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^1 USER MANUAL
^2 Accessory 29
^3 MLDT Interface Board
^4 3Ax-602243-xUxx
^5 October 15, 2003
Copyright Information
© 2003 Delta Tau Data Systems, Inc. All rights reserved.
This document is furnished for the customers of Delta Tau Data Systems, Inc. Other uses are
unauthorized without written permission of Delta Tau Data Systems, Inc. Information contained
in this manual may be updated from time-to-time due to product improvements, etc., and may not
conform in every respect to former issues.
To report errors or inconsistencies, call or email:
Delta Tau Data Systems, Inc. Technical Support
Phone: (818) 717-5656
Fax: (818) 998-7807
Email: support@deltatau.com
Website: http://www.deltatau.com
Operating Conditions
All Delta Tau Data Systems, Inc. motion controller products, accessories, and amplifiers contain
static sensitive components that can be damaged by incorrect handling. When installing or
handling Delta Tau Data Systems, Inc. products, avoid contact with highly insulated materials.
Only qualified personnel should be allowed to handle this equipment.
In the case of industrial applications, we expect our products to be protected from hazardous or
conductive materials and/or environments that could cause harm to the controller by damaging
components or causing electrical shorts. When our products are used in an industrial
environment, install them into an industrial electrical cabinet or industrial PC to protect them
from excessive or corrosive moisture, abnormal ambient temperatures, and conductive materials.
If Delta Tau Data Systems, Inc. products are directly exposed to hazardous or conductive
materials and/or environments, we cannot guarantee their operation.
EN
Dispose in accordance with applicable regulations.
Accessory 29
Table of Contents i
Table of Contents
INTRODUCTION ....................................................................................................................................................... 1
Connectors ................................................................................................................................................................. 1
P1 .......................................................................................................................................................................... 1
J1 .......................................................................................................................................................................... 1
J2 .......................................................................................................................................................................... 1
J3 .......................................................................................................................................................................... 1
J4 .......................................................................................................................................................................... 2
J5 .......................................................................................................................................................................... 2
J6 (JS3) ................................................................................................................................................................. 2
J7 (JS4) ................................................................................................................................................................. 2
J8 .......................................................................................................................................................................... 2
TB1 ....................................................................................................................................................................... 2
MLDT OPERATIONAL PRINCIPLE ...................................................................................................................... 3
Linearity .................................................................................................................................................................... 4
Resolution ................................................................................................................................................................. 4
Range .................................................................................................................................................................... 4
Circulation ............................................................................................................................................................ 4
Update Time ......................................................................................................................................................... 5
Acc-29 to MLDT Connections .................................................................................................................................. 5
Acc-29 Compatible MLDT Timing ........................................................................................................................... 6
PMAC Parameter Setup ............................................................................................................................................ 7
Encoder Conversion Table Setup.......................................................................................................................... 7
Timer (1/T Counter Capture) Register Addresses for Acc-29 ............................................................................... 7
Encoder Decode I-Variable Setup (I940-I975) ..................................................................................................... 9
Servo Cycle Extension .......................................................................................................................................... 9
User Unit Definition ........................................................................................................................................... 10
Nonlinearity Compensation ..................................................................................................................................... 10
CONNECTION TO ACC-28 .................................................................................................................................... 11
Incremental Encoder Input ...................................................................................................................................... 11
DSPGATE General Purpose Outputs ...................................................................................................................... 11
Incompatibility with Acc-24P/V ............................................................................................................................. 11
An Example of Parameter Setup ............................................................................................................................. 11
Servo Cycle Extension Setup ............................................................................................................................... 11
Encoder Conversion Table Setup ............................................................................................................................ 12
I-variable Setup .................................................................................................................................................. 12
Timing Considerations ........................................................................................................................................ 12
A List of Tested MLDT Devices ............................................................................................................................. 12
CONNECTOR PINOUTS......................................................................................................................................... 15
J2 (10 Pin Header) ................................................................................................................................................... 15
J3 (10 Pin Header) .................................................................................................................................................. 15
J4 (34 Pin Header) .................................................................................................................................................. 16
J5 (34 Pin Header) .................................................................................................................................................. 17
J6 (16 Pin Header) .................................................................................................................................................. 18
J7 (16 Pin Header) ................................................................................................................................................... 18
J8 (37 Pin DB Connector)1,2,3 .............................................................................................................................. 19
TB1 (4 Pin Terminal Block) ................................................................................................................................... 20
ACC-29 E-POINT JUMPER DESCRIPTIONS ..................................................................................................... 21
Interrogation Pulse Echo Enable ............................................................................................................................. 21
Incremental Encoder Interface ................................................................................................................................ 22
LDT Single-Ended/ Differential .............................................................................................................................. 23
J2 Output Supply Voltage Configuration ................................................................................................................ 23
Accessory 29
ii Table of Contents
J3 Output Supply Voltage Configuration ................................................................................................................ 24
Interrogation Pulse Width ....................................................................................................................................... 24
Servo Clock Extension for Channels 1 to 41 ........................................................................................................... 24
Servo Clock Extension for Channels 5 to 81 ........................................................................................................... 25
DCLK Divide Jumpers1,2 ....................................................................................................................................... 25
Power Supply Jumpers ............................................................................................................................................ 26
Accessory 29
Introduction 1
INTRODUCTION
PMAC’s Accessory 29 (Acc-29) is a standalone printed circuit board which is designed to interface with
up to eight channels of Magnetorestrictive Linear Displacement Transducers (MLDTs). Acc-29 can be
used in conjunction with both the PMAC PC and the PMAC VME. It communicates to PMAC via its J1
connector. This connector should be linked to PMAC CPU board’s J2 (JEXP) connector via the supplied
50-pin flat cable. Since PMAC STD does not have a JEXP connector on its CPU board, it is not
compatible with Acc-29.
