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Silverberg, Larry

Publications and source records attributed to Silverberg, Larry.

8 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Fuel-optimal slewing of an experimental hinged-free beam

With the recent development of numerical methods for exactly solving larger order fuel-optlmal control problems, the implementation of exact real-time fuel-optimal control becomes possible. This paper describes a physical experiment in which a hinged-free beam is slewed in a fuel-optimal manner. A comparison between experimental results and the analytical predictions highlights the sources of errors typical of this class of problems.

Silverberg, Larry↗
NASA NTRS1993

Fuel optimal reorientation of axisymmetric spin-stabilized satellites

The fuel optimal spin axis reorientation problem for large and small maneuver times is solved using a new numerical technique. The approach, which employs the adaptive grid bisection search, is shown to be useful in determining the fuel optimal impulsive control strategy, particularly when rapid maneuvers are desired. For large enough maneuver times, the method produces the two-impulse reorientation maneuver. For even larger maneuver times, the existence of multiple optimal pulsing schemes is demonstrated.

Redmond, Jim↗
NASA NTRS1992

Fuel consumption in optimal control

A method has been developed for comparing three optimal control strategies based on fuel consumption. A general cost function minimization procedure was developed by applying two theorems associated with convex sets. Three cost functions associated with control saturation, pseudofuel, and absolute fuel are introduced and minimized. The first two cost functions led to the bang-bang and continuous control strategies, and the minimization of absolute fuel led to an impulsive strategy. The three control strategies were implemented on two elementary systems and a comparison of fuel consumption was made. The impulse control strategy consumes significantly less fuel than the continuous and bang-bang control strategies. This comparison suggests a potential for fuel savings in higher-order systems using impulsive control strategies. However, since exact solutions to fuel-optimal control for large-order systems are difficult if not impossible to achieve, the alternative is to develop near-optimal control strategies.

Redmond, Jim↗
NASA NTRS1992

Fuel optimal propulsive reboost of flexible spacecraft

This paper presents for the first time an exact solution to the fuel optimal propulsive reboost problem for flexible spacecraft. The spacecraft undergoes rigid-body motion and flexible-body motion and reboost is achieved propulsively through the use of reaction control jets. The exact fuel optimal solution to the associated minimization problem is found numerically based on an adaptive grid bisection search. The reboost of the floating harmonic oscillator reveals properties of the fuel optimal solution. Nondimensional plots of minimum fuel versus maneuver time expose the nature of the solution classes depending on the maneuver time. Some very interesting properties are observed, among them, the shifting of impulses to the smaller oscillator mass, and comparisons are made with near fuel optimal solutions obtained by other investigators.

Silverberg, Larry↗
NASA NTRS1990

Modal identification of gyroscopic distributed-parameter systems

A new modal identification method for gyroscopic distributed-parameter systems is presented. The method represents an extension of previous work for the class of self-adjoint distributed-parameter systems. The modal identification method is formulated as a variational problem in which stationary values of a functional quotient are sought. The computation of the functional quotient is carried out using a set of admissible functions defined over the spatial domain of the system. As an illustration, the modal identification of a whirling shaft undergoing bending vibration is carried out and the effectiveness of the method is verified.

Norris, Mark A.↗
NASA NTRS1989

Globally optimal maneuver of distributed systems

This paper examines the globally optimal maneuver of distributed systems undergoing large overall rigid-body motion and small relative elastic motion. Using floating coordinates the rigid-body motion and the elastic motion are decoupled thereby allowing the globally optimal maneuver problem to be separated into components associated with the rigid-body and elastic motions. The maneuvers are performed using distributed maneuvering forces based on modal measurements. The modal measurements are extracted from the physical measurements using modal filters. Rest-to-rest maneuvers of a uniform beam illustrate the decentralized nature of the globally optimal solutions.

Silverberg, Larry↗
NASA NTRS1989

Dynamics and control of multibody/robotic systems with space applications; Proceedings of the ASME Winter Annual Meeting, San Francisco, CA, Dec. 10-15, 1989

The present conference on the dynamics and control methods of multibody robotic systems applicable to outer space applications first gives attention to such topics in multibody dynamics and control as the substructure synthesis approach to flexible multibody system control, an elastic finite-element kinematic analysis of a multirigid body, computational methods for high speed vehicles on flexible guideways, and multiarm coordination and control. Attention is then given to such issues in space manipulator dynamics and control methods as the global navigation of a free-flying space robot, dynamic singularities in the control of free-floating space manipulators, experimental results for compact space robot actuator control, and a 17-degree-of-freedom dexterous manipulator.

Joshi, Suresh M.↗