Omron R88D-UA User manual

About this Manual:
This guide describes the installation and startup procedures of the Servo System so that it can
be efficiently put in actual operation in a short time.
This guide provides detailed descriptions of key points for efficiently starting up the Servo Sys-
tem as follows:
•Check the wiring by efficiently using the monitor function.
•Perform gain adjustments properly.
•Find the causes of alarms quickly and take the appropriate countermeasures.
•Take appropriate countermeasures for position deviation that might be caused by
noise.
This guide applies to the following OMRON products:
•OMNUC U Series
•OMNUC H Series
•OMNUC M Series
•OMNUC R Series
It is recommended that the following manuals be referred to when actually performing the work.
Item Catalog No. Model
OMNUC U Series I501 R88D-UA Analog Input with Power Supply
I502 R88D-UP Pulse-train Input with Power Supply
OMNUC H Series I508 R88D-HT/HS
OMNUC M Series I511 R88D-MT
OMNUC R Series I503 R88D-RA Analog Input with Power Supply
I505 R88D-RP Pulse-train Input with Power Supply
I504 R88D-RB Analog Input without Power Supply
I506 R88D-RR Pulse-train Input without Power Supply
Finally, please read this guide carefully and be sure you understand the information provided
before attempting to install and startup the Servo System. The guide includes the sections de-
scribed below.
Chapter 1 provides a summary of the Servo System and all gains used for the Servo System
loops.
Chapter 2 describes wiring checks, possible system startup errors, and countermeasures
against position deviation when constructing the Servo System.
Chapter 3 describes the probable causes of Servo Driver alarms that may occur and the counter-
measures required to deal with them.
Chapter 4 describes the types and generation of noise and provides countermeasures against
noise.
The Appendix provides an example of the configuration of the Servo Driver’s main circuitry.
WARNING Failure to read and understand the information provided in this manual may
result in personal injury or death, damage to the product, or product failure.
Please read each section in its entirety and be sure you understand the
information provided in the section and related sections before attempting any of
the procedures or operations given.
!

OMRON, 1997
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted,
in any form, or by any means, mechanical, electronic, photocopying, recording, or otherwise, without the prior
written permission of OMRON.
No patent liability is assumed with respect to the use of the information contained herein. Moreover, because
OMRON is constantly striving to improve its high-quality products, the information contained in this manual
is subject to change without notice. Every precaution has been taken in the preparation of this manual. Never-
theless, OMRON assumes no responsibility for errors or omissions. Neither is any liability assumed for dam-
ages resulting from the use of the information contained in this publication.

TECHNICAL GUIDE
Servo System
Startup
Cat. No. I801-E1-1

Table of Contents
Chapter 1. Gain Adjustment 1-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-1 Types and Meanings of Gain 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-1-1 Summary of Servo System 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-1-2 Gain 1-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-1-3 Types of Gains 1-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-2 Gain Adjustment 1-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-2-1 Gain Adjustment Procedure 1-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-2-2 Relationship between Gain Adjustment and Response 1-5. . . . . . . . . . . . . . . . . . . . . . . .
1-3 Special Adjustment Parameters 1-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 2. Connection to Position Control Unit 2-1. . . . . . . . . . . . . . . . .
2-1 Wiring Check 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2-1-1 Wiring Check with I/O Monitor 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2-1-2 Wiring Check without I/O Monitor 2-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2-2 System Startup Errors 2-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2-3 Countermeasures Against Position Deviation 2-9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 3. Servo Driver Errors 3-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3-1 Alarms and Countermeasures 3-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 4. Countermeasures Against Noise 4-1. . . . . . . . . . . . . . . . . . . . .
4-1 Generation and Types of Noise 4-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-1-1 Noise 4-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-1-2 Types of Noise 4-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-1-3 Noise Transmission Paths 4-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-2 Noise Suppression 4-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-2-1 Countermeasures 4-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-2-2 Practical Noise Suppression 4-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-2-3 Other Countermeasures 4-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-2-4 Noise Suppression Example 4-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 5. Appendix 5-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5-1 Configuration of Main Circuitry 5-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Revision History R-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chapter 1
Gain Adjustment
1-1 Types and Meanings of Gain
1-2 Gain Adjustment
1-3 Special Adjustment Parameters
1
.

