OMS MAXnet User manual

USER’S MANUAL
INTELLIGENT MOTION CONTROLLER
FOR ETHERNET
MAXnet
OMS Motion, Inc.
15201 NW GREENBRIER PARKWAY
B-1 RIDGEVIEW
BEAVERTON, OR 97006
PHONE [phone]
FAX [phone]
mailto:[email protected]
http://www.omsmotion.com/

COPYRIGHT NOTICE
© 2013 OMS Motion, Inc. ALL RIGHTS RESERVED
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system, or translate into any language in any form or by any means, electronic, mechanical, magnetic, optical,
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Inc..
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Interest Group. LabView is a registered trademark of National Instruments. Windows, 7, Vista, XP, 2000, & Win NT
are registered trademarks of Microsoft Corporation.
DISCLAIMER
OMS Motion, Inc. makes no representations or warranties regarding the contents of this document. We reserve the
right to revise this document, or make changes to the specifications of the product described within it at any time
without notice and without obligation to notify any person of such revision or change.
3301-1800000
Rev. E

TABLE OF CONTENTS
MAXnet User’s Manual
i
TABLE OF CONTENTS
1. GENERAL DESCRIPTION..........................................................................1-1
1.1. INTRODUCTION ...................................................................................1-1
1.2. SYSTEM OVERVIEW............................................................................1-1
2. GETTING STARTED ..................................................................................2-1
2.1. INSTALLATION .....................................................................................2-1
2.2. CONFIGURING COMMUNICATION.....................................................2-1
2.3. CONFIGURING THE CARD FOR USE WITH ENCODERS.................2-3
2.4. SOFTWARE INSTALLATION................................................................2-6
2.5. CONNECT TO STEPPER MOTOR SYSTEM.......................................2-6
2.6. CONNECT AND CHECKOUT THE SERVO SYSTEM .........................2-9
2.7. CONNECT AND CONFIGURE THE MOTOR/AMPLIFIER...................2-9
2.8. TUNE THE SYSTEM ...........................................................................2-11
2.9. SETTING THE USER DEFAULT CONFIGURATION .........................2-17
2.10. POWER SUPPLY REQUIREMENTS ..................................................2-18
3. COMMUNICATION INTERFACE................................................................3-1
3.1. INTRODUCTION ...................................................................................3-1
3.2. RS-232 AND TCP/IP FLAG NOTIFICATION PROTOCOL ...................3-2
3.3. ASCII COMMAND RING BUFFER ........................................................3-3
3.4. ASCII RESPONSE RING BUFFER .......................................................3-3
3.5. DYNAMIC LINK LIBRARY .....................................................................3-3
3.6. MAXnet COMMUNICATION ARCHITECTURE ....................................3-4
3.7. REAL-TIME POSITION CAPTURE .......................................................3-5
4. CONTROL SIGNAL INTERFACE ...............................................................4-1
4.1. INTRODUCTION ...................................................................................4-1
4.2. LIMIT INPUTS........................................................................................4-3
4.3. HOME INPUTS ......................................................................................4-3
4.4. GENERAL PURPOSE DIGITAL I/O ......................................................4-3
4.5. ANALOG I/O ..........................................................................................4-3
4.6. MOTOR CONTROL OUTPUT ...............................................................4-4
4.7. ENCODER FEEDBACK.........................................................................4-6
4.8. HOME PROCEDURES..........................................................................4-6
4.9. ABSOLUTE ENCODERS WITH SSI .....................................................4-8
4.10. IOMAXnet ADAPTER MODULE..........................................................4-10
5. HOST SOFTWARE.....................................................................................5-1
5.1. INTRODUCTION TO MAXnet SUPPORT SOFTWARE .......................5-1
6. STAND ALONE COMMANDS.....................................................................6-1
7. SERVICE 7-1
7.1. USER SERVICE ....................................................................................7-1
7.2. THEORY OF OPERATION....................................................................7-1
8. FIRMWARE UPGRADE..............................................................................8-1
8.1. MAXnet ETHERNET MODE FIRMWARE UPGRADE ..........................8-1
8.2. MAXnet SERIAL MODE FIRMWARE UPGRADE.................................8-5
A. LIMITED WARRANTY
B. TECHNICAL INFORMATION / RETURN FOR REPAIR PROCEDURES
C. SPECIFICATIONS
INDEX

