THORLABS KBD101 User manual

KBD101
K-Cube Brushless DC Servo
Driver
User Guide
Original Instructions

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Contents
Chapter 1 Safety ............................................................................................. 4
1.1 Safety Information .................................................................................. 4
1.2 General Warnings .................................................................................. 4
Chapter 2 Overview and Setup ..................................................................... 5
2.1 Introduction ............................................................................................. 5
2.2 APT PC Software Overview ................................................................... 7
2.2.1 Introduction......................................................................................................... 7
2.2.2 APTUser Utility ................................................................................................... 8
2.2.3 APT Config Utility ............................................................................................... 9
2.2.4 APT Server (ActiveX Controls) ........................................................................... 9
2.2.5 Software Upgrades ........................................................................................... 11
Chapter 3 Getting Started ............................................................................ 12
3.1 Installing APT Software ........................................................................ 12
3.2 Mechanical Installation ......................................................................... 13
3.2.1 Environmental Conditions ................................................................................ 13
3.2.2 Mounting Options ............................................................................................. 13
3.2.3 Using the Baseplate ......................................................................................... 14
3.3 Electrical Installation ............................................................................. 14
3.3.1 Rear Panel ....................................................................................................... 14
3.3.2 Front Panel ....................................................................................................... 15
3.4 Connect The Hardware ........................................................................ 16
Chapter 4 Standalone Operation ................................................................ 18
4.1 Introduction ........................................................................................... 18
4.2 Control Panel Buttons and Indicators .................................................. 18
4.2.1 Digital Display - Operating Mode ...................................................................... 19
4.3 Velocity Wheel Operation ..................................................................... 20
4.3.1 Homing ............................................................................................................. 20
4.3.2 Go to Position ................................................................................................... 20
4.3.3 Jogging ............................................................................................................. 20
4.3.4 Velocity Moves ................................................................................................. 21
4.4 Settings Menu ...................................................................................... 21
4.5 External Triggering ............................................................................... 29
4.5.1 Trigger In .......................................................................................................... 29
4.5.2 Trigger In Latency ............................................................................................ 29
4.5.3 Trigger Out ....................................................................................................... 30
4.5.4 Trigger Out Latency .......................................................................................... 30
Continued...

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Brushless DC Servo Driver K-Cube
Chapter 5 PC Operation - Tutorial ............................................................. 31
5.1 Introduction ........................................................................................... 31
5.2 Verifying Software Operation ................................................................ 32
5.2.1 Initial Setup ...................................................................................................... 32
5.3 Using the APT User Utility .................................................................... 33
5.4 Homing Motors ..................................................................................... 34
5.5 Moving to an Absolute Position ............................................................ 35
5.6 Changing Motor Parameters ................................................................ 36
5.7 Jogging ................................................................................................. 37
5.8 Graphical Control Of Motor Positions (Point and Move) ....................... 38
5.9 Loading Parameter Settings ................................................................. 39
5.10 Setting Move Sequences ...................................................................... 40
5.11 Creating a Simulated Configuration Using APT Config ........................ 43
Chapter 6 Software Reference .................................................................... 46
6.1 Introduction ........................................................................................... 46
6.2 GUI Panel ............................................................................................. 46
6.3 Settings Panel ...................................................................................... 48
6.3.1 Moves/Jogs tab ................................................................................................ 48
6.3.2 Stage/Axis tab .................................................................................................. 52
6.3.3 Advanced - Control Loop SettingsTab ............................................................. 55
6.3.4 Advanced - Misc. Tab ...................................................................................... 58
6.3.5 Panel/Triggering Tab ....................................................................................... 62
6.3.6 Triggering Latency ........................................................................................... 67
6.3.7 Rotation Stages Tab ......................................................................................... 68
6.4 Troubleshooting and Restoring Default Parameters ............................ 69
Appendices
Appendix A Rear Panel Connector Pinout Details .................................... 70
Appendix B Preventive Maintenance ......................................................... 71
Appendix C Specifications and Associated Parts .................................... 72
Appendix D Motor Control Method Summary ........................................... 73
Appendix E Regulatory ................................................................................ 77
Appendix F Thorlabs Worldwide Contacts ................................................ 80

