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Chapter 8 Conclusions,

Chapter 8 Conclusions, Status and Open Work A voice coil actuator driven shutter based on a flexible hinge structure was concluded in the study [5] for the design of the MERTIS short term shutter. Within this master thesis, it could be showed, that the implementation of this selection is capable to fulfill all requirements. The electromagnetic and mechanical parts were designed with help of analytic and FEM calculations in view of harmonizing all parameters and resulted in the construction of the MSTS DM. To reach this goal, investigations in the fundamen- tals of material properties, flexible hinges and electromagnetics had to be performed. The parameters were adjusted to minimize the power consumption, the dimensions and the mass of the MSTS DM. However, this couldn’t be performed staightforward due to reciprocal relations, what rather caused a parameter optimization. The mechanical structure with the flexible hinges was deviated from a the linear stage with necked down flexures presented in [4]. But for the voice coil actuator, an uncon- ventional design based on two anti-coupled coil was proposed, realized and labeled as Helmholtz VCA. This VCA design shows an improvement of the generated Lorentz force of around 80 % compared to an equivalent single coil VCA. Theoretic considerations of this electromagnetic design let assume a lot of advantages, which could be proved with adequate measurements. The low damping ratio of the MSTS DM is a result of the force reducing sanctions for fulfilling the power and open/close time requirements. Therefore, a control electronics was designed to achieve the required blade switching mode. A laser triangulator was applied as feedback sensor, whereby satisfying results of the closed loop system could be optained. 58

8 – CONCLUSIONS, STATUS AND OPEN WORK As a result from the MERTIS shutter study, life time and fail safe are quoted as most important requirements, which can be met with the designed and constructed MSTS DM. Up to the day of submission of this thesis, the constructed MSTS DM performed almost 50 million cycles without identifiable damage. However, this must be investigated in regard to occuring microcracks in the thin FH blades. Detailed material and lifetime tests must be noted as open work, as well as the definition of a space qualified sensor and control electronics. Albeit the MSTS DM must be sligthly adpated for the ultimate integration in the MERTIS instrument due to continual structur and optics changements, a solid base was achieved with the presented construction, whereon the following engineering and flight models can be built. It is still a long way to go until the scheduled launch of BepiColombo in 2013. So, let’s use the time for upgradings and—as free side effect—to learn from every performed step. 59

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