I volunteer for the Relay for Life, a fund-raiser for cancer treatment and research. I did this last year, and in addition to raising a good bit of funding we all had a blast. This year our team is doing a silent auction along with all the same fund-raising efforts we did last year. Our coordinator thought that to keep things interesting, the items should be hand-made or should be services that we, ourselves, would provide. Hey, what a perfect opportunity for someone with a home shop!
Seeing as how I used to make pens and pencils in the shop, I volunteered to do that. A few years back I got out of the pen and pencil business because I'd cranked out far too many as presents. I vowed that if I couldn't at least make it interesting (nice inlay work, mixing different woods, etc.) I simply wouldn't make them any more. I started doing a lot more creative setups, but they ate more time and more materials, and eventually I tapered off so I could spend my time doing other things like making parts for RC cars. I still have all my stuff, though, so I pulled it all out and started rummaging. Insert kits, wood blanks, even all my bushings were all there. I even had some tube sets already made up that never got assembled into pens. Great! Now all I needed to do was make them!
After a number of failed attempts at even getting out in the shop in the evening, I came to a realization: By the end of the day I'm absolutely zonked. Every time I tried to get up the energy to make pens after dinner, I realized I really didn't have it in me, and worried I might hurt myself in the process. Before you laugh, if you've seen the kinds of injuries you can get on a lathe by not having your wits about you, you'd realize this is a very real concern. So far I consider myself lucky, and I've nearly broken a finger when a three-jaw caught my hand. Yes, that's "lucky".
I got in a funk last night, figuring this was a sign of getting old. But my wife reminded me that I wake up at 5:30am on a normal morning (closer to 4:30am for an early-out morning) and she typically keeps me up 'till well after 10:00pm, so it probably has a lot less to do with getting old as it does just getting tired. This cheered me up, but there was still the matter of making pens and pencils when I'm exhausted. I just couldn't figure out how I'd get them done in time.
Then I realized I could charge my rig's batteries, check my gear, and offer my KAP services as a low-altitude aerial photography service. Yahoo!! So I printed up a little flyer I could put on the auction table, and let the coordinator know of the change in plans. I'm still going to crank out all the completed tube sets I've got, but it's going to be only a handful of pens rather than the dozen I was hoping for.
Oh how the hobbies have changed... Used to be I'd get home on a Wednesday night, give my shop buddy a call, and we'd get together out in my shop once the kids were in bed, about 9:00pm or so. We'd crank away 'till 3:00am, then we'd both get up for work the next morning. It was exhausting! It was exciting! My GOD we made a lot of pens and pencils (and rocket parts, and sailboat parts, and, and, and)! We used to eat, drink, breathe, live this stuff. And now? Now I'm trying to figure out how to use the tubes I've already made up, and not have to go make more. Have to? Boy have the times changed.
Maybe my wife is right. Maybe I'm just tired. Maybe I like the kite idea because kite flying is something that's typically done during the day when I'm awake and alert. (Well, that and it's fun as heck to do.) Maybe also it's that I now do machining as part of my daytime job. It's not the forbidden fruit it once was; it's part and parcel of daily life. Maybe I've simply moved on.
Or maybe I'm finally catching up on all the sleep I missed when I spent all those Wednesday nights doing shop-night... In that case I have a long way to go...
- Tom
Wednesday, September 26, 2007
Thursday, September 20, 2007
ROV Teams - More Ideas
Pololu Robotics recently released a truly novel electronic speed controller (ESC) called the TReX. It will drive two bidirectional motors up to 13A continuous, 30A peak from 6V-16V and one unidirectional motor up to 15A continuous. It can be controlled through RC inputs, analog inputs, or through a serial port that has either RS-232 or TTL voltage levels available on it. The control mode can be changed on the fly, which makes it a truly unique device:
http://www.pololu.com/products/pololu/0777/
So here's the idea for teams building underwater ROVs for competition:
Several people have demonstrated that you can replace an RC transmitter antenna with a coax cable that can run underwater and terminate inside the dry box of an ROV. The dry box termination is basically to leave N inches of the coax core exposed as an antenna (N depends on your transmitter frequency, and needs to be wavelength-matched). The coax acts like a waveguide so the transmitter is essentially transmitting inside the dry box. Place the RC receiver nearby, but not in contact with the antenna coax. Voila, you now have RC feeding into your ROV.
