Beckhoff AX5000 Series Quick start guide

Dokumentation
AX5000 Tuning - Guide
1.0
2017-03-01
Version:
Date:

Table of content
AX5000 Tuning - Guide 3
Version: 1.0
Table of content
1 Foreword ...................................................................................................................................................4
1.1 Notes on the documentation........................................................................................................... 4
1.2 Documentation issue status............................................................................................................ 5
2 Safety..........................................................................................................................................................6
2.1 Safety instructions .......................................................................................................................... 6
3 Tuning Velocity Controller (Ziegler&Nichols).........................................................................................7
3.1 General Information ........................................................................................................................ 7
3.2 Preparation ..................................................................................................................................... 7
3.3 Determining the stability limit for Kp ............................................................................................... 8
3.4 Setting up TwinCAT Scope View.................................................................................................... 8
3.5 Starting the test movement............................................................................................................. 9
3.6 Evaluating the oscilloscope pattern .............................................................................................. 10
3.7 Reducing Kp ................................................................................................................................. 10
3.8 Determining Tn ............................................................................................................................. 10
4 Support and Service................................................................................................................................11

Foreword
AX5000 Tuning - Guide4 Version: 1.0
1 Foreword
1.1 Notes on the documentation
This description is only intended for the use of trained specialists in control and automation engineering who
are familiar with the applicable national standards.
It is essential that the documentation and the following notes and explanations are followed when installing
and commissioning the components.
It is the duty of the technical personnel to use the documentation published at the respective time of each
installation and commissioning.
The responsible staff must ensure that the application or use of the products described satisfy all the
requirements for safety, including all the relevant laws, regulations, guidelines and standards.
Disclaimer
The documentation has been prepared with care. The products described are, however, constantly under
development.
We reserve the right to revise and change the documentation at any time and without prior announcement.
No claims for the modification of products that have already been supplied may be made on the basis of the
data, diagrams and descriptions in this documentation.
Trademarks
Beckhoff®, TwinCAT®, EtherCAT®, Safety over EtherCAT®, TwinSAFE®, XFC® and XTS® are registered
trademarks of and licensed by Beckhoff Automation GmbH.
Other designations used in this publication may be trademarks whose use by third parties for their own
purposes could violate the rights of the owners.
Patent Pending
The EtherCAT Technology is covered, including but not limited to the following patent applications and
patents:
EP1590927, EP1789857, DE102004044764, DE102007017835
with corresponding applications or registrations in various other countries.
The TwinCAT Technology is covered, including but not limited to the following patent applications and
patents:
EP0851348, US6167425 with corresponding applications or registrations in various other countries.
EtherCAT® is registered trademark and patented technology, licensed by Beckhoff Automation GmbH,
Germany
Copyright
© Beckhoff Automation GmbH & Co. KG, Germany.
The reproduction, distribution and utilization of this document as well as the communication of its contents to
others without express authorization are prohibited.
Offenders will be held liable for the payment of damages. All rights reserved in the event of the grant of a
patent, utility model or design.

Foreword
AX5000 Tuning - Guide 5
Version: 1.0
1.2 Documentation issue status
Version Comment
1.0 First Edition
0.1 internal Version

Safety
AX5000 Tuning - Guide6 Version: 1.0
2 Safety
2.1 Safety instructions
Safety regulations
Please note the following safety instructions and explanations!
Product-specific safety instructions can be found on following pages or in the areas mounting, wiring,
commissioning etc.
Exclusion of liability
All the components are supplied in particular hardware and software configurations appropriate for the
application. Modifications to hardware or software configurations other than those described in the
documentation are not permitted, and nullify the liability of Beckhoff Automation GmbH & Co. KG.
Personnel qualification
This description is only intended for trained specialists in control, automation and drive engineering who are
familiar with the applicable national standards.
Description of symbols
In this documentation the following symbols are used with an accompanying safety instruction or note. The
safety instructions must be read carefully and followed without fail!
DANGER
Serious risk of injury!
Failure to follow the safety instructions associated with this symbol directly endangers the
life and health of persons.
WARNING
Risk of injury!
Failure to follow the safety instructions associated with this symbol endangers the life and
health of persons.
CAUTION
Personal injuries!
Failure to follow the safety instructions associated with this symbol can lead to injuries to
persons.
Attention
Damage to the environment or devices
Failure to follow the instructions associated with this symbol can lead to damage to the en-
vironment or equipment.
Note
Tip or pointer
This symbol indicates information that contributes to better understanding.