The Acc-29 board is designed as a 1/2-size PC extension board. However, it uses the PC bus only for
digital power supply (+5V). In standalone operations, or for use in conjunction with PMAC-VME, a
terminal block is provided for power supply connections. The basic Acc-29 interface board can handle a
maximum of four channels of MLDT inputs through one on-board DSPGATE. Acc-29 with Option 1
extends the board's capability to eight channels by adding a second on-board DSPGATE.
This manual is intended to provide the relevant information for the use of Acc-29 in conjunction with
PMAC. The PMAC and the transducer connections to Acc-29 will be explained. In addition, the
required changes to the relevant I-variables of PMAC, and the modifications to its default Encoder
Conversion Table entries will be pointed out. We start by describing the connectors on the Acc-29
interface board. This is followed by a brief description of the operation principle of the categories of
MLDTs which are compatible with Acc-29. Acc-29 to MLDT connections, compatible timing sequences,
and the required PMAC parameter modifications will be described next. Acc-29’s complete connectors
and jumpers definition lists are provided at the end of this manual.
Connectors
Refer to the schematic layout diagram of Acc-29 for the connectors’ locations on the board. Also, refer to
the connectors’ pin definition listings at the end of this manual.
P1
This connector provides structural support as well as the power supply (+5V) for digital side of the on-
board opto-isolation circuits. It is also possible to bring in the +12V and +5V power supplies required for
the transducer side of the on-board opto-isolation circuits through P1. To do this, jumpers E32 and E33
must be installed
Note:
The installation of these jumpers voids the opto-isolation feature of Acc-29.
J1
This connector provides the link between Acc-29 and PMAC via the J2 (JEXP) connector on the CPU
board. A 50-pin flat cable is provided for this task (see Figure 2, the connection diagram). J1 must be
connected to the PMAC CPU board’s J2 (JEXP).
J2
This connector brings out the four Compare-Equal signals (EQU9 to EQU12) and the four general-
purpose output signals (OUT9 to OUT 12) associated with the first DSPGATE on Acc-29. Jumpers E18
and E19 determine the signals polarities. For MLDT interfacing this connector is not required.
J3
This connector brings out the four Compare-Equal signals (EQU13 to EQU16) and the four general-
purpose output signals (OUT13 to OUT16) associated with the second DSPGATE on Acc-29. Jumpers
E21 and E22 determine the signals polarities. For MLDT interfacing this connector is not required. (This
connector is available only on Acc-29 with Option 1).
Accessory 29
2 Introduction
J4
This connector brings in all the encoder channels and the home flags associated with the first DSPGATE
on Acc-29. For MLDT interfacing this connector is not required.
J5
This connector brings in all the encoder channels and the home flags associated with the second
DSPGATE on Acc-29. For MLDT interfacing this connector is not required. (This connector is available
only on Acc-29 with Opt. 1).
J6 (JS3)
This connector contains miscellaneous I/O signals related to the first DSPGATE on Acc-29. It is
typically used for direct connection to an Acc-28 (the four channel analog-to-digital converter board).
For MLDT interfacing this connector is not required.
J7 (JS4)
This connector contains the miscellaneous I/O signals related to the second DSPGATE on Acc-29. It is
typically used for direct connection to an Acc-28 (the four channel analog-to-digital converter board).
For MLDT interfacing this connector is not required. (This connector is available only on Acc-29 with
Option 1)
J8
This is a 37-pin DB connector used for interfacing with up to 8 channels of MLDTs. In addition, in order
to take full advantage from the opto-isolation feature of the board, the +5V and the +12V (to +15V)
power supplies for the transducer side of the board should be brought in through this connector.
TB1
This is a 4-pin terminal block which provides an alternative power supply input for standalone
applications outside the PC bus. The +5V power supply input is intended for digital side of the on-board
opto-isolation circuits. However, it is possible to bring in the +12V and +5V power supplies for the
circuits on the MLDT side of the opto-isolation through TB1. To do this, jumpers E32 and E33 must be
installed.
Note:
The installation of these jumpers voids the opto-isolation feature of Acc-29.
Accessory 29
MLDT Operational Principle 3
MLDT OPERATIONAL PRINCIPLE
For a detailed discussion of a particular MLDT device the reader should refer to its manufacturer’s
manual. In addition, the article by J. Smith and S. Deiters in the Nov./Dec. 1990 issue of Motion Control
provides a general discussion of these transducers and their motion control applications. For the users
convenience, a brief discussion of MLDT operational principle will follow here.
Figure 1 on the following page shows the essential elements of a typical MLDT. It consists of three basic
elements: the processing head, the waveguide, and the magnetic ring. The cylindrical waveguide, which
is attached to the processing head, has a ferromagnetic (typically steel) outer shell. Inside this shell, a
conducting wire runs longitudinally. The magnetic ring is typically attached to the moving part whose
relative displacement with respect to the processing head is to be measured. A magnetostrictive
transducer provides (indirectly) position information based upon the travel time of a strain pulse between
two points on a conducting medium (the waveguide's outer shell). This pulse, which is propagated at
ultrasonic velocity (typically around 9.01 to 9.3 ms/in.), is generated underneath the magnetic ring
whenever an interrogation pulse is transmitted from the processing head via the conducting wire. This
strain pulse (also known as the return pulse) is then detected in the receiver circuit of the processing head.
