High-resolution positioning systems in miniaturised design. By Steffen Arnold
Today, piezo ceramic drive concepts provide a suitable solution for practically every task in the field of precision positioning. The common factors in all of the concepts are the compact dimensions and the high positioning accuracy, which is substantiated by the functional principle. Piezo actuators convert electrical energy directly into mechanical energy and make motion in the sub-nanometre range possible even with short response times and high acceleration.
However, the displacement caused by the piezo effect is only a fraction of 1% of the actual component size. Achieving larger travel ranges can therefore be complex and expensive. PI (Physik Instrumente) has responded accordingly by introducing its Q-Motion range of positioning systems. The range is based on piezoelectric inertia drives and stands for high resolution in the nanometre range with theoretically unlimited travel ranges, miniaturised design and attractive price.
Piezo-based inertia drives utilise the stick-slip effect: the actuator expands slowly and moves a runner. Due to its inertia, the runner is unable to follow the fast contraction of the actuator and remains at its position. At rest, the piezo-based inertia drives are self-locking and therefore do not consume any power.
Precise positioning of up to six axes
The functional principle allows easy configuration of the actuators and the control. The piezo-based drive is deployed as a module. This makes it possible to realise long travel ranges or rotary motion and individual axes can be easily combined with each other. At the same time, it is also possible to realise very compact designs.
The smallest linear positioning stage currently available is only 22mm wide and 10mm high. It is suitable for travel ranges of 6.5, 13 or 26mm and achieves velocities of up to 10mm/s. At the same time, it develops a feed and holding force of 1N. When equipped with an incremental encoder, it achieves a resolution of up to 1nm. There are a large number of typical areas of application for the small precision stage, especially since it is also available as a vacuum version and if required, can be combined with further linear axes or rotary stages and this is possible without additional adapters.
Small yet extremely powerful
The miniature rotation stages have a diameter of only 14mm, achieve resolutions in a range of 1 µrad; the holding force of the linear positioning stage is up to 8N in a de-energised state and the maximum velocity is 10mm/s, rotationally up to 70°/s. For those applications where samples, detectors, optical components or tools need to be moved and rotated in space, there are six-axis, parallel kinematic positioning systems. These SpaceFABs are so small that they can be easily placed on the palm of the hand. The design is based on combined linear positioning stages and can be quickly and easily adapted to application requirements, for example, even for use in a high or an ultra-high vacuum.
The stages are being used in numerous applications in both industry and research. The small form factor and the vacuum compatibility make Q-Motion stages ideal positioning tasks in beamline instrumentation or electron microscopy. The small form factor combined with the self-locking means that the stages can be integrated in mobile devices for metrology or medical applications.
For more information at www.scientistlive.com/eurola
Steffen Arnold is with PI (Physik Instrumente).