Tuning Velocity Controller (Ziegler&Nichols)
AX5000 Tuning - Guide 7
Version: 1.0
3 Tuning Velocity Controller (Ziegler&Nichols)
3.1 General Information
The main velocity controller parameters are the proportional gain Kp (S-0-0100) and the integral action time
Tn (S-0-0101).
On selection of the motor default values are set,
which enable the motor to be operated safely without
load.
During commissioning the two parameters should be
adjusted in order to find a good compromise between
drive responsiveness (controller bandwidth) and
noise generation.
The method described below initially determines the
stability limit of the control loop. The value
determined for the gain is then multiplied with a field-
proven factor, based on the rules of Ziegler and
Nichols, in order to obtain a stable control loop.
If the bandwidth of the control loop turns out to be inadequate for the application, other methods should be
used. A description of these methods would be beyond the scope of this documentation.
Attention
Nature and source of the danger
This does not apply to vertical axes that are subjected to a continuous force, since it would
cause the axis to drop. In order to minimize the influence of the integral controller, Tn
should be set to a large value, e.g. 100 ms. Be sure to test carefully!
3.2 Preparation
For the tuning process the axis must be able to move in both directions, without reaching the mechanical end
stops. For example, it should be pushed manually to the center of the travel path.
In most cases the AX5000 operates in mode "11:
Position control feedback 1". In order to eliminate the
influence of the position controller, Kv should be 0 for
the tuning process in the position controller. In
addition, Tn is set to 0 in the velocity controller.
Following-error monitoring should be disabled for the
NC axis or set to a large value so that it is not
triggered in the following tests.

Tuning Velocity Controller (Ziegler&Nichols)
AX5000 Tuning - Guide8 Version: 1.0
3.3 Determining the stability limit for Kp
To determine the stability limit, while the axis is active, Kp is increased in the velocity controller in small steps
until the axis starts to oscillate. Depending on the axis type and the environment in which the axis is
operated, it may be sufficient to determine the stability limit based on the noise generation. When Kp
reaches a critical value, many axes start "squeaking" audibly. In noisy environments and for axes for which
oscillation must be avoided, the TwinCAT "Scope View" oscilloscope should be used. The next chapter
describes the setup. If the oscilloscope is not used, you can skip the next chapter and continue reading at
"Starting the test movement [}9]".
3.4 Setting up TwinCAT Scope View
Use the function:
• File → Add → New project
to add a "TwinCAT Measurement" project of type
"Scope YT NC Project".
Right-click on the chart to add two axes, so that a
total of three axes are available.
Notice!
If you have a sufficiently large monitor, right-click on
the chart again and select "Stacked Axes" for a better
overview.
The axes are then shown one below the other. Add
the "Torque feedback value" (S-0-0084), the velocity
command value and the actual velocity value
(P-0-0504 and S-0-0040) to the AX5000 process
data.
In the process image of the EtherCAT master activate
the ADS server and the symbol generation facility.

Tuning Velocity Controller (Ziegler&Nichols)
AX5000 Tuning - Guide 9
Version: 1.0
Now reactivate the configuration.
Right-click on an axis in the oscilloscope and open the target
browser.
Select:
• the controller,
• the ADS port,
• the drive and the channel.
Use “drag and drop” to assign the signals to the oscilloscope
axes, as shown (picture below).
The signal scaling is not important for determining the stability
limit. To establish the relationship with the drive axis it may be
useful to enter the scaling factors in the property window of
the axis. The values can be taken from the "Scaling and NC
Parameters" window in the TC DriveManager.
If you start the recording now, the oscilloscope should not
issue an error message.
Nature and source of the danger!
If a German keyboard is used, the decimal symbol must be comma!
3.5 Starting the test movement
From "NC Functions" select the function "Velo Step
Sequence". To make the axis reverse, you have to
specify two velocities with different sign. Enter 1
second as "Idle time", for example, and a number of
cycles.
Attention
Nature and source of the danger
Since the position controller and the integral component of the velocity controller are not
active, the axis may drift into another positioning range during reversing.

Tuning Velocity Controller (Ziegler&Nichols)
AX5000 Tuning - Guide10 Version: 1.0
3.6 Evaluating the oscilloscope pattern
While the axis reverses, observe the behavior with the
oscilloscope. The following oscilloscope pattern shows the
velocity command value and actual velocity value in the upper
diagram and the current or torque ("torque feedback value") in
the lower diagram.
The red line is based on an increased value for Kp. The next
motion shows that an oscillation occurs, which continues for
the whole motion.
Depending on the mechanical system, the value that was
reached can be regarded as Kpcrit, or Kp can be increased
further, until the oscillation also shows up in the velocity
value. It will then also be more audible.
In the sample application with a ball screw, the oscillation in
the current signal starts at Kp = 0.22. Only a soft "squeaking"
can be heard, which is inaudible in a noisy environment.
At Kp = 0.25 the oscillation also shows up in the speed signal.
3.7 Reducing Kp
Based on the rules of Ziegler and Nichols, the correct value for Kp should be determined using the following
formula.
Kp = 0.45 x Kpcrit
In the example,
• Kp = 0.45 x 0.22 = 0.10 or
• Kp = 0.45 x 0.25 = 0.11
is the correct value.
3.8 Determining Tn
Tn determines the integral action time of the integral controller. The smaller Tn, the larger the gain of the
Integral controllers. The correct value for Tn is mainly dependent on the type of coupling between motor and
load. Many applications run satisfactorily with the default value Tn = 8 ms. At the Rigid coupling and if the
tracking error appears to be too large, Tn can e.g. up to 5 ms.
Attention
Value ranges from Tn!
Do not reduce Tn any further without using the TC ScopeView to ensure that the current or
speed actual value does not start to oscillate! Values ≤ 5 ms are not required in most appli-
cations. With elastic coupling between engine and load or even with long straps it may be
useful for Tn Values> 10 ms. Swinging of the axis is thereby prevented.