Sensors Overview
In order to complete its mission, Nova uses a wide array of sensors for vehicle control and environmental sensing, including a Dopper Velocty Log, an altimeter, a compass, a depth sensor, a 3DM-GX1 and two cameras.
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Nova's hydrophone system uses four Reson TC4013 piezoelectric elements to detect incoming sound waves. The elements output electrical signals to an analog front-end circuit board. This board provides pre-amplification, filtering, variable gain amplification and analog-to-digital conversion. Eight Microchip MCP6S21 variable gain amplifiers (VGAs) provide up to 40 dB of software adjustable gain on each channel. The signals from the VGAs are sampled at 2 MHz with 12 bits of resolution using two AD7266 ADCs. These ADCs use a proprietary SPI protocol to communicate with a Blackfin digital signal processor (DSP), which lies on a separate circuit board within the hydrophone enclosure. The DSP estimates the heading and azimuth of the sound source and sends this information to Nova's computer. More information on the passive acoustic array.
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Doppler Velocity Log
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An RDI Workhorse Navigator DVL gives position and enables closed-loop velocity control. |
Depth Sensor
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The depth sensor board provides real-time information about the craft's depth below the surface of the pool. Analog pressure data (up to 100 PSI, or approximately 55 meters below the surface) is obtained from an MSI UltraStable-300 pressure transducer, operating in a 4-20 mA current loop. A 24-bit AD7791 Sigma-Delta Analog to Digital Converter is used to capture pressure data, which is converted into a depth reading by an on-board microcontroller and reported over RS232. Depth Sensor Board datasheet |
Cameras
Triton uses two cameras, one forward facing and one downward facing.
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Forward: A Logitech QuickCam Pro for Notebooks webcam is used for the vehicle's forward vision. |
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Downward: An AVT Guppy F-046 Color CCD Camera is used for the vehicle's downward vision. |
Orientation Sensor
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A Microstrain 3DM-GX1 Orientation Sensor provides the vehicle's heading, pitch, roll and velocity rates in 3D space. The sensor has had its top cover removed and replaced with a custom printed circuit board connected to an internal header to allow the sensor to use the standard vehicle connectors. This data is used in the Kalman filter of the controller to allow for better sensor fusion and faster control response |
Altimeters
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A Tritech PA500 altimeter provide distance to the nearest forward wall. |
