Optical modeling for dynamics and control analysis

Redding, David C.; Breckenridge, W. G.

doi:10.2514/6.1990-3383

Cited by 5 publications

(5 citation statements)

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“…r = 0, this, however, is not always the case. The shaped disturbances w are then propagated through the opto-structural plant dynamics, which include the structural dynamics of the spacecraft and the linear sensitivity optics matrices [120]. A compensator is often present in order to stabilize the observable rigid body modes (attitude control) and to improve the disturbance rejection or tracking capability (optical control).…”

Section: 1)mentioning

confidence: 99%

Multivariable Isoperformance Methodology for Precision Opto-Mechanical Systems

Weck

Ladislas

2002

43rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference

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Precision opto-mechanical systems, such as space telescopes, combine structures, optics and controls in order to meet stringent pointing and phasing requirements. In this context a novel approach to the design of complex, multi-disciplinary systems is presented in the form of a multivariable isoperformance methodology. The isoperformance approach first finds a point design within a given topology, which meets the performance requirements with sufficient margins. The performance outputs are then treated as equality constraints and the nonuniqueness of the design space is exploited by trading key disturbance, plant, optics and controls parameters with respect to each other.Three algorithms (branch-and-bound, tangential front following and vector spline approximation) are developed for the bivariate and multivariable problem. The challenges of large order models are addressed by presenting a fast diagonal Lyapunov solver, apriori error bounds for model reduction as well as a governing sensitivity equation for similarity transformed state space realizations. Specific applications developed with this technique are error budgeting and multiobjective design optimization. The goal of the multiobjective design optimization is to achieve a design which is pareto optimal, such that multiple competing objectives can be satisfied within the performance invariant set. Thus, situations are avoided where very costly and hard-to-meet requirements are levied onto one subsystem, while other subsystems hold substantial margins.An experimental validation is carried out on the DOLCE laboratory testbed. The testbed allows verification of the predictive capability of the isoperformance technique on models of increasing fidelity. A comparison with experimental results, trading excitation amplitude and payload mass, is demonstrated. The predicted performance contours match the experimental data very well at low excitation levels, typical of the disturbance environment on precision opto-mechanical systems. The relevance of isoperformance to space systems engineering is demonstrated with a comprehensive NEXUS spacecraft dynamics and controls analysis. It is suggested that isoperformance is a useful concept in other fields of engineering science such as crack growth calculations in structures. The isoperformance approach enhances the understanding of complex opto-mechanical systems beyond the local neighborhood of a particular point design. Sharon-Leah Brown provided encouragement and professional financial management.

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Section: 1)mentioning

confidence: 99%

Multivariable Isoperformance Methodology for Precision Opto-Mechanical Systems

Weck

Ladislas

2002

43rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference

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“…Kissil prepared a number of internal memos on the various finite element models of the yardstick design [9], which were used as a basis for structural modeling in this paper. The fundamental work that allows formulating the linearized models of complex optical systems in state space form was performed by Redding and Breckenridge [10]. Bialke published papers on the sources of reaction wheel disturbances [11].…”

Section: Previous Workmentioning

confidence: 99%

“…The reason for this phenomenon (details are shown in reference [2] ) is that cryocooler disturbances, specifically the fundamental at 40 Hz, have now become the dominant disturbance sources. The cryocooler disturbance by itself is sufficient to exceed the requirements for the RMS WFE and the RMS LOS 10 . This leads to the conclusion that further mitigation of cryocooler disturbances along with RWA isolation is necessary.…”

Section: Performance Improvement Strategies (Optimization)mentioning

confidence: 99%

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<title>Integrated modeling and dynamics simulation for the Next Generation Space Telescope (NGST)</title>

et al. 2000

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NGST represents a challenging problem from the point of view of maintaining a milli-arcsecond level pointing accuracy and diffraction limited wavefront performance in the presence of dynamic onboard disturbances during science observations in a cryogenic environment. A Dynamics-Optics-Controls-Structures framework is being developed in support of the NGST dynamics and controls modeling program. First, an integrated model comprising multiple disturbance sources, structures, optics and control systems was developed in order to predict the expected dynamic wavefront error and line-of-sight jitter. A disturbance analysis was carried out using frequency domain and Lyapunov techniques. An indexing technique was subsequently used to analyze the sensor-actuator topology of the system. A sensitivity analysis revealed which modal parameters contribute significantly to the root-mean-square errors. The critical frequencies were found to be in the range from 5-50 Hz. This information was subsequently used to recommend performance improvements including stiffening the secondary mirror tower, isolating reaction wheels and adding passive damping treatments. The combination of improvements was implemented numerically, resulting in good performance with sufficient design margins. Isoperformance analysis was introduced as a means of trading system parameters, while holding the performance constant. This research is motivated by the fact that it will not be possible to test the fully deployed observatory in a 1g environment before launch.

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“…A simple overview of the optical layout is shown in Figure 2. One of the three interferometers of the FMI has been modeled using the Controlled Optics Modeling Package (COMP, based on Reference [5]). One purpose of this tool is to determine the partial derivatives of the optical pathlength to the motion of the individual optical elements.…”

Section: Structural and Optical Modelmentioning

confidence: 99%

Active Structural Control for Damping Augmentation and Compensation of Thermal Distortion

Sirlin

1992

Journal of Intelligent Material Systems and Structures

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A large space-based interferometer (FMI) is used as a testbed for ideas developed in the NASA Controls and Structures Interaction (CSI) program. An end-to-end simulation of the optical performance of the system has been developed and used to demonstrate impedance-based adaptive structural control and control of thermal disturbances. Other issues briefly addressed include integrated optical/structural modeling and a hierarchical, layered control strategy.

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Optical modeling for dynamics and control analysis

Cited by 5 publications

References 0 publications

Multivariable Isoperformance Methodology for Precision Opto-Mechanical Systems

Multivariable Isoperformance Methodology for Precision Opto-Mechanical Systems

<title>Integrated modeling and dynamics simulation for the Next Generation Space Telescope (NGST)</title>

Active Structural Control for Damping Augmentation and Compensation of Thermal Distortion

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