Since the velocity is a material constant for a given waveguide, the travel time is directly proportional to
the instantaneous distance between the processing head and the traveling magnetic ring.
When used with PMAC through an Acc-29, this travel time is measured by one of the timer registers (1/T
binary counters) within its DSPGATEs. For each MLDT device one period counter is required. First, at
the beginning of each servo cycle, the interrogation pulse is generated on Acc-29. This pulse is
transmitted to the processing head via the appropriate pins of the J8 connector. Either the interrogation
pulse, or its echo (jumper selectable), would initiate the counting process of the designated counter. The
counting continues until the strain pulse is returned from MLDT device via the same connector. The
strain pulse stops the counting and latches the counter's value for a PMAC read. This value is a direct
measure of the relative displacement between the magnetic ring and the processing head.
Processing Head
Wire Guide
Conducting Wire
Magnetic Ring
Traveling Marker
Power supply,
Interrogation, and
Return (strain)
pulse signals
Typical Timing:
Echo Time (measure of distance)
(Typ. 1
m
s)
(Typ. 1
m
s)
Interrogation Pulse
(from ACC-29)
Return Pulse
(to ACC-29)
Figure 1: Typical Elements and Timing
for a MLDT device
(MLDT)
Accessory 29
4 MLDT Operational Principle
Linearity
Typical deviations from linearity are quoted as 0.05%. However, it is possible to compensate for such
nonlinearities using look up tables (e.g. PMAC’s Leadscrew Compensation Table). Some of the MLDT
manufacturers provide a linearity compensation table which can be used in conjunction with the PMAC’s
Leadscrew Compensation feature (see the section on "Nonlinearity Comp.").
Resolution
The positional resolution (minimum increment of stroke that can be detected) of an MLDT transducer is
directly proportional to the resolution of time measurement between the initial interrogation pulse and the
echoed strain pulse. Typically, a digital counter is used to measure this travel time (e.g. DSPGATE’s
timers for the case of Acc-29). The higher, the counter clock frequency, the higher the resolution, or the
smaller the minimum detectable incremental motion. In general, the resolution is given by the following
formula:
Resolution = 1/ (G x F)
Where F is the clock frequency, and G is the manufacturer supplied transducer gradient (typically 9.05
s/in. or 0.356 s/mm). For example, the DSPGATE 1/T counters used in Acc-29 run at 29.4912 MHz.
Hence,
Acc-29 Resolution=(9.05 x 29.4912)-1 = 0.00375 inches.
Note that this resolution will vary slightly with different makes of MLDTs due to slight changes in the G
values.
A 50 MHz version of Acc-29 may be special ordered direct from factory. With this version, the
resolution improves to 0.00221 inches.
Range
The range of measurable displacement is directly proportional to the counter size (its number of bits). For
example, the effective size of the timers within the DSPGATES is 23 bits. Thus, for the above example
the Acc-29 displacement range will be
Acc-29 Range = (0.00375 x 223) = 31,457 inches
Circulation
Circulation or recirculation is a digital process that improves the resolution of an MLDT by (artificially)
increasing its gradient G. This provides more counting time for the counter, improving resolution. The
process involves retriggering an interrogation pulse, a fixed number of times, by the return pulse.
Required Circulation # = Int.[1/(G x F x DR)]
Where DR is the Desired Resolution, and Int.[x] means x’s integer value when rounded up to the next
higher number. Thus for the above example, in order to increase the resolution to (better than) 0.001 in.,
the number of circulation required is given
Required Circulation # = int. [(9.05 x 29.49 x 0.001)-1] = int.[3.747]= 4
Note that the Update Time will now be increased to 36.2 (9.05 x 4) ms/in. This delay may become
unacceptable for longer ranges of motion. As a result, circulation is not recommended for high
performance servo applications. The best way to improve resolution is to increase the clock frequency F.
Note that Acc-29 does not support Circulation due to its adverse effects on the servo performance.
However, some MLDT processing heads contain electronics that carry out circulation internally. This
leads to larger manufacturer specified equivalent G values and improved resolution. As far as Acc-29 is
concerned, still one return pulse is expected per each interrogation pulse.
Accessory 29
MLDT Operational Principle 5
Update Time
For a given counter clock frequency, and a fixed transducer gradient, the Update Time is proportional to
the stroke length (relative distance between the traveling magnetic ring and the processing head).
Update Time= S x G x Circulation
where S is the stroke length. Note that for Acc-29, since Circulation is not supported, Update Time
reduces to:
Acc-29 Update Time= S x G
For example, the update time to measure 100 inches of relative distance is given by:
Acc-29 Update Time (for 100 in.) =100 x 9.05 = 905 ms
This period is more than twice the default PMAC servo cycle which is approximately 442 ms. The servo
cycle clock is used on the Acc-29 board for generation of the interrogation pulse. To handle long strokes
with Acc-29 and because only one interrogation pulse can be generated per servo cycle, Acc-29 is
equipped with jumpers which can divide down the servo clock for the purpose of interrogation pulse
generation. These jumpers (E25 and E26) can divide the servo clock by 2, 4, 8, 32, 64, 128, or 256 (see
the jumper definition section at the end of this manual). For instance, to handle 100 in., the servo clock
should be divided by 4 (E25C or E26C should be installed). Also, note that for this particular channel,
PMAC’s Ix60 (the servo cycle extension parameter) should be modified accordingly. In this particular
case, the appropriate Ix60 should be set to 3 (see the I-variable Specification section in the PMAC User
Manual and the Servo Cycle Extension section of this Manual).
