Rotorcraft operating in the thin and cold Martian atmosphere typically encounter unique aerodynamic conditions characterized by low Reynolds numbers and high Mach numbers, resulting in degraded performance compared to Earth operations. This study investigated the aerodynamic characteristics of the CLF5605 low-Reynolds-number airfoil under Martian atmospheric conditions through three-dimensional unsteady incompressible Reynolds-averaged Navier-Stokes simulations using the k-ω SST turbulence model. The analysis reveals unsteady laminar separation at the airfoil trailing edge, leading to periodic vortex formation and shedding, low-frequency lift and drag oscillations, and overall aerodynamic performance deterioration. To address these challenges, we proposed implementing Gurney flaps on the trailing edge. A comprehensive study was conducted to evaluate the aerodynamic performances of airfoils equipped with 2% chord-length Gurney flaps across varying Reynolds numbers, Mach numbers, and angles of attack. The results demonstrate that Gurney flaps effectively suppress unsteady laminar separation and enhance lift generation. However, their effectiveness is constrained to specific operational regimes: Reynolds numbers ranging from 5000 to 30000, Mach numbers below 0.65, and angles of attack between 0° and 3°. Additionally, while lift is improved, the lift-to-drag ratio remains unaffected due to proportional increases in drag. Furthermore, we developed and analyzed three Gurney flap-integrated rotor designs, which exhibited superior thrust generation, torque characteristics, and hovering efficiency compared to clean rotors. These findings provide critical insights and practical design guidelines for optimizing rotor performance of Mars unmanned aerial vehicles.

The tilt-hinge rotor has a simpler structure because it doesn’t need a swashplate and can provide cyclic pitch control just by accelerating and decelerating the motor. However, the tilt hinge coupled with the rotor lag and pitch motion complicates the modeling of rotor dynamics. However, the rotor lag and pitch motion are coupled with the tilt hinge, which makes the rotor dynamics modeling more complicated. The nearby linkage coordinate system of the blade was created based on the enhanced Denavia-Hartenberg approach in order to address the issues of low model prediction accuracy in the current modeling techniques and inadequate disclosure of the difference between forward and reverse blade flap-motion. The Newton-Euler recursion algorithm is used to calculate the velocity and acceleration of each linkage and the interaction force and torque of each linkage in the local linkage coordinate system. The dynamic model of the tilt-hinge rotor is established. On this basis, the mechanism of periodic pitch variation of the tilt-hinge rotor is further revealed through simulation calculation. At the same time, the calculation results show that this model can predict the flapping difference between forward and reverse blades more accurately. The prediction accuracy of blade lagging amplitude is improved by 9.05%.

Flight dynamics modeling for the Mars helicopter faces great challenges. Aerodynamic modeling of coaxial rotor with high confidence and high computational efficiency is a major difficulty for the field. This paper builds an aerodynamic model of coaxial rotor in the extremely thin Martian atmosphere using the viscous vortex particle method. The aerodynamic forces and flow characteristics of rigid coaxial rotor are computed and analyzed. Meanwhile, a high fidelity aerodynamic surrogate model is built to improve the computational efficiency of the flight dynamics model. Results in this paper reveal that rigid coaxial rotor can bring the Mars helicopter sufficient controllability but result in obvious instability and control couplings in forward flight. This highlights the great differences in flight dynamics characteristics compared with conventional helicopters on Earth.

It is of great significance to reasonably distribute the slung load to each helicopter while considering difference in power consumption, relative position and interaction comprehensively. Therefore, the load distribution strategy based on power consumption and robust adaptive game control is proposed in this paper. The study is on a “2-lead” multi-lift system of four tandem helicopters carrying a load cooperatively. First, based on the hierarchical control, the load distribution problem is divided into two parts: the calculation of expected cable force and the calculation of the anti-disturbance cable force. Then, aimed at minimizing the maximum equivalent power of helicopter, an optimization problem is set up to calculate the expected cable force. Specially, the agent power model is trained by BP neural network, the safe distance constraint between helicopters is set to 2.5 rotor diameters to reduce aerodynamic interference, and the helicopters with different performance can be considered by introducing the equivalent power factor into the objective function. Next, considering the difference and interaction between helicopters, the robust adaptive differential game control is proposed to calculate the anti-disturbance cable force. Particularly, to solve the coupled Hamiltonian equations, an adaptive solving method for value function is proposed, and its stability is proved in the sense of Lyapunov. The simulation results indicate that the proposed load distribution method based on power consumption is applicable to the entire flight trajectory even there are differences between helicopters. The game control can consider interaction between helicopters, can deal with different objective functions, and has strong robustness and small steady-state error. Based on the entire strategy, the cable force can be reasonably allocated so as to resist disturbance and improve the flight performance of the whole system.