Adaptive Control for a Microgravity Vibration Isolation System
Microgravity Science Glovebox (MSG) Method
Most active vibration isolation systems that try to a provide quiescent
acceleration environment for space-science experiments have utilized
linear design methods. In this research, we address adaptive control
augmentation of an existing classical controller that combines a high-gain
acceleration inner-loop feedback together with a low-gain position
outer-loop feedback to regulate the platform about its center position.
The control design considers both parametric and dynamic uncertainties
because the isolation system must accommodate a variety of payloads having
different inertial and dynamic characteristics. An important aspect of
the design is the accelerometer bias. Two neural networks are
incorporated to adaptively compensate for the uncertainties within the
acceleration and the position loop. A novel feature in the design is that
high-band pass and low pass filters are applied to the error signal used
to adapt the weights in the neural network and the adaptive signals, so
that the adaptive processes operate over targeted ranges of frequency.
This prevents the inner and outer loop adaptive processes from interfering
with each other. Simulations show that adaptive augmentation improves the
performance of the existing acceleration controller and at the same time
reduces the maximal position deviation and thus also improves the position
controller.
Control objective
The g-LIMIT is required to transmit low-frequency accelerations to move
with the space vehicle while rejecting high-frequency disturbances for
quiescent experimental environment.
Existing Controllers
To achieve the above objective, the existing control system consists of a
high-gain acceleration controller in an inner-loop and a low-gain position
controller to center the platform in an outer-loop.
Collaborators
The research was supported by NASA Marshall Space Flight Center, and Dr.
Young Kim and Dr. Mark S. Whorton at NASA MSFC collaborated with us.
Related links:
- Dynamic concepts, Inc.-g-LIMIT project
- Space station glove box for science experiments
- Microgravity Vibration Isolation Subsystem(MVIS)