It is important to realize that reducing the servo loop closure frequency can adversely affect the closed
loop performance for an otherwise unchanged set of gains. Thus if, due to long stroke lengths, servo
cycle period extension is required, all the servo gains (especially the derivative gain Ix31) would often
have to be reduced. Still, the servo performance is very likely to be negatively impacted, especially if the
servo loop was originally tuned for a very fast closed loop response.
Acc-29 to MLDT Connections
All the connections between the Acc-29 and MLDT processing heads are through the 37-pin DB
connector J8 (refer to the pin description lists at the end of this manual). Up to four MLDT devices may
be interfaced with the basic Acc-29. With its Opt.1, Acc-29 can handle a maximum of eight MLDTs.
Each MLDT’s interface consists of two signals LDTOx (x=1 to 8) and LDTIx. LDTOx is the
interrogation pulse sent from Acc-29 to the MLDT processing head. LDTIx is the return (strain) pulse
sent back to Acc-29 from the processing head. Acc-29’s default jumper setting accepts LDTIx signals as
single-ended inputs. When used as differential inputs, the matching LDTIx/ should also be connected for
each channel. Jumpers E9 through E16 determine the type of input signals for channels 1 through 8
respectively. LDTOx and LDTOx/signals are also and differential. However, if single-ended
interrogation pulse is required, either LDTOx or LDTOx/ may be connected. The signal, which is not
used, must be left floating. Both of these signals are TTL level type. The maximum allowable voltage
level on the input signals LDTIx and LDTIx/ should not exceed +15V with respect to the GND signal.
J8 also brings in the power supply (+12V to +15V) for the transducer side of the opto-isolation circuitry
on Acc-29. To take full advantage of this feature, the power supply connectors on J8 should be connected
to a separate power supply from that used for the digital side of the opto-isolation circuitry. This digital
power supply is brought in through either P1 or TB1. It is possible to use the digital power supply for the
transducer side of the opto-isolators by installing jumpers E32 and E33. However, this would defeat the
opto-isolation feature of the board and should not be done if an unacceptable level of electrical noise is
suspected to be present.
Accessory 29
6 MLDT Operational Principle
Acc-29 Compatible MLDT Timing
Figure 4 shows the three types of MLDT timing sequences which are compatible with Acc-29’s
DSPGATE counting operations. As mentioned above, each of the four 1/T counters within each
DSPGATE measures the time between the interrogation pulse and the return pulse for a single channel of
MLDT interface.
ACC-29
TRANSMIT
RS422 4
m
s
LDTOX
LDTOX/
ACC-29
RECEIVE
RS422
LDTIX
LDTIX/
TYPE A
ACC-29
TRANSMIT
RS422
1
m
s
LDTOX
LDTOX/
ACC-29
RECEIVE
RS422
LDTIX
LDTIX/
TYPE B
ACC-29
TRANSMIT
RS422
1
m
s
LDTOX
LDTOX/
ACC-29
RECEIVE
RS422
LDTIX
LDTIX/
TYPE C
Figure 4: ACC-29 Compatible MLDT Timing Diagrams
0.1
m
s(min.)
0.1
m
s(min.)
For type A (e.g. Magnetek Quick-Stik transducer), the interrogation pulse width must be 4 ms. This is
achieved by removing jumper E23 for the first DSPGATE (channels 1 to 4), or removing jumper E24 for
the second DSPGATE (channels 5 to 8). In addition, since the interrogation pulse is not immediately
echoed back from the processing head, the corresponding channel's jumper ExA must be installed. Here
x refers to the channel number (from 1 to 8). In addition, the corresponding channel’s Encoder Decode I-
variable (I940 to I975) should be set for pulse and direction. More about I-variable settings will be said in
the next section.
Accessory 29
MLDT Operational Principle 7
For type B (e.g. Temposonics II RPM, or Balluff’s MLDTs), the period of the interrogation pulse is 1 ms.
Thus the default (installed) values of E23 or E24 must be used. In addition, Jumpers ExA need not be
installed, however, if installed, the counting will still work. As with the type A timing, the corresponding
Encoder Decode I-variable should be set to pulse and direction.
For type C (e.g. Norstat’s model GYRG), the interrogation pulse width is 1 ms. Thus the default
(installed) values of E23 or E24 should be used. In addition, since the interrogation pulse is not
immediately echoed back from the processing head, the corresponding channel’s jumper ExA must be
installed. In addition, the corresponding channels Encoder Decode I-variable (I940 to I975) should now
be set for x4 quadrature decode.
PMAC Parameter Setup
PMAC’s default feedback sensor decode parameters are set for incremental encoders. In this mode,
PMAC reads the contents of the encoder counters within the DSPGATEs every servo cycle. It then
calculates incremental distance traveled during that cycle. When using MLDTs through Acc-29, the timer
registers are used instead of the encoder counters, and their contents represent absolute distance.
Therefore, the default values of these sensor decode parameters must be modified. This requires changes
to PMAC's Encoder Conversion Table. In addition, for longer distances, it is very likely that servo cycle
extension is required (see the update time definition above). In addition, usually the PMAC’s default
feedback gains need to be tuned for optimum response.
