X-Stewart mechanism for vibration isolation with nonlinear translational-to-rotational motion properties

Abstract

A novel X-Stewart mechanism is proposed and studied as an advanced passive vibration isolation system, featured by a compact semi-X-unit (SXU), which can be regarded as a half variant of the one unit of the X-shaped structure but retains the main nonlinear stiffness properties of a full X-shaped counterpart, together with an ample loading capacity, adjustable mechanic properties in a large range, and a special nonlinear rotational inertia mechanism, thus completely different from a traditional Stewart platform. The SXU is a specially designed compact component in this structure for taking advantage of the adjustable and controllable nonlinear properties of the X-mechanism method, and 3 SXUs form an X-Stewart platform. Theoretical analysis, comparisons and experimental validation indicate that the SXU can demonstrate diverse nonlinear properties for nonlinear manipulation, and the resulting X-Stewart has several unique nonlinear static and dynamic properties demonstrated in its enlarged quasi-zero stiffness (QZS) areas with high loading capacity and its capability for achieving different nonlinear stiffness, damping, and inertia in vibration isolation resulting lower resonant frequency, higher nonlinear damping effect, and sharp decay ratio. The nonlinear translational-to-rotational transform shows another unique feature of the X-Stewart which can have great application potentials. Therefore, the X-Stewart is completely different from other Stewart-type platforms and it can be applied as a basic unit to construct more complex structures of diverse functions for nonlinear manipulation in various engineering systems.