PROCEEDINGS ARTICLE | July 18, 2014
Proc. SPIE. 9152, Software and Cyberinfrastructure for Astronomy III
KEYWORDS: Human-machine interfaces, Switches, Control systems, Computer programming, Software development, Photonic integrated circuits, Optical proximity correction, Picosecond phenomena, Standards development, Motion controllers
More than a decade ago, due to obsolescence issues, ESO initiated the design and implementation of a custom-made
CANbus based motion controller (CAN-RMC) to provide, together with a tailor-made software library (motor library),
the motion control capabilities for the VME platform needed for the second generation VLT/VLTI instruments. The
CAN-RMC controller has been successfully used in a number of VLT instruments but it has high production costs
compared to the commercial off-the-shelf (COTS) industrial solutions available on the market today.
In the scope of the selection of a new PLC-based platform for the VLT instrument control systems, ESO has evaluated
motion control solutions from the company Beckhoff. This paper presents the investigation, implementation and testing
of the PLC/TwinCAT/EtherCAT motion controllers for DC and stepper motors and their adaptation and integration into
the VLT instrumentation framework. It reports functional and performance test results for the most typical use cases of
astronomical instruments like initialization sequences, tracking, switch position detections, backslash compensation,
brake handling, etc. In addition, it gives an overview of the main features of TwinCAT NC/PTP, PLCopen MC,
EtherCAT motion control terminals and the engineering tools like TwinCAT Scope that are integrated into the
development environment and simplify software development, testing and commissioning of motorized instrument
functions.