1-2
1-1 Types and Meanings of Gain
The word “gain” appears frequently in this technical guide. The gain is one of the indis-
pensable parameters of the Servo System. If the gain adjustment of the Servo System is
insufficient, the operation of the Servo System will be unsatisfactory, in which case the
Servo System will cause machinery vibration and an alarm will result. A summary of the
Servo System and all gains used for the Servo System loops are described below.
1-1-1 Summary of Servo System
The Servo System uses feedback loops. In a feedback loop, the response value is fed back after the
command so that the difference between the response and command values will be as close as pos-
sible to zero. The Servo System consists of three feedback loops (i.e., position loop, speed loop, and
current loop). Refer to the following block diagram.
Position Loop
•The position loop is used to let the rotation angle of the motor reach the desired position (i.e., the de-
sired rotation angle) that was externally designated.
•The speed command is output from the position loop to the speed loop.
•The position loop feeds back the position data (i.e., the information on rotation angle) of the encoder or
resolver.
Speed Loop
•The speed loop is used to let the motor rotate at the speed designated by the external analog speed
command or the speed command that is output from the position loop.
•The current command is output from the speed loop to the current loop.
•The speed loop feeds back the speed data of the encoder or resolver.
Current Loop
•The current loop provides the motor with the current designated by the current command that is output
from the speed loop.
•The current loop feeds back the motor current value.
The gain is a parameter to adjust the response speed of a feedback loop.
Gain Adjustment Chapter 1

1-3
Configuration Example of Servo System
Command pulses
(Position command) Deviation counter
Position gain Speed gain Current gain
Motor
Current feedback
Speed feedback
Speed detection
Feedback pulse (position feedback)
Encoder
or resolver
Position Control Unit with analog output
Position Control Unit with
pulse-train output
Servo Driver with analog input
Servo Driver with pulse-train input
Servomotor
1-1-2 Gain
The gain is another word for magnification.
The difference between the command and response values in a feedback loop is multiplied by the gain
and the result is output from the feedback loop. The difference between the target position and present
position in the position loop, for example, is obtained as a position deviation or deviation counter value.
The value multiplied by the position loop proportional gain is output as a speed command.
In the actual Servo System, the target position is expressed by command pulses and the present posi-
tion is expressed by feedback pulses, both from which the position deviation per time unit is calculated.
The deviation counter totals all the per-time-unit position deviations to obtain the position deviation of
the Servo System.
Target
position
(Position
command)
Position deviation
x Position loop proportional gain
(Position gain: Kp)
Present position
Speed
command
to speed
loop
The higher the gain of any feedback loop is, the higher the output of the feedback loop is. In other words,
if the gain increases, the output power to fix the deviation will increase. The Servo System with high
gains is ideal because the gains ensure a high response speed and reduce errors. If the gains are too
high, however, the Servo System will cause machine vibration according to the size and rigidity of the
machine system. The Servo System, therefore, requires gain adjustment according to the machine sys-
tem.
Note Rigidity indicates the engagement strength of the machine system. The backlash or spring por-
tion of a machine system reduces the rigidity of the machine system.
Gain Adjustment Chapter 1

1-4
1-1-3 Types of Gains
The following table describes gains and adjustment parameters that will improve the response charac-
teristics of the Servo System.
Gain and adjustment
parameter Function Parameter name for each series
Current loop command
filter The current (torque) response speed will change by adjusting this gain.
Adjust this gain if the Servo System
does not stop causing machine
vibration after other gains are adjusted.
There is no need to adjust this gain in
normal operation.
U: Torque command filter time constant
H: ---
M: Current command filter time
constant
R: High-range filter frequency selection
(Only for models with independent
power supplies)
Speed loop proportional
gain The response characteristics of the Servo System in accelerating or
decelerating operation will change by
adjusting this gain.
Adjust this gain to suppress the
overshooting or undershooting of the
Servo System and improve the
response characteristics of the Servo
System.
U: Speed loop gain
H: Speed loop proportional gain
M: Inertia ratio
R: AC gain (See note 1)
Speed loop integral gain The response characteristics of the
Servo System in slow operation will
change by adjusting this gain.
Use this gain to adjust the servo-lock
strength of the Servo System.
U: Speed loop integral time constant
(See note 2)
H: Speed loop integral gain
M: Speed gain
R: AC gain
Position loop
proportional gain The positioning time of the Servo System will change by adjusting this
gain.
Adjust this gain to suppress the
overshooting or undershooting of the
Servo System and minimize the
positioning time.
U: Position loop gain
H: Position loop proportional gain
M: Position gain
R: Loop gain
(Only for models with pulse-train input)
Note 1. The AC gain of the R Series varies the speed loop proportional gain and speed loop integral
gain simultaneously. For details, refer to 1-3 Special Adjustment Parameters.
Note 2. The integral gain of the speed loop of the U Series is adjusted with the speed loop integral time
constant. (Speed loop integral gain ∝1/Speed loop integral time constant)
Gain Adjustment Chapter 1

