Non-magnetic Linear Actuator with Low-profile Design and Position Control
Frictionless flexure joints made of titanium guide the motion of the drive with a crosstalk of just a few micrometers. Strain gauge sensors with approx. 0,25 % linearity are used as position sensors; this guarantees a positioning accuracy of approx. 5 µm on the entire travel range. The result is a position-controlled linear actuator with micrometer precision, having a height of just 7,4 mm and a travel range of 2 mm. Due to its guiding and sensor technology, the linear actuator can be used in strong magnetic fields or in vacuum. Its fields of use include, for example, sample manipulation in electron microscopy, adjustment of imaging elements or magnetic resonance tomography. For the simple and precise operation of N-603, PI developed a compact controller that controls the motion of the piezo stepping drives and the integrated strain gauge sensors. PI uses directly driven NEXACT® stepping drives if the aim is to achieve a uniform motion over long travel ranges with the highest possible accuracy: This drive technology is based on minimum four piezoceramic benders preloaded against a guided runner. During operation, the piezo actuators work in pairs as clamping and feed elements on a runner; cyclical, phase-shifted control induces the stepping motion of the actuators and the runner is moved forwards and backwards. In a position-controlled system with NEXACT® drive, the motion is executed in nanostepping mode along a predefined motion profile to the target position. The nanostepping mode allows for a constant and smooth feed of the runner. This is achieved by an overlapping of the feed motion of the actuator pairs. Thanks to this functional principle, maximum positioning accuracy and path accuracy during the motion of the NEXACT® drives can be achieved.