Neural-Adaptive Constrained Flight Control for Air–Ground Recovery Under Terrain Obstacles

Abstract

This paper contrives a neural-adaptive constrained controller of the cable towed air-ground recovery system subject to terrain obstacles, unmeasurable cable tensions, trailing vortex, wind gust, and actuator saturation. In air-ground recovery system modeling, the towed vehicle's nominal 6 DOF affine nonlinear dynamics and the cable system's finite links-joints dynamics are formulated. To achieve accurate air-ground recovery under terrain obstacles, an asymmetric barrier Lyapunov function-based flight controller of the towed vehicle is proposed, by transforming the terrain obstacles into time-varying constraints on the vehicle's trajectory. Then, to approximate the towed vehicle's lumped unknown dynamics caused by the unmeasurable cable tensions and airflows, several echo state network (ESN) approximators are established for velocity and attitude subsystems. By using the state approximation errors-based neural weights learning strategy and minimal learning parameter technique (MLP), these ESNs possess better transient behaviors and lower online computational burden. sss Furthermore, the actuator saturation is automatically monitored and released, by incorporating a specially designed auxiliary compensating system into the angular rate control law for compensation. The stability of the closed-loop system is analyzed. Finally, numerical simulations under two air-ground recovery scenarios are performed to demonstrate the performance of the proposed controller.

Tethered Unmanned Aerial Vehicles—A Systematic Review

“…One observation that can be made is that, while publications that used lighter-than-air aircraft tUAVs predominantly focused on altitudes that were higher than 100 m [144,146,[148][149][150][151]154,155] and which reached up to 20 km [147], those that prefered multirotor propulsion were almost evenly distributed in all altitude classes. Fixed-wing solutions in terms of operational altitude were a little less concentrated, with some publications using altitudes in the 11 m to 20 m range [107,109,195] or in the 21 m to 100 m range [22,159]; however, just like with lighter-than-air vehicles, most publications focused on altitudes that were higher than 100 m.…”

“…Load transportation: where a load such as a delivery parcel [29], a weight [21], a planar platform [38], or a military payload [22] is transported by one [39] or more tUAVs [20] using a tether [23] or some other connection such as a rigid rod [42]. Some typical examples of the usage of tUAVs in this application are shown in Figure 7 • Hose transportation: where a hose is transported by one or more UAVs, usually in order to provide some liquid content to a specific location, such as in firefighting [47] and building painting [48].…”

“…One subcategory inside the load transportation application that is worth mentioning is the use of tUAVs to either recover a military payload in a dangerous area [22,35] or to transport a load by dragging it (instead of lifting it in the air) using a multicopter UAV [60] or a high speed vehicle performing circular motion [34,45]. These applications differ from the bulk of the load transportation publications, as their system configuration is slightly different: in the military payload recovery, the load needs to be quickly attached while the UAV is moving (so precise slow maneuvering of the UAV is not an option), and in the load dragging scenario, the payload weight may surpass the maximum lifting capacity of the UAV.…”

Aerial refueling rendezvous routes for UAVs based on nonlinear guide laws

“…This is why airborne autonomous refueling technology for UAVs is a priority for air support technologies. The U.S. Defense Advanced Planning Agency, the U.S. Air Force, and the U.S. Navy are participating in the Joint Unmanned Aerial Vehicle the Joint Unmanned Air Combat System (JUCAS), in which the U.S. Defense Advanced Planning Agency, the U.S. Air Force, and the U.S. Navy are jointly involved; this states that existing models of UAVs are often limited by load and fuel capacity [4]. The load and fuel limitations often result in insufficient safe flight time to meet cross-continental air power deployments and Ultra-Long-Range Mobilization.…”

Event-triggered anti-disturbance control for aerial recovery drogue stabilization with guaranteed transient performance constraints

“…To our knowledge, some related works on the general drogue control in some other scenarios can be referred to, such as aerial refueling drogue 7,8 and towed vehicles. 9 In aerial refueling, Ro et al stabilized the refueling drogue based on an approximate linearized model of the hose-drogue assembly. 10 This single-input-single-output method took the drogue as a mass point.…”