I'm curious about your statement that you're going to get location accuracy of an inch, by timing the transmit to receive event. To get this accuracy you need to resolve the transmit / receive event to an accuracy of .08 nanosecond. I trust the radio waves to do their thing correctly, but will the relaying bot's STAMP and the timing (observing) bot's STAMP do the timing and the transmit - receive - retransmit - receive work consistently to that accuracy? The radio wave will travel 12.9" during each cycle so you have to detect the signal in about 1/25th of a cycle at each end to get 1" resolution, if there are no other delays anywhere in the system. Doesn't seem possible to detect the signal accurately. Aren't 100 GHz systems required to get this resolution?
Yes, FerretMK4, you are correct. I was trying to figure out how to do the math on the triangulation part of the system, but after a comment by daniel, I realized exactly what you said. The BS2 can't count quick enough to get this done. Maybe I could change the accuracy to a foot. Do you know how tight I would be able to get using the BS2 with simple code of transmit the ID # of the bot, start counting, receive the return signal, and compute the distance.
If I could figure out within a couple of feet where the "Lost Bot" is, I could then narrow it down to within an inch with visual (IR detector triangulation). The only reason I wanted to use RF is it propegates in a sphere, therefore triangulation would be easier. If I used IR triangulation, I would have to spin the IR while going up and down until the receiver accuired the signal. That is time consuming and bulky in code.
I don't believe I can use the transmitter listed above with the BS2 to measure distance. The max line of sight for the xmtr is 500', that would be in the transmit time range of nanoseconds and the BS2 cannot count that fast. Any suggestions on how I can locate a robot on a foreign planet without using GPS and maintaining cost and size restrictions.
well if you do know how fast it takes for a bot to send a "PAUSE 2" signal IR or some radio pulse then maybe the receiving bots could count the time between the signals. Otherwise you will need a device to measure the time between locating beacon (not com signals the bots use) on each bot and that device can send a number to the bot to do it's calcs.
pause 2 can be any known pulse.
I haven't tore an electronic guitar tuner apart but maybe with the way they can determine a freq and indicate it with a LED maybe with a little doppler science and some type of analog to digital type of device the frequency received can be used to determined distance of the bot. remember the lost bot is sending a known freq (needs high precision).
Post Edited (cyplesma) : 8/29/2007 12:13:20 AM GMT
I'm just getting started with a BS2p myself (bought it at least a year ago and got distracted by ugly things like working for a living), now I'm getting back up to speed. My intent is to use it for data acquisition and I'm concerned about the system speed also. I'd be concerned in your project about whether the second bot would receive the signal and return it in a fixed amount of time. All these events are clocked, so random analog events such as a radio signal's "arrival" has to pass some threshold and then the next clock pulse begins the process of acknowledgement and generation of a return signal. But you can't guarantee that the threshold is passed immediately before a clock pulse, so the time between passing the threshold and starting the next process can vary from essentially zero to one clock pulse. The same happens when you receive at the first bot, so you have a possible (and probable) timing error of two clock pulses and this is likely to be a fatal size error. This is where IR or other reflective systems have an advantage; they don't involve unknowns in the turn-around.
I'd also be concerned about the process of "receiving" the signal is done, that is, does the receiver say "I got it" at some reliable point in the first cycle, or does it take up to three cycles before there is a logic level reached? You'd have to know that it always triggered at exactly a certain part of a certain cycle otherwise you've got another unknown time delay.
When you're trying to capture analog events with digital systems you've got to sample faster than you at first think, and you've got to make sure that the analog level you're looking for is present for at least one sample interval. This is a big issue when you're trying to sychronize analog sensor signals with physical activities via keyphasors or encoders. Digital is pretty good once the stuff gets into the clocked stream, but it's tricky getting analog info into there.
Could you use the signal strength as a rough distance estimator until you get into IR range? Some sort of directional antenna network from which you could compute direction by comparing relative signal strengths and then triangulate using reference angles instead of distances?
Willsworld.org said...
The max line of sight for the xmtr is 500', that would be in the transmit time range of nanoseconds and the BS2 cannot count that fast. Any suggestions on how I can locate a robot on a foreign planet without using GPS and maintaining cost and size restrictions.
You'all probably know this, but do keep in mind that IR and RF are, just like light, electromagnetic radiation and all travel at the same speed--approximately 983,571,056 feet per second, or roughly one foot per nanosecond ( en.wikipedia.org/wiki/Speed_of_light ).
