Effect of boundary conditions on a high-performance isolation hexapod platform

TL;DR

This paper investigates how boundary conditions affect the vibration isolation performance of hexapod platforms, proposing a new pin-slider boundary condition that improves system dynamics without active control.

Contribution

It introduces a novel pin-slider boundary condition for hexapod platforms, demonstrating its advantages over traditional configurations through analytical and numerical validation.

Findings

Pin-slider BC alleviates limitations of all-rotational joints.

Numerical tests show improved disturbance suppression.

A new planar joint design enables physical realization of the BC.

Abstract

Isolation of spacecraft microvibrations is essential for the successful deployment of instruments relying on high-precision pointing. Hexapod platforms represent a promising solution, but the difficulties associated with attaining desirable 3D dynamics within acceptable mass and complexity budgets have led to a minimal practical adoption. This paper addresses the influence of strut boundary conditions (BCs) on system-level mechanical disturbance suppression. Inherent limitations of the traditional all-rotational joint configuration are highlighted and shown to originate in link mass and rotational inertia. A pin-slider BC alternative is proposed and analytically proven to alleviate them in both 2D and 3D. The advantages of the new BC hold for arbitrary parallel manipulators and are demonstrated for several hexapod geometries through numerical tests. A configuration with favourable performance is suggested. Finally, a novel planar joint that allows the physical realisation of the proposed BC is described and validated. Consequently, this work enables the development of platforms for microvibration attenuation that do not require active control.