CONTROL OF 6 DEGREE-OF-FREEDOM PARALLEL MANIPULATORS FOR SYNCHROTRON-RADIATION APPLICATIONS

This high precision parallel manipulator is a well-adapted support for optical instrumentation in synchrotron radiation beamlines. It consists of a single moving element that obtains its six degrees-of-freedom from the combined movement of six independent actuators. This arrangement offers new control possibilities, together with fewer constraints for instrument mounting and alignment. Control of this kind of manipulator requires a special approach in order to exploit its full capabilities while keeping a reasonable simplicity of operation. In this paper the details of the control procedure and associated software package are presented. Special emphasis is given to the geometry: definition and ability to follow smooth trajectories, optimized calculations and special interface features like the possibility of defining virtual axes: logical motors associated with any particular rotation or translation of the instrument. By defining adequate virtual axes, it is now simple to execute a sequence of movements that were difficult with serial manipulators. The program includes special help for the alignment and calibration process and global instrument security features. It was written in a modular way, so that it can be easily adapted to different geometries, motor controllers and other site-dependent parameters. At present three ESRF beamlines have installed and used these programs and around ten new installations are foreseen. © 1995 American Institute of Physics.