Since you need a slower signal, you could use sound (nominally 1,100 feet per second--en.wikipedia.org/wiki/Speed_of_sound). Why not trigger a Strobe flash and a Audible signal at the same time. The receiver(s) could start their timer on noticing the flash, and count how long it takes the sound to reach them.
Perhaps you would use a "seismic" disturbance to signal position instead of air-carried sound waves.
Perhaps, instead of a flash, the bots could use RF links to coordinate the reporting of who is speaking and the triggering of both the sound and the timer start.
If you have unlimited power (and a relatively long time), you could use a heat rate-of-change sensor (thermometer?) to estimate how close the sender of an IR (heat) beam is to the receiver.
All very good points from everyone. I'm impressed with all the knowledge everyone displays.
The reason I started this thread is to figure out how to locate a "Lost Bot". I believe that RF is out of the picture due to the BS2 not being able to count quick enough. IR is very bulky coding and time consuming. GPS doesn't exist, (on the foreign plant). Sound waves don't travel in a vacumn (I could be mistaken, but not sure).
Just to give everyone a hint, I plan on building a Bucket Loader robot to load a Dump Truck robot. When the Dump Truck robot is full, he will go to a predetermined location upto a mile away, and then return to the Bucket Loader robot. I could use a decoder wheel to determine distance, but that would not determine direction. What if the robot gets high centered and "Thinks" he is still moving? That will change the actual location. Is there a solution to this problem?
although it still breaks down to location finding and what is it going to take to know that the bot is moving, accelerometer?
or switches on each wheel or the drive wheel to know that it's off the ground?
kinda like the old style curb feelers
you may want to look into the darpa project that involves suvs (mainly for their size) to autonomously drive from one point to another, some use gps, but some don't. they use road tracking methods. do a road tracking method, but use geological points (may need some electronic reference at said points) as your guides, until you get to either the dump site / load site where you have some type of carpet that has lines leading to the points of operation.
I think if you initially establish a "work zone perimeter" (WZP) before any digging commences, then IR beacons at various "known" locations around the WZP would probably be your best bet.
RF would be subject to distortion depending on the geography of your location. ... You say "IR is very bulky coding and time consuming." - for a truck hauling some kind of foreign land debris, I'm surprised this is even a raised issue.
You’re correct; sound waves don't travel in a vacuum, and also widely vary in speed depending on the atmospheric temperature, pressure, and humidity.·I dare say, that the atmospheric temperature, pressure, and humidity probably affect the speed of light as well, but the difference is·negligible. In addition to atmospheric sound issues, the same goes·for seismic detection.· Different land geographies would alter the seismic response characteristics for a given location also.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ Beau Schwabe
IC Layout Engineer
Parallax, Inc.
I think the best solution is to use IR Beacons.· The IR Beacons will have an ID#.· This ID# will be listed on the Main System Control (MSC) robot.· The "Lost Bot" will locate several IR Beacons nearby, and will transmit the Angle and Distance between each IR Beacon.· The Transceiver Bot will send this info towards the MSC which will compute the location.· The MSC will then return a signal telling the "Lost Bot" where he is, what he should do, and where to go.· The instruction to the "Lost Bot" could keep him busy for several hours.· I will only need to know every so often what to do and where to go.· The MSC could record the location and elevation of the "Lost Bot" and draw a map, so the MSC would be able to tell the "Lost Bot" 'Go this direction for x number of feet'.
I am willing to pay for a program and schematics to help accomplish this project.· Please keep in mind I'm just an average working person and am limited on my financing.· I have started a web site to help with this project, and can be seen at http://www.willsworld.org·.· It is updated on the weekends.·
Not sure, but this forum is usually for helping pople do it themselves, not do it for them. There is a post somewhere in these forums (robotics recently, I think) about IR beacons. I am not so sure that a stamp could function as the MSC, I think you might need something more powerful (prop might work?) Depending on the terain that you are working with, you might need toi update the map every 10 minutes or so. Encoders are only so accurate.
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ON subnum GOTO Hope_this_helps, Thanks!, WOW!!
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Comments
If I could figure out within a couple of feet where the "Lost Bot" is, I could then narrow it down to within an inch with visual (IR detector triangulation). The only reason I wanted to use RF is it propegates in a sphere, therefore triangulation would be easier. If I used IR triangulation, I would have to spin the IR while going up and down until the receiver accuired the signal. That is time consuming and bulky in code.
I don't believe I can use the transmitter listed above with the BS2 to measure distance. The max line of sight for the xmtr is 500', that would be in the transmit time range of nanoseconds and the BS2 cannot count that fast. Any suggestions on how I can locate a robot on a foreign planet without using GPS and maintaining cost and size restrictions.
pause 2 can be any known pulse.