1-5
1-2 Gain Adjustment
Gain adjustment is indispensable to the functionality of the Servo System. If the gain
adjustment of the Servo System is insufficient, the performance of the Servo System will
be unsatisfactory and the Servo System will therefore cause machine vibration or not
ensure precise positioning. Adjust the current loop, speed loop, and position loop gains
of the Servo System in this order. The current loop is, however, adjusted before ship-
ping. The user, therefore, need not adjust any parameter of the current loop.
1-2-1 Gain Adjustment Procedure
The following describes the gain adjustment procedure for the Servo System.
1. Speed Loop Adjustment
SSpeed loop proportional gain
SSpeed loop integral gain (Speed loop integral time constant)
SCurrent loop command filter
Basic adjustments of the Servo System are possible with the proportional and integral gains only, in
which case however, the machine system may not stop vibrating or may have a slow positioning
operation due to insufficient gains. If the machine system has a slow positioning operation or does
not stop vibrating, adjust the filter time constant of the current loop.
2. Position Loop Adjustment
SPosition loop proportional gain
This gain adjustment is required only for pulse-train input and is irrelevant to analog input.
1-2-2 Relationship between Gain Adjustment and Response
HSpeed Loop Adjustment
The following graph indicates how the response characteristics (i.e., the frequency characteristics) of
the Servo System will vary with changes in the speed loop gain and adjustment parameter value.
Compensating force
Strong
Weak
Speed loop integral gain
(Changes the strength
in low frequencies.)
Speed loop proportional gain
(Changes the total strength.)
Slow action Frequency (Operating speed)
Current command filter
(Changes the strength
in high frequencies.)
Quick action
In the above graph, the X axis indicates frequency (movement speed) and the Y axis indicates compen-
sating force for reducing the difference between the response and command as much as possible.
Gain Adjustment Chapter 1

1-6
DSpeed Loop Proportional Gain
•The response characteristics of the Servo System in all frequency bands change by adjusting this
gain.
•The compensating force and response characteristics rise if the gain increases.
•Increase the gain as much as possible provided that the adjusted gain does not cause machinery
vibration.
DSpeed Loop Integral Gain
•The response characteristics of the Servo System in low frequencies change by adjusting this gain.
•The servo-lock force rises if the gain increases.
•Increase the gain as much as possible provided that the adjusted gain does not cause machine vibra-
tion.
In the case of the U Series, decrease the value of the speed loop integral time constant.
DCurrent Command Filter
•The response characteristics of the Servo System in high frequencies change by adjusting this gain.
•If the value of the filter time constant is large, command changes will be made less extreme and will
then be provided to the current loop.
•The adjustment of the current comment filter will be effective if machinery vibration does not stop with
the adjustment of the speed loop proportional gain and integral gain.
Adjustment Example 1
•Refer to the following for the normal adjustment of the Servo System that will not require any adjust-
ment of the current command filter to stop machine vibration (i.e., the current command filter is used
with factory settings).
•Adjust the proportional gain first, and then the integral gain.
Before Adjustment
Machine resonance point
Frequency (operating speed)
After adjustment
Increase the integral gain pro-
vided that the adjusted gain does
not cause machine vibration.
Increase the proportional gain
provided that the adjusted gain
does not cause machine vibration.
Frequency (operating speed)
Compensating force
Compensating force
Gain Adjustment Chapter 1