Plug in two of the TReX speed controllers. Channels 1 and 2 drive the fwd/rev/turn thrusters. The TReX can be set up to do onboard channel mixing, so the primary joystick of the RC transmitter could be used as a fwd/rev/turn control, just like a video game. (For those who are slow to pick up on hints, by just like a video game I mean it gives your operator an interface they're already more than comfortable with, which means less seat time is required for them to become proficient in using the ROV!)
Channels 3 and 4 use the second TReX drives two vertical thrusters that can be used for ascent/descent/tilt. Considering how many ROVs wound up in a massive down-pitch after picking up a mission prop, having the ability to counter imbalances is a huge plus.
This leaves two aux outputs. Provided you are using at least a six channel radio, one could be used for a spring-loaded manipulator. The drive motor would have to fight the spring in order to close, but it would allow for pretty fine control over a manipulator.
An alternate idea would be to use the aux outputs to drive ballast pumps. Since there's always a chance an ROV challenge will involve lifting a payload, ballast tank designs may be more competitive than strictly thruster-based designs. This gives you a way to drive the pumps.
Now for Nifty Part #1: Your umbilical is now miniscule. Two 14-12ga wires carry DC power to the ROV (this is a requirement of some of the ROV competitions or I'd argue for on-board SLA batteries.) A single coax carries the RC signal to the ROV. A single coax can carry video back to the surface. You can get very narrow 75ohm coax that would do a dandy job of this, and not add much at all to the umbilical. The umbilical is much narrower and lighter weight than the typical umbilical, leading to less drag in the water and fewer issues in balancing it for neutral buoyancy.
Nifty Part #2: You now have a completely electronically controlled sub. If, at a later date, you decide to add an onboard microprocessor to the sub it's dead-easy. The TReX controllers can be daisy-chained (they're addressable, and treat the serial connection as a common bus), so a single UART micro would do the job. And since TTL connections are available you don't even need level shifters on board in order to drive the TReX controllers (though it supports that mode as well.)
Nifty Part #3: Already mentioned, but RC radios present a tried, true, and pretty common interface to the ROV. Any kid who's played video games or flown an RC helicopter or airplane will be more than familiar with the control layout. Since older AM proportional radios would do the job as well as a higher-end newer radio, a second-hand radio can be had for not much money off Ebay. I picked up a six-channel Futaba AM system for $45 at a garage sale years ago. They're even cheaper now.
Now let's talk cost, because none of this comes for free:
The TReX controllers retail for $99 each. Figure another $50-100 for a radio off of Ebay. Figure another $50-100 for an IP66-rated enclosure and a set of IP66-rated connectors such as the Bulgin Buccaneer connectors that are sold by Digikey. Voila. You now have two speed controllers mounted in a dry box with hermetic waterproof connectors to hook it up to your thrusters, and a complete user interface at the top.
I realize that tacking $250-400 onto the price of an underwater ROV may be more than most teams are in for. However at the last competition I saw there were teams that spent well into the thousands on their ROVs, so it's not out of the question. Considering how many teams were tripped up by their user interface, I'd consider $300 as money well-spent if it gives the team full proportional control over every thruster and high current outputs for driving additional devices like thrusters, pumps, and solenoid valves.
Tom
http://www.pololu.com/products/pololu/0777/
So here's the idea for teams building underwater ROVs for competition:
Several people have demonstrated that you can replace an RC transmitter antenna with a coax cable that can run underwater and terminate inside the dry box of an ROV. The dry box termination is basically to leave N inches of the coax core exposed as an antenna (N depends on your transmitter frequency, and needs to be wavelength-matched). The coax acts like a waveguide so the transmitter is essentially transmitting inside the dry box. Place the RC receiver nearby, but not in contact with the antenna coax. Voila, you now have RC feeding into your ROV.
