시스템학회 2017 제어·로봇·시스템학회 논문지 Vol.23 No.11
The research target is to design and implement an attitude controller for a multicopter to fly in an arbitrary 3D curved trajectory in 3D space using a rotation matrix and a rotation vector. For the singularity-free attitude representation, a rotation matrix is used. To calculate the attitude error, which is the key point in attitude control laws, the rotation vector, which is a type of axis-angle representation, is used. The attitude control algorithm was designed for two schemes: a scheme with only one angle control loop and a scheme with an angle control loop and an angular velocity control loop. The attitude control schemes were implemented on an open-platform PX4 flight control computer by modifying the existing software. To validate the developed algorithm, several flight tests were performed. A 3D curved trajectory tracking flight was stably performed. Attitude control flight tests of the two developed schemes and the original scheme of PX4 were performed and compared with each other. The comparison shows that the developed scheme and the original scheme have similar performance errors.
장종태(Jong Tai Jang),공현철(Hyeon Cheol Gong),유준(Joon Lyou) 제어로봇시스템학회 2018 제어·로봇·시스템학회 논문지 Vol.24 No.6
In this research, an attitude update method using rotation matrix is verified and validated. First, a continuous time rotation matrix update formula is derived newly without any assumptions or approximations. The continuous time method is compared with other existing methods that use quaternion or Euler angles, by a computation experiment of a Matlab Simulink program. The discrete time version of the method is derived and implemented on a quadcopter and validated through a real flight. For a more severe experiment condition, the flight control computer is separately rotated quickly multiple times by hand. From the experimental result, the attitude angle difference between this method and the quaternion method is evaluated.
회전 행렬을 이용한 다수 쿼드콥터의 3차원 궤적 추종 실내 비행 제어
장종태(Jong Tai Jang),공현철(Hyeon Cheol Gong),유준(Joon Lyou) 제어로봇시스템학회 2017 제어·로봇·시스템학회 논문지 Vol.23 No.5
This paper describes an effective solution for multiple multicopters to track their 3D curved trajectories in indoor environment. The research was performed by both imulation and real flight. As aircrafts, the organization’s own developed small quadcopters were used. As a flight control computer, a popular open-platform PX4 autopilot was utilized. To provide accurate position measurement to crafts and to evaluate their flight traces accurately, a commercial motion capture system is used. For generating time-constrained curved reference trajectory, the time adjusted C-spline method developed in previous research is adopted. To represent singularity-free 3D target attitude to track 3D trajectory, rotation matrix is used instead of quaternion. Typical structures of flight controllers are compared with each other by simulation. The flight results for arbitrarily given trajectories of various shapes are shown to verify the capability of the controller. The solutions for various cases occurring in real flights are presented, including gravity compensation, battery voltage drop compensation, indoor geomagnetic field distortion, straightness improvement for linear movement by adopting speed profile, control gain scheduling, and the effect of feedforward with the reference velocity and acceleration.
드론의 곡선 비행을 위한 구간별 등가속 조건의 기준 궤적 생성 방법
장종태(Jong Tai Jang),공현철(Hyeon Cheol Gong),유준(Joon Lyou) 제어로봇시스템학회 2016 제어·로봇·시스템학회 논문지 Vol.22 No.3
This paper describes a three-dimensional reference trajectory generation method for giving commands to an unmanned air vehicle (UAV). The trajectory is a set of consecutive curves with constant acceleration during each interval and passing through viapoints at specified times or speeds. The functional inputs are three-dimensional positions and times (or speeds) at via-points, and velocities at both boundaries. Its output is the time series of position values satisfying the piecewise constant acceleration condition. To be specific, the shape of the trajectory, known as the path, is first represented by splines using third degree polynomials. A numeric algorithm is then suggested, which can overcome the demerits of cubic spline method and promptly generate a piecewise constant acceleration trajectory from the given path. To show the effectiveness of the present scheme, trajectory generation cases were treated, and their speed calculation errors were evaluated.