The Large Millimeter-wave Telescope/Gran Telescopio Milimé trico (LMT/GTM), is a 50-m diameter radio telescope designed to operate at 1-mm wavelengths. To achieve its surface accuracy requirements, the telescope relies on an actively controlled primary surface. The active primary enables active correction of errors in the reflecting surface caused by thermal and gravitational deformations of the supporting backstructure. In addition to these slowly varying loads, there are higher frequency disturbances caused by some observation techniques. In a conventional telescope, the observer must wait for the vibration to decay naturally before continuing an observation. However, for an active surface telescope (such as the LMT/GTM), the mass of the surface and the large number of actuators can be used to add damping to the support structure. The use of active surfaces in vibrational damping of their support structures is investigated. A method is presented that enables decoupling of the vibrational modes in such a way that the surface figure can be controlled simultaneously. © 1997 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(97)00107-4]

No abstract

Active surfaces are introduced, defined, and modeled as a cooperating set of parallel manipulators. In this context, active surfaces may be viewed as a means of approximating complex shapes or as hyper-redundant in-parallel force manipulators for modal vibration control. Such surfaces may be employed to correct for support structure deformations or vibrations, as well as to achieve other shape dependent performance requirements. As a result of these features, active surfaces have applications in many types of intelligent structures, such as telescopes, communications antennas, bridges, and airfoils. The paper provides an overview of the kinematics of active surfaces. Additionally, it outlines the vibration control problem, and demonstrates how active surfaces can be employed as a modal force manipulator.

No abstract