TABLE OF CONTENTS
MAXnet User’s Manual
ii
This page is intentionally left blank

INTRODUCTION GENERAL DESCRIPTION
MAXnet User’s Manual 1-1
1. GENERAL DESCRIPTION
1.1. INTRODUCTION
The OMS Motion, Inc. MAXnet family of motion controllers are high performance Ethernet products. The
MAXnet motion controller can manage up to 10 axes of open loop stepper, closed loop stepper or servo
systems, in any combination. The OMS MAXnet controller synchronizes all independent or coordinated
motion of up to 10 axes, while incorporating other critical signals, such as hard or soft limits, home, and
other digital and/or analog I/O signals, to provide the motion solutions to perform virtually any task. With
high level functionality, such as circular and linear interpolation, multi-tasking, custom profiling, etc., the
MAXnet can satisfy the needs of most any motion control application. See Appendix C “Ordering
Information” for specific MAXnet family models.
The MAXnet communicates as a “slave only” device and functions as a motion co-processor to the
Ethernet host. It utilizes patented and proprietary technology to control the trajectory profile, acceleration,
velocity, deceleration and direction of selected axes. In response to commands from the host computer
the MAXnet controller will calculate the optimum velocity profile to reach the desired destination in the
minimum time, while conforming to the programmed acceleration and velocity parameters. In addition,
the MAXnet can provide motion control information such as axis and encoder position as well as the state
of over-travel limits, home switch inputs, and done notification flags. The MAXnet motion controllers
utilize a PowerPC processor, configured to operate as an efficient and powerful co-processor with the PC
host via the Ethernet or RS-232.
The stepper control of the MAXnet produces a 50% duty cycle square wave step pulse at velocities of 0
to 4,194,176 pulses per second and an acceleration of 0 to 8,000,000 pulses per second per second.
The servo control utilizes a 16-bit DAC and outputs either +/- 10V or 0 to +10V. The encoder feedback
control can be used as feedback for the servo PID, position maintenance for the stepper axes or as
strictly a position feedback of any axis. The incremental encoder input supports differential or single
ended quadrature TTL signals at a rate of up to 16 MHz. The absolute encoder using SSI (Synchronous
Serial Interface) technology also supports differential or single ended inputs at a rate up to 4MHz. The
MAXnet motion controller has 2 general purpose analog inputs that utilize a 16-bit ADC, with a DC range
of –10 to +10 VDC*. There are six analog outputs that utilize a 16-bit DAC with a range of -10 to +10
VDC. Complete specifications for MAXnet can be found in Appendix C.
The MAXnet command set employs two or three ASCII character commands which can be combined into
character strings. Using virtually any programming language, these ASCII command strings can be sent
to the MAXnet Motion Controller over the Ethernet or RS-232. Refer to the Command Reference Manual:
MAX Family for the complete command reference.
1.2. SYSTEM OVERVIEW
The MAXnet motion controller can manage up to 10 axes of motion. For 1 through 5 axes, the MAXnet is
a single board motion controller, and measures 6.5” x 4” x 0.75”. For 6 to 10 axes of motion, the MAXnet
utilizes a stackable expansion board, and when combined, measures 6.5” x 4” x 1.78”. The
communication interface is accessed through either the Ethernet or RS-232. The MAXnet receives power
(5V, +/-12VDC) from an external power supply and can be applied to either the MAXnet board (1 – 5
axes) or the MAXnet expansion board (6 – 10 axes).
The MAXnet utilizes an optimally configured PowerPC RISC based 32-bit micro-controller and FPGA
technology for extensive logic integration and flexibility. The firmware, which resides in flash memory
(2MB), can be upgraded through the communication interface without having to remove the controller
from the system. 32MB of system RAM is used for firmware and data storage.

GENERAL DESCRIPTION SYSTEM OVERVIEW
1-2 MAXnet User’s Manual
All general purpose digital and analog I/O and all motor control signals are available on the 100-pin
connector (J1). Each digital I/O bit can be set as an input or output and is controlled by firmware
commands, so there are no jumpers to set.
Aside from extending MAXnet for 6 through 10 axes of motion, the optional expansion board is available
for extending I/O capabilites and for custom solutions.
Data communication is performed by sending and receiving strings of data (ASCII characters) via
standard Ethernet communication protocol or RS-232.
While not strictly required, DLLs are provided to allow applications written in high level languages to
communicate with the controller. Software provided by OMS Motion, Inc. directly supports the use of
Microsoft C, C++ or Visual Basic. In addition, any language that has a mechanism for utilizing a standard
Microsoft DLL Library can be used for application development.
The MAXnet I/O Breakout Module, the IOMAXnet, provides an efficient means of connecting the MAXnet
signals to external devices.
More details on the functionality of the controller are included in the following chapter.

