A key element of our virtual satellite is the real-time simulation of the kinematic and dynamic behavior of the satellite components when manipulated by the user. We assume that the servicing robot has already docked to the target satellite, so that the complex flight dynamics of the flying body dynamics can be neglected. We only concentrate on the simulation of rigid bodies that make up most of the virtual satellite and robot components. Apart from the multi-body dynamics of the rigid components of the satellite, a further aspect is the simulation of the realistic behavior of a foil for the scenario in which the multi-layer insulation (MLI) has to be removed from a satellite. This involves modeling and simulating the dynamics of bending, cutting or tearing the deformable MLI material.
Fig.: Physics scene as seen by the user.
Fig.: Rigid bodies as seen by the physics engine.
Fig.: Collision shapes of the rigid bodies.
The simulation of multi body physics is currently implemented using the open-source physics engine Bullet. It offers real-time rigid body dynamics including various constraint solvers and generic constraints with support for constraint limits and motors, as well as support for soft body dynamics for simulating deformable objects. However, the collision and force computation for haptic interaction is done by our software module described in the section Collision Detection and Response: Haptic Rendering.
The modular design of the system architecture of VR-OOS allows for the evaluation of alternative implementations of the physics simulation with little integration effort. In the near future, we plan to investigate the suitability of other real-time physics engines, such as NVIDIA PhysX and Newton, as well as interfaces to commercial simulation systems often found in the engineering area, such as Simulink and Modelica.