Group 16Karena Stout

Ryan SivekAlex Balogh

Background• US Army currently uses the

Multiple Integrated Laser Engagement System (MILES) for combat training

• System is expensive and somewhat inaccurate

• Consists of laser emitters attached to rifle barrels and laser receptors on soldiers' helmets and harnesses to simulate combat

AEAS In A Nutshell…• A collection of live, inexpensive, and realistic modern combat simulation

tools• Will use electronic sensors to pinpoint weapon and user locations as

well as monitor weapon orientation• Detected trigger pulls will cause a message to be sent from the weapon

to the main server containing position and orientation information• Server will receive these messages and calculate bullet trajectories using

simple Newtonian principles• Users detected to be in the path of the simulated bullet will receive

indications that they were hit• A web accessible GUI will provide real-time scenario visualization and

data

ComparisonMILES AEASExpensive Inexpensive

Lasers cannot penetrate soft obstructions

Obstructions can be modeled and accounted for in software

Not very realistic ballistics Ballistics can be modeled in software

Users must use specified MILES gear Users can use their own weapons and apparel

Random number roll or “casualty cards” for damage assessment

Software determines location of hit and estimates damage

Positioning System

Requirements:• Relatively low cost• Minimum virtual bullet accuracy

(deviation/distance) of 0.2%• Minimum weapon orientation precision of

• Minimum field dimensions: 25m x 25m x 5m

Positioning System

Compared optical, GPS, and ultrasonic.Optical: cost effective with webcams, but

inaccurate at rangeGPS: best range, but precision is too expensive.Ultrasonic: poor range, but low cost with recorded

absolute error of within 3 centimeters*Our Solution: Ultrasonic positioning– Receivers measure time of arrival of signals from pre-

positioned beacons to determine distance.*Bjerknes, J. D., Liu, W., Winfield, A. F., and Melhuish, C. (2007). Low Cost Ultrasonic Positioning System for Mobile Robots. In Wilson, M.S., Labrosse, F., Nehmzow, U., Melhuish, C., and Witkowski, M., editors, Proceeding of Towards Autonomous Robotic Systems, pages 107 - 114, Aberystwyth, UK.

Ultrasonic Beacons

• Maxbotix MB1200 XL-Maxsonar-EZ0 rangefinders attached to raised plastic rods.

• Beacon transmission timing will be controlled by the AEAS server directly.

• The Maxsonar-EZ0 has the widest beam of any Maxbotix Range Finder.

• Maximum range finding depth of approximately 25 ft (7.6 meters).

Positioning Subsystems• Murata MA40S4R ultrasonic receivers.• Modules will have a metallic cone attached to the receiving sensor and

be positioned upward to be able to accept signals from all directions.• Will use a two stage amplifier to send signals to the weapon and user

modules.

Trilateration• Subsystems will use

trilateration to determine position.

• Uses distances from known beacon positions to determine its own position.

• Distance From Beacon = Time of Arrival * Speed of Sound.

Height Measurement

• Although we could compute height using the trilateration data, we can achieve a more accurate calculation by using the distances from two points on the same pole.

Beacon Timing

Beacon Timing

Beacon Timing (Actual Speed)

Communication Requirements

• In order for the server to collect information from the weapon and body attachments a link must be established

• The communication must be wireless to support the users running, twisting, ducking, and jumping

Wireless Communication Choices

• Bluetooth – too expensive• Wifi – not designed for point-to-point

communication• Infrared – Line of Sight is crucial• Zigbee module – relatively slower and shorter

range, but well within requirements of the AEAS system

Xbee vs. Xbee-Pro

• Size – Xbee-Pro is a bit longer• Power Consumption – Xbee-Pro uses more

power• Range – Xbee-Pro has a longer range• Cost – Xbee-Pro is more expensive

• Size, power, and cost are worth the longer range -> Xbee-Pro!

Network Topology

Type of Antenna

Attached Monopole

Whip

U.FLRPSMA

Dipole Chip

Antenna

Xbee-Pro circuit design

Receiving Base Station

User Identification

The AEAS system needs a way to track statistics of the users’ shots fired to hit ratio to track progression of training soldiers.

1. Each user will make an account2. Each time trigger sensor is asserted it will be

paired with an ID3. Server will collect and calculate statistics

User Identification Input

• Keypad – too bulky• Barcode Scanner – temperamental and over

complicated• RFID – user friendly, fast, and light weight

-> The AEAS solution is RFID

Type of RFID System• Capacitive – (< 1 cm) Smart

cards inserted into a reader, too big with card sticking out

• Inductive – (1 cm – 1 m) Smart cards held up to a reader

• Backscattering – (> 1 m) security systems in stores, WAY too big!

-> Inductive RFID system!

RFID Reader

1. Voltage is induced by mutual inductance between the reader’s and the card’s induction coil antennas to power the chip, along with an ID query to the chip

2. The load is changed on the coil antenna to rectify the query signal and return its ID

Weapon Orientation Attachment

Requirements:• Detachable• Minimum battery life: 5 hours• Minimum clock rate: 1MHz– Must be able to do calculations quickly to get a reasonable bullet

response.• Maximum weight: 5 lbs

10cm

Orientation Measurement

• Invensense MPU-6050.• Includes a Digital Motion Processor

(DMP)– offloads the computation of motion

processing algorithms from the host processor.

