1. Diamond Motion Control Emma Shepherd & Matthew Pearson May 2011
High level look at motor control software
EPICS Motor record
EPICS Motor driver organisation
PMAC Co-ordinate systems (synchronized motion)
PMAC PLC programs
Python motor control software
Plans

2. The EPICS Motor Record Generic user interface to most kinds of motor:
Move, Stop, Home
User offset
Change sign of motion
Motion retries in case of failed move
Handles backlash
Software limits
Axis status
Set velocity, acceleration, etc
Call-back when motion complete
>100 fields in the record

3. Diamond User Interface (EDM)

4. Axis Status
Motion Parameters

5. Soft Limits and Calibration
User adjustable direction and offset

6. High level look at motor control software
IOC
Motor Record
Axis 2
Motor Record
Axis 1
User interface
Driver abstraction layer
Motor Controller
Device Support
Device Support
User Program
Controller Tasks
(servo loop, etc)
Device Driver
VME Bus,
Ethernet,
Etc
Record/Device Support/Device Driver is generally
how EPICS software is organised.

7. PMAC Co-ordinate System Driver
Can define virtual axes that look (almost) the same as standard motors. We use a customised PMAC driver to operate/readback the co-ordinate systems.
Example: Table with 3 jacks Y1 Y2 Y3
Pitch Angle - X
Height - Y
Advantages:
True synchronized motion
Pushes complexity down into
controller
Disadvantages:
Requires EPICS PMAC driver changes
More to maintain
#1 J=100
X(0.5)Y(100)

8. Example: Hexapods Complex kinematics
Suppliers adhere to Diamond PMAC programming conventions so that we can use the motor record co-ordinate system driver to control it:
Q71..Q79: Axis demand positions – written down from the motor record
Q81..Q89: Axis readback positions – constantly calculated in a PLC from the real motor (leg) positions

9. ‘Soft’ Motor Driver Calc Define output and readback links to other PVs
An alternative to PMAC co-ordinate systems
Commonly used to control piezo motors via simple analogue interface
X+ Blade
Calc
X- Blade
X Centre

10. Motor Record Closed Loop Control
Define output to the motion controller axis
Setup readback link to a PV
Turn ‘Use Readback If Present’ ON
Setup maximum retries and retry deadband

11. Example Control Screen (a PGM)
Different motor record parameters for fast vs high precision moves
Encoder averaging done in EPICS

12. PMAC Status

13. PMAC PLC Programs Run in the background PLC 0 can be used for more
Monitor digital inputs / set outputs
Setup motion related parameters
Provide safety checks (encoder loss and motion stop)
Reset controller state
Power on/off amplifiers between moves
Axis homing
Run in the background
PLC 0 can be used for more
critical tasks.
PLC 1 is run first at power-on /
reset
CLOSE
DELETE GATHER
OPEN PLC 2
CLEAR
{PLC statements here}
ENABLE PLC 2

14. Diamond Standard PLCs
Try to standardise PLCs run on all PMACs and Geobricks:
PLC1 – PMAC/UMAC initialization
PLC2 – Monitors the motion stop input
PLC3 – Auto-energises motors
PLC4 – Encoder loss detection
PLC5 – CPU load monitoring
PLC6 – Geobrick internal amplifier setup
PLC7 – Powers down motors after a move

15. Homing PLC programs We use PLCs to:
Widen soft limits when homing
Search for home flag on encoder
Drive quickly (in right direction) to home position
Move back to old position after home
Provides feedback (success, fail, following error, etc.)
1 PLC to handle a ‘device’ – pair of slits, mirror jacks, etc.
Provides a 1-click ‘home’ button for a device.
Python script is used to generate
the PLC at IOC build time.

16. Nanomotor Duty Cycle PLC 0 used to enforce the duty cycle
Motor is killed after maximum move time
Enforced rest time is 3*actual move time
EPICS interrogates PMAC variables to display status

17. Python motor applications
Expert control
Configuration upload/backup

18. Similar software for XPS controller

19. Build framework for scanning / data gathering
Future/Ongoing work
Build framework for scanning / data gathering
Currently have software for XPS,
but no equivalent for PMAC.
Need to build abstract interface for this.
Re-implement driver layers in C++
There is a new Epics motor driver framework, developed
by Mark Rivers (Chicago/APS).
Will make it easier to implement and maintain
drivers in future.
Make our PMAC python motor software and utilities more
widely available.
Attempt to standardise use of PMAC advanced functions
(PLCs, co-ordinate systems, etc) across EPICS sites, which will
lead to common EPICS software.
Bug fixes, etc…..

20. Questions?

21. Backup Slides

22. Driver Layers XPS drvMotorAsyn.c drvXPSAsyn.c pmacAsynMotor.c TCP
Socket
XPS_C8_Drivers.c
Asyn Interpose
pmacAsynIPPort.c
pmacDriver.c
pmacVme.c
XPS
drvAsynIPPort.c
VME PMAC
Ethernet PMAC

23. EPICS motor control software summary
Motor Record 1 ai
Motor Record 2
DTYPE=asynFloat64
devMotorAsyn
devAsynFloat64
devMotorAsyn
Asyn Port
Asyn Port
drvMotorAsyn
drvMotorAsyn
pmacAsynMotor
drvXPSAsyn
Asyn Octet
Socket
pmacAsynIPPort (interpose - optional)
XPS
VME or Socket or Serial Port interface
PMAC

24. EPICS IOC startup (XPS example from I16 diffractometer)
#XPSSetup(number of controllers)
XPSSetup(3)
#XPSConfig(card,IP,PORT,number of axes,active poll period (ms),
#idle poll period (ms))
XPSConfig(0, " ", 5001, 7, 50, 500)
#Configure ASYN motor controller.
#(asyn port, driver name, controller index, max number of axes).
drvAsynMotorConfigure("XPS1", "motorXPS", 0, 7)
#XPSConfigAxis(card, axis, group.positioner,
#number of steps per user unit)
XPSConfigAxis(0,0,"Z1_Z2_Z3.Z1_BASE", 10000)
XPSConfigAxis(0,1,"Z1_Z2_Z3.Z2_BASE", 10000)
XPSConfigAxis(0,2,"Z1_Z2_Z3.Z3_BASE", 10000)
XPSConfigAxis(0,3,"GROUP4.Y_BASE", 1000)
XPSConfigAxis(0,4,"GROUP6.X_sample", )
XPSConfigAxis(0,5,"GROUP7.Y_sample", )
XPSConfigAxis(0,6,"GROUP8.Z_sample", )
Allocate memory for driver data
structures for each XPS
Configure driver for each
XPS. Open sockets, etc.
Set up Asyn driver. Pass in
type of driver and name of
XPS port.
Set up controller axis names
in driver.

25. Example Coordinate system (slit gap and centre)
; Change to coordinate system 2 and set relevant
; axes to use kinematics
&2
#1->I ; +ve blade (B+)
#2->I ; -ve blade (B-)
OPEN FORWARD
; Calculate Gap and Centre
; X = Q7 = centre in mm = ({B+}+{B-})/2
; Y = Q8 = gap in mm = {B+}-{B-}
CLEAR
Q7=(P1+P2)/2
Q8=P1-P2
CLOSE
+ similar for inverse
+ actual position readback PLC program
+ motion program to execute move
Q-variables are local to coordinate systems
Python script is used to generate the
coordinate system and PLC at IOC build time.