Download apt™ Modular Stepper Motor Driver Rack System See

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Page 338
Motion Control
Translation Stages
apt™ Modular Stepper Motor Driver
Motorized
Mirror Mounts
The apt™ modular rack system is a sophisticated, self-contained, extendible
architecture, precision motion control platform for high channel count motion
Rotation Stages
control applications (see page 352 for details of the rack enclosure). Our modular
3 Axis Flexure Stages apt™ stepper motor driver provides a scalable motion control solution which
& Accessories
allows the independent control of up to 12 stepper motors within a single 19" rack
enclosure. The USB interface and advanced application software, allow multiple
4, 5 & 6-Axis Stages
channel systems to be seamlessly integrated into a single large scale solution.
Drive Electronics
Additionally, it is possible to combine the apt™ rack systems with one or more bench
& Auto-Alignment
top apt™ units. The plug-in modules have all the same performance and ease of use
Actuators &
features as our bench top drivers presented on pages 334 through 337. They combine
Adjusters
the latest high-speed digital signal processors (DSP), low-noise analog electronics, and
ActiveX® software technology. The modular apt™ stepper motor controller is supplied
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Features
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Dual (Synchronised) Drive Channels
Supports 2 Phase Bipolar Steppers up to 50W
Differential Encoder Feedback (QEP inputs)
Maximum 128 Microsteps per Full Step
25,600 Microsteps per Rev (200 Step Motor)
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User Controlled Digital I/O Port
Motor Control I/O Port
Full Software GUI Control Suite
ActiveX® Graphical Panel Controls
ActiveX® Programming Interfaces
Seamless Software Integration with apt™ Family
with a full suite of software support tools. An intuitive
graphical instrument panel allows immediate control
and visualization of the operation of the stepper
controllers, and any other plug-ins that are installed in
the system. See pages 354-356 for a full description of
the apt™ system software.
Driver Functionality
A wide range of 2-phase bipolar stepper motors and
associated actuators are commercially available, each
with its own characteristics, such as step resolution,
See pages 354-356
peak phase current or voltage, and lead screw pitch. Operation of the apt™ stepper
for more information motor controller is fully configurable (parameterized) and all of the key settings are
on the apt™ software accessible through a number of graphical interface panels. For example, the motor step
included with the
resolution and lead screw pitch can be set for a particular motor/actuator combination,
MST Controller.
phase currents can be limited to suitable peak powers as required, and limit switch
configuration is accommodated through a flexible set of limit switch logic settings.
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.
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Stepper Controller Specifications
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338
Input/Output:
• Motor Drive Channel
(25 Pin D-type Female)
– 2 Phase Bipolar Motor Drive Output
– Differential Quadrature Encoder Interface
– Forward, Reverse Limit Switch Inputs
• Motor Control (15 Pin D-type Female)
– Jog Forward
– Jog Back
– Enable/Disable Interlock
– Jog Control Handset Available
• User I/O (26 Pin D-type Female)
– RS 485 Communications Channels
– Logic Level Trigger Input/Output
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ITEM#
$
MST601
$ 1,358.30
Sales: 973-579-7227
Stepping (Assumes 200 Step Motor)
– 25,600 Microsteps per Revolution
– Maximum 128 Microsteps per Full Step
Compatible Motors:
• Peak Powers: 5 to 50W
• Average Power: 25 W Maximum
• Step Angle Range: 20° to 1.8°
• Coil Resistance (nominal): 4 to 15Ω
• Coil Inductance (nominal): 4 to 15mH
• Rated Phase Currents (nominal):
100mA to 1A
General:
• One Slot apt™ Rack
• Dimensions (W x D x H):
190 x 270 x 50mm
• Weight: 1.5kg (3.3 lbs)
£
£
799.00
€
€ 1.198,50
¥
¥
223,720
MST601
For simplicity of operation, the apt™ software
incorporates pre-configured settings for each of
the Thorlabs’ stages and actuators, while
highlighting and making available all operating
parameters for use with other manufacturer's
stepper motor systems. For convenience and ease
of use, adjustment of many key operating
parameters is also accessible through the software
generated control panels. Furthermore, move and
jog commands can be performed directly from
the GUI panels. All settings and parameters are
also accessible through the ActiveX®
programmable interfaces for automated
alignment sequences. See pages 354-356 for
a full description of the apt™ system software.
