Control & Instrumentation for Insertion Devices

A description of the control and electronic design capabilities of ADC's controls group is presented along with examples of past projects.

Controls and Electronic Capabilities

Advanced Design Consulting has several electrical /software engineers and build techs capable of providing custom circuit design and complete turn-key control systems. Some of our skills include integrated PLC design and programming, analog and digital circuit design, logic design including PLA and FPGA programming, stepper and servo motor applications, microprocessor, RFID, serial and RF communications, and system controllers.

We have a suite of instrumentation tools for test and measurement of temperature, position, angular displacement, tolerance, acceleration, vacuum, and motor controls with extensive stock components for prototyping and breadboard. Our electrical lab includes various precision DVMs, oscilloscopes, power supplies, and other tools.

Our design tool set includes Cadence Capture for circuit board design, Xilinx ISE for FPGA design, ModelSim for simulation, and StateCad. Schematics are drawn on various platforms with output to DXF.

Microprocessor experience is broad but recent projects focus on the PIC Micro Family from MicroChip. ICE units and code simulation for the PIC microprocessors are in-house.

Software skills and development platforms include Microsoft Visual C++, PERL, LabView, Visual Basic, CNC, and generic PLC (AB, NAIS, GE-Fanuc, Schneider, etc.) and Parker 6K and Accroloop.

Our primary skill, however, is the integration of these components into a functioning system, fully debugged, documented, and ready for operation.

Some of the controllers we have delivered are described below.

Max-Lab and NSRRC

ADC built 3, 2.8 meter, Insertion devices for Max-Lab at Lund, Sweden. The first was a full EPU, the second a planer, the third a partial EPU (2 fixed and 2 moveable magnet arrays). All three used the same Allen Bradley ControlLogix PLC with a Kinetix servo controller. All axes are servo controlled. The EPU used 8 axes; 4 on gap (2 top, 2 bottom) and one for each phase. The four servo gap control concept allowed exceptional gap control without helper springs. As the phases move through different polarities, the girders can alternately attract and repel each other to the point of levitation of the girders. High resolution absolute linear encoders (.1 um per count) were used to feed back position on each gap motor. In addition, redundant absolute rotary encoders on the motors closed a velocity loop while providing a backup to the linear encoders closing the position loop. The effect was dramatic. One could actually see the gap motors correcting for load changes as the phase axes moved. Gap repeatability was 1 micron or better. The motors follow a virtual master axis; this virtually eliminates following error between axes. This same controller will be applied to NSRRC's 4.6 meter EPU later this year.

SRC Planar

This was a controller based on a Delta-Tau PC104 PMAC which was specified by SRC. The software was written by SRC but the hardware implementation and debug was performed by ADC. It consisted of a single stepper motor for gap control and 4 analog correction coil controls.

MAX-LAB and NSRRC 8 Axis Control Concept

Brookhaven In-Vacuum Planar

The Brookhaven X25 MGU in-vacuum planar was based on the same 4 motor gap control concept although stepper motors were used. Linear absolute encoders feed back position for each motor. It is difficult to find controllers that will contour motions using steppers, most require servos; however, the Parker 6K does allow master-slave contouring using steppers. The Parker 6K was chosen mainly for this reason but also because the software development time is somewhat reduced over other VME based controllers. Delivery time was critical on this project. The other major requirement was +/- 2 um repeatability on the magnet arrays through cryogenic temperature cycles. This problem was solved by the application of 2 Keyence optical micrometers that directly measured features on the magnet arrays through view ports in the chamber. This approach compensated for thermal growth at any temperature. The Parker 6K also provided a means to read the Keyence devices and then calculate and inject a correction factor into the positioning loop.

Australian Synchrotron Project Wiggler/SSRF China

The Australian Synchrotron Project Wiggler controller used a single stepper motor controlled by a Schneider Modicon Premium PLC. (China Wiggler used a SIEMENS S7-315.) The magnetic forces on a wiggler are much greater than an EPU so an extremely large stepper motor was required. The gap control program is much simplified with a single motor but then the positioning requirement is wide, +/- 100 um. The real challenge for this project turns out to be the interface to the EPICS program which is growing in acceptance in synchrotrons around the world. This interface was accomplished using a custom Schneider driver (written by ASP) that runs under EPICS on a Linux OS platform. Data is passed via located variables at the PLC. The data consists mainly of gap commands and status response but also data points are passed to arrays that control the correction coils. The PLC calculates an interpolation factor for the correction coil data based on the current gap and updates the control outputs for 4 correction coils all in 2 ms without impacting the position control.

ASP Wiggler Control Concept