Real-time Simulation of Complex Space Systems

This paper presents a framework for the modeling and simulation of the dynamics of complex deformable space systems. It is based on a suite of free software, mostly developed and distributed by the ‘Dipartimento di Ingegneria Aerospaziale’ of Politecnico di Milano (DIA-PM), that allows the real-time simulation of arbitrarily complex mechanical, mechatronic and aeroservoelastic systems. Real-time simulation is key to efficient, safe and cost-effective development of critical systems, whose testing is either virtually impossible, unsafe, or very expensive. The capability to test the functionality and the performance of critical components, like control systems, without using the real hardware allows Hardware-In-the-Loop (HIL) virtual experimenting. The modeling of the physics of the problem is delegated to the free general-purpose multibody dynamics software MBDyn ([1], http://www.mbdyn.org/). It integrates the equations of motion of constrained mechanical systems as Differential-Algebraic Equations (DAE), using implicit schemes. The free Real-Time Application Interface (RTAI, http://www.rtai.org/) takes care of scheduling the hard real-time execution of all involved tasks: the multibody simulation of the problem, process control, and monitoring. Control design is delegated to graphical modeling environments: Scilab/Scicos, Matlab/Simulink or MatrixX. Only the first is free software. Applications of the proposed framework to the dynamic analysis of typical space systems are presented: openand closed-loop controlled rigid and flexible manipulators, parallel robots, and deployment of large deformable structures [2, 3, 4].