It is difficult for a human operator to find roll, pitch, yaw (RPY) that indicates the desired direction of unmanned aerial vehicle (UAV) in a three-dimensional space. Herein, a controller for UAV was developed allowing the human operator controlling the direction of UAV without finding RPY information. The algorithm implemented in the controller automatically calculated RPY information of UAV from the normal vector of the end effector. The developed controller was designed using a parallel mechanism. The joint angles of the controller were measured using potentiometers to estimate the normal vector of the end effector. Five subjects participated in an experiment to control a vector in three-dimensional space to follow a randomly generated target vector using the developed controller and the thumb sticks. The performance of the two controllers was evaluated by two methods: measuring the required time to reduce the error between the controlled vector and the target vector to be less than 0.1 cm and calculating a normalized error between the controlled vector and the target vector after manipulating the controlled vector for 10 seconds. When using the developed controller, the difference in control ability between subjects was reduced, and both required time and normalized error were generally reduced.

In this study, a numerical analysis for predicting the internal pressure of the flight vehicle system with relief valve and N2-injection type cooler was conducted to operate the system safely in an unsteady-state condition. By adopting an incompressible ideal gas equation to computational domain at each time step, internal pressure was calculated without iteration. To increase the accuracy of the numerical analysis results, numerical model was correlated by modifying the volume of the computational domain. To modify the volume of computational domain, internal pressure along time was compared with experimental results. It showed good agreement within system operating time. Air mass flow rate at the relief valve is calculated by interpolating the performance curve data. For accurate and rapid calculation of the internal pressure in an unsteady-state condition, time step size convergence study was conducted additionally. By using a correlated numerical model, Pcr of the relief valve is conducted to remain the flight vehicle system within an internal pressure range of 0.6-2.0 atm, in each flight profile. Finally, specific Pcr of relief valve was applied to the system and the experimental results showed that the internal pressure remained in a safe range.