Typewriter Repairmen 2019 NURC Robot

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This is The Typewriter Repairmen's page for the 2019 National Underwater Robotics Challenge, a competition put on by Si Se Puede in Tempe, AZ.

The Typewriter Repairmen is a family robotics club. Jim, the Principal Instigator, is a "retired" mechanical engineer. He has worked with the local FIRST high school robotics team NERDS for the past 13 seasons as an engineering mentor, and discovered that it's about the most fun thing there is. Janet, his wife, is a retired engineer. Jim's brother David is an Electrical Engineer at the University of Arizona's Steward Observatory, and also runs a side business Cathode Corner, which sells neat electronic gadgets.

Link to the 2009 NURC robot notBob

Link to the 2010 NURC robot Babs

Link to the 2011 NURC mission

Link to the 2012 NURC autonomous robot Biff

Link to the 2013 NURC mission

All through the project we have been posting videos on youtube.

Contact us at jforb427@gmail.com

June 17, 2019

The team met up in Tucson for a birthday party Sunday, and some robot testing. Linus played with our new ROV for a while, and decided that it works ok. It's pretty zippy, but not balanced quite right. He also played with Babs for a while, practicing picking up pool toys and putting them in a basket, and generally getting the feel of how it is flying an ROV. He seems to be quite quick about learning how to operate the ROVs, which is not surprising, since he's played with land robots and video games quite a bit.

After getting home with the ROV, Jim worked on repairing the camera servo power supply, installing the light assembly that David had made, and fiddling with the depth sensor. He took apart another car type USB power adapter, and soldered some wires to it, and installed it in the robot. It works now. He also did a little rearranging of the light assembly, and installed it, and it works, too. The lights are dimmable, using PWM, which required only a little configuration in QGroundControl. But the lights seem to flicker sometiems at their dimmest setting, which may or may not be a problem--we can eithe run them full power, or install a resistor to dim them, which might not make them flicker so much.

Janet has been working on the report and display. Carol has been working on the claw some more, and made some parts. Jim is going to see if he can get it finished and on the robot soon.

June 8, 2019

Jim finished assembling the robot today, and took it for a test swim. There are a few problems, the depth sensor is a bit flaky, it won't admit to having a signal when attempting to calibrate it. But when the robot is in the pool, it does indicate depth. And give error messages. The servo for the camera is not working, the new old power supply that David wired up appears not to actually work. We will figure out a replacement for it. The enclosure was difficult to assemble, it uses really thick O rings, and the fit in the end flanges is a bit tight. But after chamfering the tube on the inside at the ends, and adding plenty of silicone grease, and propping the thing up on it's end so he could put all his weight on it, Jim was able to get it put together. He also made a handle, so it's easier to carry around. And he added weight to the bottom of the frame, to get it heavy enough to sink. It still needs some trimming, but it's pretty close to neutrally buoyant, and level. The test in the neighbor's pool went well, although we need to fiddle with the joystick configuration, to get the directions correct. It goes backwards when it should go forwards, and left when it should go right. But up is up, fortunately.

June 8, 2019

David anbd Linus visited today. We did several things, including making the tether (weaving foam "backer rod" in with the power and ethernet cables), mounting the pixhawk, cleaning up the 5v power supplies, designing the light mounting bracket, and making skids for the frame. We still need to install the tether after the potting epoxy cures, wire in the thruster cables, and bolt the skids on and add a bit more bracing to them.

June 7, 2019

The frame is now going to be mostly 3/4 inch by 1/8 inch aluminum extrusions, both angle and strap. The new angles are made, mostly. Jim drilled holes in one end plate for cable penetrators, and started potting them. He also weighed the robot so far, it's probably going to work, if the calculations are correct about the water displacement. We will find out when it finally goes for a swim, in the next few days.

Janet has started on the technical report, including the list of materials used. And David and Linus are planning to visit tomorrow, and help with the building.

June 6, 2019

Jim has been tinkering with electronics more. Most of the control system is mounted in the Sealed Compartment for Underwater Light and 'Lectronics (SCULL). The lights are not installed, but the power supplies, camera, Pi, Pixhawk, speed controllers, and servo are. Most of it is working. The Pixhawk and two of the power supplies still need to be mounted, as they are just hanging by their cables. Fitting all the parts in was a bit more complicated than expected, mostly because it's a pain to figure out how to route the cables. Perhaps making more compact USB cables might help.

