Variable Aerodynamic Damping via Co-Contraction: A Dynamic Isomorphism with Variable Stiffness Actuators

2026-05-08

AI Summary

This study addresses the challenge of actively tuning passive damping in aerial vehicle aerodynamic systems under constant net thrust by proposing a novel approach based on redundant dual-rotor aerodynamic co-contraction. By decomposing actuation into common-mode and differential-mode components and employing blade element theory to formulate a first-order thrust model, the work establishes a dynamic isomorphism between incremental damping coefficients and variable-stiffness actuators. It is demonstrated for the first time that aerodynamic co-contraction monotonically enhances the damping coefficient, revealing a dynamic isomorphism with biological muscle co-activation mechanisms for stiffness modulation. Experimental results confirm that this mechanism retains tunable damping even under aerodynamic stiffening conditions, enabling decoupled control of equilibrium velocity and passive impedance, thereby significantly improving the aerodynamic response agility of redundant multirotor systems.

Abstract

We prove that aerodynamic co-contraction in a redundant dual-rotor actuator can tune a passive, trim-defined aero-mechanical damping while keeping the commanded net force constant. In particular, we define an incremental damping coefficient as the local sensitivity of net thrust to air-relative velocity at a trim and prove that it increases monotonically along constant-force fibers under a mild aerodynamic hardening condition. We then validate the required damping and hardening properties from a first-principles Blade Element Theory derivation, which yields a minimal thrust model affine in inflow and explicitly reveals the speed--inflow coupling driving the effect. The resulting mechanism is formalized as a Variable Aerodynamic Damping Actuator (VADA) and shown to be dynamically isomorphic to stiffness modulation in antagonistic variable-stiffness actuation (VSA), similar to the co-contraction of tendons by muscle co-activation. The same fiber-density principle also enhances the active aerodynamic promptness measure of redundant multirotors. Finally, an impedance-form representation clarifies the roles of common-mode and differential-mode actuation in the control of passive impedance and the equilibrium velocity of the VADA system.

Problem

• aerodynamic damping
• co-contraction
• variable stiffness actuators
• redundant dual-rotor actuator
• passive impedance

Innovation

• Variable Aerodynamic Damping
• Co-contraction
• Dynamic Isomorphism
• Blade Element Theory
• Redundant Multirotor Actuation