Deployable Tensegrity Structure
As a research assistant to Dr. Julian Rimoli and PI Franco Ruffini, I am currrently helping build an assembly fixture for a tensegrity structure with four other teammates. The structure is intended to collapse after assembly so that it can be stored aboard rovers and deployed while on missions. Each part must be easily assembled and dissassembled while being slim enough to be removed from within the tensegrity structure.
My main contributions:
Redesign the fixture so that each part could be manufactured in aluminum. The initial prototype was modeled for 3d printing, but there was too much flex in fixture when attempting to assemble the structure.
Confirm which parts we could make on campus and which would need to be manufactured elsewhere.
The initial fixture design was intended for 3d printing. The kevlar strings are tied to nodes that are being held by the bolted clamps. After tying the strings, carbon bars would be placed into the nodes to stabilize the structure. Ideally the structure would be able to collapse and spring back up when needed.
The initial version could not withstand the tension built as the strings were tied and bars we're placed into the nodes. The above model was the second iteration, which also had significant deflection. I joined the groups at this point with the goal of redesigning the fixture to improve rigidity and manufacturability, optimized for aluminum.
The version I designed significantly simplified the fixture while still fulfilling requirements. Certain geometries were chose to ensure that the parts could be held and machined properly.
To keep cost and manufacturing time low, I chose to have the cross arms laser cut.
Unfortunately, due to requirements of the laser cutting service, I had to thicken the arms. The kerf of the laser on parts greater than 1/4" thick becomes very apparent.
This left the parts fairly out of spec and required looking into alternative methods for reliable repeatatbility.
Although more time consuming, I manually machine the cross bars. With some fixturing, this could easily be reproduced in the CNC.
The most defelection was occuring within the cross bars. We decided to test the structure with the other pieces 3d printed.