Modular Driver Assistance Package

1. Modular Driver Assistance Package ECE 445: Senior Design Group 14 Bryan Clodfelter, Joseph Ekstrom, & Swati Acharya December 3rd, 2008

2. Three Goals: Adaptive cruise control (ACC) Short-range vehicular communication (“Wolf Pack”) Effective driver assistance Three Components: Scanning laser rangefinder High-end microprocessor Low-latency RF transceiver Concept

3. Concept, Illustrated (1 of 3) • Adaptive Cruise Control • Uses radar or laser transceiver to perform “time of flight” (TOF) calculations in order to gauge distance to obstructions ranging from 30 to 300 feet up ahead. • Rangefinder data is relayed to an on-board microprocessor, which filters out extraneous data and determines instantaneous closing velocity. • With ACC enabled, the on-board system will automatically slow the driver’s car to avoid crashing into a slower vehicle ahead; once that vehicle moves away, the system will bring the car back to its original velocity.

4. Concept, Illustrated (2 of 3) • Vehicular Communication • According to the “Big Rig Myths” episode of the Discovery Channel’s show, Mythbusters, drafting behind a semi-trailer at a range of 10 feet boosted the fuel efficiency of a 25 mpg car to 44.5 mpg—a 39% improvement. • Presently, those kind of driving conditions are impossibly dangerous. At 55 mph (80.67 feet per second), 10 feet of separation equates to 0.124 seconds of separation—faster than many humans can react. Conceptually speaking, vehicles with low-latency RF communications hardware and ACC systems could make these traveling conditions feasible.

5. Concept, Illustrated (3 of 3) • Effective Driver Assistance • An augmented display cluster offers three new pieces of driving data to the the user: distance, closing velocity, and a recommended course of action. • Additionally, “Wolf Pack” drive mode is operated through the display cluster. Due to its autonomous nature, the driver only requires connection options and a RF connection status display. • Even with ACC off, as circumstances progress from normal to dangerous to perilous (where a collision is deemed imminent), the microprocessor may choose to brake the car if the driver is non-responsive (or insufficiently responsive).

6. Objectives • Heightened Driver Awareness • Faster acquisition of threats • Better comprehension of vehicle-vehicle dynamics • Reduced reaction time to adverse conditions • Low Cost Alternative • Mercedes-Benz “Distronic PLUS Package”: $2880 on the S550 • Microwave radar transceiver + ultrasonic parking transceivers • Our system: << $1000 at low volumes • Modular & Universal Design • Future expansion capability • Suitable for all types of vehicles

7. Overall Design – Block Diagram EPSON 2.5” QVGA display (peripheral board, included with EV-AFV850 kit) Opti-Logic RS400 laser rangefinder (905 nm @ 200 Hz) Linx HP3 RF transceiver (900 MHz band) NEC EV-AFV850 microprocessor (32 bit – 32 MHz) 144 pin GPIO Lin Engineering 4209 stepper motor (400 step resolution) Dual H-Bridge (driver) 1 MHz External Oscillator

8. NEC AF-EV850 Micro Kit • Functionality Utilized: • 160 TTL Programmable GPIO pins • RF transmitter (UART) • RF receiver (UART) • Stepper motor driver (UART) • Optical encoder output (interrupt) • DB9 (RS-232) port • Perfect match for RS400 rangefinder • Selectable baud-rate • Touch Sensitive 2.5” QVGA LCD (320x240 @ 32 bpp) • Powerful SEGGER development environment • External Interrupt Counter (Crystal Oscillator) • Integrated 16-bit CRC registers • Essential for data integrity on the noisy 900 MHz band • 10-bit A/D & 8-bit D/A converters

9. NEC AF-EV850 Micro Kit • Touch Sensitive 2.5” (QVGA) LCD Implementation • Functions Offered: • Distance and closing rate in real time • User-selectable units of measurement (feet, yards, and meters) • Graphical driver advisory warnings (slow down, speed up, panic brake) • RF connection interface and status • Graphical overview of laser rangefinder position and target (if relevant) • Selected Example (following slide): • Simulated situation: inattentive driver rapidly bearing down on slower driver • Note as GUI becomes more and more obtrusive

10. NEC AF-EV850 Micro Kit No Danger Extreme Danger Mild Alert

11. Motor, Driver & Encoder • Lin Engineering 4209S-01P stepper motor • Low Impedance and Resistance per Phase • 2.4 Ohms/phase & 4.6 mH/phase reduces back EMF • Frame size (NEMA) 17 • Bipolar Design (single winding per phase) • Four input lines (N, S, E, W) • Current must be reversed in each winding, making it harder to drive than uni-polar steppers • Advantage (over unipolar design) is higher torque per unit weight ratio • 400 step resolution (0.9 degrees per step) • 800 steps possible through micro-stepping (or “wave drive”) • Through-shaft allows for optional encoder attachment • Optional E2 optical encoder offers a multitude of cycle per revolution options.

