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Position Measurement

Take a Closed Loop to Find Your Way Back

The Nanomotor has a positioning stroke of up to some centimeters while operating with atomic resolution. The Nanomotor thus bridges eight orders of magnitude. On this scale absolute positioning is impossible. The piezo ceramic exhibits hysteresis, creep and temperature drift, limiting its absolute reproducibility to about 10%. The Nanomotor has a repeatability for each direction of about 1%.

"Direction" means: the Nanomotor is an asymmetric device, the mounting is only on one side. So the mean step size of coarse steps upwards and downwards is different. But in one direction without changing load or forces the step size of coarse steps varies only about 1%. Although the driving piezo has a hysteresis of about 10%, we can obtain 1% repeatability by the precision of the internal mechanics of the Nanomotor and by decoupling the step size from variation of step amplitudes made by the imperfect piezo.

Still, 1% is often not good enough, especially if the load is changing, e.g. by applying forces during microengraving. The eight orders of magnitude between resolution and stroke made by the Nanomotor cannot be measured with any conventional device.

Two solutions are offered that form the best methods with respect to resolution and price:

  • PMS - Position Measuring System
    Optical position sensors can be integrated into the Nanorobotics modules. They allow a resolution of +- 2 nm over the whole stroke of the module. The sensor does not increase the size of the modules.

  • Electrical contacts
    A cheap and easy solution for many applications. The Nanomotor determines its position by electrical end switches and can thus adjust desired positions by counting steps. The carrier tube of the Nanomotor (or a moved part of a Nanomotor-positioner) will be one electrode, moved against a second electrode, e.g. at an end position. One of the electrodes is GND, the second forms the trigger signal for the electronics.

 

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