In this paper, variable sweep is used as a replacement for the conventional control surfaces for flight control on a tandem-wing micro aerial vehicle (MAV). This configuration allows the MAV to be folded into and launched from a tubular catapult while also retaining an adequately high effectiveness and a simple structure. As new control inputs, the four sweep angles of the MAV are planned as symmetric and asymmetric morphing to eliminate the reactive forces between the airfoils and fuselage during morphing. The aerodynamic characteristics of the MAV are presented through numerical simulations to study the effects of variable sweep morphing. An accurate nonlinear multibody dynamic model of the variable sweep MAV is established using the Kane method. Next, open-loop dynamic responses of sweep morphing based on the nonlinear dynamic model are analyzed and compared with the responses caused by the elevons control mode to examine the control effectiveness. Moreover, a flight control law based on sweep control is designed and verified using a height and yaw tracking simulation with different actuator response rates. The results show that the sweep control mode produces weaker coupling between the longitudinal and lateral dynamics than the elevons control mode and that the innovative approach for flight control is feasible and effective.

In recent years, land-air locomotion robot has emerged in an endless stream. However, the increasingly complex working conditions pose higher challenges to the stability, flexibility, and other characteristics of robots. In this article, the two-wheel-legged self-balancing robot (TSR) is adopted as the crawling mechanism for the first time, and a new two-wheel-legged land-air locomotion robot (TLR for short) is designed. It has three independent modes of flight, two-wheel and four-wheel designed for various working environments. In flight mode, TLR has the fastest speed. In two-wheel mode, TSR as the crawling mechanism has the advantage of flexibly moving at high speed and being adaptive to complex terrains. The four-wheel mode provides TLR with maximum stability and load capacity. To achieve flexible mode switching and high energy utilization efficiency, we studied the cooperative control of rotor power and leg power. Two cooperative algorithms are proposed: stable cooperative algorithm with better impact resistance and stability and walking cooperative algorithm with better mobility. Both algorithms improve the stability, load capacity, and uphill ability of two-wheel mode, even breaking the constraint of the inverted pendulum, which demonstrates that TLR can balance at the specific pitch angle for completing more complex tasks.

Since the advent of flying machines, engineers have strived to develop aircraft that can fly as flexibly as birds. From the original traditional control surface to the controllable morphing wing design, they all aim to improve the flight performance of drones, including the load capacity, maneuverability and stability. We believe that a single control method has certain limitations. For example, for roll control, the aileron rudder effect will be significantly reduced when flying at a high angle of attack (AOA), and the asymmetric deformation control of a wing is almost useless under the conditions of low-speed and small AOA. Until now, solutions to the above problems have remained largely unexplored. Therefore, the combination of wing deformation and ailerons is proposed to improve the roll control ability of drones. In this research, a new bionic deformable wing drone is designed, which demonstrates the advantages of the combination of ailerons and wing morphing in roll control and verifies that the symmetrical folding of a wing can change the flight envelope. The aerodynamic characteristics of the drone were tested in a numerical simulation, and its flight capabilities for different configurations were characterized in flight experiments.

Turbojet engines have a slow response and require mechanical assistance to perform vertical take-offs and landings. In this paper, we propose a vertical take-off and landing (VTOL) aircraft that contains one-dimensional thrust vectoring nozzle modules to solve the problem of dependence on the response of the turbojet. The turbojet engine is placed horizontally in the module, the rotational speeds are fixed, and the force along the turbojet axis remains constant as the nozzle rotates from the horizontal to the vertical position. The aircraft is composed of four modules, whose position and attitude control are realized by using the thrust difference caused by the different angles of the four vector nozzles. The modules no longer rely on the response speed of the turbojet engine, and controlling the angles of four nozzles makes it easier to operate the aircraft. The horizontal placement of the turbojet can reduce the thickness of the aircraft fuselage and decrease air resistance. The process of moving the nozzle from a horizontal to a vertical position prevents the engine from blowing directly on the ground and, thus, reduces the ground effect.

Morphing aircraft can alter their aerodynamic configuration to obtain multitask adaptability and improve flight performance. In this paper, we apply the variable sweep concept on a tandem-wing micro aerial vehicle (MAV) for multitask adaptability, the two canards of which can undergo backward sweep and the two wings can undergo forward sweep. The variable sweep morphing mode can not only weaken the additional inertia forces and moments caused by morphing, but can also maintain the longitudinal dynamic balance without elevator changes, which generates trim drag. What is more, it was demonstrated that sweep morphing can exert a great effect on the aerodynamic characteristics during the transition process, which are functionalized with the sweep inputs. The effect of addition forces and moments during the transition process was analyzed by dynamic response, and the longitudinal stability of the MAV were evaluated based on a linear parameter varying (LPV) model. Due to the dramatic effects of sweep morphing on the longitudinal stability, a gain scheduled transition controller based on a convex hull algorithm is proposed to guarantee the transition stability and improve the robustness, and a linear quadratic regulator (LQR) is used to guarantee the stability of the boundary point with the consideration of input saturation. Finally, the superior performance of the proposed controller was demonstrated by a theoretical simulation based on a nonlinear model.

Studies have shown that the suspended backpack, a wearable device allowing the backpack moving relative to user’s back, can effectively reduce the accelerative vertical force of the backpack to reduce the metabolic cost of users. However, the existing suspended backpack cannot eliminate the accelerative vertical force due to the nonzero suspension stiffness. This paper proposes a constant force suspended backpack adaptable to the varying load to eliminate the accelerative vertical force on the load. To this end, a spring constant force balancing mechanism is designed to achieve near-zero-stiffness suspension. Moreover, a multi-pulley compensation mechanism is proposed for compensating the balance error caused by the pulley diameter to achieve constant force theoretically, and an adjustable mechanism is added to the suspended backpack to nearly achieve constant force balance under different loads. We conducted experiments to validate the efficiency of the constant force suspended backpack. The results demonstrate that the suspended backpack can effectively reduce the maximum net metabolic power of the human by 13.1%, the displacement of the load is reduced by 87.5%, and the peak average acceleration vertical force reduction rate is 88.5%.