Autonomous Sensor and Control
Platform Rover
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Tae Lee
Josh Reitsema
Scott Zhong
Mike Chao
Mark Winter
Detailed Subassembly
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Scott – Main control and Processing
Tae – Motor Control Hardware
Mark – Sensor interfaces
Mike – Wireless Communications
Josh – Video and High Level Control
Software
System Overview
Mainboard
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68HC11K1
XCS10
EPROM and SRAM
Bus Drivers
Motor Controls
• What we have:
• Two Pittman GM8000 series DC GearMotors
• HEDS-9000 series optical encoder
• The plan:
• Use two LMD18200T H-Bridges to control the motors
• PWM is used to control speed (Duty Cycle)
• High/Low logic for direction
• Brake feature
• HEDS – 9000 series optical encoder
• These will give rotational/direction information of each motor
• HCTL 2020 Decoder 16-bit
• Decodes quadrature signal from the HEDS-9000
• Outputs a count (rotational speed) and direction signal
• Provides interface to MPU
Motor Current Delivery
• H-Bridge
• Use two LMD18200T H-Bridges to control the motors
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Duty Cycle of PWM determines current sent to motors (Speed)
Direction pin determines which way the motor spins
Brake Pin
Thermal sensor
Note: Optical Isolation between MPU and H-bridge
FROM THE MOTORS
HEDS-9000 Encoder/
HCTL 2020 Decoder
• HEDS-9000
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Optical Incremental Encoder Module
Used with a code wheel, detects rotary position (Shaft Encoder)
Fairy accurate – 500 CPR (counts per revolution)
Produces two signals which need to be decoded
• HCTL 2020 Decoder
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Decodes two signals into a count signal and direction signal
The decoded signals are available on external Pins (5 & 16)
Provides bus interface between encoder and MPU/FPGA
Operates well in noisy environments (Motors)
• Note: Optical Isolation Between Decoder and FPGA
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To the MPU/FPGA
MPU / FPGA
• FPGA
• Create latches in FPGA, work as registers
• Registers hold decoded position information
• The registers are updated continually with new position
information (we can control how often it latches the new signal)
• HC11K1
• When needed, goes out to FPGA and grabs contents of register
• HC11 will use information and compute PWM adjustments
• PWM is sent out from HC11
Recent Discovery
LMD18200T with a LM629 Motion Control Device
The Sensor Subsystem and
Interface
• Polling logic in the FPGA requests data
from a sensor address on the sensor
address bus.
• The sensor addressed is enabled and gets
data, which it outputs to the sensor data
bus.
• The data is taken off the sensor data bus
into a memory mapped latch and the
polling logic continues to the next address.
Advantages
• This interface should allow for the addition
of several more sensors without any
hardware changes as long as they have a
unique address
• This interface could be modified to use the
I2C bus interface, thereby reducing the
sensor interface footprint.
Schematic for Polling Logic
IR Sensors/Driver
• Upon enable, begin outputting a clock
signal of ~38kHz to IR LEDs.
• Wait a few clock cycles. Then enable
output from all 6 of the IR sensors and
place it on the data bus.
Schematic for IR Sensor/Driver
Ultrasonic Sensor/Driver
• Once enabled send a single pulse of width
period ~25.3us to selected transducer unit.
Begin counting time units.
• Blank input from transducer for a short
period in order to avoid hearing the sound
as it leaves.
• Once input is received stop counter and
output its value to the data bus.
Simplifications
• In order to get the sensor interface up and
running, we will put all of the logic into the
FPGA, which means that the interface will
be internal to the FPGA for now.
• One of the possible extensions would be
to use a second FPGA or discrete logic so
that other sensor could indeed be added
on at a later date.
WiFi communication
Lantronix WiPort
• Communicates with HC11 using
RS232
• Wireless gateway for RS232
transmission
• Advertised indoor range of 300 ft.
• Bandwidth limited by serial clock
RS232
• HC11 uses a UART with the standard
non-return-to-zero format
• Same format as RS232
• Selectable bit rate up to 20 kbps
SCI (Port D) Pinouts
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RXD
TXD
GND
receive data
transmit data
ground
pin 2
pin 3
pin 5
Sample Transmission
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Received interrupt from RDRF (received data register full
Read from input buffer SCDR
Decode the character received
Change the duty cycle of the PWM output.
Interrupt From
Data Register
Read From
SCDR
Decode
Transmission
Write to
PWDTY1/2
Web Based Control
• The wi-fi creates an IP-address for a web page
which is where the user interface will be located.
• The web-page will utilize Java applets as a GUI
for the user to send information to the robot
such as turn, or speed up, run preset
autonomous programs, etc. and also to receive
information such as video and positioning
measurements in a user friendly manner.
• The web-control basically will call basic sub
functions that are preset into the ROM or RAM
which will then send instructions to the motor
controller.
Video System
• The video camera will be mounted into the
front of the robot
• The data will not be sent through the wi-fi
due to bandwidth concerns
• A button on the webpage will access the
direct feed through an applet
• No significant processing of the video will
be done
Example Webpage
Autonomous Control and Sensor Platform Rover
F
Velocity
KILL SWITCH
L
R
Incoming Data:
B
X: 1.8 M
Y: 25 M
Open Video Applet
Wall Follow
Search Area
Speed : 3 m/sec
...
Avoid Objects
Parts List
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Rover (Pebbles III)
H-Bridge and Control Circuit
Lantronix WiPort
Mainboard and FPGA
IR and Sonar
Baby Monitor w/Video Capture
Quality hours spent in Capstone
• Total
$0
$100
$300
Charge it to Tom
Included
$400
Priceless
$800
Schedule
Thanks