Practical Implementation of Attitude-Control Algorithms for an Underactuated Satellite

The challenging problem of controlling the attitude of satellites subject to actuator failures has been the subject of increased attention in recent years. The problem of controlling the attitude of a satellite on all three axes with two reaction wheels is addressed in this paper. This system is controllable in a zero-momentum mode. Three-axis attitude stability is proven by imposing a singular quaternion feedback law to the angular velocity trajectories.Two approaches are proposed and compared to achieve three-axis control: The first one does not require angular velocity measurements and is based on the assumption of a perfect zero momentum, while the second approach consists of tracking the desired angular velocity trajectories. The full-state feedback is a nonlinear singular controller. In-orbit tests of the first approach provide an unprecedented practical proof of three-axis stability with two control torques. The angular velocity tracking approach is shown to be less efficient using the nonlinear singular controller. However, when inverse optimization theory is applied to enhance the nonlinear singular controller, the angular velocity tracking approach is shown to be the most efficient. The resulting switched inverse optimal controller allows for a significant enhancement of settling time, for a prescribed level of the integrated torque

Passivity Based Adaptive Attitude Control of a Rigid Spacecraft

An adaptive control scheme for the attitude control of a rigid spacecraft is derived using a linear parameterization of the equation of motion. The tracking error is described with the Euler parameter vector. Global convergence of the tracking error to zero is shown using passivity theory. This allows for the use of time-varying positive definite feedback gain matrices, and the results can easily be extended to other passive parameter update laws

A note on Lyapunov stability for an adaptive robot controller

Stability in the sense of Lyapunov for the adaptive robot controller proposed by Slotine and Li is proved in this note. The result is a generalization of previous work, where the feedback gain matrix was assumed to be constant and diagonal, while in this paper the feedback gain matrix is only assumed to be uniformly positive definite

Control of Nonholonomic Systems with Drift Terms

In the present paper nonholonomic systems with drift terms are studied. The discussion is focused on a class of Lagrangian systems with a cyclic coordinate. We present an approach to open--loop path planning in which the system evolution is studied on manifolds of dimension equal to the number of control inputs. A control algorithm is derived and it is applied to the planar diver. A similar algorithm is derived for the study of what states can be reached within a given time. An exponentially stabilizing feedback controller is derived for tracking of the planned trajectories. The results are illustrated with simulations. 1 Introduction Driftless nonholonomic control systems have been studied in recent years by Walsh and Sastry (1991), Teel et al. (1992), Murray and Sastry (1993), Bloch et al. (1993), Kolmanovsky and McClamroch (1995), and others. Several important results have been derived based on the structure of Lie algebras generated by the control vector fields. A dual point of ..

Control of Nonholonomic Systems with Drift Terms

In the present paper nonholonomic systems with drift terms are studied. The discussion is focused on a class of Lagrangian systems with a cyclic coordinate. We present an approach to open--loop path planning in which the system evolution is studied on manifolds of dimension equal to the number of control inputs. A control algorithm is derived and it is applied to the examples of a hopping robot and a planar diver. A similar algorithm is derived for the study of what states can be reached within a given time. An exponentially stabilizing feedback controller is derived for tracking of the planned trajectories. The results are illustrated with simulations. Research supported in part by ARO under grants DAAH04-95-1-0588, DAAH04-94-G0211 (AASERT), and DAAH04-96-1-0341 (MURI). y Address: Seatex, Pirsenteret, 7005 Trondheim, Norway, e-mail:[email protected]. z Address: Dipartimento di Sistemi Elettrici e Automazione (DSEA), Universit`a degli Studi di Pisa, Via Diotisalvi 2, 56126 Pisa, Ital..