DIY Motion Platform Servo Drive System -
UPDATE March 2015, the 64SPU-2 card
replaces the older 64SPU-1, 12ADC-1 and I2C Isolator cards
in a single card.
INFORMATION: for an excellent example of a
drive system build using the older 64SPU-1 and other cards
please see Roland van Roy's write-up here -
http://simprojects.nl/electrical_drive_iv.htm The wiring
is slightly different for the 64SPU-2 but it still gives
relevant examples of good practice.
Roland has helpfully provided advice and
his technical wiring diagrams for his system on the page.
The NEW 64SPU-2 card works with the BFF 3 DOF
Motion Driver and
BFF PID Servo Controller software
to provide cost effective DIY 3 DOF motion platform drive system
control for flight simulation.
It combines the functions previously provided
by 3 separate cards to simplify system wiring and operation.
The main features of the 64SPU-1 are:
I2C data output for use with Devantech MD03 motor speed
12 bit potentiometer
position feedback via built-in ADC circuit.
2 or 3 channel output for 2 or 3 DOF motion systems.
Built-in "Drive Enable" trip loop.
64MHz operation giving up to
70Hz refresh rates.
Direct connection to PC USB via included FTDI
chipset USB/TTL cable.
Included external DPST (double pole single throw)
card logic power switch to power-up card and isolated
LED status indicators, screw connectors.
On-board 20X2 microcontroller re-programmable in-situ
for firmware upgrade.
Illustrative system wiring:
For 64SPU-2 use with alternative Dimension
Engineering Sabertooth /
SyRen controllers see here...
The main components that make up the DIY
motion platform servo drive are:
The 64SPU-2 64MHz Signal Processor Unit
card - see the order pages
MD03 Motor Speed Controllers - 24V 20 Amp DC
controllers delivering up to 480 Watts of electrical
power per controller.
24V DC PM Motors to suit the DIY
platform project. The MD03 controllers will support up
to a maximum 20 Amps rating, sustained currents above this
level will cause overheating and current limiting by the
Position feedback potentiometers. (Pots/encoders fitted to the
drive actuators or elsewhere on the platform to report
actual platform position.)
DC power supplies for the drive motors
Actuator travel limit switches, fuses,
cables and wiring.
PLEASE NOTE - I do not supply all of
the above hardware, just the 64SPU-2 card (with USB cable and
switch), and the motion
software. If you want to build the servo drive for your own
project then you will need to source the motors,
controllers, potentiometers, switches etc yourself.
IMPORTANT - The 64SPU-2 card is part of a
closed loop position feedback servo drive. The position
feedback potentiometers/encoders shown on the wiring
diagrams MUST be fitted to the drive motors/actuators to
report platform position to the 64SPU-2 card. Without this
the closed loop position control can NOT operate. If you are
not sure what a closed loop position control servo drive is
then I recommend you try and read-up a bit before attempting
to use this hardware. It is very important to understand
that this is not a "plug and play" system intended for
consumer use - it is intended for use by informed DIY system
builders. Read both the motion software user manual and the
64SPU-2 data sheet before using the hardware.
64SPU-2 Signal Processor Unit
For DIY Motion
Platform DC Servo Drives
64SPU-2 Card - The new
64SPU-2 signal processor card is at
the heart of the servo drive and acts as the
communications bridge between the MD03 motor controllers, feedback pots/encoders and the BFF PID Servo Controller
software running on the PC. It also acts as a system
monitoring and information feedback unit - it monitors for
communications interruptions and stops the motor drives when
required and also
feeds back MD03 current and temperature information to the
Servo Controller software.
The 64SPU-2 is available to buy as a
ready-to-connect card (80 mm x 80 mm) and replaces the older
64SPU-1, 12ADC-1 and I2C Isolator cards as a single board.
For full details read the 64SPU-1 data sheet
64SPU-2 Data Sheet
The card is available to buy on its own or bundled
with the V2 Motion Driver software -
see the order page here.
SERVO SYSTEM OPERATION
Older 40SPU-1 and
The servo system hardware works in
conjunction with the BFF PID Servo Control software running on
The servo software receives platform position demand
information from the BFF Motion Driver and
also receives actual platform
position feedback data from the position feedback
pots/encoders connected to the 64SPU-2 card. Using this data it calculates
motor speed demand outputs which control the direction and
speed of the actuator drive motors to drive the
platform to the demanded positions. The motor control
commands are sent to the MD03 motor controllers via the
64SPU-2 signal processor card.
The servo control loop can run at up to 70Hz
(PC and connection dependent) - ie the speed and direction of each motor is
adjusted by the system up to 70 times each second and this
makes for an effective system response under most platform
(using the PID
The servo software uses a PID (proportional -
integral - derivative) control algorithm and the PID
parameters that define the control response can be set through the BFF Servo Controller GUI.
This makes tuning the servo system easier as small changes
can be made to the control algorithm and the resulting
effects on the motion assessed immediately.
Actuator limit switches and an Emergency Stop
switch should be wired in series in the 5V supply line from
the 64SPU-2 to the MD03 motor controllers to cut the drive
to the motors to prevent damage if the actuators over-stroke.
Motor controller "live" current and
temperature data is continuously fed back by the 64SPU-2 to
be displayed on the PC by the BFF Servo Controller software.
This makes for interesting viewing, however it can also be
of significant assistance during platform set-up work as it
direct indication of the system electrical loading. The servo software also
includes a virtual
oscilloscope to view demanded and actual actuator positions
and motor speed demand.
Video clip of
the older 40SPU-1
The platform is being driven with no pilot load
so against the unbalanced force of the support
For the best performance of the servo drive
built-in 12bit ADC is used for the
Overall the 64SPU-2 and associated servo
software can provide an effective servo drive for DIY motion
platforms at a seriously low price. The 64SPU-2 is however a
relatively simple card and although it contains a number of
safety features such as comms time-out monitoring, some
feedback error detection and feedback limit detection the
price does not allow the types of system monitoring
capabilities that can be found on much more expensive commercial motion
controllers. You must take care to ensure the platform
drive is properly protected by over-travel limit switches
and an accessible Emergency Stop button.
If you wish to buy the 64SPU-2 please read
the data sheet
carefully and follow the installation and use
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