Capability Enhancements for Autonomous Mobile Wireless Sensor Platforms Advisor: Dr. S. Jay Yang – CE Team Members Andrew Mullen – CE Edgar Martin – ME Khoa Nguyen – CEDarnelle Haye - ME Stephen Ortiz – CE Adam Haun - EE Sponsor

Presentation Overview Project Background –Sponsor’s Desires Objectives –Project Timeline –Specifications Design Process –Project Needs Design Challenges –Different areas of concern Final Design –Component Overview Outcome Assessment

Project Background Sponsor – Directorate of Central Intelligence (DCI) –Sponsoring research in autonomous vehicles and wireless communication –These are areas of active interest in the near future. Overall Project –This team is the first step in a much larger mission – Create a completely autonomous sensor platform –Need to develop a suitable robust, extensible platform –Allow future students to develop algorithms and processes that can simulate autonomy

Autonomy, what is it? Autonomous –Functioning independently of other components or systems; self- governing –Operating without pre-programmed behaviors and without supervision from humans Implementation Aspects –It can sense the environment through its sensors and navigate using it’s motors –Internal processing and decision making capability –Can anticipate and correlate information

Autonomy, why do we want it? Various Military or Domestic applications –Independent robots examining locations too dangerous for humans –Small vacuuming robot to clean the house Essentially embedding intelligence into a device

Project Schedule

Objectives Four mobile sensor platforms Upgradeable with minimal redesign. Able to recognize objects in their immediate vicinity and accurately measure and calculate distances. Implement communication Precise movement and turning Compact chassis Powered by a single rechargeable battery.

Project Specifications Chassis Specifications –Each platform will be no larger then 10” x 10” x 10” –Each platform will have a total weight of under 5 lbs –Each platform must cost less than 350 dollars to build –Each platform will have a battery life of at least ½ hour under normal conditions (2000mAh, 9.6 volts) –The batteries must be rechargeable –Each platform must be able to move in a straight line at a speed of 10 cm/s –Each platform must be able to rotate in place at a speed of 45 degrees/sec –Each platform must be able to travel 1 meter with under ±5% error –Each platform must be able to rotate accurately to within 5 degree error Sensor Specifications –Each platform must be able to sense objects within 1.5 meters to within 5% error –Each platform must be able to obtain a global direction heading to within 5 degrees –All interpretation and use of the sensors will be done by the platform

Project Design Process Needs Assessment –Basic components and functionalities Concept Development –Integration and Design options to facilitate the needs –Chassis Construction –Sensor Kit Selection –Power Requirements Feasibility Assessment –Budget Limitations –Equipment Limitations –Man hour Limitations

Project Needs Main Controller Individual Motors Motor Controllers Distance Sensor Wireless Communication Protocol Converter Orientation Sensor PC Interface Object Detectors Control View

Major Design Challenges Obtain accurate sensor data –Maximize sensor capabilities –Ignore Errors Develop an Effective Electrical Layout – Printed Circuit Board Understand and install TinyOS –Mica2dot operating system Implement Accurate Moving and Turning –Solved by choice of motor –Reduce power consumption Debugging the PIC assembly Code –Available Debug tools don’t allow for real time sensor input

Sensor Specialization Ultrasonic Sensor – Distance Measurement –Strengths Returns the amount of time from the sending of the sound wave to its return Allows for simple, accurate conversion to distance as perceived by the platform –Weaknesses Sound pulse is not very focused Infrared Sensor –Strengths Very focused beam Extremely fast –Weaknesses Shorter range Difficult to measure exactly

Sensor Error Get what you pay for –Sonar sensor is accurate “most” of the time –Needed to remove erroneous data Ultrasonic Sensor Examination –Two main types of Error Frequent reflections from the floor Occasionally the object was not sensed by the pulse –Error is very diverse, average not possible Must select the best reading Compass and IR sensors –Generally far more consistent –Used a median of three values MINMAX 6 Ordered Sensor Readings

Initial Electrical Layout Used breadboard for wiring –Fast, simple, effective –Unreliable, un-documentable, unprofessional

Final Electrical Layout Reliability was a serious requirement for the team –On the Prototype, a breadboard was used wires can come loose Breadboards prone to noise Once testing was complete on the prototype –Finalized the design –Developed a Printed Circuit Board Problems –Expensive – can only be done once –Team had no prior experience

