Wireless Motion Capture Mid-Year Design Review

1. Wireless Motion CaptureMid-Year Design Review Seth Berkowitz Dean Howarth Eric Marklein Ashesh Rastogi Advisor: Professor Daniel Schaubert

2. Remote Unit Base Units Project Overview • Optical motion capture confines to small area • Self referencing system gives user freedom of motion • Find distances and calculate 2D position

3. MDR Specifications • “Wireless Ruler” – 1 dimensional static distance measurement • Transmit wave between remote and base units (breadboarded) • Digital acquisition of raw data • SRAM storage of raw data • Offline algorithm for distance calculation

4. PDR Flashback • Phase based distance measurement • Two frequency transmission from base • Up-convert at remote unit • Retransmit to base • Ultrasound vs. RF

5. 8 8 13 System Block Diagram Zero-Crossing Detector Phase Comparator BPF Clock MUX Phase Diff Trigger Amplifier Microcontroller Temperature Sensor Receive Transducer Data Address Free Space R/W Computer Interface Memory Transmit Transducer

6. Analog Zero Crossing Comparator Schmitt Trigger Buffer Receive transducer Transmit transducer BPF BW = 377kHz Free Space Non-Inverting Amplifier Clock MUX To Phase Comparator

7. Received Signal

8. -Transducers 14 cm apart -3V square pulse wave

9. Phase Comparator

10. D Q CLK RESET Phase Comparator ftransmit Ф ftransmit freceive Ф RESET D Q freceive CLK

11. Tx and Φ Tx and RX

12. Pulse Width Counter ∆Ф CLK (8 MHz) Trigger (from microcontroller) CLK Gate 8 bit counter Microcontroller

13. Microcontroller Wait Over Timer 8 Phase A/D Acquisition Time Over Trigger Pulse Start Phase Acquisition 2 Analog Voltage Clock MUX Temperature Sensor A / D 8 Phase Distance Computation And Temperature Error Correction 10 Digitized Voltage 13 Memory Address 8 SRAM 8 k word x 8 bit Volatile Memory 2 Memory Routine Read / Write Distance 8 PIC16F877 Microcontroller Distance

14. Microcontroller’s Task • Change clock frequency • Waits for transducer to settle (30 ms) • Sends Trigger pulse to phase comparator • Acquires 8-bit phase shifts (1 and 2)

15. Microcontroller’s Task (cont.) • Digitizes analog voltage from Temperature Sensor (10 bit A/D) • Sends 8-bit phase and Read/Write control signals to external memory

16. Test Setup

17. Calculated Vs Actual Distance μerror = 0 σ = 3.4 mm

18. Calculated Vs Actual Distance μerror = 0 σerror = 3.4 mm

19. Sources of Error • Phase difference jitter • Oscillator drift • Zero-crossing • Multipath Effects • Component phase shifts • Humidity • Temperature

20. Temperature Offset

21. Current Budget • Transmit/Receive: $6.95 • Phase Comparator: $2.81 • Microcontroller: $5.11 • Memory: $3.94 • Temperature Sensor: $3.15 • Additional Components: $1.35 • Budget so far: $23.31

22. MDR Specifications - Recap • “Wireless Ruler” – 1 dimensional static distance measurement • Transmit wave between remote and base units (breadboarded) • Digital acquisition of raw data • SRAM storage of raw data • Offline algorithm for distance calculation

23. CDR Goals • Distance calculation on microcontroller • Computer link with USB • Simultaneous frequency transmission • 1-D motion capture (30s) • 2-D position and motion • Display motion on animation software