Actuated truss system
AssigneeMassachusetts Institute of Technology
InventorsEdward F. Crawley, Nesbitt Hagood
Life of this patent
Estimating the term…
Abstract
A truss member includes a piezoelectric stack and a cylindrical shell formed of composite material surrounding the stack and bonded thereto, such that the axial load is distributed between the shell and the stack. The truss is fitted to a structural assembly via end pieces, and electrodes are attached to the stack, which may be selectively actuated to achieve different effects. In one aspect, a shunt or resonant feedback circuit damps a truss resonance mode; in another aspect an electrode bus attached to partial electrode surfaces on the stack allows the selective excitation of bending moments. The composite shell shields the stack from the environment, resulting in a robust control structure of low effective mass.
Claims20
A truss member comprising
- an elongate cylindrical shell having first and second endpieces adapted to couple to a truss structure and place said shell in load-bearing relation to the structure, said shell being formed of a composite material,
- a plurality of cylindrical elements of Piezoelectric material axially juxtaposed in said shell to form a load bearing inner column extending between said first and second endpieces, and
- conductive means for interconnecting a circuit with opposed faces of the cylindrical elements to actuate said piezoelectric elements, and
- wherein said cylindrical shell is fitted about and bonded to said plurality of cylindrical elements to form a radially-varying axially-homogeneous truss member.
A truss member comprising
- a cylindrical column of piezoelectric material having first and second ends along an axis, and also having actuating electrodes on radially opposed surfaces thereof,
- a shell of load-bearing material contacting the exterior of said column between said first and second ends to couple a load carried by said column along the length of said shell, and
- end connector means coupled to opposing ends of said shell for attaching said column and shell in a truss,
- wherein said shell has a stiffness of about one to five times that of the cylindrical column and a thickness not substantially greater than that of the cylindrical column.
A truss member comprising
- opposed endpieces axially spaced along a longitudinal axis and each including means adapted for mechanical interconnection with a load or load-bearing element,
- an internal first and an external second column held in concentric parallel load bearing relation between the opposed endpieces,
- wherein aid internal first column is formed of a piezoelectrically actuatable material, and said external second column includes a shell of structural load-bearing material surrounding and supporting said first column in isolation from the environment, said second column being attached to said first column in load-sharing relation to said first column such that it is extended or contracted by extension or contraction of the piezoelectrically actuable material.
A Controllable truss member comprising
- a tubular structural member having a central axis and an interior face,
- a hollow piezoelectric core fitted in said tubular member and mechanically coupled to said interior face, such that said core and said tubular structural member share a load directed along said central axis, and
- electrode means attached to said piezoelectric core for interconnecting the core with control circuitry so as to selectively vary a mechanical property of the truss member by application of a control signal.
A truss structure comprising
- a plurality of elongate members each having first and second ends, various ones of said ends being connected together at lattice points so as to constitute said truss structure,
- one of said elongate members including an inner cylindrical column of piezoelectric material covered by and bonded to an outer cylindircal column of composite material, and
- means for applying a signal to the piezoelectric material of the inner column to attenuate a resonance of said truss structure.
Dependencies are inferred from the claim text.