Attitude Control of a Flexible Triangular Truss in Space

Abstract

Large structures are being considered for future missions in space. They will make efficient use of material and hence are likely to be quite flexible. Flexible structures are distributed parameter systems with infinite-dimensional discrete spectra. They are often approximated by using a finite number of modes. When this is done, using finite element methods, many more elements must be used than the number of modes required, to ensure acceptable accuracy in the required modes. In this paper, we derive an infinite dimensional model for a planar flexible structure, an equilateral triangular truss. Exact poles (natural frequencies) and zeros are determined for transfer functions from control torques to local attitude angles, and simple control logic is given that stabilizes the attitude and all the vibration modes.