Encoder Conversion Table Setup
The first DSPGATE on an Acc-29 board is memory mapped to the address of the Gate Array 3. The
second DSPGATE (which comes with Acc-29 Option 1) is memory mapped to the address of Gate Array
4 (see the I/O memory map in the PMAC User Manual). The address map for the eight timer registers
within these two DSPGATEs are given in the following table
Timer (1/T Counter Capture) Register Addresses for Acc-29
(See the PMAC Users Manual for detailed I/O map)
Channel Number
GATE Number
Hex Address
Dec Address
9
3
Y:$C020
49184
10
3
Y:$C024
49188
11
3
Y:$C028
49192
12
3
Y:$C02C
49196
13
4
Y:$C030
49200
14
4
Y:$C034
49204
15
4
Y:$C038
49208
16
4
Y:$C03C
49212
To set up the Encoder Conversion for Acc-29, the above timer registers contents should be treated as
absolute position. This requires the use of the Parallel Position Feedback option for the conversion table
setup. In addition, it is recommended that the filter option be used. This safeguards against spurious
changes, while not delaying legitimate changes at all. For more details on the Encoder Conversion Table,
refer to the Feedback Features section of the PMAC User Manual.
As an example, to use four channels of MLDT feedback with no other feedback device installed, the
following two-step procedure should be carried out:
Accessory 29
8 MLDT Operational Principle
Step 1 - Modify the Conversion Table to the Following Form:
Address
Y-word
Meaning
$720
$30C020
Parallel from Channel 9
$721
$07FFFF
Use low 19 bits
$722
$000006
Filter is 6 counts*
$723
$30C024
Parallel from Channel 10
$724
$07FFFF
Use low 19 bits
$725
$000006
Filter is 6 counts*
$726
$30C028
Parallel from Channel 11
$727
$07FFFF
Use low 19 bits
$728
$000006
Filter is 6 counts*
$729
$30C02C
Parallel from Channel 12
$72A
$07FFFF
Use low 19 bits
$72B
$000006
Filter is 6 counts*
$72C
$000000
Signifies end-of-table
*The filter count size is very much application dependent (amount of noise, maximum speed
etc.). The exact size of this filter should be chosen by the user by considering the maximum
amount of clock counts per one servo cycle. This is of course, directly related to the maximum
speed of motion being sensed. Usually numbers between 2 to 8 cover the majority of
applications. These correspond to the maximum speeds of 16 in./s to 64 in./s when running
Acc-29 with the 29.49 MHz clock and using the default servo cycle time of 442 ms.
To actually carry out the above modification, use the conversion table editor screen in the PMAC
Executive program. If this editor is not being used, replace the default conversion table entries with the
above entries using the Write (W) command. For example for the first three word entry of the above table,
command WY:$720,$30C020,$7FFFFF,$000006. To verify these changes, use the Read Hex.
command (RH).
The same procedure would be used to extend the Conversion table for channels 5 to 8.
Note:
If I9 is 2 or 3 the addresses I-variables are reported back to the host in hexadecimal
form which is usually desired).
Step 2 - Modify the Following I-Variables Related to Feedback Addresses:
Ix03, Ix04, and possibly Ix25 must be modified. Bits 0 to 15 of Ix03 tell PMAC where to look for its
position feedback for motor x in the PMAC X address space. For the case of an MLDT feedback via
Acc-29, this should point to the X address of its third entry in the conversion table. This is always the
case with all Parallel Conversions with Filter. If no homing is desired for the above example, Ix03 should
set as: I103=$722, I203=$725, I303=$728, and I403=$72B. Ix04 holds the address of
position feedback device which is used for velocity feedback information by PMAC. In most MLDT
applications, this is going to be the MLDT device itself. In such case, the value of Ix04 would set equal
to that of the corresponding Ix03 lowest 16 bits. Thus for the above example, I104=$722,
I204=$725, I304=$728, and Ix404=$72B. The lowest 16 bits of Ix25 designate the address
location of PMAC inputs corresponding to limit switches, home switches, and amplifier (actuator) fault
flag inputs for each motor. For MLDT use, these bits should be set to the corresponding addresses of the
first or the second DSPGATE on the PMAC main board (usually the default values). This is because the
limit switches etc., for each servo channel, are always directed to PMAC via its JMACH connectors.
Accessory 29
MLDT Operational Principle 9
These signals are not brought into the DSPGATEs on Acc-29. Note that since MLDT devices are
absolute position sensors the homing (initialization) function is often not required. However, PMAC will
allow this function anyway. To do so Bit 16 of Ix03 should be set to 1 in order to indicate that the
position capture for homing should be done in software. This is because Ix25 often points to a
DSPGATE channel which is within the main PMAC board. As a result, automatic hardware home
capture is not possible. Thus for the above example, I103=$10722, I203=$10725,
I303=$10728, and I403=$1072B. In addition, usually I14=1 is set in order to match the axis
position to the absolute sensor position automatically whenever a motor move (jog, open loop, abort, or
limit) changes the motor position without letting the axis position know of the change.