I haven't tore an electronic guitar tuner apart but maybe with the way they can determine a freq and indicate it with a LED maybe with a little doppler science and some type of analog to digital type of device the frequency received can be used to determined distance of the bot. remember the lost bot is sending a known freq (needs high precision).
Post Edited (cyplesma) : 8/29/2007 12:13:20 AM GMT
I'd also be concerned about the process of "receiving" the signal is done, that is, does the receiver say "I got it" at some reliable point in the first cycle, or does it take up to three cycles before there is a logic level reached? You'd have to know that it always triggered at exactly a certain part of a certain cycle otherwise you've got another unknown time delay.
When you're trying to capture analog events with digital systems you've got to sample faster than you at first think, and you've got to make sure that the analog level you're looking for is present for at least one sample interval. This is a big issue when you're trying to sychronize analog sensor signals with physical activities via keyphasors or encoders. Digital is pretty good once the stuff gets into the clocked stream, but it's tricky getting analog info into there.
Could you use the signal strength as a rough distance estimator until you get into IR range? Some sort of directional antenna network from which you could compute direction by comparing relative signal strengths and then triangulate using reference angles instead of distances?
You'all probably know this, but do keep in mind that IR and RF are, just like light, electromagnetic radiation and all travel at the same speed--approximately 983,571,056 feet per second, or roughly one foot per nanosecond ( en.wikipedia.org/wiki/Speed_of_light ).
Since you need a slower signal, you could use sound (nominally 1,100 feet per second--en.wikipedia.org/wiki/Speed_of_sound). Why not trigger a Strobe flash and a Audible signal at the same time. The receiver(s) could start their timer on noticing the flash, and count how long it takes the sound to reach them.
Perhaps you would use a "seismic" disturbance to signal position instead of air-carried sound waves.
Perhaps, instead of a flash, the bots could use RF links to coordinate the reporting of who is speaking and the triggering of both the sound and the timer start.
If you have unlimited power (and a relatively long time), you could use a heat rate-of-change sensor (thermometer?) to estimate how close the sender of an IR (heat) beam is to the receiver.
Daniel
Post Edited (daniel) : 8/29/2007 1:38:00 AM GMT
The reason I started this thread is to figure out how to locate a "Lost Bot". I believe that RF is out of the picture due to the BS2 not being able to count quick enough. IR is very bulky coding and time consuming. GPS doesn't exist, (on the foreign plant). Sound waves don't travel in a vacumn (I could be mistaken, but not sure).
Just to give everyone a hint, I plan on building a Bucket Loader robot to load a Dump Truck robot. When the Dump Truck robot is full, he will go to a predetermined location upto a mile away, and then return to the Bucket Loader robot. I could use a decoder wheel to determine distance, but that would not determine direction. What if the robot gets high centered and "Thinks" he is still moving? That will change the actual location. Is there a solution to this problem?
although it still breaks down to location finding and what is it going to take to know that the bot is moving, accelerometer?
or switches on each wheel or the drive wheel to know that it's off the ground?
kinda like the old style curb feelers
you may want to look into the darpa project that involves suvs (mainly for their size) to autonomously drive from one point to another, some use gps, but some don't. they use road tracking methods. do a road tracking method, but use geological points (may need some electronic reference at said points) as your guides, until you get to either the dump site / load site where you have some type of carpet that has lines leading to the points of operation.
Post Edited (cyplesma) : 8/29/2007 2:50:37 AM GMT
RF would be subject to distortion depending on the geography of your location. ... You say "IR is very bulky coding and time consuming." - for a truck hauling some kind of foreign land debris,
I'm surprised this is even a raised issue.
You’re correct; sound waves don't travel in a vacuum, and also widely vary in speed depending on the atmospheric temperature, pressure, and humidity.· I dare say, that the atmospheric temperature, pressure, and humidity probably affect the speed of light as well, but the difference is·negligible.
In addition to atmospheric sound issues, the same goes·for seismic detection.· Different land geographies would alter the seismic response characteristics for a given location also.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Beau Schwabe
IC Layout Engineer
Parallax, Inc.
that may help with changing the roads dynamically.
I am willing to pay for a program and schematics to help accomplish this project.· Please keep in mind I'm just an average working person and am limited on my financing.· I have started a web site to help with this project, and can be seen at http://www.willsworld.org·.· It is updated on the weekends.·
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You could put those ir beacons to sleep until they receive a wakeup command to help lower battery consumption also.