4
Chapter 1 Safety
1.1 Safety Information
For the continuing safety of the operators of this equipment, and the protection of the
equipment itself, the operator should take note of the Warnings, Cautions and Notes
throughout this handbook and, where visible, on the product itself.
The following safety symbols may be used throughout the handbook and on the
equipment itself.
1.2 General Warnings
Shock Warning
Given when there is a risk of injury from electrical shock.
Warning
Given when there is a risk of injury to users.
Caution
Given when there is a risk of damage to the product.
Note
Clarification of an instruction or additional information.
Warnings
If this equipment is used in a manner not specified by the manufacturer, the
protection provided by the equipment may be impaired. In particular,
excessive moisture may impair operation.
Spillage of fluid, such as sample solutions, should be avoided. If spillage does
occur, clean up immediately using absorbant tissue. Do not allow spilled fluid
to enter the internal mechanism.
Caution
If your PC becomes unresponsive (e.g due to an operating system problem,
entering a sleep state condition, or screen saver operation) for a prolonged
period, this will interrupt communication between the APT Software and the
hardware, and a communications error may be generated. To minimize the
possibility of this happening it is strongly recommended that any such modes
that result in prolonged unresponsiveness be disabled before the APT
software is run. Please consult your system administrator or contact Thorlabs
technical support for more details.

5
Chapter 2 Overview and Setup
2.1 Introduction
The KBD101 Brushless DC Motor K-Cubes are ideal for motion control applications
demanding high speed (100s of mm/s) and high encoder resolution (<100 nm)
operation. These single channel drivers offer high-precision motion control in a wide
range of applications, and in particular when used along with our DDSM100 fast
translation stage where speeds of up to 500 mm/sec can be achieved. Designed
using latest digital and analog techniques and with high-bandwidth high-power servo
control circuitry, these new drivers are capable of driving a range of rotary and linear
brushless 3-phase DC motors of up to 2 Amp peak coil current.
Integrated into the apt family of products, it offers Thorlabs standard control and
programming interface, allowing easy integration into the customer’s own automated
motion control applications. These units are cable of being reprogrammed in-field,
allowing the option of upgrading the units with future firmware releases as soon as
new programming interfaces (such as microscopy standard command sets) are
added.
Fig. 2.1 K-Cube Brushless DC Servo Motor driver (KBD101)

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Chapter 2
Operation of the KBD101 brushless DC motor unit is fully configurable
(parameterized) with key settings (e.g. PID settings, min and max position values, and
joystick response) exposed through the associated graphical interface panels.
PID control loop values can be adjusted for a particular application, minimum and
maximum position values can be entered to suit different stages as required, and the
response of the key pad joystick can be adjusted for speed or precision. Moreover,
relative and absolute moves can be initiated with move profiles set using velocity
profile parameters. Similarly, home sequences have a full set of associated
parameters that can be adjusted for a particular stage or actuator. For simplicity of
operation, the apt™ software incorporates pre-configured settings for each of the
Thorlabs stages and actuators, while still exposing all parameters individually for use
with other DC motor driven systems.
For convenience and ease of use, adjustment of many key parameters is possible
through direct interaction with the graphical panel. For example a move to the next
position can be initiated by clicking directly on the position display and entering a new
value (see the tutorial in Chapter 5 for further details). Furthermore, all such settings
and parameters are also accessible through the ActiveX® programmable interfaces
for automated alignment sequences.
In the remainder of this handbook, the Tutorial section (Chapter 5) provides a good
initial understanding on using the unit, and the reference sections (Chapter 6) covers
all operating modes and parameters in detail.
2.2 Power Options
For power, a single way wall plug supply (KPS101) is also available for powering a
single K-Cube Driver.
As a further level of convenience when using the new K-Cube Controllers Thorlabs
also offers the 3-channel and 6-channel K-Cube Controller Hubs (KCH301 and
KCH601). These products have been designed specifically with multiple K-Cube
operation in mind in order to simplify issues such as cable management, power
supply routing, multiple USB device communications and different optical table
mounting scenarios.
The K-Cube Controller Hub comprises a slim base-plate type carrier with electrical
connections located on the upper surface to accept the K-Cubes.
Internally the Controller Hub contains a fully compliant USB 2.0 hub circuit to provide
communications for all K-Cubes – a single USB connection to the Controller Hub is
all that is required for PC control. The Controller Hub also provides power distribution
for the K-Cubes, requiring only a single power connection.