Encoder Decode I-Variable Setup (I940-I975)
In the previous discussion on Acc-29 / MLDT timing, it was mentioned that the return pulse from the
transducer can be either a pulse signal (types A and B), or a level change signal (type C). Both kinds are
acceptable to Acc-29. However, since these signals are directed into the DSPGATEs’ timer registers, the
gate arrays must be set up properly. These counters’ normal task is to measure the period of time between
two subsequent encoder pulses in the quadrature form. For MLDT devices using the type C timing
pattern, the corresponding Encoder Decode I-variable should be set as x4 quadrature. For example for the
first counter within the first DSPGATE on Acc-29, this setting will be I940=3 or I940=7. For the
second counter this setting would be I945=3 or I945=7 and so on. For type A and type B timing
patterns, the pulse and direction mode is required. For the pulse and direction mode, I940=0, and
I945=0.
Servo Cycle Extension
In our previous discussion of the update time, it was mentioned that due to MLDTs’ physical
characteristics, long displacements could cause a delay time which may exceed one PMAC servo cycle.
For a typical MLDT, a distance greater than 48 in. would generate a delay approximately equal to one
PMAC default servo cycle (442 s). As a result, if longer distances are to be measured the servo cycle
extension I-variable Ix60 must be modified accordingly. To carry out this task the following calculation
should be performed:
Required Servo Extension= Maximum UpdateTime/ default Servo Cycle Time
Since Ix60’s valid values are one less than power of two (2n-1), the nearest valid odd integer number
which allows for this extension should be chosen. For example for 350 inches of travel, we have:
Required Servo Extension =(350 x 9.05) / 442 = 7.166
If this particular MLDT (with 9.05 gradient and 350 inches of travel) is to be used for say the channel 1 of
an Acc-29, then I160=7 would be the correct setup. Note that the corresponding servo clock divide
jumpers on Acc-29 should be also installed. In this case, E25D should be installed.
Important Note:
If using PMAC firmware version V1.14 or later, it is necessary to use motor setup
variable Ix10 to get the absolute power-on position from the MLDT sensor. Ix10
specifies the register to read for absolute power-on position, and how to read the
data in that register. If Ix10 is set to 0, PMAC will set the power-on position for
that motor to 0, even if an absolute position device is used for the motor.
Ix10 must use the raw data register for the sensor, not the processed data register in the conversion data.
For the Acc-29 MLDT interface, the values of Ix10 to use are:
MLDT1 Timer 9 (Y:$C020) Ix10 = $18C020
MLDT2 Timer 10 (Y:$C024) Ix10 = $18C024
MLDT3 Timer 11 (Y:$C028) Ix10 = $18C028
MLDT4 Timer 12 (Y:$C02C) Ix10 = $18C02C
Accessory 29
10 MLDT Operational Principle
MLDT5 Timer 13 (Y:$C030) Ix10 = $18C030
MLDT6 Timer 14 (Y:$C034) Ix10 = $18C034
MLDT7 Timer 15 (Y:$C038) Ix10 = $18C038
MLDT8 Timer 16 (Y:$C03C) Ix10 = $18C03C
The 18 in the first two hexadecimal digits specifies that this is a 24-bit register that is being read (18 hex
=24 dec). The last four hex digits specify the Y address of the register to be read.
User Unit Definition
To command motion in user units, the axis definition within a coordinate system must be modified. The
appropriate scaling value should be set according to a particular transducer’s resolution. In addition, an
offset may be added if desired. For example for a typical Acc-29 with the resolution of 0.00375 inches,
the command #1->266.67X, specifies the axis definition in units of inches.
Nonlinearity Compensation
If a transducer’s displacement measurement is unacceptably nonlinear with respect to the length of travel,
PMAC's leadscrew compensation feature may be used for correction. This correction is done for the end
point of each commanded move if I13=0. If I13>0, then this correction is carried out continuously every
I13 milliseconds (move segmentation). The correction is computed as a number of counts linearly
interpolated between two closest entries in a table created by using the DEFINE COMP command. For
more details, refer to the Feedback Features section of the PMAC User Manual.
Accessory 29
Connection to Acc-29 11
CONNECTION TO ACC-28
Through connectors J6 and J7, two Acc-28s (the 4 channel analog-to -digital converters) may be
interfaced to the two DSPGATEs on Acc-29 and its Option 1. The ADC registers within Acc-29’s
DSPGATEs are memory mapped to the addresses of PMAC’s DSPGATE 3 and DSPGATE 4 (see the I/O
Map section of the PMAC Users Manual).
The required DCLK clock (used for Acc-28 analog conversion) is generated on Acc-29 by dividing down the
29.49 MHz clock. Jumpers E27A to E27E determine the divide down ratio. This clock frequency should be
set according to Acc-28’s maximum allowable clock input specification (typically less than 2 MHz).
Incremental Encoder Input
Through connectors J4 and J5, eight channels of incremental encoder pulses (A, B, and C) and their
associated home flags may be brought in for the two DSPGATEs on Acc-29 and its Option1. For those
channels of DSPGATEs which are not used for MLDT interfacing, these encoder inputs may be directed
to the DSPGATEs by removing the corresponding ExB jumpers. These inputs are expected to be TTL
level compatible. Internal pulls up resistors (3.3K) are installed on all inputs through J4 and J5
connectors. However, they are not protected by PMAC’s usual opto-isolation circuitry.
DSPGATE General Purpose Outputs
The eight compare equal signals (EQU9 to EQU16) and the eight general-purpose outputs (OUT9 to
OUT16) associated with the two DSPGATEs on Acc-29 and its Option 1 are available for user functions.
J2 and J3 connectors provide the outlet. Jumpers E18, E19, E21, and E22 determine the signals’
polarities. These signals may be defined by M-variable assignments. Their addresses correspond to those
for the third and the fourth PMAC DSPGATEs (See the I/O map section in the PMAC User Manual).