INSTALLATION GETTING STARTED
MAXnet User’s Manual 2-1
2. GETTING STARTED
2.1. INSTALLATION
For installation of the MAXnet you will need a computer with either an Ethernet or RS-232 connection or
both.
Read through the following two sections before beginning the installation. Do not turn on the power to the
MAXnet until you have properly configured the controller per the following instructions. Note that the
header at location J2 is used to choose the mode of communication (Ethernet or RS-232). The MAXnet is
set for RS-232 communication mode from the factory.
Though the MAXnet is a low power device, there should be ventilation, including forced air, around the
circuit board.
2.2. CONFIGURING COMMUNICATION
The first requirement for communication through the RS-232 interface is to ensure that the MAXnet is
securely and safely mounted where damage is unlikely. This includes the exposure to possible static
discharge, moisture, debris, etc. Special mounting efforts may be required to protect the extended pins
on the bottom of the MAXnet.
CAUTION:
The RS-232 communication port is a DTE com device so that straight connection can be used for
communication; RxD to TxD, TxD to RxD. Two handshake signals are supported, CTS and RTS, that
can also be connected straight through, baud rates of 9600, 19200, 38400, 57600 and 115200 are
supported. Any terminal device that supports these signals and baud rates, be it a computer, dumb-
terminal, etc., can be used to communicate to the MAXnet.
TABLE 2-1 MAXNET DEFAULT SERIAL COMMUNICATION PARAMETERS
Default Baud Rate 115200
Data Length 8
Stop Bits 1
Parity Bit None
Select an unused COM-Port, COM1, COM2, etc., on the computer or terminal to be used. Set the baud
rate and other communication parameters on the PC to match the default settings of the MAXnet.
Connect a straight-through 9-pin RS-232 cable between the host terminal and the MAXnet. To prevent
motors, switches or other devices from unexpected activation do not connect the cable to output
connector J1 at this time.
The MAXnet is a static sensitive device and standard Electro Static
Discharge (ESD) techniques are required when handling and installing the
MAXnet.

GETTING STARTED CONFIGURING COMMUNICATION
2-2 MAXnet User’s Manual
FIGURE 2-1
LED AND COMMUNICATION JUMPER SETTINGS
Ensure that J2 is set for RS-232 communication mode.
Connect a +5VDC, 1 Amp power source to the power connector at J5.
NOTE: +/- 12VDC is required only for servo operation.
Caution
When power is applied to the MAXnet and the firmware has booted, there should be two solid green
LEDs lit. The LED labeled D100 located by the J5 power connector indicates the FPGA successfully
configured. The LED labeled D3 on the opposite edge of the card from the J1 connector indicates a
successful boot of the firmware. If both of these LEDs are on solid, and all other LEDs are off, the
MAXnet is ready to communicate. With the MAXnet expansion board for 6 – 10 axes of motion the green
LED D1 next to the J5 power connector is lit when power is applied.
If the red LED labeled D101 located by the J5 power connector is
ON, this indicates a power problem. Check power supply and all
power connections.
MAXnet
ETHERNET
RS232
PWR
100-pin connector
J2
D5
D4
D3
D2
J2
1
2
3
4
5
6
7
8
Default setting
J2
1
2
3
4
5
6
7
8
RS232 setting
J2
1
2
3
4
5
6
7
8
Ethernet setting
D100
D101

