Aerotech provides enabling positioning technology for ORC

Positioning systems and motion controls from Aerotech are being used in cutting-edge laser writing technology at the University of Southampton's Optoelectronics Research Centre (ORC).

The research project at ORC involves direct UV laser writing of integrated optical circuits on specialised glass substrates and on its own patented 'flat' optical cable. With application potential from telecom network components through to lab-on-a-chip (LOC) biological and chemical sensors, the photonic circuits are produced with the help of nanometre level precision positioning systems and motion controls from Aerotech.

The positioning system used at the ORC is an Aerotech ABL9000 series air bearing stage complete with the A3200 Digital Automation Platform motion control system with FireWire networked Ndrive linear stage amplifiers. With a 300 mm x 300 mm travel range, this brushless linear servomotor driven, ultra-high precision stage features a balanced air-on-air preload system for maximum stiffness and glass scale encoder feedback with an encoder resolution of just one nanometre.

The H-bridge design maintains both axes and their respective encoders at the same level which co-locates the centrelines of mass, force and feedback - effectively ensuring that errors are minimised for best performance straightness and flatness. With dual linear motor driven Y axes and active yaw control, the ABL9000 is able to produce perfectly parallel scans, straight lines and interpolated curves over its entire working surface. Each axis is also factory calibrated by Aerotech against a laser interferometer with the error map information added to the controller. In operation this ensures optimum translation stage accuracy.

The combination of Aerotech's BLM series brushless linear servomotors and HLe series linear servo amplifiers provide the smoothness and stability required for nanometre resolution positioning whilst ensuring the required high bandwidth, zero crossover distortion and ultra-quiet EMC characteristics which are essential for this application.

Aerotech's A3200 Digital Automation Platform provides fully deterministic PC based motion control with advanced diagnostics, set-up and tuning features that ensure perfect results. As well as the PSO feature mentioned earlier, the A3200 includes trajectory generation with multi-block look ahead to minimise geometry errors in tight profiles by regulating the speed and/or the position on each axis. The ORC use G-code programming for their particular application but the A3200 is also equipped for programming in Aerotech's own AeroBASICTM or in C, C++, and Visual Basic. For complete application integration, the optional Ncontrol® SDK software development kit may be used with Windows based ActiveX components, C++, VB and .NET class libraries. There are also a number of advanced software and hardware features available to optimise throughput performance and further improve overall machine operation.

The complete system was supplied to the ORC on a customised granite base with an additional fixed bridge arrangement that provides a stable platform for the ORC supplied interferometer optical system. The scope of supply also included direct drive rotary and vertical lift stages with comparable resolution and precision that are used together for pre-alignment of the substrate. Full cable management was included in the design which greatly assisted commissioning at the ORC.

Paul Fanning

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