Modeling and experimental study on orientation dynamics of a Mars rotorcraft with swashplate mechanism

Abstract

The Mars rotorcraft is an auxiliary aerial exploration platform to expand the rovers' patrol range. Attitude control is a fundamental aspect of autonomous flight control. So far, there has been no detailed investigation of the orientation dynamics of the rotor in the Martian atmosphere. A swashplate mechanism for manipulating isolated rotors is proposed to control the blade pitch angle, whose kinematics equation is established based on the closed condition of space vectors. Considering the blade as a rigid beam flapping around a central hinge, the flapping equation of the hingeless rotor is established to analyze the aerodynamic load for orientation adjusting. The Mars rotorcraft orientation dynamics model is constructed to develop an attitude control algorithm by combining the swashplate kinematics equation and the rotor flapping equation. The orientation experiment is conducted to verify the theoretical model and investigate the response law of the body's heading angle to the cyclic pitch input. The experimental results indicate that the attitude response is more sensitive to the blade pitch angle input under a smaller collective pitch angle or a higher rotor speed. The rigid rotor hypothesis may be unsuitable for the case where the collective pitch angle is smaller than 22°. The hovering flight tests prove that the orientation dynamics model proposed in this paper can effectively support the development of the Mars rotorcraft attitude control system.