311 research outputs found
Nonlinear Attitude Control of Planar Structures in Space Using Only Internal Controls
An attitude control strategy for maneuvers of an interconnection of planar bodies in space is developed. It is assumed that there are no exogeneous torques and that torques generated by joint motors are used as means of control so that the total angular momentum of the multibody system is a constant, assumed to be zero. The control strategy utilizes the nonintegrability of the expression for the angular momentum. Large angle maneuvers can be designed to achieve an arbitrary reorientation of the multibody system with respect to an inertial frame. The theoretical background for carrying out the required maneuvers is summarized
Optimal Control of a Rigid Body using Geometrically Exact Computations on SE(3)
Optimal control problems are formulated and efficient computational
procedures are proposed for combined orbital and rotational maneuvers of a
rigid body in three dimensions. The rigid body is assumed to act under the
influence of forces and moments that arise from a potential and from control
forces and moments. The key features of this paper are its use of computational
procedures that are guaranteed to preserve the geometry of the optimal
solutions. The theoretical basis for the computational procedures is
summarized, and examples of optimal spacecraft maneuvers are presented.Comment: IEEE Conference on Decision and Control, 2006. 6 pages, 19 figure
Space station attitude disturbance arising from internal motions
A source of space station attitude disturbances is identified. The attitude disturbance is driven by internal space station motions and is a direct result of conservation of angular momentum. Three examples are used to illustrate the effect: a planar three link system, a rigid carrier body with two moveable masses, and a nonplanar five link system. Simulation results are given to show the magnitude of the attitude change in each example. Factors which accentuate or attenuate this disturbance effect are discussed
Efficient reorientation of a deformable body in space: A free-free beam example
It is demonstrated that the planar reorientation of a free-free beam in zero gravity space can be accomplished by periodically changing the shape of the beam using internal actuators. A control scheme is proposed in which electromechanical actuators excite the flexible motion of the beam so that it rotates in the desired manner with respect to a fixed inertial reference. The results can be viewed as an extension of previous work to a distributed parameter case
Lagrangian Mechanics and Variational Integrators on Two-Spheres
Euler-Lagrange equations and variational integrators are developed for
Lagrangian mechanical systems evolving on a product of two-spheres. The
geometric structure of a product of two-spheres is carefully considered in
order to obtain global equations of motion. Both continuous equations of motion
and variational integrators completely avoid the singularities and complexities
introduced by local parameterizations or explicit constraints. We derive global
expressions for the Euler-Lagrange equations on two-spheres which are more
compact than existing equations written in terms of angles. Since the
variational integrators are derived from Hamilton's principle, they preserve
the geometric features of the dynamics such as symplecticity, momentum maps, or
total energy, as well as the structure of the configuration manifold.
Computational properties of the variational integrators are illustrated for
several mechanical systems.Comment: 19 pages, 7 figure
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