Full Support for Encoder Feedback
The modular apt™ stepper motor controller also
supports encoder feedback through dedicated
quadrature encoded pulse (QEP) inputs, one for
each channel of the two channels of operation.
Through conversion routines, the apt™ software is
able to use this feedback signal to generate encoder
position for access either through the GUI or via
programmable interfaces for use in custom closed
loop algorithms. A “built in” algorithm can be
enabled to allow the stepper system to reach and
maintain an encoded position through an iterative
move sequence.
Rack System
See Page 352
MOTOR DRIVE
DESCRIPTION
apt™ 2 Channel Stepper Motor Controller Module
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Motion Control
Stepper & DC Servo Motors… A Brief Tutorial
Thorlabs offers a range of benchtop and rack mounted motor
controllers covering both low and high power applications. These
are described on page 331 to 338. The following two pages contain
a brief tutorial on how stepper motors and DC motors operate,
together with a comparison of the two types.
Translation Stages
Motorized
How a Brushed DC Motor Works
Mirror Mounts
A DC motor works by converting electric power into mechanical
Rotation Stages
energy (movement). This is achieved by forcing current through a
coil and producing a magnetic field, which in turn, spins the motor. 3 Axis Flexure Stages
& Accessories
How A Stepper Motor Works
Stepper motors operate using the principle
of magnetic attraction and repulsion to
convert digital pulses into mechanical shaft
rotation. The amount of rotation achieved
is directly proportional to the number of
input pulses generated and the speed is
proportional to the frequency of these pulses.
4, 5 & 6-Axis Stages
Drive Electronics
& Auto-Alignment
Actuators &
Adjusters
A basic stepper motor has a permanent magnet and/or an iron rotor,
together with a stator. The torque required to rotate the stepper
motor is generated by switching (commutating) the current in the
stator coils as illustrated below.
Simplified concept of stepper motor operation
DC Servo motor actuators, please see our
actuator section that starts on page 357 for details.
Simplified concept of DC motor operation
To describe the operation of a DC motor, consider the single coil
example shown above.
Stepper motor actuator, please see our actuator
section that starts on page 357 for details.
Simplified concept of stepper motor operation
Although only 4 stator poles are shown above, there are really
numerous tooth-like poles on both the rotor and stator. The result is
that positional increments (steps) of 1.8 degrees can be achieved by
switching the coils i.e. 200 steps/rev. If the current through one coil
is increased as it is decreased in another, the new rotor position is
somewhere between the two coils and the step size is a defined
fraction of a full step (microstep). When used with the apt™ motor
controller, the smallest angular adjustment is 0.014 degrees,
resulting in a resolution of 25,600 microsteps per revolution for a
200 full step motor.
In this diagram, current is forced through the coil via sliding
contacts (brushes) that are connected to the voltage source. The
brushes are located on the end of the coil wires and make a
temporary electrical connection with the DC supply. When
current is flowing, a magnetic field is set up as shown.
At 0 degrees rotation, the brushes are in contact with the voltage
source and current is flowing. The current that flows through the
wire from A to B interacts with the magnetic field and produces
an upward force. The current that flows from C to D has a similar
effect, but because the flow is in the opposite direction with
respect to the magnetic field, the force is in the downward
direction. Both forces are of equal magnitude. At 180 degrees, the
same phenomenon occurs, but segment A-B is forced down and
C-D is forced up. In the 90 and 270-degree positions, the brushes
are not in contact with the voltage source and no force is
produced. In these two positions, the rotational kinetic energy
of the motor keeps it spinning until the brushes regain contact.
In reality, DC motors have several such coils, wound onto an
armature, which produces a more even torque. The magnetic field
is provided by an electromagnet.
