I like the idea of a timer, but, unless I missed something, how do you know how much time it will take before the rover is on the ground and the parachute to detach?
What other ways could you signal the parachute to detach, if there are any? (I'm sure there are)
Obie and others,
An idea to consider is utilizing the MAWD (Mini Altimeter with Deployment) which currently outputs the altitude to the ASP-2 program. One possible solution is to have the parachute detached by whatever mechanism we design, only when the MAWD's altitude has first increased (launch) and then stopped increasing (touchdown). This of course is a very general concept, and you'd have to think about how exactly the parachute would detach.
...one possible solution is to have the parachute detached by whatever mechanism we design, only when the MAWD's altitude has first increased (launch) and then stopped increasing (touchdown).
Andrew
Andrew,
Conceptually this could work but practically I'm not sure where to begin. Think about it: the MAWD reads "0" feet altitude at lift-off then goes to 12-13,000 feet at apogee, right? Then the MAWD (altimeter) readings start to decrease. Right? Seems like it would be "simple" (I say that cautiously) to have the BOE activate a servomotor, cog, gear, etc. when the MAWD-BOE reads "0" again ===> at touchdown. It seems like something that could be done through programming...
Dr. Allen, if you're out there listening could you please give us some feedback on this idea? Sylvie (and others): what are your thoughts?
.
ROCKETEERS (for those of you new to the team, that specifically means ARLISS Team NH):
The more I think about things the more I wonder whether we should narrow our focus to ONE managable mission and throw all of our resources (our limited "build" time and our knowledge) into ONE "primary" mission. After (and only after) our primary mission has been successfully completed we could move into the next "stretch" mssion(s). What are your thoughts on this?
We could indentify three (four or five) missions we would like to do, then prioritize our missions according to what we need to do first. Let's all think about the ideas we've discussed so far and list them here on the forum, one by one. I won't bias the process by listing any ideas but I do look forward to your replies.
ASSIGNMENT: Here on the forum list the mission ideas we've discussed so far. There are no right or wrong answers. If you get stumped, just read back through the last three or four pages of the forum.
Maybe another alternative would be to use the Atla spectrometer to detect ground underneath which would then run a program to release the parachute. I don't know if that would work but its a possibility. Or maybe we could put a pressure sensitive piece to detect the arrival on the ground but I think it would be too risky and go off before hand. Any other ideas? So far the MAWD looks best, at least conceptually, but we should look for more alternatives.
.
Interesting idea, Kenobi, but the ALTA spectrometer has several drawbacks:
1) Size and space: It's as big as the ASP = Probably no room in the payload bay
2) Complexity: It would be quite complicated to get the BOE to "read" and interpret the ALTA's multiple lightwave outputs, then convert them to a signal that detaches the parachute.
3) BOE/program space: Assuming we did figure out how to get the ALTA to output a readable signal to BOE, we might find that we don't have enough memory space (EPROM) and/or physical space on the BOE.
If you have the time, see what Sir William of Ockham (or Occam) has to say about this idea. Then check back in on the forum and let everyone know what Will Ockham says. His sage advice is sometimes called "Occam's Razor." *NOTE: Don't try shaving with it!
The article is called "How to Build A Lightweight GPS Datalogger for Model Rocket Applications" (submitted to Parallax by Karl Upton.) It includes the program (source) code and schematics (drawings.)
There are many, many other excellent project ideas and links right here on the Parallax website, ideas that we can probably adapt and use. I hope that everyone will do some research to see what's available
Using the MAWD will be the best way to know that you have landed. Its job is to know the rocket's altitude, and it does a good job of that.
Because of my involvement with your group, I learned to tap the output of the MAWD (just like you guys are doing), and I managed to send it out by radio to a ground station. That means I've been able to watch the MAWD's altitude readout at the same time my rocket was flying, so I know how closely the "0 foot altitude" output from the MAWD corresponds to the time the rocket actually hits the ground. At least on my flights (which, admittedly, have only been in the 1500-3000 foot range), they correspond quite well. When the MAWD reads out "0" for (say) 10 consecutive readouts (that is, one-half second), you're on the ground. I used this for the system I've flown a couple of times that sounds a buzzer when various flight events occur, including landing, and it did work.