CONFIGURING THE CARD FOR USE WITH ENCODERS GETTING STARTED
MAXnet User’s Manual 2-3
Using your communication terminal send the characters “WY” to the MAXnet (Windows Hyperterminal
program can be used). If communication and power are configured properly the MAXnet will respond in
ASCII with its model, version and serial number.
The default IP address of the MAXnet is 10.40.30.60 and the port is 23. To configure the MAXnet IP
address for use in your network, the IP and port addresses must be set with the appropriate commands
and the settings should be archived to flash. Use the #NI command to set the IP address and the #NP
command to set the network port number. Use the APP command to archive the settings to flash so that
these settings will be the default after each power-up. See Command Reference Manual: MAX Family for
further details on these commands.
Set J2 for Ethernet communication and cycle the power on the MAXnet. You may now connect an
Ethernet-capable terminal to the IP address previously programmed into the MAXnet. If the
communication interface is properly configured, sending the characters “WY” to the MAXnet will produce
the same model, version and serial number as it did in the prior RS-232 test. However, when using
Ethernet communications for each packet sent to the MAXnet controller, the controller responds with an
acknowledgement packet that contains data consisting of a single ACK character.
TABLE 2-2 ETHERNET CONNECTOR
J8 – Pin-out
Pin # Signal Function
1 BI_DA+ Bi-directional pair +A
2 BI_DA- Bi-directional pair –A
3 BI_DB+ Bi-directional pair +B
4 BI_DC+ Bi-directional pair +C
5 BI_DC- Bi-directional pair –C
6 BI_DB- Bi-directional pair –B
7 BI_DD+ Bi-directional pair +D
8 BI_DD- Bi-directional pair –D
TABLE 2-3 RS232 CONNECTOR
J6 – Pin-out
Pin # Signal Function
1 No Connect -
2 RXD Receive Data
3 TXD Transmit Data
4 No Connect -
5 Ground Ground
6 No Connect -
7 RTS Request to Send
8 CTS Clear to Send
9 No Connect -
2.3. CONFIGURING THE CARD FOR USE WITH
ENCODERS
Quadrature encoder with TTL level outputs can be connected directly to the appropriate axis (via the J2
connector on IOMAXnet). The MAXnet has biasing to allow single ended encoders for each axis on
board. This biasing is automatic. Single-ended encoders should be wired to the positive (+) connections
of each signal. The negative (-) side of the differential signal should be connected to ground.

GETTING STARTED CONFIGURING THE CARD FOR USE WITH ENCODERS
2-4 MAXnet User’s Manual
FIGURE 2-2 MAXNET DIAGRAM
FIGURE 2-3 CONNECTOR LOCATIONS
0.34
0.34
0.06" overhang
0.35
Tyco/Amp
5787169-9
J1
0.20
1.55
0.29
0.64
Tyco/Amp
5788797-2
J6
0.05" overhang
0.40
1.01
Bel-Stewart Connector
08B0-1X1T-36-F
J8
0.05" overhang
0.50
0.48
Molex
43045-0600
J5
0.35 Ethernet/Serial
3.05
All dimensions are in inches +/- 1%, unless otherwise specified
J9 - Expansion Connection
0.05
0.62
6.50in.
4.00
0.140
0.140
Ø 0.1255
0.140
Ø 0.1255
0.140 0.120
Ø 0.1255
0.120
Ø 0.1255
0.140
Ø 0.1255
Ø 0.1255
Ø 0.1255 0.140
3.125
Ø 0.1255
0.390
0.140
0.72
1.841.84
0.140
All dimensions are in inches +/-1%, unless otherwise specified
2.12

CONFIGURING THE CARD FOR USE WITH ENCODERS GETTING STARTED
MAXnet User’s Manual 2-5
A
ll
d
im
e
n
s
i
o
n
s
a
r
e
in in
c
h
es
+
/
-1
%,
u
nl
ess
2.12”
0.72”
1.84
” 1.84”
0.120”
0.390”
0.140
”
0.140”
A
ll hole diameters are 0.1
3.125”
0.120”
0.140”
0.140
”
0.140”
0.140” 0.140”
0.140”
6.50”
4.00
”
FIGURE 2-4 MAXNET EXPANSION BOARD DIAGRAM
FIGURE 2-5 MAXNET EXPANSION BOARD CONNECTOR LOCATIONS
0.48”
0.05” overhang
0.50”
3.05”
0.62”
0.05”
0.34”
0.05” overhan
g
0.34”
0.35”
0.25”
J1
A
ll dimensions are in inches +/- 1% unless
6.5”
4.0”
J
J4 - Expansion Connection
Molex
4305-0600
Tyco/Amp
5787169-9