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Brushless DC Servo Driver K-Cube
2.3 APT PC Software Overview
2.3.1 Introduction
As a member of the APT range of controllers, the KBD101 Brushless DC motor driver
shares many of the associated software benefits. This includes USB connectivity
(allowing multiple units to be used together on a single PC), fully featured Graphical
User Interface (GUI) panels, and extensive software function libraries for custom
application development.
The APT software suite supplied with all APT controllers, including the KBD101
drivers, provides a flexible and powerful PC based control system both for users of
the equipment, and software programmers aiming to automate its operation.
For users, the APTUser (see Section 2.3.2.) and APTConfig (see Section 2.3.3.)
utilities allow full control of all settings and operating modes enabling complete ‘out-
of-box’ operation without the need to develop any further custom software. Both
utilities are built on top of a sophisticated, multi-threaded ActiveX ‘engine’ (called the
APT server) which provides all of the necessary APT system software services such
as generation of GUI panels, communications handling for multiple USB units, and
logging of all system activity to assist in hardware trouble shooting. It is this APT
server ‘engine’ that is used by software developers to allow the creation of advanced
automated positioning applications very rapidly and with great ease. The APT server
is described in more detail in Section 2.3.4.
Aside
ActiveX®, a Windows®-based, language-independent technology, allows a user
to quickly develop custom applications that automate the control of APT system
hardware units. Development environments supported by ActiveX® technology
include Visual Basic®, LabView™, Borland C++ Builder, Visual C++, Delphi™,
and many others. ActiveX® technology is also supported by .NET development
environments such as Visual Basic.NET and Visual C#.NET.
ActiveX controls are a specific form of ActiveX technology that provide both a user
interface and a programming interface. An ActiveX control is supplied for each
type of APT hardware unit to provide specific controller functionality to the
software developer. See Section 2.3.4. for further details.
Caution
On start up, wait until the initialization sequence is completed before running
the APT software - see Section 3.4.

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Chapter 2
2.3.2 APTUser Utility
The APTUser application allows the user to interact with a number of APT hardware
control units connected to the host PC. This program displays multiple graphical
instrument panels to allow multiple APT units to be controlled simultaneously.
All basic operating parameters can be altered and, similarly, all operations (such as
motor moves) can be initiated. Settings and parameter changes can be saved and
loaded to allow multiple operating configurations to be created and easily applied.
For many users, the APTUser application provides all of the functionality necessary
to operate the APT hardware without the need to develop any further custom
software. For those who do need to further customise and automate usage of the
driver (e.g. to implement a positioning algorithm), this application illustrates how the
rich functionality provided by the APT ActiveX server is exposed by a client
application.
Use of the APT User utility is covered in the PC tutorial (Chapter 5) and in the
APTUser online help file, accessed via the F1 key when using the APTUser utility.
Caution
On start up, wait until the initialization sequence is completed before running
the APT software - see Section 3.4.

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Brushless DC Servo Driver K-Cube
2.3.3 APT Config Utility
There are many system parameters and configuration settings associated with the
operation of the APT Server. Most can be directly accessed using the various
graphical panels, however there are several system wide settings that can be made
'off-line' before running the APT software. These settings have global effect; such as
switching between simulator and real operating mode, and associating third party
mechanical stages to specific motor actuators.
If a KBD101 driver is used with the DDSM100 Direct Drive Translation stage, all
stage-associated settings are made automatically when the stage is connected to the
driver.
The APTConfig utility is provided as a convenient means for making these system
wide settings and adjustments for third party brushless DC motor driven stages. An
overview of APTConfig is provided in Section 2.3.3. Full details are contained in the
online help supplied with the utility.
2.3.4 APT Server (ActiveX Controls)
ActiveX Controls are re-usable compiled software components that supply both a
graphical user interface and a programmable interface. Many such Controls are
available for Windows applications development, providing a large range of re-usable
functionality. For example, there are Controls available that can be used to
manipulate image files, connect to the internet or simply provide user interface
components such as buttons and list boxes.
With the APT system, ActiveX Controls are deployed to allow direct control over (and
also reflect the status of) the range of electronic controller units, including the KBD101
DC motor drivers. Software applications that use ActiveX Controls are often referred
to as 'client applications'. Based on ActiveX interfacing technology, an ActiveX

