An automated methodology for dynamic force analysis of adaptive spatial trusses

Abstract

The purpose of this thesis is to develop a formal methodology for determining the loads occurring in the members of an adaptive truss due to both gravity and acceleration. This force analysis can be used as the basis for a design code which will provide truss member dimensions and actuator characteristics. Three different truss structures are considered. The first is a planar, triangular truss consisting of one actuated member and two fixed length members. The second structure is a spatial, double-octahedral truss with three active members and eighteen fixed length members. The third structure is a truss consisting of several double-octahedral bays connected together as a chain. For each structure, the active link motion is first simulated and the position, velocity, and acceleration history of each of the member connecting points is calculated. The dynamic equations of motion for each member are developed and combined to form a system of equations describing the motion of the entire truss. These equations are then solved to find the forces occurring at each node. Once the forces are determined, the internal forces in each member can be found, and the resulting stresses are calculated. The members are also checked for buckling using Euler buckling theory. The stress calculations are checked against experimental values and show good agreement for both static only and static and dynamic loading.