GETTING STARTED CONNECT TO STEPPER MOTOR SYSTEM
2-6 MAXnet User’s Manual
2.4. SOFTWARE INSTALLATION
OMS provides Windows DLL’s. For other operating systems please contact OMS Motion, Inc., refer to
Appendix B.
For Windows NT, XP & 2000
After applying power and communication connections to the MAXnet controller, apply
power to the host PC and insert the software support disk or CD-ROM supplied by OMS or
download the software from the OMS website (http://www.omsmotion.com/). Follow the
installation instructions found in README.TXT or README.DOC. The instructions will
show you how to properly install the appropriate DLL.
To begin communicating with the MAXnet, systems that require console application can
run the MAXnEcom.exe (Ethernet) or MAXnScom.exe (RS-232) utility. Systems that prefer
GUI applications can run OMSuite.exe. You can begin interactively sending commands
and receiving responses immediately if all has been properly installed. If the board has
been configured with something other than the default communication parameters, then
the appropriate command line switches need to be entered along with the command. For
example:
MAXnEcom /I:<IP Address> /P:<port number>
or
MAXnScom /b:<baud rate> /P:<comm port>
or
OMSuite.exe
(Select the communication parameters from the “Boards” drop-down menu.)
Type WY and observe the response from the MAXnet. If you are communicating to the MAXnet it would
return its version number, number of axes, FPGA version number, etc. You should receive a reply similar
to “MAXn-5000, Ver: x.xx, S/N: 000001, FPGA:20” from the MAXnet. If you receive nothing, double
check that the MAXnet communication and power cables are firmly seated and that communications have
been properly configured (see Section 2.2). For technical support, refer to Appendix B for contact
information.
2.5. CONNECT TO STEPPER MOTOR SYSTEM
The MAXnet control signals are located on the J1 connector. This section will explain how to connect a
stepper motor driver to the controller board.
Begin this procedure with a MAXnet controller board connected to your system. Be sure that
communication to the board has been established. This can be checked by issuing a WY command to
the board and verifying that the board responds with its model type and revision levels (i.e. MAXnet-4000
ver 1.00 S/N 0000).
NOTE: Reference section 2.4 SOFTWARE INSTALLATION
Once communication has been established with the controller, shut down the system and turn power off
to the controller board.
NOTE: It is not recommended to continue with the hardware connection if communication has
not been established.

CONNECT TO STEPPER MOTOR SYSTEM GETTING STARTED
MAXnet User’s Manual 2-7
Connect the motor phase signals from the motor to the stepper driver output signals. Use the motor and
stepper driver manufacturer’s manuals for instructions.
Now, connect the controller signals from J1 of the MAXnet, or from IOMAXnet, if it is used, to the stepper
driver. Short cable lengths and shielded cables are recommended for improved signal integrity and
reduction in signal noise.
NOTE: Using the IOMAXnet interface module is strongly recommended as it provides an easy
way to connect to the 100-pin connector (J1) on the MAXnet.
If you are using the IOMAXnet, connect the IOMAXnet to the MAXnet using a shielded 100-pin cable
From the terminal block on the IOMAXnet connect the appropriate wires to your motor drivers and system
I/O.
Attach the STEP outputs from the controller to the STEP inputs on the stepper driver. Do the same for
DIR signals.
Next, connect an external power supply (which is OFF) to the stepper driver. Again, refer to the
manufacturer’s manual for instructions. (Note that power supply requirements differ from driver to driver.)
Once all wire connections have been made, power can be restored to your system. It is recommended
that you bring the controller board up first (so it is in a known state), and then apply power to the stepper
driver.
Refer to Figure 2.6 for an example wiring diagram of OMS’ MAXnet connected to a stepper driver on the
X axis.
Using your communication terminal connected to the MAXnet to send a “JG100;” command. The X axis
motor should step at a rate of 100 steps per second.
Figure 2-6
Example of Wiring Diagram of MAXnet Controller Connected to a Stepper Driver / Motor
MAXnet
J1
DRIVER MOTOR
GROUND
GROUND
5V
DIRECTION
STEP
AUXILIARY
PHA-
AUXILIARY INPUT
PULSE
DIRECTION
Vi
PHB-
PHB+
PHA+
PHA-
PHB-
PHB+
PHA+
+24 Vdc