The reality does diverge a bit from the theory, in a way that you'll have to account for in code.
First of all, you don't want to just assume that you've landed the first time the MAWD reports a "0" in altitude, because the data can be a bit noisy. Wait for it to report zeroes for a certain number of times in a row. That part is easy.
This part is a little more difficult. Sometimes it settles in at a negative altitude, rather than at zero. Here are some of the data from a flight back in 2006, a 15 pound rocket on a K550:
(start of the flight as normal, then...)
00010
00010
00010
00010
00010
00010
00010
00010
00010
00000
00000
00000
00000
00000
-00010
-00010
-00010
-00010
-00010
-00010
-00010
-00010
Notice that there were never ten 0s in a row. You have to be on the lookout (more accurately, have your program on the lookout...) for negative altitudes. I suppose you could set up a flag so that if it were 0 or negative for ten consecutive readings, you assume you're on the ground. But remember that the Basic Stamp doesn't handle negative numbers the way that you and I do. If I remember correctly, they'll show up as huge positive numbers (numbers over 32767). You'll want to verify this. If that's the case, you can look for "either 0 or greater than 32767", which is, I believe, what I did when I programmed the buzzer on the XBee-MAWD device.
So do you think detaching the parachute at touchdown is as "simple" as having the MAWD signal a servomotor to open a cog (etc.) when it reads "0" (for 10-20 consecutive times, etc.) after lift-off...? Seems almost too easy. But easy it good in this case since we have a plethora of newbies.
What's new in WI? What happened to the 'Pack? We're having Wisconsin-like weather here lately. No school for two days last week because of snow (and lots of it!) and -15 F this morning.
Would the MAWD actually read out 0's, or whatever the altitude would be from sea level in that location? If so, wouldn't that account for extra time to program the ASP before we launched? I remember that it didn't out out 0's on our flashdrive last year, but I could be wrong.
Every year at my school we have a 2 week period at the end of February in which we choose a project that we're interested in and do it, or at least attempt to. This year I want to try and learn the PBASIC language and I was wondering if you could help me learn it when I need it, via the internet of course. Mr. Kibler already agreed to be my adviser and he suggested asking you to assist as well. If you need anymore information you can contact me on the forum or email me at obiewanhelmers@gmail.com.
I think that it would be a good idea for all of us to work on one project, If I am correct the projects we have discussed would be the soil sampler and the come back rover.
Here is a list of mission ideas (we think) we've discussed so far. Let's all work to complete the list. Then think about how you would prioritize them 1,2,3 based on your interest AND simplicity/difficulty.
1) Soil sampler (Emily)
2) "Come back" rover (Emily)
3) Parachute detachment device (Mr. Kibler)
4) ??? ======> who will be next???
I think it's wise to focus on one mission and complete it rather than scatter our thoughts and our resources across two or three missions at the same time. But that's just me thinking out loud. What are your thoughts?
Would the MAWD actually read out 0's, or whatever the altitude would be from sea level in that location? If so, wouldn't that account for extra time to program the ASP before we launched? I remember that it didn't out out 0's on our flashdrive last year, but I could be wrong.
Dylan,
The MAWD reads out the actual altitude as real numbers (1, 2, 3, 378, 993, etc.) When it lands after flight it will read '0' again. We would, of course, do any programming here in New Hampshire before we leave... no need to reprogram the MAWD in Nevada.
From: KEN WILKENS <k1mid@tds.net>
Date: Mon, Jan 24, 2011 at 4:41 PM
Subject: SPEAKING ENGAGEMENT AT THE CONTOOCOOK VALLEY RADIO CLUB
To: "L. Mark Kibler, M.Ed." <mkibler@alumni.unity.edu>
Cc: Dale & Mickie Clement <dpclement@tds.net>
HI MARK:
THE RADIO CLUB MEETS ON TUESDAY* FEBRUARY 8
I GET THE ROOM OPEN BETWEEN 6:30 AND 7:00 P.M.*AND START THE COFFEE.
