Hyeon Cheol Gong

Trajectory generation with piecewise constant acceleration and tracking control of a quadcopter

This paper describes a 3D reference trajectory generation and tracking control method for a quadcopter. The flying trajectory is a piecewise curve that passes through viapoints at specified times or speeds and has constant acceleration within each interval. The path is first represented as the third degree polynomials, and to overcome demerits of the C-splines, a numeric algorithm is suggested and implemented. The feasibility of the generated trajectory is checked by nonlinear dynamics model of a quadcopter. After executing several flying experiments for a quadcopter, tracking errors are evaluated.

Computed Torque Control of an aerospace craft using nonlinear inverse model and rotation matrix

This paper newly presents how to apply the Computed Torque Control scheme to the flight control of a 4-DOF controllable aerospace craft, such as a multicopter and a rocket, by using a nonlinear inverse model to track a reference trajectory arbitrarily given in the 3D space of gravity condition and it shows the simulation results for some cases. Aerodynamics is neglected for the clarity of the explanation of the subject. The nonlinear inverse model of the rigid body are used to calculate and feedforward the ideally desired torque and force in the scheme without linearizing the nonlinear model of the craft. The analytic formula of the nonlinear inverse kinematics is newly presented for a 4-DOF controllable rigid body in the 3D space of gravity condition. The rotation matrix is used to represent the attitude of the craft. The attitude error is represented by using the rotation vector (the product of a rotation angle and a rotation unit vector) from the current attitude to the desired attitude and its calculation method is newly presented. The stability of the system is indirectly checked by the simulations for a reference trajectory with various deviated initial positions. It shows by simulations that the computed torque improves steady state errors and the PID control in the scheme compensates modeling errors and copes with incorrect initial conditions and abrupt changes of input commands.

Development of the Multi-Propeller based Attitude Control Method for VTOL type Compound Aircraft

In recent decades, many researchers have been struggling to developing the compound aircraft that is capable high speed and VTOL flight. And in recent years, multi-copters are very popular because of having advantages of VTOL and easy handling, but they are lack of doing long-range mission. Therefore, we presents simple aircraft architecture which is equipped fixed wing, multi propellers and no control surfaces. In this paper, we designed the attitude control for the compound aircraft prototype and measured the attitude control performance with flight test for validating prototype’s performance. We analysed the attitude control test result comparing with similar size of a fixed wing aircraft. The performance was almost same as fixed wing aircraft.