For the European Space Agency (ESA), MicroMegaDynamics and ULB were developing an active control vibration isolator based on the so called Stewart Platform: a specific 6 degrees of freedom positioning device.
This vibration isolator is intended to be installed between the structural truss of a satellite and high precision measuring systems, typically laser metrology or telescopes, typically used for inter-satellite optical/laser communication or to observe stellar objects in the deep/early universe.
The noise sources onboard a satellite typically come from reaction positioning wheels, stepping motors, cryocoolers, thermal ‘crinkling’, optics motion, micro-thrusters, Field-Emission Electric Propulsion propellers.
I knew the CEO of MicroMegaDynamics, Nicolas Loix, and after some discussions together, I accepted to lead the team trying to get rid of those problems, bringing my knowledge and competences learnt at LMS.
The problem were solved by:
- building a few experimental test benches to measure with laser beams the real dynamic behavior of each element of the assembly and of the whole assembly,
- Building an accurate Finite element model (SAMCEF) of each element and of the entire assembly
- Updating the FEM so that the theoretical behavior perfectly matches the reality
- Accurately understanding the parasitic behaviors: the lateral stiffness of the membrane of the actuators needed to be improved with a decrease of the axial stiffness, and very important, the joints between the actuators and the platform needed to be stronger and with the least stiffness.
- by use of the FEM and a matlab program, optimize those critical elements with design for experiment with a fully parametrized calculation chain.
- proposed a new design for the membrane and for the joints, with a specific super elastic material, the NiTiNol, developed by NASA as as Shape Memory Alloy:
- Construction of the new membrane and of the new joint,
- Tested and validated the parasitic behavior disappeared.
- Technical lead of a 4 people team to resolve the issue, team work coordination within the department and with the client
- Experimental analysis, FE modelling and FEM updating,
- Calculation chain and design optimisation
- Follow-up of suppliers, construction and validation of the modified prototype