• Utilizes the I2C communication protocol.

• Maximum theoretical precision of approximately 0.008 degrees.

1mm

Orientation Calculations

To increase accuracy, our implementation will use a weighted average between accelerometer data and the calculated gyroscope measurements to get the final estimated values.

Fire Signal Detection

• Fire detection will consist of a modified FlexiForce® 25lb pressure sensor placed on the trigger.

• When the trigger is pressed to a predetermined pressure threshold, the module will send fire data to the server.

2cm

Body Attachment

Requirements

• Location Determination– Interface with ultrasonic positioning system to

retrieve position data• Hit Notification– Activate/Deactivate indicator closest to the

computed hit location on the user• Communication with Server– Send user position data at regular intervals,

receive hit notifications

Microcontroller

• Requires a large number of available pins• 16MHz clock should be sufficient to perform

I/O functions• Analog-to-digital conversion required by

positioning system• Support for serial communications with

communications subsystem

TI MSP430G2553 Atmel ATMega328 PIC 18F2520

I/O Pins 22 23 25

Clock Frequency 16 MHz 20 MHz 40 MHz

ADC Resolution 10-bit 10-bit 10-bit

Serial Communications

UART, SPI UART, SPI, I2C UART, SPI, I2C

Architecture 16-bit 8-bit 8-bit

Cost $1.00 $4.30 $9.38

Vibration Motors

• Must be small and produce a noticeable response. – 10mm Shaftless Vibration Motor 3.4mm Button Type

Vibration Motor Control

• Needs to turn on/off a set of 5 vibration motors• Should require as few pins as possible on the MCU• Component must be fast to minimize the delay

observed by the userShift Register (SIPO) 74HC595

3 to 8 Line Decoder74HC238

Output Lines 8 8Pins Required 4 (CLK, CLK Enable, Shift,

Data)3 (Select lines A, B, C)

Cost $1.50 $.95

Body Attachment Circuit

Server

Requirements

• Compute bullet trajectories– High-precision floating point computations

• Compute intersections between trajectories and user positions

• Send hit notifications to body attachments• Provide front-end accessible web GUI• Synchronize timing of positioning system• Compute and store statistics of each user

Trajectory Computation

• Operating area will have a max bullet travel distance of 35.4 meters

• Trajectories can be simplified– At the proposed distance the bullet drop due to

gravity is very small (less than one centimeter)

Web GUI

• To make the system more useful, a visualization of the current state will be included.– Monitor user positions, outgoing trajectories, and

hits with minimal delay– Make scenario data available afterward for review

GUI Concept Design

GUI Implementation

• User positions displayed through HTML5 Canvas element (possibly rendered with WebGL)

• GUI hosted by Java server client utilizing Java.net classes to perform TCP/IP communications

• Server accumulates state information and makes it available via a web interface

Server Hardware

• Server not required to support a large number of concurrent users– Sophisticated server implementation is not be

necessary• Hardware must support floating point

operations– Network interface (Ethernet, Wi-Fi) is also

required

Server HardwareConsumer PC Raspberry Pi Model B

Instruction Set x86 ARMv6

Processor AMD or Intel dual core 2 GHz or higher

700 MHz ARM1176JZF-S

Floating Point Unit Yes Yes

RAM 1 GB or more 512 MB

Secondary Storage 80 GB SD Card (up to 32GB)

Networking 10/100/1000 Ethernet 10/100 Ethernet

USB ports 4 2

Cost $300 $40

Server Hardware

• Raspberry Pi Model B– 700 MHz ARM1176JZF-S– 10/100 Ethernet– GPIO Pins

BudgetComponent Quantity

Estimated Cost Per Unit

Estimated Total Cost

DevelopmentAtmel Inertial Two Sensors Xplained development board 1 $85.54 $85.54

Unit OrientationInertial Measurement Unit 4 $13.00 $52.00Magnetometer 4 $6.00 $24.00Unit PositioningMB1200 XL-Maxsonar-EZ0 8 $45.00 $360.00

Power9v Snap Connectors 4 $3.00 $12.009v Battery 4 $5.00 $20.00Vibration Device10mm Shaftless Vibration Motor 5 $5.00 $25.00

Wireless CommunicationsXBee Wireless Pack 1 $117.00 $117.00XBee Pro Chip Antenna 1 $57.60 $57.60Server HardwareRaspberry Pi Model B 1 $50.00 $50.00User IdentificationParallax RFID Read/Write Module - Serial 2 $50.00 $100.00RFID Tag 2 $2.50 $5.00Trigger SensorParallax Flexiforce Pressure Sensor 2 $21.95 $43.90

PCB FabricationPrinted Circuit Boards 4 $16.68 $66.72Miscellaneous Cables / Parts / Shipping costs / Unforeseen expenditures NA $300.00

TOTAL $1318.76

Progress

Total

Testing

Prototyping

Design

Research

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60%

20%

30%

90%

95%

Plans

• Ultrasonic ranging transceivers were not applicable– Back to our original design– Acquiring separate transmitters and receivers

• Finish testing circuit designs with breadboards– Purchase PCB

Notes

• Further additions and changes may be made.• Component images provided by sparkfun.com

and distributed under Creative Commons License.

• Other images were created by Ryan Sivek.