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Chapter 2
Control is a language independent software component. Consequently ActiveX
Controls can be incorporated into a wide range of software development
environments for use by client application developers. Development environments
supported include Visual Basic, Labview, Visual C++, C++ Builder, HPVEE, Matlab,
VB.NET, C#.NET and, via VBA, Microsoft Office applications such as Excel and Word.
Consider the ActiveX Control supplied for the KBD101 APT Brushless DC Servo
driver unit.
This Control provides a complete user graphical instrument panel to allow the motor
unit to be manually operated, as well as a complete set of software functions (often
called methods) to allow all parameters to be set and motor operations to be
automated by a client application. The instrument panel reflects the current operating
state of the driver unit to which it is associated (e.g. such as motor position). Updates
to the panel take place automatically when a user (client) application is making
software calls into the same Control. For example, if a client application instructs the
associated DC motor Control to move a motor, the progress of that move is reflected
automatically by changing position readouts on the graphical interface, without the
need for further programming intervention.

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Brushless DC Servo Driver K-Cube
The APT ActiveX Controls collection provides a rich set of graphical user panels and
programmable interfaces allowing users and client application developers to interact
seamlessly with the APT hardware. Each of the APT controllers has an associated
ActiveX Control and these are described fully in system online help or the handbooks
associated with the controllers. Note that the APTUser and APTConfig utilities take
advantage of and are built on top of the powerful functionality provided by the APT
ActiveX Server (as shown in Fig. 2.2).
Fig. 2.2 System Architecture Diagram
Refer to the main APT Software online help file, for a complete programmers guide
and reference material on using the APT ActiveX Controls collection. This is available
either by pressing the F1 key when running the APT server, or via the Start menu,
Start\Programs\Thorlabs\APT\APT Help.
2.3.5 Software Upgrades
Thorlabs operate a policy of continuous product development and may issue software
upgrades as necessary.

12
Chapter 3 Getting Started
3.1 Installing APT Software
DO NOT CONNECT THE STAGE TO YOUR PC YET
1) Download the software from www.thorlabs.com.
2) Locate the downloaded setup.exe file and move to a suitable file location.
3) Double-click the setup.exe file and follow the on-screen instructions.
Caution
If your PC becomes unresponsive (e.g due to an operating system problem,
entering a sleep state condition, or screen saver operation) for a prolonged
period, this will interrupt communication between the APT Software and the
hardware, and a communications error may be generated. To minimize the
possibility of this happening it is strongly recommended that any such modes
that result in prolonged unresponsiveness be disabled before the APT
software is run. Please consult your system administrator or contact Thorlabs
technical support for more details.
Caution
Some PCs may have been configured to restrict the users ability to load
software, and on these systems the software may not install/run. If you
are in any doubt about your rights to install/run software, please consult
your system administrator before attempting to install. If you experience
any problems when installing software, contact Thorlabs on +44 (0)1353
654440 and ask for Technical Support.

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Brushless DC Servo Driver K-Cube
3.2 Mechanical Installation
3.2.1 Environmental Conditions
Location Indoor use only
Maximum altitude 2000 m
Temperature range 5oC to 40oC
Maximum Humidity Less than 80% RH (non-condensing) at 31°C
To ensure reliable operation the unit should not be exposed to corrosive agents or
excessive moisture, heat or dust.
If the unit has been stored at a low temperature or in an environment of high humidity,
it must be allowed to reach ambient conditions before being powered up.
3.2.2 Mounting Options
The K-Cube Brushless DC Driver is shipped with a baseplate, for use when fitting the
unit to a breadboard, optical table or similar surface.
For multiple cube systems, a 3-channel and 6-channel K-Cube Controller Hub
(KCH301 and KCH601). ) are also available - see Section 2.2. for further details. Full
instructions on the fitting and use of the controller hub are contained in the handbook
available at www.thorlabs.com
Warning
Operation outside the following environmental limits may adversely affect
operator safety.
Caution
When siting the unit, it should be positioned so as not to impede the
operation of the control panel buttons.
Ensure that proper airflow is maintained to the rear of the unit.

