NaviRutgers University2012 Design Presentation

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Mechanical Design

• Entirely custom chassis– Designed using SolidWorks– 80/20 aluminum framing– 0.25” polycarbonate casing– 240 lb, including payload

• Brushed DC drive motors– 80 W, 500 CPR optical

encoders– 5.6 mph maximum speed– 27% maximum grade

• Actively air cooled by six fans– 100 cfm airflow through

chassis– Modeled using CFD

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Electrical: Power Distribution

• Optima YellowTop Battery (×2)– 12 V lead acid batteries (in

series)– 35 A·h capacity

• Low power consumption– 400 W loaded, 215 W idle– 2+ hour battery life

• 24 V, 12 V, and 5 V DC buses– 85%+ efficiency DC-DC

regulators– Isolated grounds limit noise

• Dashboard– Switches for major components– Dot matrix display status

indicator

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• Use and contribute to open source software when possible

• Built on the Robot Operating System (ROS) framework• Three-dimensional Gazebo simulation of driving and

sensors

Software Architecture

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Gazebo

GazeboLocalization

Perception

Planning

Gazebo Simulation

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Localization: Sensors

GPS: Novatel ProPak V3• 2 Hz sample rate• 15 cm accuracy (1 sigma)• OmniSTAR HP corrections

Compass: PNI Fieldforce TCM• 50 Hz sample rate• 0.3° heading accuracy

(RMS)• 360° tilt correction

Odometry: US Digital Encoders• 500 CPR, 0.5 mm

resolution

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Localization: Extended Kalman Filter

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(Source: Probabilistic Robotics)

• Fuse sensors to estimate pose– Odometry: fast, relative pose– Compass: fast absolute orientation– GPS: accurate absolute position

• Non-linear “turn-drive-turn” model

Hardware Simulation

Perception: Sensors

Laser: Hokuyo UTM-30LX• 40 Hz sample rate• 240° field of view• 30 m maximum range

Cameras: AVT Manta G-125C (×2)• 15 FPS, synchronized• 646 × 482 resolution• 90° × 65° wide angle lens• 130° combined field of view

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Perception: Laser Field of View

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240°

Perception: Sensors

Laser: Hokuyo UTM-30LX• 40 Hz sample rate• 240° field of view• 30 m maximum range

Cameras: AVT Manta G-125C (×2)• 15 FPS, synchronized• 646 × 482 resolution• 90° × 65° wide angle lens• 130° combined field of view

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Perception: Camera Field of View

1120 m

Perception: Line Detection

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Original Image Color Transformation

Width Filter

• Uses the HSV color space to limit the impact of illumination

• Width filter is generated from the calibrated camera matrix

• Pipelined with left and right images processed in parallel

• Total processing time is 100 ms per image pair• Pipelining allows for a 50% increase in sample rate

Mapping

Local Costmap: (10 m)2

• 5 cm square cells; high resolution• Always centered on the robot Used by the local planner

Global Costmap: (1000 m)2

• 25 cm square cells; low resolution• Origin fixed by a GPS coordinate Used by the global planner

• Sensors mark and clear observations• Based on the ROS navigation stack

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Planning

Global Planner (on demand)• Weighted A* Search• Inverse of distance for <1

m• Constant for ≥1 m

Local Planner (20 Hz)• Dynamic Window

Approach• 10 linear velocity samples• 15 angular velocity

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Questions?

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