More and more UAVs are developed for various purposes and their flight controllers are required to have sufficient robustness and performance to realize their versatile missions. To design these sophisticated controller is pretty much time-consuming task by traditional design method. Neural network based adaptive control with dynamic inversion is applied to solve this problem. This method has two advantages. One is that the gain scheduling is not necessary because nonlinear dynamic inversion is applied to control nonlinear systems. The other is that neural network improves the controller performance by estimating parameters of the actual plant. Numerical examples show its effectiveness and its ability to adapt to modeling errors. This paper concludes that proposed method reduces the workload of controller design task and it has ability to adapt various errors of nonlinear systems.
This paper describes results of an exploratory study to investigate the capability of a passive approach for controlling the characteristic spanwise length of Görtler vortices generated in hypersonic flows: a serrated leading edge. Heat transfer, pressure measurements, encapsulated thermochromic liquid crystal, schlieren and glow spark visualizations were conducted with a flat plate/ramp model whose leading edge had a triangular wave shape in a gun tunnel at Mach number 10. Effect of wavelength Λ of the triangular waves on downstream flows was studied. Aerodynamic heating patterns observed with the liquid crystal confirmed that the vortex wavelength was equal to Λ. This was also supported by the spark results that filamentary bright lines perpendicular to an installed line-anode parallel to the spanwise direction at the ramp surface emerged at intervals of Λ. Phase lag was observed only between heat transfer data measured in the spanwise direction, which suggests that the vortex structure existed in the reattaching boundary layers. Pressure distribution in the streamwise direction was similar among all of the Λ tested. In contrast, the heat transfer data points exhibited a large scatter and the peak heating value for the finite Λ was somewhat larger than that for the infinite Λ. Schlieren results indicated that the appropriate Λ can mitigate flow separation.
Controlling of a space robot without actuators on the main body is an underactuated control problem. As stabilization methods, various methods such as time-varying feedback controllers, discontinuous feedback controllers, center manifold based methods, zero-dynamics methods, and sliding mode controllers have been proposed. However, in these methods, modeling errors and delay time have not been sufficiently considered. In order to obtain faster convergence time and compensate modeling errors and delay time, the adaptive invariant manifold based switching control method has been proposed. In this paper, experiments are carried out to validate the proposed method using the experimental setup of a planar two-link space robot. The experimental results show that the proposed method was capable of stabilizing the state variables to the goal one even if there exist the delay time and modeling error in the system.
The moving surface method based on Quette Flow-type momentum addition was proposed as a new flow separation control method in order to suppress the flow separation over a flap at high attack angles and make lift enhancement. The effectiveness of the proposed method as well as the mechanism for suppressing the separation was studied by numerical simulations and experimental measurements in this study. The numerical results show that the moving surface works well to suppress the flap flow separation, so that lift coefficient can be increased significantly. In addition, the moving surface decreases pressure not only in the original separated flow region, but also in the leading edge region. Furthermore, the experimental result agrees with the numerical one in the case of a lower Mach number, which can validate the numerical results. Thus, the moving surface method proposed here is a promising method for controlling the flow separation over the flap.