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1975 |
| Title |
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High Precision Modular Long Range Travel Vertical Axis |
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Equipment, Machines & Instruments: Design & Testing |
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| Content |
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High precision positioning and measuring machines have to face the demand for large moving volumes and accuracy in the nanometer range. In three dimensional high precision systems a setup of fixed interferometers and a moving stage mirror are often used [1]. Many applications need a vertical movement with a high positioning resolution of object and mirror. Because of both masses this objective is challenging. Therefore high precision guides and drives are needed to fulfill the requirements. Unfortunately high precision drives like voice coils are not self locking. Thus they need to actively hold the masses and induce unwanted heat into because of power loss. Self locking spindle drives don’t have the needed resolution and high precision piezo elements have a limited moving range. Also guides have great influence to the properties of the vertical axis. Known ball guides are stiff but they are a source of stick-slip effects. Aerostatic guides are free of stick-slip but can cause vibrations. Spring guides seems to be favorable but their moving range is limited. For these reasons a systematic analysis of different combinations of drives and guides is necessary.
The paper presents systematic design, virtual prototyping and realization of a modular long range travel vertical axis with high precision. This axis is connected to the development of a positioning and measuring machine with a moving range of 200 x 200 x 15 (25) mm³ [2]. The machine design uses parallel kinematic. That means the vertical axis is planar guided on a base and the guides of the horizontal axes used only to reduce to degrees of freedom.
The vertical axis was designed modularly under use of design principles. Three drives and guides are arranged symmetrically to the center of gravity of a frame which holds the mirror. All guides stay in contact to the base through planar guides and realize a very short and direct force flow. Through the modular design an exchange of guides and drives is possible to test different combinations. The first combination consists of ball guides and a serial alignment of spindle and piezo drives. This design realizes a moving range of 25 mm with a positioning resolution of 1 nm. First measurements show a good behavior of the guides as well as the drives. For the analysis of the dynamic behavior of the axis a multi body system model using Alaska 5.0 was developed [3]. Designs of further combinations consisting of voice coils, aerostatic guides, weight compensation mechanisms and spring guides will be shown. The aim of the research is to find an optimal combination of elements.
1. G. Jäger et al., “Operation and Analysis of a Nanopositioning and Nanomeasuring Machine“, Proceedings of 17th ASPE Annual Meeting
2. R. Theska et al., “Design Principles for Highest Precision Applications”, Proceedings of 19th ASPE Annual Meeting
3. A. Tröbs et al., “Untersuchung der Dynamik einer hochgenauen x-y-Verfahreinheit für eine Nanopositionier- und Nanomessmaschine anhand eines Konstruktionsentwurfes”, Proceedings 50. IWK TU Ilmenau |
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