Incompatibility with Acc-24P/V
The maximum number of DSPGATEs used with each PMAC is four providing 16 channels of feedback.
The DSPGATEs are used for PMAC’s specific motor/amplifier/encoder (or MLDT) interface functions.
Each DSPGATE handles these functions for four channels. Thus, the basic four axes PMAC talks to one
DSPGATE. A PMAC with Option1 talks to two on-board DSPGATEs providing eight channels. An
Acc-29 with one DSPGATE provides 12 channels. Option 1 provides the remaining allowable four
channels. Since the Acc-24, the Axis Expansion board, also provides channels 8, 10, and 16, whenever
an Acc-29 is interfaced with a PMAC, the Axis Expansion board (Acc-24) should not be used with the
same PMAC.
An Example of Parameter Setup
As an example, consider the case of the connection a MLDT device with Type B timing to an Acc-29
through its first channel (LDTI1 and LDTO1). Assume that the G value provided by the manufacturer is
9.05 ms/in., and the stroke length is 45 inches. Also, assume that PMAC is running with its default servo
cycle frequency (442 ms per servo cycle). In addition, suppose that the limit switches and the home switch
corresponding to this MLDT are connected to the first channel of the first DSPGATE on PMAC itself.
Servo Cycle Extension Setup
Using the expression for the Required Servo Extension explained above, we get
Required Servo Extension = (40 x 9.05)/442= 0.819
Since this value is less than one, no servo cycle extension is required in this case (I160=0). In addition,
the default jumper position for interrogation pulse frequency generation for DSPGATE 1, E25A, must be
installed. Note that this installation also limits any other MLDT channel connected to the first DSPGATE
to be less than 48 inches long.
Accessory 29
12 Connection to Acc-29
Encoder Conversion Table Setup
Since the address of the first DSPGATE’s timer register (LDT channel 1) is $C020, the following
command should be used to set up the conversion table:
WY:$720,$30C020,$7FFFFF,000006
Note that, as explained previously, the filter size of 6 is very much application dependent.
In addition, the conversion table editor screen in the PMAC Executive software may be used to facilitate
the conversion table setup
I-variable Setup
Since the conversion table entry for this channel is now three words long,
I103=$10722
I104=$00722
I125=$xxC000
Note that bit 16 of I103 is set in order to specify that the software method of home position capture is
required. As explained above this method is always required for homing with MLDTs. However, since
MLDTs are absolute sensors, homing is often not needed. In addition, since the home/limit/ amplifier
fault inputs are directed to the channel one of the first DSPGATE in PMAC, I125 is made to point to this
gate's address. The most significant eight bits of I125 should be set according to the particular desired
operating mode (see the PMAC User Manual).
Timing Considerations
Since the transducer is assumed be interfacing with Acc-29 through the type B timing pattern, E23 should
be installed (default setting) to provide the 1 ms interrogation pulse. Jumper E1A need not be installed
since the interrogation pulse is immediately echoed back by the processing head electronics of the
transducer. However, regardless of the setting of E1A, the correct displacement measurement will be
made for the type B timing pattern. Note that for the type A and the type C transducers ExA must be
installed.
Also, setting I940=0 will take care of the required pulse and direction mode for the type B timing through
channel 1 of this Acc-29.
If using PMAC version 1.14 or later, it is necessary to use motor setup variable Ix10 to get the absolute
power on position from the MLDT sensor (see the PMAC User Manual and Addendums for version 1.14
and above). In this case, I110 = $18c020 is required for correct power on position registration for
Channel 1 of MLDT.
A List of Tested MLDT Devices
The following MLDT devices have been successfully interfaced and tested with PMAC through Acc-29
at Delta Tau’s Motion Control Laboratories:
Temposonics II RPM
MTS Systems Corporation, Sensor Div.
14000 Technology Drive
Eden Prairie MN 55344
Tel: (952) 937-4000
www.mts.com
Quik-Stik
Magnetek Controls
10900 Wilshire Bl, Ste 850
Los Angeles CA 90024
Tel: (310) 689-1610
www.magnetek.com
Accessory 29
Connection to Acc-29 13
GYRG
Norstat Inc.
300 Roundhill Drive
Rockaway NJ 07866
Tel: (201) 586-2500
www.norstat.com
BTL
Balluff Inc.
8125 Holton Dr.
Florence KY 41042
Tel: (606) 727-2200
www.balluff.com
E17
J3
J2
J6 J7
E19
E18
E20
E22
E21
E32
E12 E13
J5
J4
J1
U1
U2
E24
E26A
E25A
E26B
E25B
E26C
E25C
E25D
E26D
E25E
E27A
E27B
E27C
E27D
E27E
E26E
E26F
E25F
E25G
E26G
E26H
E25H
E25I
E26I
E1A
E4A
E1B
E2A
E4B
E3A
E2B
E3B
E5A
E8A
E5B
E6A
E8B
E6B
E7A
E7B
E9 E11
E23
E10
E16 E14 E15 E33
TB1
1 2 3 4
111
11
111
1
1
1
1
Interface Board for:
Magnetostrictive Linear Displacement Transducer
(M L D T)
4/8 channels
Figure 1: Layout of PMAC's ACC-29
7.50 in. (190.5 mm)
3.88 in (98.6 mm)
J8
Accessory 29
14 Connection to Acc-29
PMAC-PC
J2
J1
CPU
ACC-29
(MLDT Interface board)
J8
Up to
8 MLDT
connections
P1
P1
Figure 2: PMAC Connection to ACC-29, note that for
PMAC-VME the same connector is used.
