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Fax: (818) 393-4440 spano s@ c s i Abstract The paper presents analytical and experimental results with a 6-axis actively controlled vibration isolator. The isolator was designed to attenuate vibrations from reaction wheels, cryogenic coolers and other noisy machines located on board precision optical-class spacecraft. It consists of six active struts each of which includes an electromagnetic voice coil actuator in parallel with a soft spring. Six decoupled analog controllers were used to close broad-band feedback loops around six force sensors and the isolator multi-axis transmissibility was measured with twelve accelerometers (six on the noisy side and six on the quite side). Experimental results show a ten-fold improvement in performance over passive isolation alone.

This paper describes the design and performance testing of a vibration isolation and suppression system (VISS) which can be used to isolate a precision payload from spacecraft borne disturbances. VISS utilizes six hybrid isolation struts in a hexapod configuration. Central to the concept is a novel hybrid actuation concept which provides both passive isolation and active damping. The passive isolation is provided using a flight proven D-strut design. The passive design is supplemented by a voice coil based active system. The active system is used to enhance the performance of the passive isolation system at lower frequencies, and provide the capability to steer the payload.

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A new method, for the investigation of manipulator workspace, based on polynomial displacement equations and their discriminants is proposed in this paper. The approach followed enables one to obtain (a) analytical expressions describing the workspace boundary surfaces in Cartesian coordinates, (b) the distribution of the number of ways to position the hand inside the workspace, and (c) the conditions on kinematic parameters when the motion of the hand degenerates. Joint limitations are incorporated in the method. In the present paper and a companion paper [17], the method is rigorously applied to eight types of manipulators with various combinations of revolute and prismatic pairs having the last three revolute axes intersect orthogonally at at point. A numerical example is presented for illustration.