Plug in two of the TReX speed controllers. Channels 1 and 2 drive the fwd/rev/turn thrusters. The TReX can be set up to do onboard channel mixing, so the primary joystick of the RC transmitter could be used as a fwd/rev/turn control, just like a video game. (For those who are slow to pick up on hints, by just like a video game I mean it gives your operator an interface they're already more than comfortable with, which means less seat time is required for them to become proficient in using the ROV!)
Channels 3 and 4 use the second TReX drives two vertical thrusters that can be used for ascent/descent/tilt. Considering how many ROVs wound up in a massive down-pitch after picking up a mission prop, having the ability to counter imbalances is a huge plus.
This leaves two aux outputs. Provided you are using at least a six channel radio, one could be used for a spring-loaded manipulator. The drive motor would have to fight the spring in order to close, but it would allow for pretty fine control over a manipulator.
An alternate idea would be to use the aux outputs to drive ballast pumps. Since there's always a chance an ROV challenge will involve lifting a payload, ballast tank designs may be more competitive than strictly thruster-based designs. This gives you a way to drive the pumps.
Now for Nifty Part #1: Your umbilical is now miniscule. Two 14-12ga wires carry DC power to the ROV (this is a requirement of some of the ROV competitions or I'd argue for on-board SLA batteries.) A single coax carries the RC signal to the ROV. A single coax can carry video back to the surface. You can get very narrow 75ohm coax that would do a dandy job of this, and not add much at all to the umbilical. The umbilical is much narrower and lighter weight than the typical umbilical, leading to less drag in the water and fewer issues in balancing it for neutral buoyancy.
Nifty Part #2: You now have a completely electronically controlled sub. If, at a later date, you decide to add an onboard microprocessor to the sub it's dead-easy. The TReX controllers can be daisy-chained (they're addressable, and treat the serial connection as a common bus), so a single UART micro would do the job. And since TTL connections are available you don't even need level shifters on board in order to drive the TReX controllers (though it supports that mode as well.)
Nifty Part #3: Already mentioned, but RC radios present a tried, true, and pretty common interface to the ROV. Any kid who's played video games or flown an RC helicopter or airplane will be more than familiar with the control layout. Since older AM proportional radios would do the job as well as a higher-end newer radio, a second-hand radio can be had for not much money off Ebay. I picked up a six-channel Futaba AM system for $45 at a garage sale years ago. They're even cheaper now.
Now let's talk cost, because none of this comes for free:
The TReX controllers retail for $99 each. Figure another $50-100 for a radio off of Ebay. Figure another $50-100 for an IP66-rated enclosure and a set of IP66-rated connectors such as the Bulgin Buccaneer connectors that are sold by Digikey. Voila. You now have two speed controllers mounted in a dry box with hermetic waterproof connectors to hook it up to your thrusters, and a complete user interface at the top.
I realize that tacking $250-400 onto the price of an underwater ROV may be more than most teams are in for. However at the last competition I saw there were teams that spent well into the thousands on their ROVs, so it's not out of the question. Considering how many teams were tripped up by their user interface, I'd consider $300 as money well-spent if it gives the team full proportional control over every thruster and high current outputs for driving additional devices like thrusters, pumps, and solenoid valves.
Tom
Wednesday, September 5, 2007
ROV Competitions - Ideas for Teams
I was involved with an ROV competition earlier this year. "Involved" isn't really the right word, but it's the best one I can come up with. Among other things I tried to help out where I could, didn't help out nearly enough, took too long making underwater video cameras to film the event (which I hope are recycled onto someone's ROV), showed up to volunteer at the competition, wound up judging instead, and because of an incomplete understanding of the rules I likely created a situation that compromised the event. I got to see a lot of extremely hard-working kids, some really unsportsmanlike nasty infighting among some adults, and an amazing display of chivalry on the part of one team leader in particular.
Not sure I'm willing to go through that again.
So I'm helping out the best way I can: by writing. Here are my observations on the competition, and what I would do if I was to build an ROV for the MATE competition:
1 - The whole point is to have a good time.
