1. 1 Autonomously Controlled Vehicles with Collision Avoidance Mike Gregoire Rob Beauchamp Dan Holcomb Tim Brett

2. 2 Motivation Follow and Avoid Collisions Simulated Highway Driving Environment Autonomous Not Centralized  Centralized System Not Practical for Today's Highways Predictable Vehicle Behavior  First Car Moves, Others Follow

3. 3 System Block Diagram Ultrasonic Sensor Scans Area in Front of Vehicle for Objects Controller Receives Distance and Angle Information from Sensor and Decides what to do The Controller Interfaces to the Platform to Drive the Vehicle

4. 4 Overview MDR Deliverables Sonar Sensor Vehicle Interface Specification of Control Behavior Costs Spring Goals

5. 5 MDR Deliverables Functional Sonar Sensor  Distance  Direction Platform Interface to Control Vehicle  Motor (Speed)  Actuator (Turning) Specification of Control Behavior

6. 6 Functional Sonar Sensor Sonar vs. Optical Chose Sonar Precise Distance Measurement Is Not As Important as Relative Distance Minimum Range is 1.1 ft due to Ringing in Receiver Maximum Range is > 8.36ft (for a ceiling) but a Software Limit of 5.5ft is imposed Sonar Optical

7. 7 Sensor Graphs – Ceiling (Stationary) Speed Of Sound = 1100 ft/s Left Channel Median ~ 7550µs =49.83 Inches Right Channel Median ~ 7570µs =49.96 Inches 150µs Error is a 1 Inch Error in Measured Distance

8. 8 Sensor Graphs – 2x4 (Moving) 2x4 Board Moving Left to Right over Sensor The Difference Graph Shows Discreteness in Time. Differences Are Equal to 1 Period (25µs) Can See Precise Angle Change using Difference Modulo Period

9. 9 Sensor Graphs – Error and Reliability 15 Discrete Distances – 1000 Measurements at Each Software Filter on Sensor Qualifies each Point. Counter has to be between 2000us and 8000us with a Difference between -160us and 160us. Contour Shows Percentage of Points out of 1000 that are within Filter Limits Recreation of position has large error because of inaccuracy in the angle measurement. This is because the same wave front doesn’t trigger both sensors. Using Mod 25 gives accurate change in angle but not an absolute angle.

10. 10 Platform Interface No Schematics Available Need to Reverse Engineer Controls  Motor for Speed  Actuator for Steering Direct Interface Simplest Solution

11. 11 Platform Interface - Speed Motor Interface Uses Two Wires  One Wire Tied to Ground  One Wire Connected to PIC Through Current Driver PIC Outputs Using Pulse Width Modulation (PWM)  24µs PWM Period → 41.667kHZ Frequency  96 Discrete Duty Cycles with 4MHZ PIC Clock Need to Overcome Motor Inertia when Stopped

12. 12 Platform Interface - Turning Actuator Interface Uses Four Wires  2 Wires Used For VDD and GND  2 Wires From PIC Output Control Left / Right Turns Control Wires at Opposite Voltage Steps Actuator  Length of Voltage Differential → Length of Turn  20ms For Turn From Center to Full Left / Right  Angle Turned is Surface Dependent

13. 13 Platform Interface Movie

14. 14 Platform Interface Movie

15. 15 Control Behavior Follower should Not Always Drive Directly Towards Leader Follower should Trace the Path of the Leader Bad TurnGood Turn

16. 16 Control Behavior Proposal: Use a FIFO Instruction Queue For each Sensor Data Point, a New Instruction is Loaded into FIFO When Instruction Reaches Head, Follower Occupies the Same Point as Lead Car When Instruction Entered FIFO

17. 17 MDR Deliverables Functional Sonar Sensor  Distance  Direction Platform Interface to Control Vehicle  Motor (Speed)  Actuator (Turning) Specification of Control Behavior

18. 18 Product Costs $500 Total Budget Fall Expenses ≈ $150  3 Vehicles For Free  Ultrasonic Transducers ≈ $50  Op-Amps, PICs, Drivers, Etc. ≈ $100 Spring Expenses  2 More Vehicles ≈ $100  Ultrasonic Transducers ≈ $50  $200 for Unforeseen and Misc. Parts

19. 19 Spring Goals Integration of Systems  Communication From Sensor to Platform Controller Three Functional Vehicles  2 With Our System Refine Sensors  Variable Gain to Help Filter Noise Perform Demonstration  Lead Car Driven via Remote  Two Autonomous Vehicles Accurately Follow

20. 20 Thank You Questions?

21. 21 Supplemental Amplifier  2 Stage -5V to +5V Amp With a Maximum Gain of 1406 V/V With A DC offset of -1V  Output Put into a GND to +5V Amp With a Maximum Gain 37.5 V/V