Flywheel Energy and Power Tracking

Abstract

Space vehicles, typically utilize separate devices to provide energy storage and attitude control. Conventionally, the energy collected from solar arrays is stored in chemical batteries for use when the spacecraft is in the earth's shadow. Attitude control is usually accomplished through an array of reaction wheels or control moment gyros. In contrast to the standard configuration, a suitable arrangement of four or more flywheels can integrate the energy storage and attitude control functions into a single system, and thereby, reduce the spacecraft's bus mass, volume, cost, and maintenance requirements while maintaining or improving the spacecraft's performance. We will refer to this system as an Integrated Energy Management and Attitude Control system. Roughly speaking, the integration of these two functions is achieved by decomposing the model of the flywheel array into two separate control problems i.e., attitude tracking and energy/power tracking, respectively). As a result, the energy management function can be accomplished without affecting the attitude control function.

This research is devoted to the use of multiple flywheels that integrate the energy storage and attitude control functions in space vehicles. This concept, which we refer to as an Integrated Energy Management and Attitude Control (IEMAC) system, reduces the space vehicle bus mass, volume, cost, and maintenance requirements while maintaining or improving the space vehicle performance. To this end, we present two nonlinear IEMAC strategies (model-based and adaptive) that simultaneously track a desired attitude trajectory and desired energy/power profile. Both strategies ensure asymptotic tracking while the adaptive controller compensates for uncertain spacecraft inertia.

For the full conference paper, please read

B. T. Costic, M. S. de Queiroz, D. M. Dawson, and Y. Fang, "Energy Management and Attitude Control Strategies using Flywheels," Proc. of the IEEE Conference on Decision and Control, Orlando, FL, December 2001, accepted, to appear.  

Simulation Results

Desired rotation about each axis of the coordinate frame D

Model-Based control - Attitude tracking error e(t)

Model-Based control - a) Desired energy profile, b) Energy tracking error, and c) Power tracking error.

Model-Based control - Flywheel angular velocity

Model-Based control - Control torque input

Adaptive control - Attitude tracking error e(t)

Adaptive control - a) Desired energy profile, b) Energy tracking error, and c) Power tracking error.

Adaptive control - Flywheel angular velocity

Adaptive control - Control torque input

Adaptive control - Inertia matrix estimates

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