An Optimum Design Methodology for Passively Damped Truss Structures
Report Number: WL-TR-91-3078 Volume I, p. DCB-1 thru DCB-11
Author(s): Manning, R. A.
Laboratory: Wright Laboratory
Date of Publication: 1991-08
Pages: 11
Contract: Laboratory Research - No Contract
DoD Project: 2401
DoD Task: 240104
Identifier: This paper is part of a conference proceedings. See ADA241311
Abstract:
Many of the complex space structures proposed for future space missions will utilize enhanced damping to meet stringent performance requirements. The enhanced damping is necessary to prevent excessive slew /settle times, unacceptable jitter levels, and harmful controls/structures interactions. There are currently no documented integrated design methodologies for designing damping into complex structures early in the design process. In this paper, an optimum design methodology is presented for truss structures augmented with constrained layer viscoelastically damped members. The methodology is presented as a two stage procedure. In the first stage, efficient locations for the passive members are found heuristically, thus avoiding a computationally burdensome combinatoric optimization problem. In the second stage, a formal optimization procedure is used to simultaneously size both the truss members and the passive members. Values for the design variables at the optimum design are found by solving a sequence of approximate problems. Each approximate problem is constructed using design sensitivity information in conjunction with first order Taylor series expansions. The sizing-type design variables treated in the optimum design procedure are inert structural member cross sectional dimensions, passive member cross sectional dimensions, passive member viscoelastic layer and constraining layer thicknesses. The complex space structure design problem is posed as a nonlinear mathematical programming problem in which an objective function critical to adequate mission performance (e.g., line-of-sight errors or settling time following slew) is to be minimized. Limitations considered during the design procedure include an upper bound weight cap, dynamic response constraints (which represent additional mission requirements), and side constraints on the design variables.
Author(s): Manning, R. A.
Laboratory: Wright Laboratory
Date of Publication: 1991-08
Pages: 11
Contract: Laboratory Research - No Contract
DoD Project: 2401
DoD Task: 240104
Identifier: This paper is part of a conference proceedings. See ADA241311
Abstract:
Many of the complex space structures proposed for future space missions will utilize enhanced damping to meet stringent performance requirements. The enhanced damping is necessary to prevent excessive slew /settle times, unacceptable jitter levels, and harmful controls/structures interactions. There are currently no documented integrated design methodologies for designing damping into complex structures early in the design process. In this paper, an optimum design methodology is presented for truss structures augmented with constrained layer viscoelastically damped members. The methodology is presented as a two stage procedure. In the first stage, efficient locations for the passive members are found heuristically, thus avoiding a computationally burdensome combinatoric optimization problem. In the second stage, a formal optimization procedure is used to simultaneously size both the truss members and the passive members. Values for the design variables at the optimum design are found by solving a sequence of approximate problems. Each approximate problem is constructed using design sensitivity information in conjunction with first order Taylor series expansions. The sizing-type design variables treated in the optimum design procedure are inert structural member cross sectional dimensions, passive member cross sectional dimensions, passive member viscoelastic layer and constraining layer thicknesses. The complex space structure design problem is posed as a nonlinear mathematical programming problem in which an objective function critical to adequate mission performance (e.g., line-of-sight errors or settling time following slew) is to be minimized. Limitations considered during the design procedure include an upper bound weight cap, dynamic response constraints (which represent additional mission requirements), and side constraints on the design variables.