Product category:
Stepper and Servo Drives, Motors, Controls
News Release from: Micromech | Subject: 360 axis servo girder alignment control system
Edited by the Engineeringtalk Editorial
Team on 14 December 2006
Servometer control systems keeps
synchrotron going
Diamond Light Source is a new scientific facility currently being built in South Oxfordshire on the Harwell Science and Innovation campus
This giant machine, called a synchrotron can be described as a series of 'super microscopes' It is housed in a futuristic doughnut shaped building, which covers the area of five football pitches
This article was originally published on Engineeringtalk on 26 Feb 2001 at 8.00am (UK)
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Diamond will ultimately host up to 40 cutting edge research stations, called beamlines, supporting the life, physical and environmental sciences.
A synchrotron is a huge scientific machine designed to produce very intense beams of x-rays and ultraviolet light.
This 'synchrotron light' can penetrate deep inside matter and allows scientists to investigate the world around us at the scale of atoms and molecules.
X-rays and ultraviolet light are part of the electromagnetic spectrum, the family of electromagnetic waves: electric and magnetic fields that vary in intensity with space and time.
Visible light is the small range of the electromagnetic spectrum that the human eye can detect.
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Our eyes can distinguish between millions of different colours of visible light, each colour having a different wavelength.
However, there is a huge range of the electromagnetic spectrum that we cannot see directly: radio waves, microwaves, infrared light, ultraviolet light, x-rays and gamma rays.
Throughout the 20th century, mankind learnt how to use the different types of electromagnetic waves.
These uses include: radio waves to transmit television and radio signals; microwaves to cook foods; radar to locate moving objects; infrared pulses to remotely change the channel on your TV; and x-rays to image the body in hospitals.
Synchrotron light uses this knowledge and takes it further, allowing scientists to probe further into materials, to investigate smaller objects, and to reveal even more about the world we live in.
Diamond is a third generation 3GeV (Giga electron Volt) synchrotron light source.
Third generation light sources use arrays of magnets, called insertion devices, to generate extremely intense, narrow beams of electromagnetic light, about 10,000 times brighter than the UK's current facility based at the Daresbury Laboratory in Cheshire.
Micromech Systems Limited (MSL) has recently completed a GBP 1.1 million contract for providing control systems for 360 axes of servomotors for controlling 72 beam alignment girders.
Each girder weighs in the region of 15 tonnes, and they are positioned around the storage ring of the facility.
The storage ring consists of a continuous circular vacuum chamber with a circumference of 561m enclosed by over 450 powerful magnets mounted on the girders, which guide an electron beam around the ring.
Synchrotron light is produced each time the electron beam is diverted by the magnetic field, and is emitted at various points around the storage ring into a number of beamlines.
Due to possible settlement of the building it maybe necessary to realign the ring by adjusting the girders.
It is intended that, as a future development, the electron beam itself will be used as a means of feedback to form a closed loop system for required changes to the girder positions.
The servomotors used for the task are 50mm DC brushed and are coupled with a small worm gearbox with a ratio of 15:1 and a larger planetary gearbox with a ratio of 320:1 giving a final drive ratio of 4800:1.
The motor/gearboxes are fitted are fitted to cam assemblies (Movers) which in groups of five provide + or - 5mm of motion in 'sway', 'heave', 'pitch', 'roll', and 'yaw' to within a few microns accuracy.
Absolute encoders provide retention of positional data in the event of power failure.
To ensure that the encoders were zeroed relative to the correct cam position MSL designed and built a measurement system, which automatically positions the cam at a precise position from top dead centre.
Once in position the encoders can be automatically zeroed.
A major concern for DLS is that if the girders are moved too far, expensive bellows assemblies which join the vacuum tube sections will be damaged.
MSL designed and manufactured custom limit switch assemblies to protect the integrity of the vacuum.
The switches and can cope with the 'sway', 'heave', 'pitch', 'roll', and 'yaw' movements of the girders.
24 control panels were designed and built by MSL each containing a 7 and an 8 axis custom built servo rack and a VME crate.
The control systems are based on the Oregon Microsystems VME58 motion controller card mounted in VME crates, each card controls up to 8 servo axes.
Application software was written which interfaces with DLS' own high level software platform ('EPICS' used internationally by the scientific community) to provide operator level screens to control the system.
The installation required in excess of 3.5km of multicore cable, used in the numerous cable assemblies required for the system.
MSL installation engineers carried out the termination of the cables at the control rack and storage ring ends.
Final commissioning was also carried out by MSL.
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