Energy vs. accuracy vs. number of actuators trade-off studies for the shape control of space truss structures

Many proposed spacecraft have very strict accuracy requirements that demand active shape control. To meet the specifications, a large number of actuators will be needed. The spacecraft power needed to perform this continuous adjustment may be very costly. In an effort to reduce the power requirement, this paper investigates the relation between the residual shape error and the consumed energy. A generic type of actuator was selected and numerical studies were performed on a large number of mission scenarios. The results reveal the nonlinear nature of the interaction and suggest that a large energy saving may be achieved without substantial sacrifice in the accuracy. Similar trade-offs were also conducted between the number of actuators, the achieved correction, and the consumed energy. This showed a significant spike in the needed energy when the number of actuators approaches the number of controlled freedoms. Hence, an increase in the number of actuators may actually yield a savings in energy and hence total weight.