Performance of an Active Composite Strut for an Intelligent Composite Modified Stewart Platform for Thrust Vector Control

Abstract

Adaptive or intelligent structures which have the capability for sensing and responding to their environment promise a novel approach to satisfying the stringent performance requirements of future space missions. This research effort focuses on the development and performance evaluation of an active composite strut (ACS) with precision positioning and active vibration suppression capabilities for use in space structures. Such ACS has potentials to be used as active strut members in Stewart platforms, modified Stewart platforms (MSPs), space truss structures, etc. The developed ACS utilizes piezoelectric actuators/sensors providing precision positioning and vibration suppression capabilities that would enhance mission performance of space structures by fine position-tuning, and potentially eliminating the nonoperational period of a satellite while minimizing the fuel consumption utilized for its position correction in a thrust vector control (TVC) application. Precision positioning of the ACS is achieved by extending or contracting its internal piezoelectric actuator. To magnify the positioning capabilities of a stack piezoelectric actuator, a miniature inchworm mechanism is designed and incorporated within the ACS. A precision positioning experimental setup is developed and employed to demonstrate the precision positioning capabilities of the developed ACS. The axial vibration suppression capability of the ACS can also be provided by its internal piezoelectric stack actuator, and is demonstrated employing a developed vibration suppression experimental setup. Analytical and finite element analysis numerical verification, simulation, and modeling of the vibration suppression capabilities of the ACS are presented. Active vibration suppression schemes, using finite element analyses, are employed to numerically demonstrate the vibration suppression capabilities of the developed ACS. The ACS housing is a composite tubing. The numerical and experimental results show that the proposed ACS offers a promising method for achieving fine tuning of positioning tolerances as well as minimizing the effects of disturbances generated during a thruster firing of a satellite for the TVC application using a MSP.