Let me rephrase that: The whole point is to have a good time! If you get wrapped around the axle worrying about scoring high in the competition, especially if you're a mentor, you're missing the point. When in doubt, go back to #1.
2 - If you build so specifically to the competition rules as written, you can potentially design yourself out of the ability to adapt to unexpected problems.
In one instance a mission prop was slightly shorter than the design spec called for. One team designed so closely to spec that their ROV didn't fit where it was supposed to go. Think I'm kidding? I'm not.
This mirrors the real world, though. A good example is an instrument we have at work, for which a designer made provisions for a 10.00mm deep hole to take an M5x10 screw. The thing bottomed out. We pulled the screw out, measured it, and it was about 10.5mm long. This is what happens when you roll a thread onto a screw blank. The designer never knew that. M5x9 screws were not an option, so we ground the things to length, cleaned up the ends, cleaned up the threads with a die, etc. No time for that during an ROV competition. Plan for the unexpected.
3 - The operator will become disoriented.
Let's face it. You're using an underwater camera to experience your environment. Unless you replace the lens on your camera you're using a tiny field of view to tell you where you are, what orientation you're in, whether you're facing the right way, etc. No matter how much you tell yourself, "I won't lose track," you will. Everyone did.
I've come up with all sorts of instrumentation to keep an operator on target. Six axis IMUs, electronic compass, pressure transducers, video overlay boards, you name it. Want to know the simple answer to this?
Get one of those little keychain ball compasses you get in the gumball machine, epoxy it in place in view of your camera. You now have a compass and an artificial horizon. If you position it midway up your video frame, you should be staring at an even horizon on the ball compass. If you're looking at the top, you're pointing down. If you're looking at the bottom, you're pointing up. And if you note the orientation before your team lowers the ROV into the water, you know which way to head to get back to your team.
A depth gauge is also easily had. Get a long thin tube. Close it at one end and place that end up. As you submerge, the tube will fill up slightly with water. Guess what? The level will change depending on depth. Mark it. Use a tape measure in the pool and get precise values. Not sensitive enough? Stick an air resevoir at the top so you get a bigger differential change with depth. With a little experimentation you can get something that's sensitive enough to give you resolution in inches. Mark it on the tube. Voila. Depth gauge.
These two instruments will give you 90% of what you need in order to maneuver your ROV out of a blind corner. I watched one team fail to realize they were nose-down and staring at a blank pool floor for almost five minutes. Way too much time in a 15 minute competition.
4 - Trust each other and delegate duties
If you can't trust each other, you're not a team. I didn't have first-hand of this in the ROV competition, but I've seen it numerous other places: Primadonnas don't make teams. Encourage competing designs. Plan time to test them. Find out what works and what doesn't before competition. Document your tests so you don't repeat them. Document what ideas you discard and why so you revisit the ones you dropped for time constraints but not the ones you dropped because they simply didn't pan out. If in doubt, pursue two ideas and test them in a head-to-head test. Chances are there will be a clear winner. Going with one person's ideas means if they're steering you in circles, it's in circles you will go.
5 - Test test test test test!
I've heard it told to me time and time again: In Battlebots, it isn't the better robot that wins, it's the more experienced driver. In auto racing, it isn't the faster car that wins, it's the better driver. In dogfighting, it's not the superior aircraft that wins, it's... you get the idea. If you never get time in the saddle, you will choke in competition.
Before committing to something like an ROV competition, have a test site picked out. A pool, a lake, even a cattle watering tank is better than nothing. Without the ability to test you will fail.
6 - Stay on task.
This one shouldn't need saying, but apparently it was the one real show-stopper. Everyone procrastinated, and it showed. The amazing story was that one team consisting of two people built an ROV in two weeks and actually got up there in points. The sad story was that most of the other teams procrastinated, so they more or less did the same. There was no need for this. There was plenty of time.
Personally, I think this goes back to #5. If there's the prospect of driving an ROV at the end of the build session every single day, provided there's new stuff to test, chances are there will be new stuff to test. Every... single... day... This is a carrot. Use it.
7 - Do your research (aka The Rant)
Now I'll get on my soap box and rant. And rant and rant and rant.