1-7
Adjustment Example 2
•Refer to the following for the adjustment of the Servo System that has a strong machine resonance
point in a high-frequency band. In this condition, the motor may continue buzzing or vibrate at high
frequency if the gains are low.
•Adjust the current command filter time constant, proportional gain, and integral gain in this order. The
resonance of the Servo System with the machine system can be avoided by increasing the value of the
current command filter time constant. Then adjust the other gains in the usual way.
Before Adjustment
Frequency (operating speed)
After adjustment
Frequency (operating speed)
Compensating force
Compensating force
Strong machine resonance point
Vibrates at this point Stops vibrating
Strong machine resonance point
Adjust the current command filter by increasing the
value of the current command filter time constant.
Adjustment Example 3
•Refer to the following for the adjustment of the Servo System that has a strong machine resonance
point in a low-frequency band. In this condition, the motor may vibrate at low frequency if the gains are
low.
•Adjust the proportional gain and then integral gain. To avoid the resonance of the Servo System with
the machine system, decrease the value of the proportional gain. Then adjust the integral gain so that
the Servo System can maintain necessary response speed.
Before Adjustment
Frequency (Operating speed)
After adjustment
Frequency (Operating speed)
Compensating force
Compensating force
Strong machinery resonance point
Vibrates at this point Stops vibrating
Strong machinery resonance point

Increase
the integral
gain provided
that the adjusted
gain does not cause
machine vibration.
Decrease the proportion-
al gain provided that the
adjusted gain does not
cause machine vibration.
Response Speed Change vs. Speed Loop Adjustment
The following graph indicates how the response characteristics of the Servo System will vary with the
changes in the speed loop gain and adjustment parameter value.
Gain Adjustment Chapter 1

1-8
Speed Loop Proportional Gain vs. Response Characteristics
Motor
speed Speed loop proportional gain is high.
(Machine vibration will result if gain is too high.)
Speed loop proportional gain is low.
Time
Speed Loop Integral Gain vs. Response Characteristics
Motor
speed
Time
Speed loop integral gain is high.
(Integral time constant value is small.)
Speed loop integral gain is low.
(Integral time constant value is large.)
HPosition Loop Adjustment
•Adjust the position loop after adjusting the speed loop.
•Good response characteristics are obtained by increasing the position loop proportional gain provided
that the overshooting or undershooting of the Servo System does not result.
Position Loop Proportional Gain vs. Response Characteristics
Motor
speed
Time
Overshooting Position loop proportional gain is high.
Position loop proportional
gain is low. Undershooting
•Overshooting and undershooting can be easily checked by checking the output voltage of the NM ter-
minal with an oscilloscope.
Gain Adjustment Chapter 1

1-9
•If an oscilloscope is not available, visually inspect the operation of the motor shaft or machine system.
If there is undershooting, the shaft will perform positioning in the opposite direction of the rotating
direction before the shaft stops as shown in the following illustration.
Starts rotating Rotating Stop
The shaft makes a stop
in the opposite rotating
direction.
•The amount of overshooting or undershooting varies with the rotational speed of the motor. Usually,
the higher the rotational speed is, the greater the overshooting or undershooting is. Therefore, it is
recommended that the Servo System be adjusted for the top rotation speed.
Gain Adjustment Chapter 1

1-10
1-3 Special Adjustment Parameters
Gains and adjustment parameters for all OMRON Servo Drivers are described below.
The auto-tuning function incorporated by the U Series allows easy automatic gain ad-
justment according to the machine system.
HAuto-tuning Function (U Series)
•The auto-tuning function allows automatic gain adjustment according to the load while operating the
machine system.
•The ideal adjustment according to the rigidity of the machine system will be possible by just selecting
the response characteristics if the auto-tuning function is used. It is thus recommended that this func-
tion be used as much as possible.
•The auto-tuning function is available to all machine systems except the following, which may require
manual adjustment.
Machine systems with heavy friction
Machine system with low rigidity
HSemi-auto-tuning Function (H Series)
•The semi-auto-tuning function makes it possible to adjust the speed loop proportional gain and inte-
gral gain by just setting the load inertia ratio to the rotor inertia ratio of the motor.
•The most suitable gain according to the inertia ratio is preset as a table.
•Manual adjustment is required for machine systems with heavy friction or low rigidity.
•The position loop requires adjustment according to the machine system. The semi-auto-tuning func-
tion does not perform position loop adjustment.
HAC Gain (R Series)
•The AC gain is used to adjust the speed loop proportional gain and integral gain simultaneously.
•The ratio of the proportional gain to integral gain is fixed.
Compensating force
Change in Response Characteristics vs. AC Gain
Frequency (operating speed)
Gain Adjustment Chapter 1

