Variable shape three-dimensional structure using extendable arm

A variable shape three-dimensional structure, comprising:

• an upper frame;
• a lower frame;
• and
• a longitudinal coupling member that couples said upper and lower frames such that said upper and lower frames are separated from and parallel to each other, wherein
• said upper frame includes
• a plurality of cross units each formed by two rigid members crossing each other in an X-shape and pivotally coupled by a middle coupling shaft, and
• an end coupling portion that pivotally couples ends of said rigid members of adjoining ones of said cross units,
• said end coupling portion of said upper frame includes inner end coupling shafts located on an inner side of said upper frame, and outer end coupling shafts located on an outer side of said upper frame,
• said lower frame includes
• a plurality of cross units each formed by two rigid members crossing each other in an X-shape and pivotally coupled by a middle coupling shaft, and
• an end coupling portion that pivotally couples ends of said rigid members of adjoining ones of said cross units,
• said end coupling portion of said lower frame includes inner end coupling shafts located on an inner side of said lower frame, and outer end coupling shafts located on an outer side of said lower frame,
• said longitudinal coupling member includes a bent unit, said bent unit including a first bent rigid member, a second bent rigid member, and a bent portion coupling shaft, said first and second bent rigid members being bent in a V-shape so that said V-shapes of said first and second bent rigid members open in opposite directions, said bent portion coupling shaft pivotally coupling a bent portion of said first bent rigid member and a bent portion of said second bent rigid member,
• an upper end of said bent unit is coupled to said upper frame located at an upper position, and
• a lower end of said bent unit is coupled to said lower frame located at a lower position.