Hi All,
I am sure that many of you have heard of the OpenROV Project which involves building your own ROV from a kit. I am an experienced model builder with plenty of experience and a reasonably equipped workshop, but I was a little taken aback at the complexity of assembling the OpenROV from their kit of parts. It seemed to me to be a high school to college level project requiring a small team of experienced modelers to successfully put the OpenROV together though I could be wrong.
It appeared to me that there were a number of critical assembly requirements that had to be performed spot on as there was no going back to realign or reseal once the assembly was completed. Therefore I have been looking around to see if there might be an easier way to design and build a ROV similar to the OpenROV without having to perform some of the critical assemblies required to complete the OpenROV.
One area of the OpenROV design that I took exception to was the thrusters. They were not going to last very long when immersed in seawater due to the exposed bearings and stator/armature. To me this was a kind of deal breaker as to the questionable lifespan of these thrusters. I know that commercial thrusters are not cheap (think Seabotics or CrustCrawler) and the OpenROV project was just trying to overcome the high price of commercial thrusters with their homebrew design. Still the unknown lifespan of the OpenROV design did not leave me with a warm feeling to say the least.
Then came along Blue Robotics and their T100 Thruster KickStarter Project Link. Their design approach looks good and they have actually tested and characterized prototypes of the thrusters they will deliver to the pledgers. With the addition of the in-thruster water cooled ESC this design becomes very attractive in that it reduces the number of wire penetrations in the Water Tight Compartment (WTC).
Great! Now we have a source of reasonably priced thrusters so what is next? Well, that is where you, the ArduBoat members, come in.
Let's start thinking about the WTC, navigation controller, communication, power, ballast, buoyancy, etc. and attempt to come up with a reasonably priced ROV that the average ArduBoat member might want to consider building.
Regards,
TCIII AVD
Replies
Hi All,
For those of you who are going to control your BlueESC Thrusters over the I2C bus, you will obviously have to program each Thruster with its own unique I2C address.
The instructions for doing so are available from the Blue Robotics Documentation website. Changing the BlueESC I2C address is done by reprogramming each BlueESC with the correct idX.hex firmware. According to Rusty, the starting I2C hex address 0x29 corresponds to firmware id0.hex while I2C hex address 0x2A corresponds to firmware id1.hex and so on.
Presently I have programmed my Seeeduino Duemilanove with the ArduinoUSBLinker and have loaded and run the KKMulticopterTool on my laptop. So I will be ready tomorrow to begin reprogramming the I2C addresses of my six T100 BlueESC Thrusters.
Regards,
Tom C AVD
Hi All,
Good news! Today I confirmed the functionality of each Thruster by controlling them one at a time using their PWM inputs.
Following the instructions on the Blue Robotics website for the BlueESC, I powered up my trusty servo tester first, with its output set to 1500us (neutral) before applying power to each Thruster. I checked each Thruster for forward and reverse performance and was satisfied that each thruster performed as expected.
The next step will be to program each Thruster, using the PWM control signal line as a serial input, with its own unique I2C address between the range of 0x29 - 0x38. The programming will require an Arduino Uno and a PC or laptop. The programming application (either avrdude or KKMulticopter Tool) on the PC/laptop will communicate with each individual Thruster through a program on the Arduino Uno called ArduinoUSBLinker.
More to come.
Regards,
Tom C AVD
Hi All,
I have completed the battery and control signal interconnections so I can separate the Battery and Navigation Controller Tray connections from their respective ESC power and signal cables.
I will now power up each ESC individually and control it with my trusty servo PWM controller. Once I have determined that each ESC will respond to PWM input, I will program each ESC with its own individual I2C address (0x29 - 0x38). Each ESC comes with a default I2C address of 0x29. The ESC I2C address reprogramming is performed using the ESC PWM control signal per Blue Robotic's BlueESC Documentation.
Once I have completed the ESC I2C address reprogramming, I will test each ESC over its I2C control signal connection using an Arduino Uno R3 and a program available from the BlueESC Documentation.
More to come.
Regards,
Tom C AVD
@Patrick,
The marine bilge pumps have more than tripled in price over the last couple of years so they are not as cost effective as they once used to be.
Also, the deeper the ROV goes, the tighter the rubber seal on the pump shaft becomes driving up the motor current draw. I have wondered how well the shaft seal would hold up under repetitive dives to 100 feet?
Regards,
TCIII AVD
The first iteration was just a Home Depot bucket with two bilge pumps on either side. Super simple. Using the skid-steer function, it was very controllable and did not require much engineering.
Hi All,
Today, with the help of my son-in-law, I was able to check the ROV Chassis buoyancy and trim by immersing it in the Association swimming pool.
The addition of the two 2.7 pound ballast tubes to the bottom of the Chassis brought the buoyancy of the Chassis to a point such that the top of the Chassis was just awash in the pool water. This level of buoyancy puts the two vertical Thrusters just about three inches below the surface of the water. Also the present buoyancy is such that when the Chassis is manually forced downward into the water, it will slowly rise back to a point where the top of the Chassis is just slightly above the pool surface.
The following two pictures will give an idea of the ROVs present buoyancy:
Once the Chassis has dried off I will begin installing the Battery Compartment Battery Tray and then move on to the Navigation Controller Compartment Controller Tray.
More to come.
Regards,
Tom C AVD
Tom,
This was without any batteries or electronics yet, right? Do you have an estimate of the weight of those items?
-Rusty
Hi Rusty,
There are two batteries sitting in the Battery Compartment WTC in the same position as when they are attached to the battery sub tray. The two batteries just balance out the weight of the cables and cable penetrators at the back of the ROV Chassis.
Presently there are no electronics in the Navigation Controller WTC, but the addition of the navigation components (processor and interfaces) should have a very small effect on the buoyancy/trim that can be easily compensated for.
Regards,
Tom C AVD
Hi All,
I completed splitting the 5 pound 17 inch ballast tube in half and fabricated two 8 1/2 inch tubes that weigh approximately 43 ounces (2.7 pounds) each for a total of approximately 5.4 pounds of ballast.
Each ballast tube is mounted on the bottom of the ROV Chassis at the mid point of the longitudinal axis of the Chassis. The picture below will give you an idea of the ballast tube construction and their mounting location on the Chassis:
The ballast tubes are a slip fit in their U shaped clamps and can be moved fore and aft to help trim the Chassis. I plan to use tie raps around the tubes on either side of the cross brace, on which the tubes are mounted, to keep the tubes from sliding in the U shaped mount.
This weekend I plan to finish the Battery Tray and connect the Power Junction Board cables to their respective cable penetrator cable connections and complete sizing the length of and installing the connector on the Power Junction Board battery input cable.
More to come.
Regards,
Tom C AVD
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