Active control of precise vibration isolation table using two degrees of freedom controller

目前感兴趣的精密仪器如电子显微镜和微型机械必须安装在通常包括空气弹簧的精密隔振台上。工作台必须具有吸振和快速准确定位的功能。吸附用软弹簧，定位用硬弹簧。传统的被动隔振系统不能科普这一相互矛盾的要求，必须对被动隔振系统进行主动控制，将振动吸收看作是对干扰的抑制，而将定位看作是对期望输入的跟踪，采用二自由度控制的概念可以有效地协调这两种要求。此外，由于工作台是一个多自由度的运动机构，在控制中会出现各个自由度之间的耦合问题。将耦合力视为一种干扰，利用干扰抑制功能可以实现解耦。本研究探讨二自由度控制器对于气动隔振平台的可行性，并提出一种设计方法。通过与PI控制器的控制性能比较，验证了该控制器对气动隔振台二自由度控制的有效性。

Precise instruments such as an electron microscope and a micro machine currently interested have to be installed on a precision vibration isolation table generally comprising air springs. The table must provide with functions of both the vibration absorption and the fast and accurate positioning. The absorption requires the soft spring, the positioning does the hard one. To cope with such a mutually contradictory requirements, a conventional passive isolation system is not sufficient, which should be actively controlled.Considering the vibration absorption as a disturbance suppression and the positioning as a tracking to desired inputs, the concept of a two degrees of freedom control may be effective to reconcile both requirements. Further, as the table is a motion mechanism with multi-degrees of freedom, some problems of coupling among each degree of freedom appear in the control. Regarding coupling forces as a kind of disturbance, the decoupling owing to the disturbance suppression function may be expected. This study investigates the availability of two degrees of freedom controller to a pneumatic vibration isolation table, also of which a design approach is proposed. Comparing its control performance with that obtained from PI controller, the effectiveness of the two degrees of freedom control to the pneumatic vibration isolation table is assured.