An automatic center of gravity positioning system

Abstract

An automatic center of gravity positioning controller for a single axis space simulator is described. The mass distribution of the space simulator or test table is altered by the controller in such a way that the center of gravity of the table is moved toward the axis of rotation of the table. Initially, the center of gravity is assumed to be below the axis of rotation. The equilibrium position of the table is altered between two different orientations by two positioners. The positioners change the equilibrium position of the table by moving weights attached to the table in such a way that the desired equilibrium orientation is obtained. The physical arrangement of the "movable weights" is such that the center of gravity of the table is moved toward the axis of rotation each time the table orientation is changed. By repetitive alteration of the equilibrium position of the table, the center of gravity is made to approach the axis of rotation. The controller is a digital-analog system. The analog portion controls the equilibrium position of the table. The digital portion provides for the alteration or sequencing of the position of the equilibrium orientation of the table. Also, based on the pendulous period of the table, the digital circuitry determines when a certain "degree of balance" has been reached and when changes are to be made in the compensator configuration of the analog portion of the controller. The analog compensator configuration is altered to accommodate changes in the table characteristics. As the center of gravity approaches the axis of rotation, the pendulous frequency of the table decreases and its sensitivity to mass redistribution increases. Theoretical considerations are made using the method of Lagrange and root locus techniques. Theoretical predictions are compared to experimental results.