| Tensegrity is a structural concept in which a set of compressive components (rods) interacts with a network of tensile components (cables), defining a stable volume in space. For years this idea was applied to static structures in fields such as architecture and art. Recently, however, there has been a movement toward using tensegrity for robotic applications. By modifying the tensions in the cables within a structure, movement can be achieved. If actuation is performed in a coordinated manner, useful motions and changes to the overall shape of a structure are possible. The primary issue in the control of such structures is the need to maintain positive tensions in the cables. If cables become slack, the desired control inputs cannot be delivered to the system, causing a degradation in performance, or worse, instability. Tensegrity systems may be used for such applications as deployable or collapsible structures, locomotor devices, and even robotic manipulators.; This thesis addresses the use of planar tensegrity structures for robotic applications. A systematic classification and naming scheme is established which enables determination of the configuration of a particular tensegrity structure simply given its assigned name. A procedure for performing the dynamic analysis of two separate classes of planar structures is then developed. Next a null-space controller based on feedback linearization is presented, which governs system motion while maintaining positive tensions. Simulations verify the effectiveness of such a controller. Additionally, methods for generating the dynamic workspace for such devices is developed, which specifies configurations that are achievable while obeying imposed tension constraints. Finally, experimental results are presented for an actual physical device that incorporates the theories developed throughout the thesis. |