DO YOUR RESEARCH!
I can't even begin to describe how many people I talked to who asked, "Where do you get all this information?" I used Google. I read. I got on Yahoo! I read. I joined online forums and mailing lists. I read. I checked out books from the library. I read. What the heck, people? This is called doing your research.
What really amazed me was that it wasn't necessarily the students who were giving me blank stares about the idea of using Google for research, it was the mentors! It was the teachers!
Holy crap stack, Batman, there are literally thousands of people out there building ROVs not for competition, but for commercial use, for scientific research, for treasure hunting, for search and rescue, or just for the heck of it. And hundreds of them are online, reading email, writing web pages, answering questions, offering opinions, throwing out ideas, getting excited about what you are doing, and being a resource!
Before someone says that the Internet shouldn't be used for research, please let me correct you. We use it all the time at work. This is how we find out what other people are doing, and if their methods are better than what we're using. This is how we find out about new products that might make our workflow easier. This is how we get in contact with people who might eventually build stuff for us, or better yet design stuff for us. This is how a good percentage of my time is spent, and the benefits are enormous. If you want to teach kids how it's done in the so-called real world, this really is how it's done. It begins with a search.
This research can spare you months of wasted labor, because someone might already have tried your ideas out and either proved or disproved them. This research can spare you a blown competition because you might be able to read someone's blog where their ROV of similar designed for the following reasons... This research can spare you a lot of your operating budget if you find out before buying parts that parts X, Y, and Z aren't even waterproof! It's worth having everyone on the team scour the Internet for ideas for a solid week before they ever set foot in the workshop. Fish for ideas. Scratch off the bad ones. Underline the good ones. Bring them in and brainstorm. Then go back out with your plan and see if there's anything out there you can use to refine it.
If everyone did this, the competitions would be out of this world.
But enough of ranting. Go back to #1. Build. Dive. Enjoy. And dream of what you want to do next year.
-- Tom
Not sure I'm willing to go through that again.
So I'm helping out the best way I can: by writing. Here are my observations on the competition, and what I would do if I was to build an ROV for the MATE competition:
1 - The whole point is to have a good time.
Let me rephrase that: The whole point is to have a good time! If you get wrapped around the axle worrying about scoring high in the competition, especially if you're a mentor, you're missing the point. When in doubt, go back to #1.
2 - If you build so specifically to the competition rules as written, you can potentially design yourself out of the ability to adapt to unexpected problems.
In one instance a mission prop was slightly shorter than the design spec called for. One team designed so closely to spec that their ROV didn't fit where it was supposed to go. Think I'm kidding? I'm not.
This mirrors the real world, though. A good example is an instrument we have at work, for which a designer made provisions for a 10.00mm deep hole to take an M5x10 screw. The thing bottomed out. We pulled the screw out, measured it, and it was about 10.5mm long. This is what happens when you roll a thread onto a screw blank. The designer never knew that. M5x9 screws were not an option, so we ground the things to length, cleaned up the ends, cleaned up the threads with a die, etc. No time for that during an ROV competition. Plan for the unexpected.
3 - The operator will become disoriented.
Let's face it. You're using an underwater camera to experience your environment. Unless you replace the lens on your camera you're using a tiny field of view to tell you where you are, what orientation you're in, whether you're facing the right way, etc. No matter how much you tell yourself, "I won't lose track," you will. Everyone did.
I've come up with all sorts of instrumentation to keep an operator on target. Six axis IMUs, electronic compass, pressure transducers, video overlay boards, you name it. Want to know the simple answer to this?
Get one of those little keychain ball compasses you get in the gumball machine, epoxy it in place in view of your camera. You now have a compass and an artificial horizon. If you position it midway up your video frame, you should be staring at an even horizon on the ball compass. If you're looking at the top, you're pointing down. If you're looking at the bottom, you're pointing up. And if you note the orientation before your team lowers the ROV into the water, you know which way to head to get back to your team.
