Ultrasonic Position Tracking System

1. Ultrasonic Position Tracking System Dave Sekowski Farhan Ismail Tunji Yusuf

2. Introduction • Design Objective • System measures the position of an object in space in three dimensions • Allows accurate tracking of ultrasonic equipped object • Utilizes several reception units • Design • Uses reverse concept of GPS • System consists of a transmitter, several receiver units and a base station • Base station actively manages transmitter • Base station later stores time values as RF signals arrive from reception unit • Counter values can later be used in trilaturation scheme to determine transmitter location versus receivers

3. Features • Portability • Multiple Applications • Expandable

4. Applications • Sports Related Usage • Motion Sensor and Capture • Firefighters • Miners

5. Original Design • Clock synchronized across PICs in each unit • Counter values referenced to unified clock • RF transmission includes data for receiver management • Mobile units using custom power supplies • Bluetooth output to PC for post processing

6. System Overview • Hardware • Can be broken down into three main component • Base Station Unit • Transmission Unit • Reception Unit • Software • VHDL codes for FPGA

7. Base Station Overview • FPGA • Responsible for control of the entire system • RF Linx Transmitter • Initiates Transmission Unit • RF Linx Receiver • Input signals from Reception Units

8. Base Station FPGA Board • Programmed in VHDL • Replaces PIC in system • Outputs logic high to RF transmitter for a window of time (~200ns) • Starts internal counter • Waits for signal from RF receiver

9. Base Station RF Transmitter • Waits for signal from the FPGA • Once received, transmits a modulated high from the base to the transmission unit

10. Base Station RF Receiver • A modulated signal from reception module RF transmitter is received here • Converted to digital output for FPGA in receiver • Once received the FPGA is instructed to stop its counter and load value into a register

11. Base Station

12. Transmission Unit Overview • RF Linx Receiver • Receives start signal from base station • FPGA • Responsible for control of the unit • Relay • Holds required voltage and frequency back • Ultrasonic Transmitter • Emits ultrasonic burst when prompted by FPGA

13. Transmission Unit RF Receiver • Listens for modulated high from the base station • Once received, a high is sent to the transmission unit FPGA

14. Transmission Unit FPGA Board • Programmed in VHDL • Replaces PIC in system • Once signal is received from RF, the FPGA outputs a high to the relay

15. Transmission Unit Relay • Passes 20 Vpp AC 40 kHz square wave to the ultrasonic transmitter

16. Transmission Unit Ultrasonic Transmitter • The human hearing range ends at 23kHz • The ultrasonic transmitter emits a burst of sound pulse at 40kHz • Sound travels at 340.29m/s in air enabling us to resolve distances

17. Transmission Unit

18. Reception Unit Design • Ultrasonic Receiver • Takes initial output from transmission unit • High Pass Filter • Used to attenuate any low frequencies • Amplifier • Signal is amplified • Comparator • Changes analog signal to a near-digital square wave • RF Linx Transmitter • Output sent to base station

19. Reception Unit Ultrasonic Receiver • Ultrasonic transmitter sends out high voltage, 40 kHz square wave signal • Distance attenuates the signal amplitude • Ultrasonic receiver receives a low voltage, 40 kHz sine wave signal

20. Reception Unit High Pass Filter • Constructed using 0.1uF capacitors and 10k resistors • Acts as voltage divider • The impedance of the capacitor goes up as frequency goes down thus attenuating low frequencies

21. Reception Unit Amplifier/Comparator • Because of the low voltage signal amplification circuit is needed • Gain ~ 905x • Amplified signal ran thru comparator • Comparator performs analog to digital conversion • RF transmitter outputs signal from comparator to the base station

22. Reception Unit

23. Software Overview • FPGA coded in VHDL

24. Transmission Unit State Machine

25. Base Station State Machine

26. Test/Measurements • Oscilloscope reading of signal when relay is off • 20 Vpp 40 KHz

27. Test/Measurements • Oscilloscope reading at output of relay • (note: distortion)

28. Test/Measurements • Oscilloscope reading of signal at ultrasonic receiver

29. Test/Measurements • Output of high pass filter

30. Test/Measurements • Output of Amplifier

31. Test/Measurements • Output of the Comparator

32. Test/Measurements • Output to the antenna from RF transmitter

33. Test/Measurements • Input of RF receiver at Base Station

34. Test/Measurements • Output of RF receiver • (note: trigger set at 3.175V)

35. Test/Measurements • Table of distance between the ultrasonic transmitter and receiver vs the voltage read at the receiver side

36. Test/Measurements • Table of Ultrasonic transmitter and receiver tilt angle vs voltage read at the receiver

37. Obstacles • Programming/Using the PICs for each of our units • Having multiple receivers operating at different frequencies • Overcoming ambient noise from the environment • Finding a proper timing cycle that allowed our device to be as accurate as possible

38. Recommendations • Machine shop RF transmitters and receivers • Custom mount ultrasonic and RF antennas • Increased importance on filtration system

39. Future Plans • Incorporating multiple receivers • Sending Data on same frequency • Use multi-channel RF system • Setup data processing interface • Hyper terminal to PC for external post processing • Onboard trilateral calculation with custom LCD display • Interchange transmitter and receiver operation • Customize power supplies for mobility

40. Credits • Professor Jon Makela: for keeping it real • Purvesh Thakker: for patiently waiting in lab dejected and alone during weekly reviews… • The many caffeinated beverage we consumed – Red Bull gives you wings • The standup comedy that kept us up those long nights – that IS how we do business • Jake “ECE 385 monster” Foster: VHDL guru

41. Thank You • Any Questions?