This is the laptop display, showing the camera's view of the living room.

May 28, 2019

Jim has been tinkering with electronics. He got the laptop running the control program, and temporarily connected four thrusters to ESCs and the Pi and pixhawk and game controller, and made the motors run. He figured out why the heavy camera works, but the smaller board camera won't work--something about the companion comumputer (Pi) being configured to work with an H264 video but not default USB video. David ordered a board camera, that might work right. Jim is still working on a parts list of more stuff to order, it never seems to end. Carol started working on a CAD model of the overal ROV design. Jim meanwhile has been tinkering with a crude frame structure to hold thrusters sort of where they belong, so we can get a look at it. And the new T shirts that Janet ordered are now in our possession, they look great!

This is the first glimpse.

May 23, 2019

We bought more robot parts from BlueRobotics. 6 thrusters, 7 more ESCs, a motor, an enclosure, and several penetrators. We still need some more stuff, but this will get us going. Jim has been tinkering with the control system (it's in Sierra Vista now, not Tucson), and has almost figured out how it's supposed to work. He also ordered some more parts, including a USB to Ehternet adapter, so he can use a modern laptop to talk to the Pi. He is also working on the overall ROV design, trying to figure out how to stuff all those parts into the enclosure. Hopefully more updates soon.

This is the working environment.

March 31, 2019

David bought a few control system parts to play with. Linus connected stuff together, and loaded some software, and made things work. The control system includes a Rapsberry Pi 3 (not the 3+), a Pixhawk controller, an Xbox gamepad, a laptop, and a 12v power source. It also has a BlueROV motor speed controller and one T100 thruster, and a USB camera.

This is the test setup.

We discussed the robot design, and decided that we would plan on using the 6 thruster layout with two vertical in front, one vertical in rear, two forward on the sides, and a lateral thruster in the center. We discussed how to build the thing, and will start the design by making a "box" of thin 1" aluminum angle. We will try to design it so that the thrusters can be relocated easily if needed, and so the enclosure is easy to work on. Havign some expreience with redesigning Babs a few times, we know the importance of thruster location relative to the centers of mass, buoyancy, and drag, in all directions. Also we discussed the relative locations of the center of mass and buoyancy, with the tenative requirement that the robot be stable, but not too stable. The stability helps keep it level, but too much will make it hard to tilt if needed to reach down with the claw, for example.

We also talked about possible manipulators. David presented the idea of a "barb" to skewer the brain blood clots. We didn't get too far figuring out how to tilt it, though. We also looked at the BlueROV claw, and at the vEx claw. We discussed using the vEx claw with a BlueROV brushless motor, and using a combination of worm and spur gears to drive the claw. We figured that about 1 second opening/closing time would be good, and motor speed of 4000 RPM, would require about a 70:1 reduction.

We will probably order more parts soon, although we'd like to get a first draft of the overall ROV design in CAD first, and also spend some time refining the list of requirements. We are already pretty sure about a lot of the general requirements for the ROV, having played other underwater robot games. The specifics of manipulating stuff is where we have some questions.

March 10, 2019

David and I have been discussing electronics. Also talked about it with Kevin and Carol, and Linus. Some ideas include using a Pi in the ROV, and another on the surface, connected with an Ethernet cable. For power, we are considering a 48v system on the surface, with a relatively small two wire tether connected to a 48v to 12v switching power converter in the ROV. This would give us regulated power, and voltage drop on the tether would not affect motor performance much. We have a very preliminary list of requirements for the system here.

And we got Babs out, and plan to take her up to Flagstaff to show others a NURC robot. Recruiting new teams!

February 12, 2019

The first thing we need to do is analyze the requirements for this mission. Janet it working on a spreadsheet to do that.

February 1, 2019

NURC is back! We signed up for the event. Now, we have to figure out how to build a robot to play the game. We would like to design a new ROV that uses as many off the shelf parts as possible, and also we would like to get things done soon enough that other teams might get some new ideas of how to do things, by watching our progress. As usual, we are a bit late, and life is kind of busy right now with FIRST robotics.

Copyright 2009-2019 Jim Forbes, David Forbes, Steven Forbes