Jerry L. Fausz

Simultaneous attitude control and energy storage using VSCMGs: theory and simulation

This work examines the simultaneous use of single-gimbal Variable Speed Control Moment Gyroscopes (VSCMGs) as spacecraft attitude control actuators and energy storage devices. The resulting theory, initially developed in Fausz and Richie, (2000), is refined and simplified. The validity of the theory is demonstrated via numerical simulation.

Survey of Technology Developments in Flywheel Attitude Control and Energy Storage Systems

Advances in microprocessors and composite materials in the past decade, along with limitations of chemical batteries for U.S. Air Force mission concepts, have caused a renewed interest in flywheel energy storage systems for space applications. This interest has also been driven in the past by the promise of using flywheel systems for energy storage and as attitude control actuators. The primary issues are power efficiency, mass and size, and long-term stability. Flywheels as one-to-one replacements for spacecraft batteries are competitive for only a few special missions. When flywheels replace components in two major bus subsystems, the potential mass and volume benefits are attractive. This especially benefits future small satellite missions that seek agile slewing with high peak power. The objective of this paper is to describe the progression of the flywheel technology state of the art for combined energy storage and attitude control systems in space applications and the current energy storage and attitude control systems efforts.

Flywheel simultaneous attitude control and energy storage using a VSCMG configuration

Space vehicle programs consistently endeavor to reduce satellite bus mass to increase payload capacity and/or reduce launch and fabrication costs. At the same time, performance demands on satellite systems continue to increase, creating a formidable challenge to space vehicle technology development. Flywheel-based systems providing both energy storage and attitude control functionality address both of these issues. In particular, the flywheel attitude control, energy transmission and storage (FACETS) system should combine all or part of the energy storage, attitude control, and power management and distribution (PMAD) subsystems into a single system, thus significantly decreasing bus mass. The control problem of mechanically-based simultaneous energy storage and attitude control is far from trivial, however, even in its simplest conceivable form. While decoupling the attitude control and energy storage may be a workable solution to the problem, research in related areas suggests it may not be the best approach. It has been shown that simultaneous momentum management and power tracking can be accomplished with four or more wheels in reaction wheel mode using the null subspace of the angular momentum dynamics of the wheels. In this way the energy storage or power tracking function does not induce attitude disturbance torques to the spacecraft. Furthermore, the null subspace was shown to be sufficient for tracking a variety of practical satellite power profiles. For some applications, however, reaction wheels produce insufficient control torque and control moment gyros (CMGs) are required. The paper extends the null subspace approach for simultaneous power tracking and attitude control, proven for flywheels in a reaction wheel mode, to an array of flywheels in a CMG configuration.

Optimal discrete-time control for non-linear cascade systems

Abstract In this paper we develop an optimality-based framework for designing controllers for discrete-time non-linear cascade systems. Specifically, using a non-linear—non-quadratic optimal control framework we develop a family of globally stabilizing backstepping-type controllers parameterized by the cost functional that is minimized. Furthermore, it is shown that the control Lyapunov function guaranteeing closed-loop stability is a solution to the steady-state Bellman equation for the controlled system and thus guarantees both optimality and stability.

Optimal non-linear robust control for non-linear uncertain systems

In this paper we develop an optimality-based robust control framework for non-linear uncertain systems with structured parametric uncertainty. Specifically, using an optimal non-linear robust control framework, we develop a family of globally stabilizing robust backstepping controllers parametrized by the cost functional that is minimized. Furthermore, it is shown that the Lyapunov function for the closed-loop system guaranteeing robust stability over a prescribed range of structured system parametric uncertainty is a solution to the steady-state Hamilton-Jacobi-Bellman equation for the controlled system and thus guarantees robust stability and robust performance. The results are then used to design robust controllers for jet engine compression systems with uncertain system dynamics.

Passive Balancing of Rotor Systems Using Pendulum Balancers

Passive balancing techniques have received a great deal of attention in recent literature, with much of this work focused on ball balancer systems. However, for certain applications, balancing systems that use pendulums rather than rolling balls may offer distinctly improved balancing precision. This investigation seeks to provide additional insight into the performance and expected behavior of such systems. A simulation model is developed for a pendulum balancer system with isotropic supports and analyzed in detail. The influence of shaft location and friction on balancing effectiveness is considered and evaluated. In this regard, the dynamic characteristics of a pendulum balancer system are analyzed and compared to a similar ball balancer system. The conclusions and observations from the analysis and simulation studies are demonstrated and tested in a series of experimental studies.

Robust nonlinear feedback control for uncertain linear systems with nonquadratic performance criteria

In this paper we develop a unied framework to address the problem of optimal nonlinear robust control for linear uncertain systems. Specically, we transform a given robust control problem into an optimal control problem by properly modifying the cost functional to account for the system uncertainty. As a consequence, the resulting solution to the modied optimal control problem guarantees robust stability and performance for a class of nonlinear uncertain systems. The overall framework generalizes the classical Hamilton{Jacobi{Bellman conditions to address the design of robust nonlinear optimal controllers for uncertain linear systems. c 1998 Elsevier Science B.V. All rights reserved.

Nonlinear robust disturbance rejection controllers for rotating stall and surge in axial flow compressors

We develop globally stabilizing robust/disturbance rejection controllers for rotating stall and surge in axial flow compressors with uncertain compressor performance pressure flow characteristic maps. Specifically, using the nonlinear nonquadratic disturbance rejection optimal control framework for systems with bounded energy (square integrable) L/sub 2/ disturbances (W.M. Haddad et al., 1997) and the nonlinear nonquadratic robust optimal control framework for systems with nonlinear parametric uncertainty, a family of globally robustly stabilizing controllers for jet engine compression systems is developed. The proposed controllers are compared with the locally stabilizing bifurcation based controllers of R.A. Adomaitis and E.H. Abed (1992) and the recursive backstepping controllers of M. Krstic et al. (1995).

Inverse optimal adaptive control for nonlinear uncertain systems with exogenous disturbances

A Lyapunov-based optimal adaptive control-system design problem for nonlinear uncertain systems with exogenous L/sub 2/ disturbances is considered. Specifically, an inverse optimal adaptive nonlinear control framework is developed to explicitly characterize globally stabilizing disturbance rejection adaptive controllers that minimize a nonlinear-nonquadratic performance functional for nonlinear systems with parametric uncertainty. It is shown that the adaptive control Lyapunov function guaranteeing closed-loop stability is a solution to the Hamilton-Jacobi-Isaacs equation for the controlled system and thus guarantees both optimality and robust stability. Additionally, the adaptive control Lyapunov function is dissipative with respect to a weighted input-output energy supply rate guaranteeing closed-loop disturbance rejection.

Optimal nonlinear robust control for nonlinear uncertain cascade systems

We develop an optimality-based robust control framework for uncertain cascade systems with structured parametric uncertainty. Specifically, using an optimal nonlinear robust control framework we develop a family of globally stabilizing robust backstepping controllers parametrized by the cost functional that is minimized. Furthermore, it is shown that the robust control Lyapunov function guaranteeing closed-loop stability over a prescribed range of structured system parametric uncertainty is a solution to the steady-state Hamilton-Jacobi-Bellman equation for the controlled system and thus guarantees robust stability and robust performance. The results are then used to design robust controllers for jet engine compression systems with uncertain compressor characteristic performance maps.