ACC-29 cannot be connected to PMAC-STD.
JMACH1
Limit, Home,
Amp. Enable
Switches etc.
to ACC-8D or
ACC-8P
Accessory 29
Connector Pinouts 15
CONNECTOR PINOUTS
J2 (10 Pin Header)
Pin #
Symbol
Function
Description
Notes
1
OUT9/
Output
General Purpose Output
Low true*
2
EQU9/
Output
General Purpose Output
Low true**
3
OUT10/
Output
General Purpose Output
Low true**
4
EQU10/
Output
General Purpose Output
Low true**
5
OUT11/
Output
General Purpose Output
Low true**
6
EQU11/
Output
General Purpose Output
Low true**
7
OUT12/
Output
General Purpose Output
Low true**
8
EQU12/
Output
General Purpose Output
Low true**
9
+V
In or Out
+5V Power I/O
+V= +5V to +24V
+5V out of Acc-29. +5 to +24V
in from external source. Diode
Isolation from Acc-29
10
GND
Acc-29
Common
Digital Ground
* Controlled by bit 14 of the corresponding DSPGATE’s status/ Control register.
**Controlled by bit 13 of the corresponding DSPGATE’s status/ Control register.
This connector brings out the four Compare-Equal signals (EQU9 to EQU12) and the four general-purpose
output signals (OUT9 to OUT 12) associated with the first DSPGATE on Acc-29. Jumpers E18 and E19
determine the signals polarities. For MLDT interfacing this connector is not required.
J3 (10 Pin Header)
Pin #
Symbol
Function
Description
Notes
1
OUT13/
Output
General Purpose Output
Low true*
2
EQU13/
Output
General Purpose Output
Low true**
3
OUT14/
Output
General Purpose Output
Low true**
4
EQU14/
Output
General Purpose Output
Low true**
5
OUT15/
Output
General Purpose Output
Low true**
6
EQU15/
Output
General Purpose Output
Low true**
7
OUT16/
Output
General Purpose Output
Low true**
8
EQU16/
Output
General Purpose Output
Low true**
9
+V
In or Out
+5V Power I/O
+V= +5V to +24V
+5V out of Acc-29. +5 to +24V
in from external source. Diode
Isolation from Acc-29
10
GND
Acc-29
Common
Digital Ground
* Controlled by bit 14 of the corresponding DSPGATE’s Status/ Control register.
**Controlled by bit 13 of the corresponding DSPGATE’s Status/ Control register.
This connector brings out the four Compare-Equal signals (EQU13 to EQU16) and the four general-purpose
output signals (OUT13 to OUT 16) associated with the second DSPGATE on Acc-29 Option 1. Jumpers
E21 and E22 determine the signals polarities. For MLDT interfacing, this connector is not required. This
connector is available only on Acc-29 with Option 1.
Accessory 29
16 Connector Pinouts
J4 (34 Pin Header)
Pin #
Symbol
Function
Description
Notes
1
+5V
Output
Power Supply
For encoders
2
+5V
Output
Power Supply
For encoders
3
DGND
Common
PMAC Common
For encoders
4
DGND
Common
PMAC Common
For encoders
5
CHC11
Input
Encoder C Channel
Channel 11
6
CHC12
Input
Encoder C Channel
Channel 12
7
CHB11
Input
Encoder B Channel
Channel 11
8
CHB12
Input
Encoder B Channel
Channel 12
9
CHA11
Input
Encoder A Channel
Channel 11
10
CHA12
Input
Encoder Chan.
Channel 12
11
HF411
Input
Home Flag 4
Channel 11
12
HF412
Input
Home Flag 4
Channel 12
13
HF 311
Input
Home Flag 3
Channel 11
14
HF312
Input
Home Flag 3
Channel 12
15
HF211
Input
Home Flag 2
Channel 11
16
HF212
Input
Home Flag 2
Channel 12
17
HF111
Input
Home Flag 1
Channel 11
18
HF112
Input
Home Flag 1
Channel 12
19
CHC9
Input
Encoder C Channel
Channel 9
20
CHC10
Input
Encoder C Channel
Channel 10
21
CHB 9
Input
Encoder B Channel
Channel 9
22
CHB10
Input
Encoder B Channel
Channel 10
23
CHA9
Input
Encoder A Channel
Channel 9
24
CHA10
Input
Encoder A Channel
Channel 10
25
HF49
Input
Home Flag 4
Channel 9
26
HF410
Input
Home Flag 4
Channel 10
27
HF39
Input
Home Flag 3
Channel 9
28
HF310
Input
Home Flag 3
Channel 10
29
HF219
Input
Home Flag 2
Channel 9
30
HF210
Input
Home Flag 2
Channel 10
31
HF19
Input
Home Flag 1
Channel 9
32
HF110
Input
Home Flag 1
Channel 10
33
DGND
Common
Acc-29 Common
34
DGND
Common
Acc-29 Common
This connector brings in all the encoder channels and the home flags associated with the first DSPGATE
on Acc-29. For MLDT interfacing this connector is not required. All of the input signals are internally
pulled up to +5V. However, no opto-isolation circuitry is included for these inputs. For encoder input
through this connector, Jumpers E1B through E4B should be removed for channels 9 to 12 respectively.
Note that for a given channel either an incremental encoder or a MLDT device may be used.
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