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Chapter 3
3.2.3 Using the Baseplate
The baseplate must be bolted to the worksurface before the K-Cube is fitted, as
shown below. The K-cube is then located on two dowels in the baseplate and secured
by two clips.
Fig. 3.1 Using The Baseplate
3.3 Electrical Installation
3.3.1 Rear Panel
Fig. 3.2 Rear Panel Connections
The unit is supplied with a female 15 pin D-type connector as shown above, which is
compatible with the DDSM100 brushless DC driven translation stage (refer to
Appendix A for details of pin outs).

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Brushless DC Servo Driver K-Cube
3.3.2 Front Panel
Fig. 3.3 Front Panel Connections
POWER - A Standard 3.5 mm front panel jack connector for connecting the unit to a
regulated DC power supply of 15 V, 2A.
Thorlabs offers a compact, multi-way power supply unit (TPS008), allowing up to four
KBD101 K-Cubes to be powered from a single mains outlet. A single way wall plug
supply (KPS101) for powering a single Driver K-Cube is also available.
USB - USB port for system communications.
ON - Power ON/Standby switch. When in the ON position, the unit is fully powered
up. When the switch is turned to the Standby position, the unit initiates a controlled
power down sequence, saving all user-adjustable parameters to non-volatile memory
before turning off the power. For the first few seconds, the shutdown can be cancelled
by turning the switch on again, in which case the unit will save the parameters but will
remain powered up. In a powered down (Standby) state, the logic circuits are
powered off and the unit will draw only a small quiescent current. The switch should
always be used to power down the unit.
TRIG 1 and TRIG 2 - SMA connectors for use with external trigger input and output
signals (5V TTL levels). The function is set to trigger IN or OUT via the settings panel
- see Section 4.5. and Section 6.3.5.
Shock Warning
The unit must be connected only to a DC supply of 15V, 2A regulated.
Connection to a supply of a different rating may cause damage to the unit
and could result in injury to the operator.
Note
The USB cable length should be no more than 3 metres unless a powered
USB hub is being used.
_
+
TRIG 1 TRIG 2
USB
POWER
DC 15V 2A
+5V TTL +5V TTL
ON
KBD101

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Chapter 3
3.4 Connect The Hardware
1) Perform the mechanical installation as detailed in Section 3.2.
2) Install the APT Software.
3) Connect the Controller unit to your PC.
(Note. The USB cable should be no more than 3 metres in length. Communication
lengths in excess of 3 metres can be achieved by using a powered USB hub).
4) Connect the DC servo motor actuator to the driver unit - see Section 3.3.1.
5) Connect the driver unit to the power supply - see Section 3.3.2.
6) Connect the PSU to the main supply.
7) Switch ‘ON’ the unit using the switch on the front panel.
Caution
During items (3) to (6) the instructions should be followed strictly in the
order stated. Problems may occur if the process is not performed in the
correct sequence.
Caution
During item (5) ensure the power switch on the front panel of the unit is
switched off before connecting power to the K-Cube. Always power up
the K-Cube unit by its ON switch. DO NOT connect the K-Cube unit to a
'live' external power supply. Doing so (i.e. “hot plugging”) carries the risk
of PERMANENT damage to the unit. Similarly, to power down the unit,
turn the power switch off before disconnecting the power supply.

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Brushless DC Servo Driver K-Cube
The unit takes about 5 seconds from power application until warm up is finished, and
phase initialization is complete. During this time the following screens are displayed.
.
8) WindowsTM should detect the new hardware. Wait while WindowsTM installs the
drivers for the new hardware.
Note
If any problems are encountered during the connection and power up
process, power cycle the unit, which should clear the error.
Note
3-phase brushless DC motors are commutated electronically, i.e. the
controller drives the coils with a precisely controlled waveform, that
depends on the position of the rotor (or, with linear motors, the position
of the coil housing). On power up, the position of the rotor is not known.
The controller establishes this by energising the coils and measuring the
resulting movement. This is why on power up, the stage (motor) makes a
slight buzzing noise and moves about slightly for a few seconds. Phase
initialisation can only take place if the motor can move unobstructed
during this time.
Note
After initial start up, the drive channel must be enabled before the stage
can be driven - see Section 4.4.2.
Thorlabs KBD101
SwRev 10002
Stage connected:
DDSM100
Phase init
Please wait...
Phase init
completed
At 0.0000 mm
Disabled V

