Energy Efficiency Enhanced Landing Strategy for Manned eVTOLs Using L1 Adaptive Control

Abstract

A new landing strategy is presented for manned electric vertical takeoff and landing (eVTOL) vehicles, using a roll maneuver to obtain a trajectory in the horizontal plane. This strategy rejects the altitude surging in the landing process, which is the fatal drawback of the conventional jumping strategy. The strategy leads to a smoother transition from the wing-borne mode to the thrust-borne mode, and has a higher energy efficiency, meaning a better flight experience and higher economic performance. To employ the strategy, a five-stage maneuver is designed, using the lateral maneuver instead of longitudinal climbing. Additionally, a control system based on L1 adaptive control theory is designed to assist manned driving or execute flight missions independently, consisting of the guidance logic, stability augmentation system and flight management unit. The strategy is verified with the ET120 platform, by Monte Carlo simulation for robustness and safety performance, and an experiment was performed to compare the benefits with conventional landing strategies. The results show that the performance of the control system is robust enough to reduce perturbation by at least 20% in all modeling parameters, and ensures consistent dynamic characteristics between different flight modes. Additionally, the strategy successfully avoids climbing during the landing process with a smooth trajectory, and reduces the energy consumed for landing by 64%.

Performance Analysis on the Small-Scale Reusable Launch Vehicle

“…analysis of hypersonic aircraft with lift-body configuration [31], aerod characteristics analysis of X-33-like vehicles [32], longitudinal and lateral fligh research of saucer aircraft [26,27], flight quality research of short take-off and landing aircraft, criterion analysis of Robert Weissman, etc. However, there research on the manipulativeness and stability characteristics and flight quality that can take off and land vertically.…”

“…The characteristic roots of lateral-directional motion of the starship are shown in Table 4 and are compared with those of B747 [27] and a flying wing aircraft [27]. It can be seen from the table that the starship and the flying wing aircraft have no vertical tails, so their C nβ , which plays a role in the recovery of Dutch rolling motion, is small, and it is the same thing with C nr and C sβ , which play a role in damping.…”

“…A new rudder surface control that is different from the traditional lift-body aircraft is adopted in the starship for this special takeoff and landing way [26]. Traditional lift-body aircraft realize the control of attitude and path by adopting the ailerons and vertical and horizontal tails, while the starship controls its body through two pairs of wings scattered on the nose and tail, which can deflect along the axial direction [27]. Zuo [27] made a detailed analysis of aerodynamic characteristics of the shape of the early starships (2019) in the landing and low-speed stages.…”

“…Traditional lift-body aircraft realize the control of attitude and path by adopting the ailerons and vertical and horizontal tails, while the starship controls its body through two pairs of wings scattered on the nose and tail, which can deflect along the axial direction [27]. Zuo [27] made a detailed analysis of aerodynamic characteristics of the shape of the early starships (2019) in the landing and low-speed stages. Combined with aerodynamic characteristics such as lift/drag obtained from the simulation of subsonic separation flow field under a large angle of attack and the changing rules of the vertex moment along the deflection angle of leading and rear wings, a conclusion that four wings of the starship layout are subject to the three-channel control was given.…”

“…At present, domestic and foreign studies on manipulativeness stability characteristics analysis are only limited to aircraft or taxiway takeoff and landing vehicles, and the structure is relatively simple, such as studies on multivariable stability margin of reentry aircraft [28], definitions of static stability margin of aircraft [29], and state feedback control and stability analysis of hypersonic aircraft [30]. There is also research on modal stability analysis of hypersonic aircraft with lift-body configuration [31], aerodynamic characteristics analysis of X-33-like vehicles [32], longitudinal and lateral flight quality research of saucer aircraft [26,27], flight quality research of short take-off and vertical landing aircraft, criterion analysis of Robert Weissman, etc. However, there is little research on the manipulativeness and stability characteristics and flight quality of RLVs that can take off and land vertically.…”