Position Regulation and Force Transmission in Active Isolation under Axial Thrust and Synchronous Disturbances

Junjie Shen; Minglei Zhu; Yuxiang He

doi:10.6919/ICJE.202609_12(9).0028

Authors

Junjie Shen School of Mechanical Engineering, University of Shanghai for Science and Technology, Shanghai, China
Minglei Zhu School of Mechanical Engineering, University of Shanghai for Science and Technology, Shanghai, China
Yuxiang He

DOI:

https://doi.org/10.6919/ICJE.202609_12(9).0028

Keywords:

Active Vibration Isolation; Axial Thrust; Displacement Regulation; Order Tracking; Simulink; Transmitted Force.

Abstract

The two requirements for an active isolator which is subjected to a mean axial thrust are: to keep the supported mass close to its reference position and to limit the dynamic force applied to the foundation. These requirements are discussed in the context of a 1-DOF Simulink model with a passive spring and damper, a force limit and 1st order actuator dynamics. Under a thrust ramp, periodic loading, speed run-up and temporary overload, passive isolation, PID, LQR and LQI are compared. PID and LQI are able to reduce the displacement to zero (within numerical precision), however in the foundation 20 N are still present. LQR leaves a displacement of about 150 μm. In the run-up interval of 2–20 s, RMS of acceleration is decreased by 9.82 dB using PID, by 14.04 dB using LQR and by 13.89 dB using LQI when compared to the passive one. The frequency-response calculation shows a different comparison: PID provides the largest attenuation near the uncontrolled resonance, but the 25 Hz displacement response is approximately 2.44 times the passive response. Passive-parameter sweeps, order tracking and numerical checks define the circumstances leading to these results. These calculations demonstrate the reasons for considering static load support, position error and dynamic transmission separately. No physical test data are used – all results are numerical.

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