The Annular Suspension and Pointing System

Anderson, W. W.; Groom, Nelson J.; Woolley, C. T.

doi:10.1016/b978-0-08-024449-5.50010-2

Cited by 4 publications

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“…It can be shown (Ref. 4) that for small perturbations about a fixed operating point, the effect of motion in the gaps is also linear and the actuator force as a function of differential coil current and displacement can be written as (3) where K B is an equivalent electromagnet gain and K M is an equivalent unbalanced bias flux stiffness. Unfortunately, for different nominal operating points the linear small per- turbation electromagnet gain and equivalent unbalanced bias flux stiffness will change.…”

Section: Description Of Magnetic Actuator Conceptsmentioning

confidence: 99%

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Annular Suspension and Pointing System

Anderson¹,

Groom²,

Woolley³

1979

Journal of Guidance and Control

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The Annular Suspension and Pointing System (ASPS) is a general-purpose mount designed to provide orientation, mechanical isolation, and fine pointing for space experiments. The ASPS consists of two assemblies, the first being a set of two gimbals attached to a carrier spacecraft (e.g., Space Shuttle) and providing coarse pointing, and the second a magnetic vernier-pointing and isolation assembly attached to the inner gimbal of the first assembly and providing fine pointing. Discussion of the evolution of this concept, required technology, and data from analyses and simulations predicting pointing accuracies that allowed the specification of hardware design requirements is presented. Nomenclature transformation from shuttle to elevation gimbal coordinates transformation from elevation to lateral gimbal coordinates = total axial centering force acting on the payload = centering force produced by axial bearing 1 = centering force produced by axial bearing 2 = force produced by bottom electromagnet = command force = forces produced by magnetic bearings = radial payload centering force = force produced by top electromagnet = bearing-gap displacement = angular momentum of shuttle, elevation gimbal, lateral gimbal, and payload = inertia of shuttle, elevation gimbal, lateral gimbal, and payload = inertia of elevation gimbal transformed to shuttle system = inertia of lateral gimbal transformed to shuttle system = sum of inertias of shuttle, elevation gimbal, and lateral gimbal in shuttle coordinates = electromagnet constant, Eq. (1) = equivalent electromagnet gain, Eq. (3) = kinetic energy of shuttle, elevation gimbal, lateral gimbal, and payload = total kinetic energy of shuttle and coarse gimbals = equivalent unbalanced bias-flux stiffness, Eq. (3) = distance of payload center of mass from payload plate = suspended mass > TE> TL = T.MBA. VC.V V L ,V PLmass of shuttle, elevation gimbal, lateral gimbal, and payload sum of elevation and lateral gimbal masses total mass of shuttle and coarse gimbals control moment produced by axial actuators linear momentum of shuttle and payload radius of ASPS rim vector which defines the origin of the elevation-lateral system in shuttle coordinates vector which defines the base of the payload in the payload coordinates Laplace variable torques applied to shuttle, elevation gimbal, and lateral gimbal = torques produced by magnetic bearings = velocities of shuttle, elevation gimbal, lateral gimbal, and payload centers of mass expressed in their respective coordinates = elevation gimbal angle and time rate of change of same = coarse gimbal angle = lateral gimbal angle and time rate of change of samê L^PL =body rates of shuttle, elevation gimbal, lateral gimbal, and payload IntroductionT HE need for a multipurpose experiment pointing platform was established during NASA Earth-orbital systems technology guidance and control planning activities during the early 1970's. The Annular Suspension and Pointing System (ASPS) concept was developed to meet this need. The ASPS is a derivative of the Annu...

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Section: Description Of Magnetic Actuator Conceptsmentioning

confidence: 99%

“…The differences are sufficiently great that the ASPS is considered a unique device on its own. 3 This paper presents a general discussion of the ASPS concept and a discussion of the evolution of the concept that lead to a decision by NASA to build a prototype ASPS for use on the Space Shuttle.…”

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confidence: 99%