Final PCB Layout

Wireless Communication Selected the Mica2dot Wireless Transceiver Specifications Excellent –Long Range (150 m), High Bandwidth (19.2kb/s), Reprogrammable, Low Power, Small Reality –TinyOS install environment flawed, hardware and software checks often fail after the first step –Most documentation is for the Mica2 not the Mica2dot Final Analysis –Multiple groups on campus cannot successfully utilize hardware – only simulation –Motes are not “plug and play”, require significant understanding of TinyOS in order to configure installation environment Result –Team does not have necessary expertise or man hours to pursue without significant loss to rest of the project –Unable to satisfy our objective of integrating wireless However, communication to and from the PC was implemented in a fashion which would allow insertion of the Mica2dot without changing any protocol or packaging

Motor Selection Movement Accuracy a Major Concern –Stepper motors are accurate and reliable Chose a simple dual coil stepper motor Each “step” is a rotation of 1.2 degrees –Require a lot of current to lock and unlock the magnets Motor Controller Requirements –Send accurate number of pulses –Cut off power to motors at will

Initial Concepts -Does Not Rotate around Center of Mass -Simplifies Algorithm Development -Not Enough Space for Components -Circular shape saves weight -Ball Bearing Integrated -Space for Sensors -Location For Battery Pack 1 2 3

Final Design

Debug Environment Can’t tell what is happening with the assembly code when an error occurs –Needed an interactive method to debug the code –Normal debugger does not work with real time sensor input Developed a Java GUI –Can send and receive data over a serial cable –Developed a packet structure to enhance communication –GUI can interpret packet information and display the results The serial communication protocol used was modeled from the Mica2dot easing a future transition to wireless

Debug GUI

Summary: Components Integrated Global Orientation –Devantech Compass Distance Measurement –Ultrasonic SRF04 Ranger Object Detection –2 GP2Y0D02YK IR Sensors Motors –2 Dual Coil 26BYG Stepper Motors Control Chips –PIC-18F4320 Microcontroller –4 UC3770 Motor Controllers –MAX233 RS-232 Converter Power – mAhr 9.6volt rechargeable NiMH battery –Regulated to 5 volts and 3.3 volts

Summary: Cost Per Platform Sensors$109 Controllers$ 44 Wireless $105 Printed Circuit Board$ 51 –Regulators, resistors, etc. $ 30 Platform$ 45 –Motors, Wheels, Brackets, etc. TOTAL $384 Man Hours for Assembly of Additional Robots – 9 Hours

Outcome Assessment Desired Outcomes –Small Size (10x10x10) –Lightweight (5 lbs) –Distance Measurement –Object Detection –Global Orientation –PCB Layout –Wireless Communication –Debug Environment –Long Battery Life Actual Outcomes –6” x 6” x 9” –2.39 pounds –Integrated Ultrasonic Sensor –Integrated Infrared Senor –Integrated Compass –Completed PCB –Design Supports future wireless integration –Interactive Debugging GUI –Lasts over 50 minutes under full load

Conclusion The team was successful in meeting our budget requirements, while purchasing the required components Mica2dot wireless transceiver was a poor component choice –More research may have revealed the difficulties inherent in integrating it Development of a user-friendly debug environment will ease algorithm development of future programmers Sensor selection and specialization effectively targets the strengths of the platform

Testimonials Sponsor –Tuesday 10 th  Final Presentation to the Sponsor –Overall they were very pleased Performance/Cost Ratio Extensibility Advisor – Dr. S. Jay Yang

Lessons Learned Sensors work great independently –Integration and imperfect measurement cause errors –Magnetic compass sensor interference Active feedback is mandatory –Otherwise, can’t figure out what is going wrong, only that things don’t work Team morale is a key factor in success –When the team was struggling with the wireless, team unity began to drop. Setting it aside allowed the team to get back on track. The design process actually works –Seemed like a lot of useless paperwork, later in the design however, it became very useful in the later weeks of the course. Effective communication is the basis for team functionality –When everyone is on the same page, effective division of the workload as well as understanding increases.

Questions?

Object Tracking Flowchart Use IR to Examine Area in Front Robot Detected? Brief Pause Activate Sonar & Measure Is Distance > then Desired? Move Backward Move Forward Take IR Reading Robot Detected? Move Forward 1 Meter Pause Move In Arc for ¼ Meter Move Forward ¼ Meter Move In Arc for ¼ MeterScan For the Robot Object Tracking Demonstration Yes No