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Multi-disciplinary Simulation of the Deployment and Operation of a Roll-up Solar Array

B. Ross, MotionPort

The simulation of a mechanical system often requires the combination of multiple simulation technologies in order to capture the critical interactions that occur during operation. While the combination of FEA and CFD is a familiar multi-physics configuration, the detailed simulation of a mechanical assembly in motion can require a different combination. For example, consider the dynamics of the deployment and operation of space structures, such as solar arrays, solar shades, and antennas. Rigid body motion, nonlinear flexible bodies, and a controller function need to be considered simultaneously in order to simulate the behavior properly. The approach described in this presentation is to use multibody dynamics software that can efficiently handle large motions in a mechanical assembly, model nonlinear flexible bodies and also model a controller. 

The sample model is a solar array. Future missions to the outer planets require significant power that may be provided by large, 300 kW class, flexible, roll-up solar arrays. To support the development of these arrays there is high value in simulating the nonlinear dynamics of stowing, deploying, and mechanical performance of large deployable solar array structures, especially with the profound limitations of physical testing. Physical testing of prototypes on earth with gravity can be difficult or impossible. This presentation includes a dynamic simulation of the deployment of a roll-up solar array and demonstrates that the deployment torque can be predicted accurately. 

The development of a set of software utilities that automate certain tedious tasks associated with developing models of these structures is described. The utilities automate the creation of joints, connecting elements, and applied loads, and also automate the running of a series of simulations to determine the proper contact stiffness between the tubes and the mandrel that rolls-up the tubes during stowage. The utilities will aid in the development of future simulation of structures using roll-up boom technology. The user does not need to be as expert in multibody dynamics because of these utilities. 

After the solar arrays are deployed, the associated spacecraft may need to undergo potentially significant maneuvers (or dynamic loading events). Consequently there is a need to understand and possibly control the nonlinear dynamics in the spacecraft system during such maneuvers. The development of a nonlinear controller is described as well as its utility in reducing forces and motion in a solar array wing during a loading event. The result is dramatic reductions in system forces and motion during a ten-second loading event. A motion curve derived from the simulation with the closed loop controller is then used to obtain similar benefits with a simpler motion control approach. The controller causes the structure to act as if it were stiffer. Further simulation could efficiently and accurately assess not only the effectiveness of the controller but also the control structure interaction between the large flexible solar array wing structures, the local controllers, and the spacecraft attitude control system.

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