MicroStep Motor Controller
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The SIL MicroStep system allows distributed control of up to 16 individual
stepper motors. Control signals are sent via Ethernet to the system, which
appears as a standard EPICS input/output controller (IOC). In addition to
sending control signals to each motor, position and monitoring information may
be sent back to the control system.
Developed at the University of
Saskatchewan for use in the Canadian Light Source (CLS), the MicroStep design
was licensed to SIL under a technology transfer agreement. SIL, in partnership
with the Saskatchewan Synchrotron Institute (SSI), have worked to improve,
manufacture and market the MicroStep System.
The motor control system's
main application is a synchrotron or physics laboratory that currently runs
EPICS. However, the MicroStep Motor Control System could be used in any setting
where a number of individual motors need to be precisely positioned, such as
research, industrial or manufacturing operations.
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System Overview
A complete motor control system consists of
three main enclosures, Controller Subrack and two Driver Subracks. The
Controller Subrack is responsible for taking input control signals from the
control system and conditioning them for the Driver Subrack, which in turn
directly drives the motors. Each subrack is a standard 3U Eurocard rack and
requires +12V to +24V DC input power. Control signals are sent via Ethernet to
the system, which appears as a standard EPICS input/output controller (IOC).
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Controller Sub-rack
The Controller Subrack is designed to connect
directly to StepPack or MicroStep motor drivers. When used with MicroStep motor
drivers the Controller can remotely enable or disable a motor and engage/release
an electromechanical brake. Additionally, the controller is able to monitor
motor position using either quadrature shaft encoders or rotary/linear
potentiometers.
The components of a Controller Subrack are a Voltage
Regulator module, an Embedded Controller module, and an Interface module. An
Embedded Controller module may be connected to a maximum of four Interface
modules, each of which relay control signals to two Driver modules in the Driver
Subrack. There is room in the chassis for one voltage regulator, two Embedded
Controller modules and eight Interface modules, allowing for control of up to
sixteen motors.
The Interface module provides an interconnection between
the Embedded Controller module and the Driver module. Each Interface module can
be connected to two MicroStep Driver modules and two feedback potentiometers
which may be used to monitor position.
The Voltage Regulator module
contains switching regulators which accept +12V to +24V from an external DC
power source and provide +5V to the other modules. Front panel status LEDs and
test points for measuring the output of each regulator are provided.
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Driver Sub-rack
The MicroStep Driver Subrack may contain up to eight Driver modules. Each Driver
module receives input from the MicroStep Controller Subrack and can control one
motor. The current per winding can be varied from 0.2A to 3.0A in 0.2A
increments. Additionally, the number of microsteps per motor step can be set to
16 different values between 1 and 128 on the Driver module. The modules can
drive the following types of motors:
Four-lead, two-winding
Six-lead,
four-winding
Eight-lead, four-winding
Each MicroStep Driver module
takes input control signals and generates the electrical signals to physically
move a micro-stepping motor. Additionally, the Driver module passes feedback
information, such as position (from an encoder) or mechanical limit status, back
to the Control Crate.
A Regulator module, similar to the one in the
Controller Subrack, is installed in the center slot of the Driver Crate. The
regulator module contains switching regulators which convert the +12V to +24V
supply voltage to +5V for the Driver modules. Front panel LEDs indicate the
status of the power supplies. Test points for measuring the power supply and
regulator voltages are also provided.
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Embedded Controller
The workhorse of the Control Subrack is a pair of single board computers based
on the Motorola MC68360 micro controller. Each Embedded Controller module
communicates with the operator control system over a 10baseT Ethernet connection
and is able to receive and pass on control signals to individual motors. The
Embedded Controller can also pass diagnostic information back to the control
system such as clockwise/counter-clockwise limit switch and over-travel status.
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Specifications
16MB, 72 pin, 60 ns DRAM with parity
256
kilobyte Flash memory
10baseT Ethernet port
Can control up to 8
motors
Uses Motorola 68360 microprocessor
BDM connector (background debug
mode)
Console RS-232 port
37 input/output connections (general purpose
I/O)
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