Dynamics and Control of Aerospace Systems

Tensegrity structures consist of strings (in tension) and bars (in compression). Strings are strong, light, and foldable, so tensegrity structures have the potential to be light but strong and deployable. Pulleys, NiTi wire, or other actuators to selectively tighten some strings on a tensegrity structure can be used to control its shape. This chapter describes some principles we have found to be true in a detailed study of mathematical models of several tensegrity structures. We describe properties of these structures which appear to have a good chance of holding quite generally. We describe how pretensing all strings of a tensegrity makes its shape robust to various loading forces. Another property (proven analytically) asserts that the shape of a tensegrity structure can be changed substantially with little change in the potential energy of the structure. Thus, shape control should be inexpensive. This is in contrast to control of classical structures which require substantial energy to change their shapes. A different aspect of the chapter is the presentation of several tensegrities that are light but extremely strong. The concept of self-similar structures is used to find minimal mass subject to a specified buckling constraint. The stiffness and strength of these structures are determined. 17.