A depth gauge is also easily had. Get a long thin tube. Close it at one end and place that end up. As you submerge, the tube will fill up slightly with water. Guess what? The level will change depending on depth. Mark it. Use a tape measure in the pool and get precise values. Not sensitive enough? Stick an air resevoir at the top so you get a bigger differential change with depth. With a little experimentation you can get something that's sensitive enough to give you resolution in inches. Mark it on the tube. Voila. Depth gauge.
These two instruments will give you 90% of what you need in order to maneuver your ROV out of a blind corner. I watched one team fail to realize they were nose-down and staring at a blank pool floor for almost five minutes. Way too much time in a 15 minute competition.
4 - Trust each other and delegate duties
If you can't trust each other, you're not a team. I didn't have first-hand of this in the ROV competition, but I've seen it numerous other places: Primadonnas don't make teams. Encourage competing designs. Plan time to test them. Find out what works and what doesn't before competition. Document your tests so you don't repeat them. Document what ideas you discard and why so you revisit the ones you dropped for time constraints but not the ones you dropped because they simply didn't pan out. If in doubt, pursue two ideas and test them in a head-to-head test. Chances are there will be a clear winner. Going with one person's ideas means if they're steering you in circles, it's in circles you will go.
5 - Test test test test test!
I've heard it told to me time and time again: In Battlebots, it isn't the better robot that wins, it's the more experienced driver. In auto racing, it isn't the faster car that wins, it's the better driver. In dogfighting, it's not the superior aircraft that wins, it's... you get the idea. If you never get time in the saddle, you will choke in competition.
Before committing to something like an ROV competition, have a test site picked out. A pool, a lake, even a cattle watering tank is better than nothing. Without the ability to test you will fail.
6 - Stay on task.
This one shouldn't need saying, but apparently it was the one real show-stopper. Everyone procrastinated, and it showed. The amazing story was that one team consisting of two people built an ROV in two weeks and actually got up there in points. The sad story was that most of the other teams procrastinated, so they more or less did the same. There was no need for this. There was plenty of time.
Personally, I think this goes back to #5. If there's the prospect of driving an ROV at the end of the build session every single day, provided there's new stuff to test, chances are there will be new stuff to test. Every... single... day... This is a carrot. Use it.
7 - Do your research (aka The Rant)
Now I'll get on my soap box and rant. And rant and rant and rant.
DO YOUR RESEARCH!
I can't even begin to describe how many people I talked to who asked, "Where do you get all this information?" I used Google. I read. I got on Yahoo! I read. I joined online forums and mailing lists. I read. I checked out books from the library. I read. What the heck, people? This is called doing your research.
What really amazed me was that it wasn't necessarily the students who were giving me blank stares about the idea of using Google for research, it was the mentors! It was the teachers!
Holy crap stack, Batman, there are literally thousands of people out there building ROVs not for competition, but for commercial use, for scientific research, for treasure hunting, for search and rescue, or just for the heck of it. And hundreds of them are online, reading email, writing web pages, answering questions, offering opinions, throwing out ideas, getting excited about what you are doing, and being a resource!
Before someone says that the Internet shouldn't be used for research, please let me correct you. We use it all the time at work. This is how we find out what other people are doing, and if their methods are better than what we're using. This is how we find out about new products that might make our workflow easier. This is how we get in contact with people who might eventually build stuff for us, or better yet design stuff for us. This is how a good percentage of my time is spent, and the benefits are enormous. If you want to teach kids how it's done in the so-called real world, this really is how it's done. It begins with a search.
This research can spare you months of wasted labor, because someone might already have tried your ideas out and either proved or disproved them. This research can spare you a blown competition because you might be able to read someone's blog where their ROV of similar designed for the following reasons... This research can spare you a lot of your operating budget if you find out before buying parts that parts X, Y, and Z aren't even waterproof! It's worth having everyone on the team scour the Internet for ideas for a solid week before they ever set foot in the workshop. Fish for ideas. Scratch off the bad ones. Underline the good ones. Bring them in and brainstorm. Then go back out with your plan and see if there's anything out there you can use to refine it.
If everyone did this, the competitions would be out of this world.
But enough of ranting. Go back to #1. Build. Dive. Enjoy. And dream of what you want to do next year.
-- Tom
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