Post #254,641
5/6/06 3:29:38 PM
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Variation on IANK
I am not Karsten. -> I am not TonyTib. :-) Oh, [link|http://store.wmjmarine.com/s21113402.html|here] you go: Simrad HLD 2000 long dual (13" stroke) Hydraulic linear drive 21113402
For boat displacement up to 77000 lb
Stroke: 13.3 inchs Peak thrust: 2310 lb max torque: 28000 lb Tiller arm: 11.7 inchs
Works with AC40 I don't know enough about this stuff (e.g. is AC40 == 40V AC?), but it looks like [link|http://www.simradusa.net/index.php|Simrad] has what you want if you're willing to spend the $$$. HTH. Good luck! Cheers, Scott.
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Post #254,642
5/6/06 3:39:44 PM
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No hydraulics
too messy, will require engine power to drive it, and besides, I need 24" of travel.
I like the screw jack positioning mechanism - solid - no power to maintain position required.
[link|http://www.blackbagops.net|Black Bag Operations Log]
[link|http://www.objectiveclips.com|Artificial Intelligence]
[link|http://www.badpage.info/seaside/html|Scrutinizer]
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Post #254,646
5/6/06 3:59:26 PM
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Good points.
Getting the screw drive to work would be a good solution. The robot guys should be a great resource. (Where's [link|/forums/render/user?username=FuManChu|Bender] when we need him? Oh, that's right, he's [link|http://aminus.org/blogs/index.php/fumanchu|here].)
Good luck!
Cheers, Scott.
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Post #254,643
5/6/06 3:46:17 PM
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Here we go: http://www.seattlerobotics.org/
Guess I'll attend the next meeting. Hey Thane - wanna meet some robot hackers?
[link|http://www.blackbagops.net|Black Bag Operations Log]
[link|http://www.objectiveclips.com|Artificial Intelligence]
[link|http://www.badpage.info/seaside/html|Scrutinizer]
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Post #254,647
5/6/06 4:28:54 PM
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That's probably a good resource
although typically the robot enthusiast groups deal with wimpy little robots. But, it's likely some have good control experience, analog experience, and motor control experience.
Try looking up PID control (Proportional Integral Derivative) - that's what is normally used for closed loop control, e.g. on all the servo systems we build (and for temperature control, etc) (there's also fuzzy logic). We use commercial motion controllers or PLC's to do the real time stuff.
You'll have to interface to the feedback system (analog front end plus A/D converter to get from resistance to voltage to bits) and jack screw (motor driver of some sort).
I'd recommend using something with a bit of computing horsepower so it's easier to write the NMEA code. There are plenty of little boards available; if you want to use something other than assembly, BASIC, or C/C++, get something that gcc runs on (e.g. x86, PowerPC, ARM) and you should be able to use Objective C via gcc.
Also, it's likely you can visit eBay or other surplus sites to get commercial grade stuff (e.g. brush or brushless motor amplifier) to make your life easier but still be affordable.
--Tony
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Post #254,662
5/6/06 10:26:16 PM
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I'm happy with C and more familiar with fuzzy methods
for control. Anyhow I envision a couple different modes of operation. The simplest is just "keep the boat pointed that way" and this should be built into a dumb controller that works by itself using just the compass and tiller position data. So the autopilot needs a microcontroller to do this.
A more advanced strategy would be to have a computer figure out corrected headings based on actual boat motion to compensate for current/leeway and allow the boat to track a course. Final goal is I should be able to punch in lat/long and boat simply goes there - using charts and radar to avoid traffic/obstacles.
While I distrust technology - I think a staged and distributed approach will be best with each system fully manual, dumb semi-automatic (state maintaining), and then smart central control to tell the dumb systems what their states should be. This way, if the main computer dies, I only have to babysit the systems from time to time. Ditto if a subsystem (steering, motor control, whatever) fails.
Sort of a smart home approach for boats. Commodity parts for ease of replacement will be favored wherever possible.