*WE USUALLY *START THE PROGRAM AROUND 7:30 P.M.
THE PROGRAM IS THE FIRST THING ON THE AGENDA AND THEN WE BREAK FOR THE
REFRESHMENTS.
ANY CLUB BUSINESS IS LAST ON THE SCHEDULE SO THAT GUESTS OR SPEAKERS
CAN LEAVE RIGHT AFTER THEIR TALK.
THE MEETING PLACE IS THE HOPKINTON LIBRARY COMMUNITY ROOM. IT IS
LOCATED ABOUT ONE QUARTER OF A MILE PAST THE FIRE HOUSE*THE FIRE HOUSE
IS JUST OVER THE STONE BRIDGE IN* CONTOOCOOK VILLAGE. TURN LEFT AT THE
FIRE HOUSE. THAT IS PINE STREET. GO ABOUT 1000 FEET AN*START LOOKING
FOR THE LIBRARY SIGN ON THE RIGHT SIDE OF PINE ST. THE LIBRARY IS
ACTUALLY ON HOUSTON DRIVE A VERY SHORT ROAD INTO THE FACILITY. YOU
WILL SEE THE LIBRARY BUILDING AS YOU LOOK UP HOUSTON DRIVE FROM PINE
STREET.
KEN
This is our first presentation we will be attending this project year. It is not MANDATORY, but it will be extremely beneficial for anyone who can to be in attendance. Please contact Mr. Kibler personally if you will be able to make it. We usually meet somewhere commonly known, the middle school possibly, and carpool to the destination, (as stated in the email)
It may seem very nerve racking to you to present like this, but to be honest, the day after I told Mr. Kibler I was interested in robotics and the team, he invited me to a similiar presentation the morning after that day! I even got to miss a little bit of school in the morning since it was I believe a Wednesday.
Would the MAWD actually read out 0's, or whatever the altitude would be from sea level in that location? If so, wouldn't that account for extra time to program the ASP before we launched? I remember that it didn't out out 0's on our flashdrive last year, but I could be wrong.
When the MAWD is turned on, it takes a few seconds to sample and average the air pressure on the launch pad. When it has a good reading, it assigns that to the altitude "0". All of the altitude readings reported by the MAWD are relative to that point, not to sea level. In aviation terms, the MAWD output is "AGL", not "MSL" (that is, "Above Ground Level", rather than "Mean Sea Level").
The AGL/MSL distinction can be important. At my home launch field, we have a waiver to fly to 10,000 feet. What many fliers don't realize is that the waiver is to 10,000 feet MSL, not AGL. Since field elevation is about 900 feet MSL, if your altimeter reads over 9100 feet, you've busted the waiver.
Anyway, good thinking. If the readings did vary the way you suggested, then yes, you would have to reprogram out in the field. Much better to know that kind of thing now, rather than when you get out there, and find that your rocket never thinks it has landed (because it's looking for "0", and only getting whatever the field elevation at Black Rock is).
So do you think detaching the parachute at touchdown is as "simple" as having the MAWD signal a servomotor to open a cog (etc.) when it reads "0" (for 10-20 consecutive times, etc.) after lift-off...? Seems almost too easy. But easy it good in this case since we have a plethora of newbies.
What's new in WI? What happened to the 'Pack? We're having Wisconsin-like weather here lately. No school for two days last week because of snow (and lots of it!) and -15 F this morning.
Brrrrrrrrrrrrrrrrrr!
It was cold over the weekend, but recovered. I walked about 10 miles outside yesterday, only getting cold once, when facing the wind in a place that seemed a bit of a wind tunnel.
The Packers made the Super Bowl. I can't believe it. Rodgers really IS that good, and they're really clicking as a full team. Classic example of "you want to play your best football when the playoffs come around". My hat is off to the Bears, who gave us a great game despite being down to their emergency quarterback. If you put someone like Rodgers on the Bears, you'd have that 16-0 season we haven't seen in 40 years.
