Concurrent Dynamics delivers high fidelity Multibody Dynamics Simulation programs to assess dynamics and control performances of mechanisms and mobile vehicles. They expedite:
pictures are by courtesy of NASA
Equations of motion of each simulation are generated by Lagrangian formulation. They are solved by a recursive order(N) algorithm during runtime. The member bodies of the system can be rigid or flexible. The equation solver speed is order(N,sum(ni3)), where N=number of bodies, and ni=number of flexible modes for the i-th body. The simulations allow simple constraints to lock joints or to prescribe joint motion if required.
Point-to-point constraints can be defined to permit closed mechanical loops in the system. Gear constraints can be defined to permit coordinated deployment of multi-linked solar panels. Contact constraints prevent points on the mechanical system from penetrating controlled surfaces. These constraints can be turned on an off by simple commands during run time.
Our simulations run on PC's with Window XP and Window 7/8 OS equipped with Matlab/Simulink. A typical mdl file (a Simulink program) that we build is shown below. This example simulates a satellite with 2 deployable solar arrays, 3 wheels and 6 jets. (See the first picture above) The multibody equations of motion specification, mass property, geometry and all desired input/output parameters are defined by a model file. User defines it through our model editor. The xsv01.dll block (an S-function) in the mdl file reads it and executes all dynamics computations during runtime based on it. Xsv01.dll also samples user picked parameters for post simulation viewing. It is closed-loop connected to the user supplied control system to complete the mdl file.
We build streamlined mdl files by encapsulating all dynamics computations and i/o processes in one functional block, namely xsv01.dll. This dynamics engine has an easy to work with i/o interface to connect it with the user supplied control system. In short, these are our design rules:
Fig.1 A satellite simulation, bus+2arrays, LVLH attitude control with 3 rwa's, and 6 jets
Figure 2 is another mdl file simulating a satellite with a bus and 4 cmg's to maintain LVLH attitude. The control input are the 4 cmg's angles and rates, the bus angular rate and the LVLH attitude error, rpy. The control output are torque to the 4 cmg's with the jets turned off.
User defined ACS are not limited to LVLH attitude control. Sun-nadir attitude can be implemented just as easily but needs other signals from xsv01.dll than those shown in Figs. 1 and 2, i.e. bus attitude quaternion, nadir vector in the bus frame, sun vector in the LVLH and in the bus frame. We also design simulations to execute attitude slew, spin axis precession, proximity and rendezvous operations, payload pointing, separation and contact analyses. Regardless of the complexity of your assignments, our expertise and tools are ready to realize your dynamics simulations.
Fig.2 A satellite simulation, bus+4 cmg's for LVLH attitude control
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