12. Motor, Driver & Encoder • 4209S-01P (low Z, L) versus 4209S-03P (high Z, L) • 03P draws less current, but is considerably slower and less powerful than the 01P

13. Motor, Driver & Encoder • Full Step Drive Example: • Full torque, normally rated step size

14. Motor, Driver & Encoder • L298 Dual H-Bridge IC • Amplifies TTL-level input signal into output signal powerful enough to drive motor • Rated for 2 amps

15. Motor, Driver & Encoder • Dual H-Bridge Driver Circuit

16. Motor, Driver & Encoder • The importance of back EMF filtering • The L298 H-bridge switches extremely fast (as compared to the more commonplace L293), requiring Schottky diodes (1N5822) • Without them, back EMF from the motor causes intense vibration and subsequent loss of stepper torque and accuracy

17. Motor, Driver & Encoder • Quadrature Encoding Scheme • Used to determine directionality when the motor is running Index A B A B Time Index (zeroreference) (Shaft in Clock-wise direction: A leads B) Index A B Time (Shaft in Counter-Clock-wise direction: B leads A)

18. Specific Objectives of the Wolf-Pack • The ability for up to 8 cars being able to communicate in a client-server fashion. • To relay specific goals of the server, or “leader” of the pack, such as stop, disconnect, and ensuring that cars remain connected. • To switch channels in the event that a certain channel is occupied by a currently connected wolf-pack.

19. Wolf Pack Flow Chart (1 of 4) Client Side in Drive Mode

20. Wolf Pack Flow Chart (2 of 4)

21. Wolf Pack Flow Chart (3 of 4) Client Side in Wolf Pack mode

22. Wolf Pack Flow Chart (4 of 4) Server Side in Wolf Pack Mode

23. Wolf Pack Protocol • Start Message (0x42) • Opcode (8-bit) • Data (16-bit) • Wolf-Pack Code (8-bit) • Vehicular Code (8-bit) • CRC Remainder (8-bit) • via 8-bit IEEE standard divisor: 0x107 • End Message (0xFF)

24. Original Commands • Would you like to connect? • Not interested in Wolf-Pack. • Now connected. • Error in communication; resend data. • You are now assigned Wolf-Pack ID #. • Ping query-ensures connection of the car • Ping response-ensures connection. • Stop notification • Global disconnect

25. Added Commands • Channel in use - Necessary when receiving unexpected data from a car not in the Wolf Pack. • Inappropriate Opcode - Necessary when receiving unexpected data from a car within the Wolf Pack.

26. Error Checking—The Cyclic Redundancy Check • Why the CRC? • More reliable than a parity bit • Computationally more complex, but still worth it. • Method: Treat the data as a large binary number and divide it by another known number. The remainder is called the checksum and is transmitted along with the actual data. The receiver will verify that the correct checksum is calculated to ensure that there have been no errors within the data.

27. Original Block Diagram HP3 Modules DSP VGA Display Speaker

28. Finalized Block Diagram HP3 Modules V850 1Mhz Clock

29. Components • HP3 transmitters and receivers by Linx Technologies • Why these components? • Multiple channels • FCC regulations • Accessibility

30. Antennas • 916 MHz CW series monopole antenna • Omnidirectional • Low VSWR • Easy accessibility

31. HP3 Module Pin-Out Diagrams • Transmitter and receiver, separate diagrams.

32. All Hooked Up

33. Successful Packet Reception

34. Antenna Usage • HP3 modules have an internal antenna that can be used up to about 60-80 ft. • We would like to be operational at up to 300 ft • Packet loss as distance increased almost linearly.

35. Packet Loss/ConfusionOver a period of 4 seconds at 19200 baud, 48-bit packets (200 total)Average over 4 trials, varying receiver to transmitter angle by ~10°

36. Adjacent Channel Interference • Sending data on two sets of adjacent channels created significant interference: • 906.37Mhz and 907.87 Mhz ~19% more invalid packets at all distances. • 919.87 Mhz and 921.37 Mhz ~9% more invalid packets at all distances.

37. Difficulties • Randomly, channels would suddenly become cluttered with noise. It was not on every channel, nor was it all the time. • V850 that malfunctioned hours before the demo.

38. Future Recommendations • Adding a better noise filter • Using the serial channel function of the HP3 modules rather than the parallel channels • Defining the protocol such that a P2P network is possible rather than a client-server network. • Finding a more efficient antenna.

39. More Future Recommendations • External memory to store sophisticated audio and video user interfaces.

40. Acknowledgements • Special thanks to… • University of Illinois Staff • Dr. Gary Swenson (ECE 445 – Professor) • Paul Rancuret (ECE 445 - Group 14 TA) • Commercial Contacts • Michael Clodfelter (NEC Electronics contact) • Patrick and Jon Murphy (Opti-Logic contacts) • Sanley Yuen (Lin Engineering contact)

41. Additional affiliations