I've seen groups detach parachutes at landing, and yes, they used a servo to move something that released it. I wish I had photos, but your problem will be to have the parachute secure enough not to detach under the shock of opening, but still able to be detached by the mere movement of a servo. The best thing is a metal pin that runs through holes in the sides of a metal u-shaped holder, so that all of the forces in the direction the parachute pulls are metal-against-metal, but in the direction of pulling the pin, there's just a smooth unfettered sideways pull. There's probably a name for that, but I don't know it. This is the closest I come:
"...the best thing is a metal pin that runs through holes in the sides of a metal u-shaped holder, so that all of the forces in the direction the parachute pulls are metal-against-metal, but in the direction of pulling the pin..."
Sylvie,
You took a 10-mile hike in Wisconsin in January? Weren't you cold? It must have been brisk to say the least. I haven't been able to do much running in months. I've had a nagging ilio-psaos problem for months now and I really miss running. I did get to do a 5K with my son on New Year's Day though, the "Peanut Butter Chip Chase 5K Race"... it rhymes! And they had great cookies too.
I thought about the clevis pin idea too, with the clevis pin being pulled out by a servo somehow. It would have to be a fairly snug fit into the U-shaped piece though. Otherwise the clevis pin might simply slide out of the hole at apogee or during "roll-over".
What about securing a nut to the servo and using a bolt instead of a clevis pin? The servo would unthread the nut from the bolt (then somehow pull the bolt out too...?) I don't have the idea entirely evolved but the clevis pin idea is a start. I'll have the Rocketeers research it; that's how we learned about various ways to deploy parachutes (parachute bags, etc.) We have practice on Sunday.
What other thoughts are rattling around inside your cranium? Did I tell you I was invited to apply for admission into a PhD program in Aerospace Studies? It sounds daunting.
I was thinking about the parachute idea, and I just realized that magnets would be perfect! They're strong, but not to strong. We could attach them to the altimeter so that at the right height they would stop attracting the other magnet! I think this might work. The only problem is, how do we get the magnet to stop working? two pieces of metal with an electric charge that can be shut off? Curious what you think!
-Jake-
I was think about the parachute idea, and i just realized that maginets would be perfect! there strong, but not to strong. we could attach them to the altimeter so that at the right height they would stop attracting the other maginet! i think this might work. the only problem is, how do we get the magnet to stop working? two peices of metal with an electric charge that can be shut off? curious what you think!
.
Jake,
This is certainly a creative approach to the problem. Hmmmm.... I'm not sure what to think. So you're saying that the altimeter would activate a motor that pulls the magnets apart? Interesting. It makes me wonder several things:
How is the parachute attached to the magnet(s)? Are the magnets strong enough to hold the parachute (which is attached to the ASP or the robot)? Is the motor strong enough to pull the magnets apart? Will the magnetic field affect the ASP's electronics, especially the altimeter, the shortwave transmitter, and the BOE (the brains of the project)? Where will the magnets be mounted? Is there research on anything like this that's been done before? Is the a simpler way* (*Obie, what was that thing about Ockham's Razor I asked you to look up...?)
You have my interest piqued, Jake. What do others think?
Hey you guys!
Sorry I haven't talked in a LONG TIME, but I've just been sitting back and reading your posts, and the book Mr. Kibler gave me What's a Microcontroller?. Also I noticed that I never really answered the question if I could make it to the meeting this weekend, but it would be a yes.
Dylan (I think that's who posted about the midweek meeting),
I believe that I can make that meeting, let me just double check. Is it okay if I answer Sunday?
I can go to the meeting this Sunday well sorry for confirming so late. and I would love to go to the presentation but my parents both work late on tuesdays, I'll talk to my parents about it though.
Emily
Thank you for confirming that you're coming on Sunday. Are the rest of you coming on Sundsay too... Who would you like to bring cookies this time? Who can bring (healthy) drinks?
.
ALL ROCKETEERS:
.
Practice will BEGIN at 1:00 PM on Sunday as we discussed last time. Consider your team practices the same as those for a varsity sport (it is: ithis is athletics for your brain.) What would a varsity coach think or do if a player rolled in late for practice (no you won't run laps and no, coming late doesn't demonstrate leadership either.)
