The Johns Hopkins University Remotely Operated Vehicle
Dynamical Systems and Controls Laboratory
Department of Mechanical Engineering
| JHU ROV Designers/Collaborators | |
| JHU ROV Components | Movies/Pictures |
| JHU ROV History |
The Johns Hopkins University Remotely Operated underwater robotic Vehicle (JHUROV) is an uninhabited, tethered underwater robot. It's purpose is to serve as an experimental test platform for research in the areas of underwater vehicle dynamics and control, underwater navigation, and marine thrusters. The JHUROV is 1.5 m high by 1.0 m wide by 0.6 m high. In it's current configuration the dry mass of the JHUROV is approximately 200 kg and it weighs 2.5 kg in water. The JHUROV is a tethered underwater robot, which means that it's motions are completely controlled via a pilot using a computer or joystick above the water (topside). In addition to providing a way to control the robot, the tether also carries DC electrical power and sensor/video signals to and from the robot. The following is a brief introduction to the JHUROV.
Telemetry/Sensor Pressure Housing: The telemetry/sensor pressure housing is where several sensors plug in to the JHUROV and receive power and serial communication signals. The housing itself is made from AL 7075 and has a 6" ID. Including the endcaps, the length is 40". The endcaps are also made from AL 7075. The housing contains air at 1 atmosphere, made possible by both bore and face o-ring seals on the endcaps. The design for the housing is rated for 1000 meters. The telemetry uplink is provided by a DIGI TS8 Terminal server. This device contains 8 serial ports. These serial ports are used by several PC's above the water to control the vehicle and take sensor readings. Also contained within the housing is a KVH Azimuth Digital Gyro Compass. Connected to the housing via waterproof connectors on the endcaps are the fiber optic gyro, the pressure depth sensor, and a serial communication link to the motor/thruster pressure housing. Inside the housing is a DC/DC voltage converter that provides isolated DC power to the sensors and terminal server.
Motor/Thruster Controller Pressure Housing: The physical dimensions and make up are the same as for the telemetry/sensor pressure housing. Contained within the housing are six Copley 513R current mode, PWM motor amplifiers and a PC/104 form factor computer stack. The PC/104 is used to control the motor amplifiers and the Crydom solid state relays also found in the housing. The solid state relays relay power to the amplifiers. Six separate thrusters plug into the housing and amplifiers via waterproof connectors on the endcaps. Using a custom designed and built opto-isolation board, each amplifier reports the angular shaft position of it's respective thruster using emulated encoder outputs, as well as amplifier fault status. In addition the reference voltage commanded to the amplifiers is routed through the opto-isolation board.
Junction Box: The junction box is an AL 6061 oil filled structure with several waterproof cable feed-through connectors. The purpose of the junction box is to receive power and communication signals from the topside computers and power supply and redistribute them subsea to the proper places. All connections within the junction box are made using rail mounted terminal blocks. These include fuses for the main power feed from the tether.
Thrusters: The six thrusters are 1.5 kW, 3-phase DC brushless electric thrusters. They are direct dive drive units employing a Crane rotating shaft seal. Using an internal pressure compensation system comprised of a spring loaded diaphragm and oil filled housing, they are theoretically rated for full ocean depth. They use a API Harowe resolver for angular shaft position feedback. The motor uses a permanent magnet and is rated for 6.5 N-m maximum torque and 2.16 N-m continuous torque. The Vetus propeller used is a symmetrical prop, which mated to the chosen motor provides 150 N peak thrust. They are controlled via PWM current control motor amplifiers running at 150 VDC, +/- 10 A.
Floatation Block: The floatation block is composed of some home construction, foam insulation planks. These planks are glued together and coated with fiberglass and a stunning coat of red paint. Truly a work of art.
Tether: The tether is composed of a communication cable, a power cable, a video cable, two LBL acoustic transponder cables, and a power and serial line for the Doppler Velocity Log. These cables are all bonded together to form the tether. The current length of the tether is 100 feet.
Frame: The frame is constructed from aluminum tubing.
Camera/Lights: The JHUROV is equipped with an underwater color video camera and two 100 W underwater lights (not seen in photos above).
Power Supply: Electrical power for the JHU ROV is supplied using a Sorensen 10 kW, isolated, DC power supply.