GETTING STARTED CONNECT AND CHECKOUT THE SERVO SYSTEM
2-8 MAXnet User’s Manual
Figure 2-7
Example of Wiring Diagram of MAXnet Controller via the IOMAXnet Interface Module
Figure 2-8
Example of Wiring Diagram of MAXnet Controller via the IOMAXnet Interface Module to Servo Motor
MAXnet
J1
IOMAXnet
TERMINAL BLOCK
DRIVER MOTOR
GROUND
GROUND
5V
DIRECTION
STEP
AUXILIARY
PHA-
AUXILIARY INPUT
PULSE
DIRECTION
Vi
PHB-
PHB+
PHA+
PHA-
PHB-
PHB+
PHA+
+24 Vdc
MAXnet
J1
IOMAXnet
TERMINAL BLOCK
DC SERVO AMPLIFIER
SERVO MOTOR
ENCODER
X SERVO
Analog Ground
Analog Input
Ground
Ground
5V
X PHASE +A
X PHASE -A
X PHASE +B
X PHASE -B
X INDEX +
X INDEX -
SEE MANUFACTURER
DOCUMENTATION

CONNECT AND CHECKOUT THE SERVO SYSTEM GETTING STARTED
MAXnet User’s Manual 2-9
2.6. CONNECT AND CHECKOUT THE SERVO
SYSTEM
Servo systems tend not to respond gracefully to connection errors. You can reduce the chance of making
connection errors by following a step-by-step procedure:
Caution
2.7. CONNECT AND CONFIGURE THE
MOTOR/AMPLIFIER
1) Connect and configure your amplifier per the manufacturer’s instructions for “Torque” or “Open-
Loop” mode.
2) With the motor and amplifier power turned off, connect the MAXnet to the amplifier.
3) Balance your motor:
a) Configure the axis as a servo axis by sending the “PSM” command.
b) Using a voltage meter, verify that the command signal from the MAXnet is less than 500mV.
If it is not, send the command “KO0;” to the MAXnet and recheck the voltage. If the voltage is
still too high, contact OMS Motion, Inc.’s Technical Support department for guidance.
c) Turn on power to the amplifier and then to the motor.
d) Adjust the balance setting of your amplifier (if equipped) until the motor stops moving.
e) If the motor continues to revolve or your amplifier has no balance adjustment:
i) Send the command “KO100;” to the MAXnet.
ii) If the motor spins faster, reduce the command parameter and resend the command, e.g.
“KO50;”
iii) If the motor spins slower but does not stop, increase the command parameter and resend
the command, e.g. “KO150;”
iv) Continue adjusting and resending the KO command until the motor comes to rest. Write
down the final KO value for later reference as your “zero” setting.
4) Maximize your system’s usage of the MAXnet’s DAC (this method works only with incremental
encoders, skip it if you use absolute encoder only on that axis):
a) Connect the servo encoder to the MAXnet. (See section 4.4 on incremental encoder
feedback)
The servo motor may jump or spin at a very high velocity during connection
and configuration. The motor should be restrained by some means before
beginning this procedure. Keep hands and clothing clear of the motor and
any mechanical assemblies while performing this procedure.
It is recommended that the motor shaft not be connected to the physical
system until you are sure you have control over the motor.

GETTING STARTED TUNE THE SYSTEM
2-10 MAXnet User’s Manual
b) Set the signal/command gain of your amplifier to its minimum setting.
c) Send the “KO3277;” command to the MAXnet and observe the velocity of the motor. The
output of MAXnet will be near 1VDC.
d) If the motor does not move at all, your amplifier does not work well at a low velocity. In this
case, adjust the signal/command gain of the amplifier to approximately 20% of maximum or
until the motor begins to move.
e) Using a frequency meter, measure the pulse rate of Phase A of the encoder. The frequency
measured is ¼ of the actual pulse rate.
f) Adjust the signal/command gain of the amplifier until the pulse rate of Phase A is
approximately 10% of your desired peak operational velocity. If the pulse rate is already
greater than 10% of peak, your amplifier is not designed for low velocity motion and you will
likely have some difficulty tuning your motors.
g) Send the “KO-3277;” command to the MAXnet and recheck the velocity. You may need to
readjust your amplifier. If so, do not reduce the signal/command gain – only increase the
setting as needed. Increasing the gain will not impair the forward peak velocity but reduction
will.
h) Send the KO command with the “zero” value to the MAXnet.
5) Verify the direction of your servo encoder:
a) Send the “LP0; KO2000;” command to the MAXnet.
b) Send the “RE;” command to the MAXnet and observe the response.
c) If the response is positive, no further action need be taken; go to step 6.
i) If the response is negative, your encoder or analog output must be reversed use one of
the methods below.
ii) Use EDI/EDN to invert/normalize encoder direction or
iii) Use SVP-/SVP+ to invert/normalize PID analog output (inverts values of KO and KOD) or
iv) if your incremental encoder produces a differential signal, swap Phase B+ with Phase B-
and repeat from step (a.) above.
v) If your incremental encoder produces a single-ended (or TTL) signal, swap Phase A with
Phase B and repeat from step (a.) above.
d) If the RE response is still negative, contact OMS Technical Support for assistance.
6) Repeat from step 1 for the other servo axes.
7) Remember to set KO for each axis at every power-up unless you store the values in Flash.
NOTE: Most encoder problems are caused by lack of power or incorrect connections. If the encoder
position changes by only 1 count, this is an indication that one of the phases is not connected.
Do not proceed until you perform all the steps in this procedure, ensure that the outputs of the MAXnet
are as described, and ensure that the encoder is operating correctly.
Do not proceed until you perform all the steps in this procedure, ensure that the outputs of the MAXnet
are as described, and ensure that the encoder is operating correctly.

