forked from epics_driver_modules/motorBase
timmmooney
98 lines
4.0 KiB
Plaintext
98 lines
4.0 KiB
Plaintext
EnsemblePSOFly.db supports fly scans of a single motor controlled by an Aerotech
|
|
Ensemble controller. It uses the motor record to move the motor, and read
|
|
position, and to read control fields such as offset and direction. It uses an
|
|
asyn port to talk to the controller about capabilities that the motor record
|
|
doesn't support, such as the control of PSO (position synchronized output)
|
|
pulses.
|
|
|
|
Commands to tell the Aerotech Ensemble to output pulses every scanDelta units,
|
|
beginning at startPos and ending at scan_end. Note that the Ensemble fires
|
|
pulses at positions n*delta from the position at which the PSOCONTROL X ARM
|
|
command was invoked. Thus, the pre-fly ("taxi") position of the motor must be
|
|
an integer multiple of scanDelta.
|
|
|
|
{start} = startPos - scanDelta
|
|
{end} = scan_end + scanDelta/2
|
|
|
|
|
|
PSOCONTROL X RESET ' Reset PSO.
|
|
PSOPULSE X TIME 50,25 ' Define a pulse of width
|
|
' 50 usec, with 25 usec
|
|
' on time.
|
|
|
|
PSOOUTPUT X PULSE WINDOW MASK ' Set PSO output type to PULSE.
|
|
' PSO pulses are masked by
|
|
' the window.
|
|
|
|
PSOTRACK X INPUT 1 ' Track primary encoder for
|
|
' axis.
|
|
|
|
PSODISTANCE X FIXED scanDelta UNITS ' Set the incremental firing
|
|
' distance ((units).
|
|
|
|
PSOWINDOW X 1 INPUT 1 ' Track primary encoder for
|
|
' Window 1.
|
|
|
|
PSOWINDOW X 1 RANGE {start},{end} UNITS ' Set the fixed range (in units) for
|
|
' the window.
|
|
|
|
' Note that the following command establishes the origin for
|
|
' distance-based output pulses as the motor's current position.
|
|
' (i.e., it simply clears a counter that will be clocked by encoder pulses.)
|
|
PSOCONTROL X ARM ' Enable PSO and start tracking.
|
|
|
|
<user moves the motor from start to end>
|
|
|
|
PSOWINDOW X 1 OFF ' Turn off window.
|
|
PSOCONTROL X OFF ' Stop PSO tracking.
|
|
|
|
|
|
|
|
------------------------------------------------------------------------------
|
|
Start, end positions, etc.
|
|
|
|
Before the motor's fly motion begins, the motor is moved to the "taxi" position,
|
|
which is chosen so that the motor can accelerate to constant speed before data
|
|
acquisition begins. For constant acceleration from a possibly nonzero base
|
|
speed, the acceleration distance is given by
|
|
|
|
accelDist = accelTime * (baseSpeed + slewSpeed)/2
|
|
|
|
In EPICS motorRecord PVs, this is
|
|
|
|
accelDist = motor.ACCL * (motor.VBAS + M.VELO)/2
|
|
|
|
Data acquisition occurs at N locations during the motor motion, where
|
|
N = (endPos - startPos) / scanDelta
|
|
The locations are given by
|
|
dataStart + i*scanDelta*dir
|
|
where i is an integer in the range [0, N-1], and
|
|
dir = (endPos-startPos)>0 ? 1 : -1
|
|
|
|
Because of the way the Ensemble motor controller's position-synchronized output
|
|
is implemented, dataStart is determined by the taxi position and the
|
|
pulse-window open and close positions, such that the taxi position must be an
|
|
integer multiple, M, of scanDelta away from dataStart.
|
|
|
|
The taxi position must also be at least accelDist away from dataStart, giving a
|
|
lower limit on M:
|
|
|
|
taxi = dataStart - M*scanDelta*dir <= dataStart - accelDist*dir
|
|
M >= accelDist/scanDelta
|
|
M = ceil(accelDist/scanDelta)
|
|
|
|
|
|
-------------------------------------------------------------------------------
|
|
|
|
The Ensemble PSO output is RS422, via an interface cable that ends with a female
|
|
DB9 connector with an entirely custom pinout that includes 5V power. If
|
|
conversion to TTL is needed, the following chips and boards seem useful:
|
|
|
|
Analog Devices ADM483E chip
|
|
|
|
Linear Technology LTC485 chip
|
|
|
|
Microbotics SLC10422-TTL board
|
|
|
|
-------------------------------------------------------------------------------
|