[link|http://www.blackbagops.net|Black Bag Operations Log]
[link|http://www.objectiveclips.com|Artificial Intelligence]
[link|http://www.badpage.info/seaside/html|Scrutinizer]
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Post #254,704
5/7/06 6:49:17 PM
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Many different approaches
There are many different ways of building such a system. Three examples are using a PLC (more industrial approach, but more costly), using a single board computer (ZWorld, New Micros, and many others), or using an industrial PC (e.g. PC104 system)
It might be good to see what the Seattle Robotics people like - then you hopefully can good feedback and help. Or pick a system with an active mailing list.
Protection from the elements is going to be a big concern. It may be better to build your own enclosure - you can get splash resistant systems (e.g. IP67 using sealed connectors), but they cost considerably more.
BTW, they're probably too pricey and I don't have any experience (not a good fit for our applications), but I've always found [link|http://www.exlar.com/|Exlar's] linear actuators interesting.
--Tony
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Post #254,731
5/8/06 2:26:08 AM
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I've gotten a few good ideas
from the robotics people. Someone pointed me to this:
[link|http://www.digitalmarine.co.kr/prod_mif_e.htm|http://www.digitalma...kr/prod_mif_e.htm]
Unversal NMEA converters. That should make things like rudder angle/rate easier to read.
Other advice I've gotten
"By using an off the shelf PLC controller like a Siemens s7-200, or a micro logics Allen Bradley, both available in 120V or 12VDC and other voltages, could receive analog input via the NMEA universial converter on desired compass heading from a remote navigation program, the PLC controller utilizing Proportional Control (PID control build into these small controllers) would send left or right digital outputs to an electrical actuator (like those pictured at Nookindustries, but they are also availble from Graingers in South Seattle off 4th Ave) An encoder could be attached to the rudder that provided a 4-20 mA signal relative to position, BCD or several other codes could be sent back to the PLC for feed back. Both the Siemens and AB conrollers have small LCD touch screen interfaces that are easy to configure and setup."
So I'll have to research this stuff some more.
[link|http://www.blackbagops.net|Black Bag Operations Log]
[link|http://www.objectiveclips.com|Artificial Intelligence]
[link|http://www.badpage.info/seaside/html|Scrutinizer]
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Post #254,770
5/8/06 12:28:55 PM
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Avoid A-B; PLC has good and bad sides
We've used A-B, Panasonic, Automation Direct, Omron, and Siemens PLC's.
The PLC approach does have its advantages. They are industrial quality, with various input (24VDC, 120VAC, analog in, etc) and output (24V, relay, analog out, etc) options, while the C-programmable stuff is typically bare boards with TTL (5V) inputs and outputs. If you need 4-20mA, you'll have to check that the PLC has an option for it.
Some do have built-in PID; we've done PID temperature control. If you want to do PID, make sure it's built in.
Older PLC's are programmed solely in ladder logic, which is a fine fit for combinatorial logic ("when these inputs are in this state, do this"), but sucks for everything else (e.g. sequence of actions). Newer PLC's support the IEC61131 standard, which supports five langagues: ladder, function block (ladder written with AND/OR instead of wires), structured text (our favorite; a mix between Basic and Pascal), flow chart, and ladder assembly.
PLC's are horrible for any kind of data handling, so if you do use them, that recommended approach (use PLC as PID controller, don't do NMEA conversion) makes sense.
The price will be higher, and you'll have to pay for programming tools (A-B's are very pricey, and have copy protection; Siemens, Aromat, Automation Direct are more reasonable) or know someone who has them.
Some companies have starter deals which include a PLC and software. Aromat has run specials on PLC's and Operator Interfaces occasionally. Siemens runs them often (including both PLC and Operator Interface); you will need to contact your local distributor.
I recommend looking at [link|http://www.sea.siemens.com/automat/product/plc/auov.html|Siemens], [link|http://www.nais-e.com/plc/|Panasonic], and [link|http://www.automationdirect.com|Automation Direct] PLC's. Automation Direct has all their pricing on line, and it's competitive. (A-B does has on-line pricing, too, if you register, but it's quite high, even after a 30% discount). Then you can use resources such ebay and [link|http://www.plccenter.com|PLC Center] to see if you can get surplus or used equipment at much better prices.
--Tony
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Post #254,775
5/8/06 1:26:32 PM
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Maybe you could barter
an improved web site for PLC Center for some of their surplus stuff. Check out their "advanced search" web page, takes forever to load - I think because they're loading a whole long list of all the possible companies to search for.
--Tony
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