No abstract

No abstract

Abstract. Lightweight vibrating structures (such as Flapping Wing Micro Air Vehicle (FWMAV) designs) often require some form of control. To achieve controllability, local structural property changes (e.g., damping and stiffness changes) might be induced in an active manner. The stroke-averaged lift force production of a FWMAV wing can be modified by changing the structural properties of that wing at carefully selected places (e.g., changing the properties of the elastic hinge at the wing root as studied in this work). To actively change the structural properties, we investigate three different methods which are based on: 1) piezoelectric polymers, 2) electrorheological fluids, and 3) electrostatic softening. This work aims to gain simple yet insightful ways to determine the potential of these methods without focusing on the precise modeling. Analytical models of FWMAV wing designs that include control approaches based on these three methods are used to calculate the achievable lift force modifications after activating these methods. The lift force production as a result of a wing flapping motion is determined using a quasi-steady aerodynamic model. Both piezoelectric polymers and electrostatic softening are found to be promising in changing the structural properties and, hence, the lift force production of FWMAV wings. For the control of lightweight FWMAV designs, numerical simulations reveal a promising roll maneuverability due to the induced lift force difference between a pair of opposite wings. Although applied to a specific FWMAV design, this work is relevant for control of small, lightweight, possible compliant, vibrating structures in general.

No abstract

The structural resonance properties of damped structures can be exploited to obtain a required dynamic response with relatively low input power requirements. Practical applications often demand temporary modifications of this response. This paper presents a systematic approach to modify the response of harmonically driven, non-proportionally damped resonating structures using local structural property changes and excitation adjustments. The complex response is written in polar form (i.e., modulus and argument) to enhance insights. Sensitivity analysis is used to approximate the influence of the control variables on the response. A projection is proposed to determine the locations at which a specific structural change scores maximum effect to reach the desired response modifications. The introduced response normalization separates amplitude and shape modifications in a clear way. This work shows response modifications of non-proportionally damped resonating structures due to control variables in an intuitive manner.