460 likes | 577 Vues
Bryan McDonnel Michael Mize Ryan Taylor Miles Whittaker. Design Review: RoboSiM Robotic Surveillance in Motion. Outline. Project overview Project-specific success criteria Block diagram Component selection rationale Packaging design Schematic and theory of operation PCB layout
E N D
Bryan McDonnel Michael Mize Ryan Taylor Miles Whittaker Design Review: RoboSiMRobotic Surveillance in Motion
Outline • Project overview • Project-specific success criteria • Block diagram • Component selection rationale • Packaging design • Schematic and theory of operation • PCB layout • Software design/development status • Project completion timeline • Questions / discussion
RoboSiM Overview • Robotic surveillance vehicle • Navigate to a target • Avoid obstacles • Survey target location by recording audio
Project Specific Success Criteria Demonstrate an ability to: • Display the current status of the robot on an external display. • Read from and write to a portable media device. • Make navigational decisions based on sensor, GPS, and digital compass data. • Control the robot using steering and motor drive. • Capture and encode audio.
Component Selection • Microcontroller: PIC24H • Audio encoding • G.711 needs 1 MIPS • Capable of 40 MIPS • Free libraries from Microchip • Numerous peripherals • 2 SPIs, 2 I2Cs, 2 UARTs • Robust IDE • MPLAB and development board
Component Selection • GPS Module: Skytraq VENUS • Accurate • < 2.5m CEP • Configurable update rate • Up to 10 Hz • Form factor • Breakout board • SMA connector
Component Selection • Sensors: Ultrasonic • Range • 6” – 254” with 1” resolution: (Vcc/256)/in • Wide beam for general obstacle detection • Multiple interface types • Digital serial • Analog voltage • PWM
Packaging Design • RP5 Chassis • Tank treads • Small • Motors • 6” per second nominal • Forward-mounted microphone • Forward and side-mounted ultrasonic sensors
Packaging Design Top View
Theory of Operation • Obtain data from SD card and note current location • Validate SD card coordinates and initialize systems • Start motors and travel to destination while continuously sampling sensors • Navigate around objects using compass and sensors • At destination, sample microphone using ADC • Return to starting location
Theory of Operation/Schematics • Five Key Functional Blocks • Object Detection • Navigation • Motor Control & Power • Audio Capture • Display and Storage
Microcontroller Reset PICKIT-2
Microcontroller Audio
Power - Battery • Regulators designed to accept 8 – 11 V input • 8.4V NiMH AA rechargeable battery pack used as input • 2200 mAh • Buck regulators used to produce 7.2V and 3.3V output • Motors draw 2.45 A each at stall
Navigation • Digital compass and GPS used • GPS runs at 10 Hz, Digital compass at 20 Hz • Dead reckoning between GPS samples • GPS sends NMEA* string over UART that will be parsed to determine current location • Algorithm described in software narrative *National Marine Electronics Association 0183 Standard
Object Detection • Three ultrasonic sensors attached to chassis • Front-, left-, and right-facing • Sensors run in continuous scan mode at 20 Hz • Distance to object corresponds to 6.45 mV / in [(Vcc/512)/in] • Sensors sampled by ADC using 12-bit resolution
PCB Layout: Overview Low-Power High-Power
PCB Layout: Power Supply 3.3V Supply 7.2V Supply
PCB Layout: Power Supply High Current (up to 5.1A) 75mil traces
PCB Layout: Power Supply Routed to shorten current loops (both regulators) 2 4 5 1 3
PCB Layout: Power Supply Routed to shorten current loops (both regulators) 4 5 1 2 3
PCB Layout: Power Supply Additional caps Redundant caps to prevent brownout during motor load changes
PCB Layout: Motor Control H-Bridge Controllers
PCB Layout: Motor Control H-Bridge Controllers High Current (up to 5.1A) 75mil traces
PCB Layout: Motor Control Data Data & Power Traces Separated Power
PCB Layout: Motor Control Planned Thermal Relief Plane
PCB Layout: Microcontroller PIC24H Microcontroller
PCB Layout: Microcontroller four decoupling caps placed close to pins
PCB Layout: Microcontroller Two caps under board to better utilize space
PCB Layout: Microcontroller Unconnected pins configured as outputs and left floating
PCB Layout: Peripherals Analog Digital SD Card & LCD Headers Mic & Audio Amplifier Ultrasonic Sensor Inputs GPS, Digital Compass, & PICKIT Headers Reset Circuit
PCB Layout: Peripherals Analog Digital Separation of analog & digital interfaces
PCB Layout: Peripherals Analog Digital Analog and switching lines cross at right angles (2 cases)
PCB Layout: Peripherals Analog Digital Peripherals connected through headers to preserve board area & minimize traces (9 headers)
Software Design • Navigation • Haversine Formula • Used to calculate great-circle distances • Only need three points • Robot position: • Target position: • North pole:
Software Design r = Radius of Earth