Sensor Fusion

The Scout sensor suite affords increased situational awareness over comparably priced platforms1. Scout fuses long range sonar with short range IR sensors and LED reflectance sensors to provide realtime feedback about the robots' environment. Commercially available off-the-shelf components were used where possible, selected based on range, accuracy, and repeatability characteristics.

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Environment Mapping

Ultrasonic ranging sweeps 360 degrees around each Scout robot, providing up to 48 measurements per cycle. A compact stepper motor provides precise and rapid position control. The high resolution and fast scanning speed are appropriate for 2D mapping and navigation.

The Maxbotix® EZ™ line of sonar rangefinders was chosen for their proven accuracy and long term reliability2. The EZ4 provides the narrowest sensing area of the EZ™ family, allowing higher precision maps to be produced, while still providing wide coverage for obstacle detection.

Cliff Detection

A trio of short range Sharp® IR rangefinders provide early warning of sharp drop-offs that could compromise the robot's mission.

Odometry & Vehicle Dynamics

Vehicle position is tracked by quadrature encoders on each wheel resulting in 3mm linear accuracy 3. A custom IMU (inertial measurement unit) consisting of a 3-axis accelerometer and pitch+yaw-rate gyroscope provide detail of the vehicle's motion in three dimensions.

Complementary Sensing

The sonar rangefinders are optionally supplemented by short range LED reflectance sensors for close wall following. A sensor on the front bumper provides resolved impact detection for escape manuevers or when manipulating objects.

  1. Comparison with commercially available robots valued at <$500 USD.
  2. PDF: Maxbotix® EZ4™ Sensor Testing
  3. 48 clicks per revolution, 42mm diameter wheel. (42mm*pi)/48=2.7488mm


Scout communicates over several protocols, providing a robust interface over long distances. Inter-robot communications and control commands are broadcast over a self organizing high bandwidth mesh network. The robots also broadcast over IR (infrared light) for localization.

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