18
Chapter 4 Standalone Operation
4.1 Introduction
The Brushless DC Driver K-Cube has been designed specifically to operate with the
range of Thorlabs Brushless DC motorised opto-mechanical products. The unit offers
a fully featured motion control capability including velocity profile settings, limit switch
handling, homing sequences and, for more advanced operation, adjustment of PID
settings, allowing support for many different actuator configurations. These
parameters can be set via the APT Server software - see Chapter 5. Furthermore,
many of these parameters are automatically set to allow “out of the box” operation
with no further “tuning” required.
The following brief overview explains how the front panel controls can be used to
perform a typical series of motor moves.
4.2 Control Panel Buttons and Indicators
Fig. 4.1 Panel Controls and Indicators
MOVE Controls - These controls allow all motor moves to be initiated.
Velocity Wheel - Used to drive the motor at a varying speed in either forward or
reverse directions for full and easy motor control - see Section 4.3.
Digital Display - The display shows the menu options and settings, accessed via
the menu button - see Section 4.4. When the Ident button on the associated GUI
panel is clicked, the display will flash for a short period.
MENU - used to access the settings menu - see Section 4.4. Also used to stop a
move when the stage is in motion.
Brushless Motor Controller
MENU

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Brushless DC Servo Driver K-Cube
4.2.1 Digital Display - Operating Mode
During normal operation, the digital display shows the current position (in millimeters
or degrees) and the current state of the motor (Stopped or Moving). If the stage being
driven has been homed, the display will also show ‘Homed’.
Fig. 4.2 Digital Display - Normal Operation
For rotation stages, the position display will be restricted to the "Equivalent Angle"
display mode (see Section 6.3.7. for more details), so the position displayed will
always be a positive number between 0 and 360 degrees. If set to Total Angle in the
settings panel, the LED display will still show the equivalent 0 to 360° value but the
GUI screen will show the total rotation.
4.3 Velocity Wheel Operation
The velocity wheel is a sprung potentiometer, such that when released it returns to its
central position. In this central position the motor is stationary. Different types of move
can be initiated by the wheel, depending on its mode setting. The mode can be set
either via the GUI Settings panel, see Section 6.3.3. or via the top panel display menu,
see Section 4.4. The various operating modes are described in Section 4.3.1. to
Section 4.3.3.
4.3.1 Homing
A ‘Home’ move is performed to establish a datum from which subsequent absolute
position moves can be measured (see Section 5.4.) for further information on the
home position).
To initiate a ‘Home’ see Section 4.4.4.
4.3.2 Go to Position
In ‘Go To Position’ mode, two preset position values can be specified, such that the
motor moves to position 1 when the wheel is moved down, and to position 2 when it
is moved up. These ‘taught’ positions can be set through the software GUI - see
Section 6.3.3. or via the display menu, see Section 4.4.8.
Brushless Motor Controller
At 0.0000 mm
Stopped V

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Chapter 4
This mode of operation is enabled by setting the ‘Wheel Mode’ to ‘Go To Position’
through the software GUI - see Section 6.3.3. or via the display menu, see Section
4.4.6.
4.3.3 Jogging
The top panel wheel can also be configured to ‘jog’ the motor. This mode of operation
is enabled by setting the ‘Wheel Mode’ parameter to ‘Jogging’ through the software
GUI - see Section 6.3.3. or via the display menu, see Section 4.4.6.
Once set to this mode, the jogging parameters for the wheels are taken from the ‘Jog’
parameters on the ‘Move/Jogs’ settings tab - see Section 6.3.1. or via the display
menu, see Section 4.4.7.
4.3.4 Velocity Moves
The wheel can also be used to initiate a move at a specified velocity. As the wheel is
moved away from the centre, the motor begins to move. Bidirectional control of the
motor is possible by moving the wheel in both directions. The speed of the motor
increases by discrete amounts as a function of wheel deflection, up to a maximum as
set in through the software GUI - see Section 6.3.3. or via the display menu, see
Section 4.4.5. The move stops when the wheel is returned to its centre position.
Note for Rotation Stage Users
If the current absolute position is outside the 0 to 360 degree range, then "go
to position" will result in a move to the correct angular position within the
same 0..360 degree full turn "segment". This means that the move will always
stay in the current full turn segment, and from this point of view it is not always
the quickest position move. For example, if you are at 350 degrees and you
enter a "go to" position of 10 degrees, the stage will rotate anticlockwise 340
degrees and not clockwise 20 degrees.