50 push-ups instead?!
Mr. Kibler
Head Coach, Unity College "Runnin' Rams" cross country team
1996 NSCAA National Champions
Thank you for confirming that you're coming on Sunday. Are the rest of you coming on Sundsay too... Who would you like to bring cookies this time? Who can bring (healthy) drinks?
.
ALL ROCKETEERS:
.
Practice will BEGIN at 1:00 PM on Sunday as we discussed last time. Consider your team practices the same as those for a varsity sport (it is: ithis is athletics for your brain.) What would a varsity coach think or do if a player rolled in late for practice (no you won't run laps and no, coming late doesn't demonstrate leadership either.)
50 push-ups instead?!
Mr. Kibler
Head Coach, Unity College "Runnin' Rams" cross country team
1996 NSCAA National Champions
Mr. Kibler,
Just confirming that I will be in attendance on Sunday, as I previously mentioned. I would be glad to bring some healthy drinks. Also, I have accomplished a little more with my GPS movement experiment, thanks to the extra EEPROM available on the BS2e Stamp. At the moment, it's still very rudimentary and merely proof of concept, but it is making the possibility of integrating GPS-guided navigation for the rover seem like a possibility. I'll be posting more details on this soon, and will definitely bring the results to our next meeting.
Mr. Kibler,
I was in my IED class today, (Intro to Engineer Design), and was playing around with a CaD program, (Computer Aided Design). I was thinking about the parachute release mechanism, and I believe I found the most simplistic idea I could think of. I do not have the CaD program here at my house, so I am searching the web for a program that will be able to express my idea properly. I will post it soon if my searches yeild results.
Hi,
Yes I will be going to the practice/meeting this weekend, can't wait, but I don't think I'll be able to make the Tuesday/Radio Assembly due to syblings Basketball schedules.
Mr. Kibler, sorry I've been so slow about Occam's Razor, I just saw that request today. Occam's Razor is a principle used to simplify matters. Basically if you have multiple answers for the same solution you choose the simplest one. I know why you wanted me to look this up. We have many ideas about how we detach the parachute. So in other words we need to look for the simpliest one and use that because it will be easier to do and still work just as well. Currently, (to my knowledge anyway), we have three or so suggestions.
First: A timer would countdown and detach the parachute upon the end of the countdown
2. We use MAWD to determine when the parachute releases
3. We try to use the Atla spectrometer to determine when its on the ground
4. Use a pressure sensitive piece to realease the parachute
Those are the options unless Dylan can tell me what his idea is. I would say the simpliest of these choices is the MAWD. That's sums it up.
-Obie
Those are the options...[and] I would say the simpliest of these choices is the MAWD. That's sums it up.
-Obie
Obie,
So now you know Sir William of Ockham's advice, one of the most fundamental of all engineering precepts:
K. I. S. S. ===> Keep It Simple Students. Put differently, "Of all possible solutions, the simplest is usually the best." Sound advice, I think.
Another fundamental engineering principal is "F.F.F." Anyone want to take a guess at what this stands for and what exactly it means, in simple terms...?!
I have two more BOE circuit boards, another BOE-bot robot, and a bunch of new resistors, capacitors, wires, and books on the way from Parallax. Thank you, Parallax! The new kits won't be here in time for Sunday's practice but we will have them to work with. Obie, think about what parts you will need for your independent project.
I've also bought five more RTC chips, 5 more resonator crystals, 10 more SHT chips, and a Parallax book about "Programming the Parallax robot." You, young scientists, must decide what we should do with these new materials. What is our primary mission? What do you think our next step is...?
Another fundamental engineering principal is "F.F.F." Anyone want to take a guess at what this stands for and what exactly it means, in simple terms...?!
I believe F.F.F. means "Form follows function." In other words, how you design and create something should be based around it's purpose.
I have two more BOE circuit boards, another BOE-bot robot, and a bunch of new resistors, capacitors, wires, and books on the way from Parallax. Thank you, Parallax! The new kits won't be here in time for Sunday's practice but we will have them to work with. Obie, think about what parts you will need for your independent project.