New OptoDC/ST Motor Drivers, See Page 331
These new opto drivers are USB interfaced compact single channel motor drivers, designed to operate with a variety
of DC brushed motors or stepper motors. They contain a full embedded controller and driver circuit and can be
operated with and without a PC. The OptoDC driver unit is a direct replacement for the DCX-MC110B controller
modules featured in earlier editions of the Thorlabs catalog. The OptoST driver has been designed for easy manual
and automatic control of low power stepper motor actuators such as the Thorlabs ZST series. While compact in
footprint (2.5" x 2" x 1.6"), these units offer a fully featured motion control capability including velocity profile
settings, limit switch handling, “on-the-fly” changes in motor speed and direction. For more advanced operation
control over the closed loop PID parameters and adjustment of settings such as lead screw pitch and gearbox ratio
allows support for many different actuator configurations.
Sales: 973-579-7227
329
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Motion Control
Translation Stages
Motorized
Mirror Mounts
Rotation Stages
Stepper & DC Servo Motors… A Brief Tutorial – Comparison
Comparison Summary
DC Motors
3 Axis Flexure Stages
& Accessories
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4, 5 & 6-Axis Stages
■
Drive Electronics
& Auto-Alignment
Actuators &
Adjusters
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When a Voltage is Applied, Turn in One Direction at a Fixed Speed
Optimized to Run at a Fixed, Usually High RPM
Speed Can be Varied if a PWM Controller is Added
Inexpensive and Commonly Available
Available in Wide Range of Speeds and Power
Not Suitable for Positioning Unless Some Kind of Position Feedback
is Added as with the ODC001, on page 333
If the Applied Load is Greater than the Capacity of the Motor,
the Motor Will Stall and Possibly Burn Out
Stepper Motors
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Can Not Turn Without a Controller, such as the OST001 on page 332
Inexpensive and Commonly Available
Available in Wide Range of Speeds and Power
Precise Positioning Possible. Encoder Feedback Can be Used in Some Cases
Torque is Highest at the Full Stop and Decreases as Speed is Increased
If the Applied Load is Greater than the Capacity of the Motor,
the Motor Will Not Step, Thereby Making Precise Positioning
no Longer Possible
point or “Home” position in order to improve
the accuracy of the stage. Movement is allowed
right through the switch.
Home Position
Each motor in the system has an associated
electronic counter, which keeps a record of the
current position in microsteps (for stepper
motors), or encoder counts (for brushed DC
motors). If the Control PC is requested to report
the position, the value of this counter is converted
back into motion units. When the system is
powered up, the counters in the controller are all
set to zero and consequently, the system has no
way of knowing the position of the stage in
relation to any physical datum. A datum can be
established by sending all the motors to their
“Home” positions. The “Home” position is set
during manufacture and is determined by driving
the motor until the negative limit switch is
reached and then driving positively a fixed
distance (zero offset). When at the “Home”
position the counters are reset to zero thereby
establishing a fixed datum.
Note: During a manual move, (i.e. if the motor
shaft is turned by hand) no signal is sent to the
motor, the counter is not updated and any
subsequent position reporting will be false until
the motor is “Homed”.
Velocity Profiles
To prevent the motor from
stalling, it must be ramped up
gradually to its maximum velocity.
Certain limits to velocity
and acceleration result from
the torque and speed limits
of the motor, and the
inertia and friction of the
Graph of a trapezoidal velocity profile
parts it drives. The motion
employed is described by a
trapezoidal velocity profile, reflecting the shape of the velocity vs. time graph
(shown above), thereby driving the stage to its destination as quickly as
possible, without causing it to stall or lose steps. The stage is ramped at
acceleration “a” to a maximum velocity “v”. As the destination is
approached, the stage is
decelerated at “a” so that
the final position is
Stage limit switches
approached slowly in a
See
controlled manner.
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Limit Switches
Linear and rotary stages
can both contain
microswitches that
detect certain
positions of the stage,
but they typically differ
in the way these switches
are used. Most linear stages have limit switches to prevent the stage
from accidentally being moved too far in either direction. Once this
switch is activated the movement of the stage should halt. A limit switch
can also provide a physical datum used to define a “Home” position. A
rotary stage typically has only one switch, used to provide a reference
330
Sales: 973-579-7227
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