Robust control of a novel active pneumatic vibration isolator through floor vibration observer

Abstract

Active vibration control techniques have been widely applied to enhance passive vibration isolators. The active strategy can improve the common disadvantages of the passive pneumatic isolator, such as resonant character and poor isolation performance at low frequency. In the study, a novel active pneumatic vibration isolator is designed. The isolator uses a passive isolator to support the weight of the payload and a pneumatic actuator to suppress the vibration disturbance through active control strategy. This investigation proposes a robust H 1 controller in order to have good disturbance rejection ability and robustness. According to the linearized nominal plant and appropriate weighting functions, the robust controller can be obtained and implemented by measuring vibration of payload and disturbance. However, it costs higher in practical implementation because two precision accelerometers must be used to measure the vibration at the same time. Therefore, the proportional integral observer (PI observer) is designed to estimate the disturbance and achieve trade-off between cost and performance. Because the PI observer can also estimate the state variables of the active isolation system, the linear quadratic control is also adopted to compare the isolation results with robust control strategies. The simulations and the experimental results show that the proposed robust control scheme improves the disadvantages of the passive pneumatic isolator. Furthermore, the PI observer can estimate the disturbance precisely, and almost the same isolation performance is met comparing to direct disturbance measurement.

RETRACTED: Neural network-based fuzzy logic parallel distributed compensation controller for structural system

“…A novel active pneumatic vibration isolator was designed by Chen and Shih (2011). Their design uses a passive isolator to carry the weight of the payload and a pneumatic actuator to suppress the vibration disturbance through an active control strategy.…”

Performance benchmarking of an ultra-low vibration laboratory to host a commercial millikelvin scanning tunnelling microscope

“…In general, different damping stages are usually combined to achieve the possible lowest vibration levels. These include one or more layers of massive inertia block(s), supported by pneumatic isolators and/or active dampers [12][13][14][15][16][17][18].…”

“…This can be effective at low frequencies but can be found to transmit noise at higher frequencies. Active pneumatic isolators [18] have a soft spring combined with active vibration control, allowing for the isolation of large load weights over a wide frequency range. The active isolators used (Air-springs BiAir4-OC-1, and horizontal elements HAB-95000 by Bilz, Germany) have been customized to a low resonance frequency of 1.2 Hz in vertical direction, and 0.7 Hz in both horizontal directions.…”

A semi-active vehicle suspension based on pneumatic springs and magnetorheological dampers

“…It is well known that pneumatic systems have advantages over other options, the most prominent being the limited influence of sprung mass on natural frequency and the fact that the modification of its stiffness is quite straightforward. These advantages have boosted the study of possible applications, for example: a robust active control of a pneumatic vibration isolator for payloads under disturbances from the floor (Chen and Shih, 2007, 2011); a system for neonatal transport carts (Bailey-Van Kuren and Shukla, 2005); or an active control system for seat suspensions focusing on the simultaneous optimization of conflicting body acceleration and suspension travel (Maciejewski et al., 2010, 2011; Maciejewski, 2012). Other studies which also modify both stiffness and damping with the goal of improving ride comfort and handling have been carried out by Els et al.…”