That's fantastic news, and very generous of Parallax! I'm sure everything will be put to great use shortly.
I've also bought five more RTC chips, 5 more resonator crystals, 10 more SHT chips, and a Parallax book about "Programming the Parallax robot." You, young scientists, must decide what we should do with these new materials. What is our primary mission? What do you think our next step is...?
Several ideas come to mind to put the parts you've just bought to use, including the most obvious of beginning to assemble a replica of the current ASP-II . However, as you stated Mr. Kibler, we still need to clarify our primary mission goals before we proceed any further.
Team members, in your own opinion, what do you consider our current mission goals to be -- and why? As you have all realized by now, there are many options for our primary mission, some of which are more difficult than others. We need to pick one, that in my opinion is 1) within our abilities (but not necessarily "easy") 2) serves a real purpose. I believe answering these questions will also answer the other questions that Mr. Kibler has proposed.
... We need to [choose a mission] one, that is 1) within our abilities (but not necessarily "easy") 2) serves a real purpose. I believe answering these questions will also answer the other questions that Mr. Kibler has proposed.
-- Andrew
Andrew,
The two points you make are spot-on accurate. Thanks for sharing your insights.
I was not as successful in my attempt at recreating my idea in a paint program as I thought I would . I have two 90 minute periods in my IED class tomorrow, so I will try to model it in the CaD program there. If not, I will just have to draw it out at our practice. I do believe though it it will most certainly work. I say this because the only real components to it are a very small plastic arm, and a triangular shaped piece of plastic. For nuts, screws etc, only two screws and two nuts, I think.
Comments
Obie and others,
An idea to consider is utilizing the MAWD (Mini Altimeter with Deployment) which currently outputs the altitude to the ASP-2 program. One possible solution is to have the parachute detached by whatever mechanism we design, only when the MAWD's altitude has first increased (launch) and then stopped increasing (touchdown). This of course is a very general concept, and you'd have to think about how exactly the parachute would detach.
Andrew
Andrew,
Conceptually this could work but practically I'm not sure where to begin. Think about it: the MAWD reads "0" feet altitude at lift-off then goes to 12-13,000 feet at apogee, right? Then the MAWD (altimeter) readings start to decrease. Right? Seems like it would be "simple" (I say that cautiously) to have the BOE activate a servomotor, cog, gear, etc. when the MAWD-BOE reads "0" again ===> at touchdown. It seems like something that could be done through programming...
Dr. Allen, if you're out there listening could you please give us some feedback on this idea? Sylvie (and others): what are your thoughts?
Mr. (Mark) KIbler
:cool:
ROCKETEERS (for those of you new to the team, that specifically means ARLISS Team NH):
The more I think about things the more I wonder whether we should narrow our focus to ONE managable mission and throw all of our resources (our limited "build" time and our knowledge) into ONE "primary" mission. After (and only after) our primary mission has been successfully completed we could move into the next "stretch" mssion(s). What are your thoughts on this?
We could indentify three (four or five) missions we would like to do, then prioritize our missions according to what we need to do first. Let's all think about the ideas we've discussed so far and list them here on the forum, one by one. I won't bias the process by listing any ideas but I do look forward to your replies.
ASSIGNMENT: Here on the forum list the mission ideas we've discussed so far. There are no right or wrong answers. If you get stumped, just read back through the last three or four pages of the forum.
Mr. Kibler
:cool:
Obie
Interesting idea, Kenobi, but the ALTA spectrometer has several drawbacks:
1) Size and space: It's as big as the ASP = Probably no room in the payload bay
2) Complexity: It would be quite complicated to get the BOE to "read" and interpret the ALTA's multiple lightwave outputs, then convert them to a signal that detaches the parachute.
3) BOE/program space: Assuming we did figure out how to get the ALTA to output a readable signal to BOE, we might find that we don't have enough memory space (EPROM) and/or physical space on the BOE.