Navigation: Several sensor are used in the navigation of the JHUROV. For x-y-z navigation the JHUROV uses a 300 kHz LBL Sonic High Accuracy Ranging and Positioning System (SHARPS) time-of-flight hardwired acoustic transponder system and a Paroscientific depth sensor. For measurement of the angular orientation of the JHUROV either a IXSEA Octans 3 axis Fiber Optic Gyro (FOB) or KVH Azimuth Digital Gyro Compass may be used. Using the SHARPS system and the paroscientific depth sensor the JHUROV position can be determined with a resolution in the millimeter range in the x-y-z directions. The standard deviation of these position measurements is on the order of millimeter/sub-millimeter depending of the acoustic transponder layout, range, and depth of the JHUROV.
The JHUROV is also equipped with a RDI 1200 kHz Doppler Velocity Log (DVL). Utilizing the DVLNAV software program, the DVL provides an additional navigation solution.
Control System: The control systems consists of several desktop PC's running either a windows operating system or Linux. The windows OS PC's run several Graphical User Interface (GUI) programs to control several functions on the JHUROV and display all pertinent information regarding the navigation and control of the JHUROV. The Linux PC runs the actual control program that tells the JHUROV exactly what to do and handles all the data logging during experiments.
History/Designers/Collaborators
The JHUROV was conceived as a test platform on with which research in the areas of underwater vehicle dynamics and control, underwater navigation, and marine thrusters could be carried out at the Johns Hopkins University (JHU). The JHUROV design and construction involved the contributions and advice of several people. The first deployment/launch of the JHUROV took place in August 2000 in the backyard pool of Dr. Whitcomb.
Right: That is David Smallwood next to the JHUROV just prior to it's first actual water deployment.
Left: The JHUROV in Dr. Whitcomb's pool on it's first actual water deployment.
There have been several subsequent deployments at the United States Naval Academy's (USNA) Hydromechanics Laboratory in Annapolis, MD where work was done in collaboration with Dr. Dan Stilwell.
The above photo shows the JHUROV in the flooded dry dock of the USNA hydromechanics lab with Dr. Whitcomb, Dr. Stilwell, and David Smallwood in the background controlling the JHUROV from the topside computers.
Dr. Louis L. Whitcomb: The director of the Dynamical Systems and Controls Laboratory (DSCL) and Associate professor at JHU, Dr. Whitcomb provided endless advice on the layout and design of the JHU ROV drawing from his extensive experience with underwater robots.
David Smallwood: The chief designer, builder, and project manager of the JHUROV. Mr. Smallwood was actively and intimately involved in every aspect of the design and construction of the JHUROV. Mr. Smallwood is a member of the DSCL and Ph.D. student at JHU conducting research in the area of underwater vehicle dynamics and control. Dr. Whitcomb is his advisor.
Dr. Ralf Bachmayer: Dr. Bachmayer is a Ph.D. graduate of the DSCL and JHU. Dr. Bachmayer is now a post-doctoral fellow at Princeton University. He was the chief designer of the thrusters used on the JHUROV.
Dr. Dan Stilwell: Dr. Stillwell, currently with the Virginia Polytechnic Institute, has been a collaborator on several deployments of the JHUROV. Dr. Stilwell has deployed a Litton LN200 IMU on the JHU to examine the issue of IMU calibration.
Commander Steven Chism: Commander Chism is currently a member of the DSCL and a Ph.D. student working under Dr. Whitcomb. Commander Chism is currently planning to use the JHUROV to explore the area of advanced marine thruster dynamics and control.
Mr. James Kinsey: Mr. Kinsey is currently a member of the DSCL and a Ph.D. student working under Dr. Whitcomb. He is currently working on the problem of underwater navigation using the JHUROV. Mr. Kinsey recently oversaw the design and construction of a new test tank facility for the JHUROV on the Homewood campus of Johns Hopkins University. Click here to read an article about this facility.
USNA Hydromechanics Lab: THE USNA hydromechanics lab has been a gracious host of several of our deployments, allowing us to conduct our research in collaboration with USNA faculty in their first rate facilities.
Woods Hole Oceanographic Institute (WHOI) Deep Submergence Lab (DSL) : Dr. Dana Yoerger, Dr. Hanuman Singh, and Mr. Andy Bowen are all members of the WHOI DSL who have all graciously supplied on loan several key sensors that make the JHUROV navigation system possible. Dr. Yoerger has lent the JHUROV his 300 kHz SHARPS system, Dr. Singh has lent the JHUROV his Paroscientific depth sensor, and Mr. Andy Bowen has lent his IXSEA Octans unit to the JHUROV. Their contributions to the JHUROV are greatly appreciated.
Click here to view a 6 minute video of the JHUROV (12 MB)
Click here to view a 20 minute video of the JHUROV (54 MB)
For further questions and information please contact David Smallwood via email.