1-11
HFeed-forward Function (U Series: Feed-forward Value; H Series:
Position Loop Feed-forward Gain)
•The feed-forward function is enabled at the time of pulse-train input.
•This function adds the frequency of pulse-train input to the speed loop.
•The command is output to the speed loop before position deviation pulses are accumulated, thus re-
ducing the deviation counter value and saving positioning time.
•Feed-forward adjustment will not be effective if the position loop gain and speed loop gain are too high.
Gain Adjustment Chapter 1

Chapter 2
Connection to Position
Control Unit
2-1 Wiring Check
2-2 System Startup Errors
2-3 Countermeasures Against Position Deviation
2

2-2
2-1 Wiring Check
Care must be taken for Position Control Unit and Servo Driver connection, which needs
a comparatively large number of wires. Be sure that all lines connecting the Position
Control Unit and Servo Driver are wired correctly. It will be difficult to find wiring mistakes
after completing the Servo System construction.
2-1-1 Wiring Check with I/O Monitor
•U, H, and M Series incorporate an I/O monitor function.
•Wiring mistakes can be easily found by using this function.
•The contents of I/O monitor vary with the Series. Refer to the respective operation manual.
I/O Monitor Example
SYSMAC Position Control Unit
OMNUC U-series
AC Servo Driver
Force-reset the
deviation counter.
Check the ON/OFF status of signals
in monitor mode (Un-06).
OMNUC U-series
AC Servomotor
Connection to Position Control Unit Chapter 2

2-3
2-1-2 Wiring Check without I/O Monitor
•If no I/O monitor is available, use a multimeter and check the voltage as shown in the following dia-
gram.
•There will be a voltage between the terminals if the output transistor is ON. The reading of the multime-
ter will be 0 V if the output transistor is OFF.
Output Power supply Input
Multimeter
Voltage is ON : Output transistor ON
0 V : Output transistor OFF
Connection to Position Control Unit Chapter 2

2-4
2-2 System Startup Errors
The Position Control Unit may malfunction due to incorrect wiring, setting, or sequence
when power is supplied to the Position Control Unit or while the Position Control Unit is
operating. Probable causes of system startup errors and countermeasures are de-
scribed below.
System Does Not Start
•The 3G2A5-NC111-EV1 in operation may not detect the startup signal, especially when the Unit is
mounted to the following:
•CV-series Backplane
•Slave Rack
Probable cause Item to check Countermeasure
The 3G2A5-NC111-EV1 could not
detect the startup signal because
the startup signal is ON for too
short a time.
•The startup signal is ON for a
single cycle time. •Extend the period in which the startup signal is ON so that the
3G2A5-NC111-EV1 can detect
the startup signal.
Note 1. The program cycle time of the CV-series PC is shorter than that of the C-series PC. The
3G2A5-NC111-EV1, therefore, may not detect the startup signal correctly if the startup signal
is ON for too short a time.
Note 2. The remote communications cycle time is different in timing from the program cycle time. The
startup signal, therefore, may not be detected in remote communications if the startup signal
is ON for too short a time.
Communications Errors Result
•The 3G2A5-NC111-EV1 Unit in operation may cause positioning data communications errors or may have
difficulty in reading data correctly, especially when the Unit is mounted to the following:
•CV-series Backplane
•Slave Rack
Probable cause Item to check Countermeasure
The communications cycle time
clock data is not being transmitted
to the 3G2A5-NC111-EV1
correctly.
•The communications cycle time
clock timing is shorter than the
remote communications cycle
time.
•The CV’s cycle time clock does
not suit the 3G2A5-NC111-EV1.
•Extend the cycle time clock’s ON
timing so that the
3G2A5-NC111-EV1 can detect
the communications cycle time
clock data.
•Create a clock by using the re-
turn signal from the Slave.
Connection to Position Control Unit Chapter 2