Inverse Kinematics and Geometric Relations of an Intelligent Modified Stewart Platform for Thrust Vector Control

Aerospace ◽  
2004 ◽  
Author(s):  
Mehrdad N. Ghasemi Nejhad
Keyword(s):  
Vector Control ◽  
Inverse Kinematics ◽  
Vibration Suppression ◽  
Intelligent System ◽  
Research Effort ◽  
Stewart Platform ◽  
Fine Tuning ◽  
Precision Positioning ◽  
Thrust Vector Control ◽  
Thrust Vector

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 of an intelligent thruster mount structure with precision positioning and active vibration suppression capability for use in a space satellite. The intelligent thruster mount would utilize piezoelectric stacks and patches for precision positioning and vibration suppression to provide fine-tuning of position tolerance for thruster alignment and low transmissibility of vibration to the satellite structure. This vibration, if not suppressed, renders sensitive optical or measurement equipment non-operational until the disturbance has dissipated. This intelligent system approach would greatly enhance mission performance by fine tuning attitude control, potentially eliminating the non-operational period as well as minimizing fuel consumption utilized for position correction. The configuration of the intelligent thruster mount system is that of a modified Stewart platform. Precision positioning of this structure is achieved using active composite strut members that use piezoelectric stack actuators and extend or contract to tilt the top device-plate where the thruster is mounted. The geometric relationship between the Stewart platform and the modified Stewart platform is described, and an inverse kinematics analysis of the modified Stewart platform has been developed and is used to determine the required axial displacement of the active struts for the desired angular tilt of the top device-plate. The active struts can participate in precision positioning as well as vibration suppression of the top device-plate where the thruster, i.e., the source of the unwanted vibrations and misalignment, is mounted. The proposed Thrust Vector Control (TVC) intelligent platform offers a promising method for achieving fine tuning of positioning tolerances of a thruster as well as minimizing the effects of the disturbances generated during thruster firing in spacecraft such as a satellite.

Modified Stewart Platform for Spacecraft Thruster Vector Control

2002 ◽  
Author(s):  
Mehrdad N. Ghasemi-Nejhad ◽  
Kathleen M. Doherty
Keyword(s):  
Vector Control ◽  
Attitude Control ◽  
Vibration Suppression ◽  
Intelligent System ◽  
Stewart Platform ◽  
Fine Tuning ◽  
Precision Positioning ◽  
Sensors And Actuators ◽  
Active Vibration Suppression ◽  
Active Vibration

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 paper introduces an intelligent modified Stewart platform as an adaptive thruster mount structure with precision positioning and active vibration suppression capabilities for use in space satellites as an intelligent thruster vector control platform. The intelligent thruster mount would utilize piezoelectric sensors and actuators for precision positioning and active vibration suppression to provide fine-tuning of position tolerance for thruster alignment and low transmissibility of vibration to the satellite structure. Similar intelligent platform, introduced here, may be used for sensitive equipment aboard of the spacecraft to suppress the vibration that resonates throughout the spacecraft structure during a thruster firing, solar panel boom opening/reorientation, etc. This vibration renders sensitive optical or measurement equipment non-operational until the disturbance has dissipated. This intelligent system approach would greatly enhance mission performance by fine tuning attitude control, potentially eliminating the non-operational period as well as minimizing fuel consumption utilized for position correction. The configuration of the intelligent thruster mount system is that of a modified Stewart platform. This system is an intelligent tripod with two in-plane rotational degrees of freedom (2-DOF) for the top device-plate. Precision positioning of this structure is achieved using active members that extend or contract to tilt the upper device-plate where the thruster is mounted. An inverse analysis of a modified Stewart platform is employed to determine the required axial displacement of the active struts for the desired angular tilt of the upper device-plate. The active struts can participate in precision positioning as well as vibration suppression of the upper device-plate where the thruster, i.e., the source of the unwanted vibrations and misalignment, is mounted. The proposed Thruster Vector Control (TVC) intelligent platform offers a promising method for achieving fine tuning of positioning tolerances of a thruster as well as minimizing the effects of the disturbances generated during thruster firing in spacecraft such as a satellite.

SIMULATION RESEARCH OF ACTIVE VIBRATION CONTROL FOR ELASTIC MISSILE WITH SWING NOZZLE THRUST VECTOR CONTROL

2013 ◽  
Vol 04 (04) ◽  
pp. 1342002 ◽  
Author(s):  
XIAODONG LIU ◽  
YUNJIE WU ◽  
YONG DENG ◽  
SEN WANG ◽  
JIAYUN SONG
Keyword(s):  
Vector Control ◽  
Vibration Suppression ◽  
Active Vibration Control ◽  
System Stability ◽  
Minimal Order ◽  
Good Convergence ◽  
Thrust Vector Control ◽  
Thrust Vector ◽  
Active Vibration ◽  
Nozzle Thrust

Aiming at the deficiencies of notch filters on the aspect of vibration suppression for elastic missile with swing nozzle thrust vector control (SNTVC), an active vibration controller (AVC) is proposed. It is composed of an optimal state feedback controller (OSFC) and an optimal minimal order state observer (OMOSO), which can be respectively designed based on the separation principle. The design rules of these two elements are successively given. Computer simulation results present that AVC can realize strong vibration suppression and good convergence property after disturbing. Moreover, it has simple design and then it is easily implemented in engineering. In addition, the AVC scheme can also resolve the poor system stability to a great extent, which is resulted from the bad static stability of missile body.

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