If you have the time, see what Sir William of Ockham (or Occam) has to say about this idea. Then check back in on the forum and let everyone know what Will Ockham says. His sage advice is sometimes called "Occam's Razor." *NOTE: Don't try shaving with it!
Mr. Kibler
:nerd:
ROCKETEERS,
Check out this article and this link, right here on the Parallax forum. It may be helpful for robotic GPS navigation. Look under:
Resources > Applications/Contests > Hobby > How to Build A Lightweight GPS Datalogger
http://www.parallax.com/tabid/748/Default.aspx
The article is called "How to Build A Lightweight GPS Datalogger for Model Rocket Applications" (submitted to Parallax by Karl Upton.) It includes the program (source) code and schematics (drawings.)
There are many, many other excellent project ideas and links right here on the Parallax website, ideas that we can probably adapt and use. I hope that everyone will do some research to see what's available
Mr. Kibler
:cool:
Because of my involvement with your group, I learned to tap the output of the MAWD (just like you guys are doing), and I managed to send it out by radio to a ground station. That means I've been able to watch the MAWD's altitude readout at the same time my rocket was flying, so I know how closely the "0 foot altitude" output from the MAWD corresponds to the time the rocket actually hits the ground. At least on my flights (which, admittedly, have only been in the 1500-3000 foot range), they correspond quite well. When the MAWD reads out "0" for (say) 10 consecutive readouts (that is, one-half second), you're on the ground. I used this for the system I've flown a couple of times that sounds a buzzer when various flight events occur, including landing, and it did work.
The reality does diverge a bit from the theory, in a way that you'll have to account for in code.
First of all, you don't want to just assume that you've landed the first time the MAWD reports a "0" in altitude, because the data can be a bit noisy. Wait for it to report zeroes for a certain number of times in a row. That part is easy.
This part is a little more difficult. Sometimes it settles in at a negative altitude, rather than at zero. Here are some of the data from a flight back in 2006, a 15 pound rocket on a K550:
(start of the flight as normal, then...)
00010
00010
00010
00010
00010
00010
00010
00010
00010
00000
00000
00000
00000
00000
-00010
-00010
-00010
-00010
-00010
-00010
-00010
-00010
Notice that there were never ten 0s in a row. You have to be on the lookout (more accurately, have your program on the lookout...) for negative altitudes. I suppose you could set up a flag so that if it were 0 or negative for ten consecutive readings, you assume you're on the ground. But remember that the Basic Stamp doesn't handle negative numbers the way that you and I do. If I remember correctly, they'll show up as huge positive numbers (numbers over 32767). You'll want to verify this. If that's the case, you can look for "either 0 or greater than 32767", which is, I believe, what I did when I programmed the buzzer on the XBee-MAWD device.
So do you think detaching the parachute at touchdown is as "simple" as having the MAWD signal a servomotor to open a cog (etc.) when it reads "0" (for 10-20 consecutive times, etc.) after lift-off...? Seems almost too easy. But easy it good in this case since we have a plethora of newbies.
What's new in WI? What happened to the 'Pack? We're having Wisconsin-like weather here lately. No school for two days last week because of snow (and lots of it!) and -15 F this morning.
Brrrrrrrrrrrrrrrrrr!
Mark
:cool:
Every year at my school we have a 2 week period at the end of February in which we choose a project that we're interested in and do it, or at least attempt to. This year I want to try and learn the PBASIC language and I was wondering if you could help me learn it when I need it, via the internet of course. Mr. Kibler already agreed to be my adviser and he suggested asking you to assist as well. If you need anymore information you can contact me on the forum or email me at obiewanhelmers@gmail.com.
Thank you,
Obie
Good start Emily!
Here is a list of mission ideas (we think) we've discussed so far. Let's all work to complete the list. Then think about how you would prioritize them 1,2,3 based on your interest AND simplicity/difficulty.
1) Soil sampler (Emily)
2) "Come back" rover (Emily)
3) Parachute detachment device (Mr. Kibler)
4) ??? ======> who will be next???
I think it's wise to focus on one mission and complete it rather than scatter our thoughts and our resources across two or three missions at the same time. But that's just me thinking out loud. What are your thoughts?
