Feb 3 2010
Shifting scientific equipment weighing tonnes to within microns or millionths of a metre is difficult. But at the Australian Synchrotron, where scientists study matter by using the radiation beams created by "wobbling" electrons, device positioning down to 10 nanometres is required. The equipment is so sensitive that the building has isolated foundations and a rubberised girder super structure to dampen vibration, and movements need to be incredibly smooth.
The Synchrotron's motors are used to manipulate magnets that create the radiation used for study, tune the radiation beam as it travels down the transport line by controlling mirrors and other components and, finally, manipulate the sample under analysis within the radiation beam at the experiment end-station.
Because these motors range from heavy lift motors that can move tonnes to motors that move just a few grams, a flexible motor controller design was required.
The motor control system was designed and developed by Motion Solutions Australia in partnership with Australian Synchrotron engineers over twelve months, says Australian Synchrotron senior controls engineer Dr Mark Clift. The motor controllers are from Galil USA and those with integrated drive units use Parker drives. The Galil motor controllers have been tightly integrated with the Synchrotron control system EPICS (Experimental Physics and Industrial Control System).
"The system's development was a team effort, involving Clem Berenger, Manager and Tane Coe, Design Engineer, from Motion Solutions Australia, and myself - with scientists feeding in their requirements," Dr Clift says.
EPICS, the chosen control system at the synchrotron, is from the American Strategic Defence Initiative undertaken during the Reagan administration. The EPICS driver written for the Galil controller interfaces with the motor record and a collection of standard EPICS records. Standard records provide control/monitor interfaces for features that the motor record does not support (such as the gear ratio for synchronised co-ordinated motion). The EPICS driver is compatible with all motor controllers in the Galil range and has a native EPICS driver/device layer rather than an Asyn device layer. The motor controller can read two encoders per motor at all times and allows swapping between primary and secondary encoders at run time, while a standard motor record in EPICS only supports one encoder per motor.
"Our solution is highly integrated than other, more cluttered, synchrotrons overseas. This means it's more compact and serviceable. There's less cabling and troubleshooting is easier," Dr Clift says. "The only time we remove the controllers from the rack now is when we have to change the type of motor being used from stepper to servo or vice versa. All motor settings such as current, gain, and number of steps per revolution are set remotely over serial connections via laptop."
The design challenges meant fast and expert technical support from Motion Solutions Australia and Galil was vital.
"The Galil motor controllers didn't originally support the SSI encoder type used at the Synchrotron but Galil wrote software and provided hardware for us to use SSI encoders," says Dr Clift. "In fact, we selected Motion Solutions Australia because their hardware was flexible and easier to understand and they have always been incredibly responsive. When something's failed, they've been on our doorstep within 30 minutes, part in hand."
"This private/public partnership in getting the motor controllers developed in the local market has provided an opportunity for export to new Synchrotrons throughout the world," says Mr Berenger.