Multi-Duct ER Dampers

Abstract

This paper describes the design, construction, testing and modeling of controllable damping devices utilizing electro-rheological (ER) materials. The rheological properties of ER materials (yield stress and viscoelasticity) are extremely sensitive to electric fields. Modulations of the electric field in an electrorheological damper results in a corresponding change in device forces. The key feature of the ER devices described in this paper is a set of multiple concentric annular ducts through which the ER material flows. The annular ducts are formed by a set of concentric metallic tubes, which may be electrically charged with a high voltage potential, or electrically grounded. Three designs targeting different force levels (2-6 kN), are designed, tested and modeled. The device analyses used in the design incorporate a simplified closed form relation for the flow behavior of ER materials. Evolutionary and algebraic device models are fit to the measured force response of the devices over a range of harmonic frequencies and at zero and high electric field magnitudes. The evolutionary model is motivated by observations and simulations of ER materials in simple shear, and the algebraic model is convenient for control and feedback linearization applications. The algebraic model is evaluated with data collected with random excitation and with switching electric fields. The three devices display different levels of pre-yield viscoelasticity. Friction, due to seals in the device, was not accounted for in the initial design, and affected the behavior of the device as tested.