Active vibration isolation of microgravity experiments with umbilicals using magnetic actuators

Science experiments performed in space to take advantage of microgravity have often yielded poor results due to the presence of multifrequency disturbances produced by astronaut movement, on-board machinery, thruster firings and other factors. This acceleration environment has been found to be of the order of 10-³ g0, while experiment specifications have been 10-⁵-10-⁶ g0, indicating the need for vibration attenuation of about 40 dB or more.
A one-dimensional linear noncontacting magnetic actuator satisfying the motion requirements of this application in a single stage has been designed and built. This innovative Lorentz Actuator has a 2 in stroke with a saturated-core design. Its linear performance-force remaining constant with stroke, and force varying linearly with current-simplifies the design of the control system for active vibration isolation. Magnetic saturation of the core permits a low leakage design, even with a relatively small shell-to-core gap for compactness. Such an actuator, with its combination of long stroke, linearity and compactness., is potentially enabling technology for vibration isolation in the space environment, where size and weight are of much greater concern than for earthbound experiments. A comparison of test results with predictions based on finite element analysis indicated very good agreement.