Simulation of aircraft unstable motions and unsteady aerodynamic testing with cable-driven parallel suspension system

Abstract

This paper presents the development and experimental validation of a novel cable-driven parallel suspension mechanism (CDPSM) for investigating unstable, high-angle-of-attack aerodynamics in low-speed wind tunnel. Designed to overcome the limitations of conventional testing in simulating post-stall flight dynamics, the six-degree-of-freedom CDPSM enables precise execution of highly nonlinear motions, specifically amplitude-frequency sweep maneuvers. The system achieves this through a geometric mapping between aircraft pose commands and cable lengths, governed by a terminal sliding mode controller that integrates an extended state observer for high-fidelity motion control. A series of unsteady aerodynamic tests, incorporating coupled frequency-amplitude variations, were conducted with forces measured via an internal six-component balance. The results confirm the CDPSM’s capability to accurately simulate prescribed unstable motions and capture the ensuing aerodynamic responses. Critically, the measured forces revealed significantly more complex hysteresis loops and variation patterns than those obtainable from traditional sinusoidal motion tests, highlighting the unique capabilities of the proposed system for investigating advanced post-stall flight dynamics.