TUNE THE SYSTEM GETTING STARTED
MAXnet User’s Manual 2-11
2.8. TUNE THE SYSTEM
2.8.1. INTRODUCTION
The following is an introduction to the basics of tuning a servo motor. Tuning a servo system is the
process of balancing three primary gain values Proportional, Integral, and Derivative in order to achieve
optimum system performance.
In a closed loop system, an error signal is derived from the command position and actual position,
amplified, and then supplied to the motor to correct any error. If a system is to compensate for infinitely
small errors, the gain of the amplifier needs to be infinite. Real world amplifiers do not possess infinite
gain; therefore, there is some minimal error which cannot be corrected.
The three primary gain values used in servo systems are P (proportional), I (integral) and D(derivative).
The "P" term is used as a straight gain factor to get the system response "in the ballpark." The "I" term
defines how quickly the system will respond to change. The "D" term is a dampening term. This term
defines how quickly the system settles at its desired position without oscillating.
The effects of these parameters can be seen when looking at the system’s response to a step change at
the input. The shape of the step response falls into one of three categories: under damped, critically
damped or over damped. Over damped systems are slow to reach their final value and produce little or
no oscillation. Critically damped systems reach final value quickly, without overshoot. Under damped
systems reach final value quickly, but have various degrees of “ringing” or oscillation, that decay to zero
over time. Ideally, a system should be critically damped, allowing for the fastest response time with the
least amount of oscillation.
2.8.2. TUNING ASSISTANT
MAXTune.exe is a tuning assistant utility that is provided to assist the user in finding the right combination
of parameters. This utility plots the motor’s response. The user can analyze this data to arrive at the
right servo parameters for their servo system. The application and documentation can be found on the
CD-ROM supplied with the MAXnet and on OMS’ web site found at www.omsmotion.com.
2.8.3. MANUAL TUNING
In most motion control applications the optimum tuning of the servo system is achieved through a manual
tuning process. Auto-tuning algorithms typically can only get the system parameters close and require
manual steps to fine tune the parameters. An empirical trial and error approach will be discussed first.
There are some system parameters that need to be determined before attempting to tune a motor. The
encoder resolution (counts per revolution) is one element to be determined. Another is the system's
maximum velocity. Note that a motor should never exceed 90% of the motor’s maximum rate rpm. If the
system requirement is for a velocity higher than 90% of the motors top rpm, then another motor with
higher rpm capability should be used.
The system’s maximum acceleration is determined several different ways. The best method is to
determine the system time constant, which includes “hitting” or “bumping” the motor under system load
and measuring the time from 0 rpm to maximum rpm and divide this value by 5. The maximum
acceleration is either 2.5 times this value or is based on the system requirements for handling the load as
defined in the operating specifications of the system. This value is always lower than the calculated value
and if this acceleration value is not high enough then a different motor/amplifier with more power or
bandwidth should be utilized.
The MAXnet can control either current mode or voltage mode amplifiers. The servo update rate of the
MAXnet is user selectable: 976.6s, 488.3s, 244.1s, 122.1s. High "Following Error" can be

