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This research began in 1998, at the Active Structures Laboratory (ASL) at the Free University
of Brussels (ULB), our academic partner, to find a solution for the six-degree-of-freedom
vibration isolation and suppression. Both ground and space applications have been considered
throughout this research. Figure 1 shows the active isolator developed at ULB.
In this project, Micromega was in charge of designing and providing the current amplifiers
for the actuators.
The objective of this project was to develop a generic multi-purpose 6 d.o.f. isolator with
standardized architecture and voice coil actuators. This six-axis active hexapod is based on
a Stewart platform configuration, where the 6 legs are located at the edge of an imaginary
cube. This configuration provides uniformity in mechanical and control capabilities.
Figure 1 : Soft isolator based on a Stewart platform (ULB)
Such isolation interface can be used in 2 configurations:
- The payload isolation configuration: a sensitive payload should be isolated from its
vibrating environment.
- The disturbance source isolator: a disturbance source is placed in the active isolator,
to prevent the vibration propagation to the surrounding environment
These 2 configurations are illustrated in Figure 2 : sensitive optics is placed on active
isolation interfaces to be isolated from the bus vibrations, while the attitude control
system and other vibration sources are also placed on active isolation interfaces to prevent
propagation to the bus.
Figure 2: Active isolation for space applications
The successful progress of this project led to a parabolic flight testing campaign, onboard a
A300 ZERO-G aircraft. Figure 3 shows the test setup that was flown in Bordeaux (France) in
September 1999, in the frame of the PRODEX program of ESA.
Figure 3 : testing of the active isolatior in parabolic flight
(left panel is a close up of the test setup during ground preparation)
More information about research in vibration isolation carried out at ULB.
Current and future developments
In partnership with ULB, Micromega is involved in a GSTP project of ESA: "Low-Stiffness
Stewart Platform". In this project, the following improvements are under development:
- Improvement of the existing active leg (reduce weight, new flexure design,
reduce the leg local dynamics)
- Perform space-qualification testing for launch-vibration and thermal behaviour
- Develop dedicated control electronics
- Enhance the isolation range of the active interface to the sub-micron regime
- Add a steering function
- Develop an adequate launch-locking mechanism
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