Salt Lake City, Utah
June 23, 2018
June 23, 2018
July 27, 2018
Ocean and Marine
Ever since the publication of the little yellow book “Build Your Own Underwater Robot and Other Wet Projects” by Harry Bohm and Vicki Jensen [Westcoast Words, Vancouver, BC] thousands of students have built and flown the Sea Perch ROV. Made of PVC pipe, toy motors and switches, the Sea Perch has provided students with hands-on experience in hydrostatics, hydrodynamics, and basic electronics. The simplicity of the vehicle’s design makes it tractable to beginning students with little or no building experience, yet once students see it maneuver in a pool they are immediately inspired to add capabilities. This paper will focus on adding new capabilities to the Sea Perch. We have enhanced the vehicle in two ways: first, we developed an inertial measurement package that was added to the Sea Perch payload bay to record data on vehicle performance and second, we incorporated an onboard computer into the Sea Perch. An onboard computer opens the door to a constellation of new Sea Perch capabilities that can be developed by students.
We have created the Sea Perch equivalent of a “black box flight recorder” that records the performance characteristics of the vehicle for later download and analysis. A microcontroller was interfaced to an integrated inertial measurement unit to measure 3-axis angular orientation, 3-axis angular velocity, and 3-axis linear acceleration. Data was recorded at 10 Hz and stored on a micro-SD card; power was provided by a 9V battery. The system was mounted in a small waterproof polycarbonate box that was lashed to the Sea Perch payload bay. In operation the student starts the data acquisition, seals the box and installs it in the payload bay. After running the Sea Perch in a variety of maneuvers, the student retrieves the vehicle and transfers the data to a personal computer for plotting and analysis.
A microcontroller interfaced with two dual motor drivers and an integrated inertial measurement unit comprised the Sea Perch onboard computer system. Communications with a topside microcontroller was accomplished with a two-wire RS-485 half-duplex communications link in the vehicle’s RJ45 tether cable. The onboard computer was mounted in an IP67 fiberglass box and powered by a topside 12V battery via the 6 remaining wires in the tether. The pilot controls the ROV through the use of a Sony Play Station 2 controller interfaced to the topside microcontroller. Real-time sensor data can be received through a monitor program running on a PC in communication with the topside microcontroller.
Our inertial sensor system enables students to quantify the motion of their vehicles and thus let them analyze the ROVs performance as an engineer would. The onboard computer moves the Sea Perch further up the engineering ladder to make it a vehicle that provides limitless options for modification and creative design. In this paper we will discuss the design of the inertial measurement system and its use in a summer high-school program at MIT, as well as the design and performance results of the Sea Perch onboard computer and its educational potential.
Consi, T. R., & Lorrey, J. F., & Kornberg, M. (2018, June), Beyond the Sea Perch Paper presented at 2018 ASEE Annual Conference & Exposition , Salt Lake City, Utah. https://peer.asee.org/29849
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