STUT-ME 1 Vibration Control for Precision Machinery 王永鵬 南台科技大學 機械工程系

STUT-ME 2 Outline Introduction Passive Vibration Isolation System Active Vibration Isolation System Conclusions

STUT-ME 3 Introduction Vibration Sources of Precision Equipment: Environmental Vibrations On-board Disturbances Objective of Vibration Control for Precision Equipment: Isolate sensitive equipment from a vibrating environment, e.g. floor-induced vibration. Isolate vibration equipment from on-board disturbances, e.g. payload-induced vibration.

STUT-ME 4 Introduction Vibration Control Techniques: Passive Isolation System Rubber Pad Air Spring Spring Active Isolation System Soft-Mounted System Hard-Mounted System

STUT-ME 5 Passive Vibration Isolation System

STUT-ME 6 Passive Vibration Isolation System  =0.01  =0.50  =0.10  =1.00 Frequency (  /  n ) Transmissibility ( x/u, dB) Transmissibility of Passive Isolation System

STUT-ME 7 Passive Vibration Isolation System A second-order mechanical filter Eliminate vibration from the crossover frequency onward Drawbacks: Sensitive to payload forces Vibration amplification around the natural frequency

STUT-ME 8 Passive Vibration Isolation System Passive Isolation System Rubber Pad Air Spring Spring

STUT-ME 9 Active Vibration Isolation System Motion sensor Displacement, Velocity, Acceleration, Force Actuator Electromagnetic type, Piezoelectric type, Magnetostrictive type Control Feedforward, Feedback PID, Lead/Lag Compensator, LQG, Adaptive

STUT-ME 10 Active Vibration Isolation System Active Isolation System Soft-Mounted System (SMS) Hard-Mounted System (HMS)

STUT-ME 11 Active Vibration Isolation System Soft-Mounted System Hard-Mounted System

STUT-ME 12 Soft-Mounted System Soft-Mounted System (SMS) The system ’ s overall performance predominantly from the passive element. The active feedback system uses contactless electrodynamic force to overcome the weakness of the passive isolators. The system remains inherently soft. SMS are insensitive to resonance in the main structure below the isolators. SMS are sensitive to resonance in the payload. (require adaptive control to ensure optimal performance)

STUT-ME 13 Hard-mounted System Hard-Mounted System (HMS) HMS relies mainly on the control system for isolation. HMS have a much higher closed-loop bandwidth than SMS by using a piezoactuator. SMS needs for higher frequency isolation with a passive spring that is tuned to Hz. Hence, HMS is extremely stiff and allows for large payload forces without excessive motion. The major drawback of a HMS is that vibration isolation performance suffers from the passive- active compromise and never is able to come up to the performance of SMS.

STUT-ME 14 Modified Hard-Mounted Isolation System In order to improve the performance of hard- mounted isolation system, a voice-coil motor (VCM) is placed between the payload mass and intermediate mass. The VCM is used to eliminate the effects of onboard disturbances on the payload mass. The piezoactuator is used to isolate the floor vibration from the payload mass.

STUT-ME 15 Modified Hard-Mounted Isolation System VCM PZT

STUT-ME 16 Modified Hard-Mounted Isolation System Equations of Motion: Control Laws:

STUT-ME 17 Modified Hard-Mounted Isolation System Closed-Loop System: where

STUT-ME 18 Modified Hard-Mounted Isolation System Block Diagram of Modified Hard- Mounted Isolation System

STUT-ME 19 Modified Hard-Mounted Isolation System Case (a): Without feedback Case (b): Single-loop hard-mounted isolation system Case (c): Double-loop hard-mounted isolation system Case (d): Modified hard-mounted isolation system with absolute displacement feedback Case (e): Modified hard-mounted isolation system with relative displacement feedback

STUT-ME 20 Modified Hard-Mounted Isolation System Vibration Transmissibility

STUT-ME 21 Modified Hard-Mounted Isolation System System Compliance

STUT-ME 22 Modified Hard-Mounted Isolation System When the absolute displacement of the payload mass is used as the feedback signal to the VCM, the system is capable of eliminating the effects of onboard disturbances for the whole frequency range and the transmissibility can also be improved in the lower frequency range. When the relative displacement between the payload mass and intermediate mass is used as the feedback signal to the VCM, the system is capable of eliminating the effects of onboard disturbances for the range of higher frequencies but the transmissibility is indistinguishable from that of hard- mounted isolation system.