GETTING STARTED TUNE THE SYSTEM
2-12 MAXnet User’s Manual
compensated for using the feedforward coefficients explained later in this section. There are some
general formulas that have been developed to determine acceptable “Following Error” for both current
and velocity mode systems:
Current mode "Following Error" for:
KP = (3/360) (counts per revolution)
Voltage mode "Following Error" for:
KP = (90/360) (counts per revolution)
It is obvious that the voltage mode allows for much greater “Following Errors” than the current mode.
This value is the “Following Error” when the motor is at peak velocity and will be used when determining
the proportional gain (KP).
The "Following Error" for the integral term (KI) or long-term gain value will follow the guidelines below:
Current Mode “Following Error” for:
KI = 0 counts
Voltage Mode “Following Error” for:
KI = 80of 360(expressed in motor counts)
While still in open-loop mode (CL0;) use the KO command to zero the motor. This variable is used to
provide a constant output that will compensate for torque offset from the load. So, when the system
should be stationary, the necessary voltage will be sent to the amplifier to cause the motor to maintain
position. With the correct KO value, the motor should successfully maintain a zero position.
KO is the offset coefficient used while in closed-loop or open loop mode, hold on (HN). You should have
determined the correct value the KO variable before beginning to tune the PID filter.
The values for KO range from –32640 to 32640.
Set the known values for velocity, acceleration and the move distance for a trapezoidal profile with at
least a 20% flat spot at peak velocity. Formula:
Profile distance = ((peak velocity)^2/(2acceleration))2.4
Example: ((50,000)^2/(2500,000))2.4 = 6,000
Execute the move by sending the move commands to the MAXnet.
Example: MR6000;
GO;
Adjust the KP term while repeating step 3 until the “Following Error” at the flat spot of the profile is
acceptable. If the motor becomes unstable prior to obtaining the optimum KP term, then increase the
KD term until the motor stabilizes.
Example: LP0;
KP3;
CL1;
MR6000;
GO;
LP0;
KP10;

TUNE THE SYSTEM GETTING STARTED
MAXnet User’s Manual 2-13
CL1;
MR6000;
GO;
LP0;
KP25;
HN;
MR6000;
GO;
LP0;
KD100;
CL1;
LP0;
KP35;
CL1;
MR6000;
GO;
LP0;
KD125;
CL1;
The values in the above example are totally arbitrary and may vary drastically with different systems. The
LP0 command is used to set the position error to 0.
The values for KP range from 10-500.
Once the KP term has been obtained, continue executing the motion while rising the KI term until the
long-term “Following Error” is acceptable. This error can be measured at the two knees of the motion
profile. Increasing the KI term, increases the response time of your system. The motion profile
should also have a steeper slope as KI increases. (See Figure 2-9 and 2-10 below.)
However, as KI increases the system can also become unstable. When the instability becomes
unacceptable increase the 2KD parameter. This will increase the dampening on the system’s
motion profile (therefore reducing oscillation or “ringing”.) Continue adjusting the KI and 2KD
terms until the proper response time is obtained.
The values for KI range from 0.1 to 20.
FIGURE 2-09
If you are getting too much “ringing” in the motion profile, then increase KD to help dampen the
system’s response. If, instead, the system is over-damped and is reaching the final velocity too
Desired Step Response
Too Little KI

GETTING STARTED TUNE THE SYSTEM
2-14 MAXnet User’s Manual
slowly, then reduce the KD parameter. Optimally, the system’s motion profile should show the motor
reaching the desired velocity as quickly as possible without overshoot and oscillation (“ringing”).
The values for KD range from 10-100.
FIGURE 2-10
FIGURE 2-11
KP, KI, and KD are the primary parameters of concern when tuning a servo system. Once the
optimum values for these variables have been determined, you can adjust some of the secondary
parameters that will help fine tune your system’s performance. These other variables are described in the
subsequent steps.
The KV variable is used when tuning velocity controlled servos (voltage mode servo amplifiers.) This
is the velocity feedforward coefficient. KV determines how closely the system follows the desired
constant velocity portion of the motion profile. By increasing this term, the "Following Error" of the
system’s response can be minimized. However, too large of a value may result in unstable behavior
after command velocity changes.
The values for KV range from 0 to 249.99.
Desired Step Response
Too Much KD
Desired Step Response
Too Little KD