Mr. Kibler
:nerd:
Dylan,
The MAWD reads out the actual altitude as real numbers (1, 2, 3, 378, 993, etc.) When it lands after flight it will read '0' again. We would, of course, do any programming here in New Hampshire before we leave... no need to reprogram the MAWD in Nevada.
Mr. Kibler
Date: Mon, Jan 24, 2011 at 4:41 PM
Subject: SPEAKING ENGAGEMENT AT THE CONTOOCOOK VALLEY RADIO CLUB
To: "L. Mark Kibler, M.Ed." <mkibler@alumni.unity.edu>
Cc: Dale & Mickie Clement <dpclement@tds.net>
HI MARK:
THE RADIO CLUB MEETS ON TUESDAY* FEBRUARY 8
I GET THE ROOM OPEN BETWEEN 6:30 AND 7:00 P.M.*AND START THE COFFEE.
*WE USUALLY *START THE PROGRAM AROUND 7:30 P.M.
THE PROGRAM IS THE FIRST THING ON THE AGENDA AND THEN WE BREAK FOR THE
REFRESHMENTS.
ANY CLUB BUSINESS IS LAST ON THE SCHEDULE SO THAT GUESTS OR SPEAKERS
CAN LEAVE RIGHT AFTER THEIR TALK.
THE MEETING PLACE IS THE HOPKINTON LIBRARY COMMUNITY ROOM. IT IS
LOCATED ABOUT ONE QUARTER OF A MILE PAST THE FIRE HOUSE*THE FIRE HOUSE
IS JUST OVER THE STONE BRIDGE IN* CONTOOCOOK VILLAGE. TURN LEFT AT THE
FIRE HOUSE. THAT IS PINE STREET. GO ABOUT 1000 FEET AN*START LOOKING
FOR THE LIBRARY SIGN ON THE RIGHT SIDE OF PINE ST. THE LIBRARY IS
ACTUALLY ON HOUSTON DRIVE A VERY SHORT ROAD INTO THE FACILITY. YOU
WILL SEE THE LIBRARY BUILDING AS YOU LOOK UP HOUSTON DRIVE FROM PINE
STREET.
KEN
This is our first presentation we will be attending this project year. It is not MANDATORY, but it will be extremely beneficial for anyone who can to be in attendance. Please contact Mr. Kibler personally if you will be able to make it. We usually meet somewhere commonly known, the middle school possibly, and carpool to the destination, (as stated in the email)
It may seem very nerve racking to you to present like this, but to be honest, the day after I told Mr. Kibler I was interested in robotics and the team, he invited me to a similiar presentation the morning after that day! I even got to miss a little bit of school in the morning since it was I believe a Wednesday.
When the MAWD is turned on, it takes a few seconds to sample and average the air pressure on the launch pad. When it has a good reading, it assigns that to the altitude "0". All of the altitude readings reported by the MAWD are relative to that point, not to sea level. In aviation terms, the MAWD output is "AGL", not "MSL" (that is, "Above Ground Level", rather than "Mean Sea Level").
The AGL/MSL distinction can be important. At my home launch field, we have a waiver to fly to 10,000 feet. What many fliers don't realize is that the waiver is to 10,000 feet MSL, not AGL. Since field elevation is about 900 feet MSL, if your altimeter reads over 9100 feet, you've busted the waiver.
Anyway, good thinking. If the readings did vary the way you suggested, then yes, you would have to reprogram out in the field. Much better to know that kind of thing now, rather than when you get out there, and find that your rocket never thinks it has landed (because it's looking for "0", and only getting whatever the field elevation at Black Rock is).
It was cold over the weekend, but recovered. I walked about 10 miles outside yesterday, only getting cold once, when facing the wind in a place that seemed a bit of a wind tunnel.
The Packers made the Super Bowl. I can't believe it. Rodgers really IS that good, and they're really clicking as a full team. Classic example of "you want to play your best football when the playoffs come around". My hat is off to the Bears, who gave us a great game despite being down to their emergency quarterback. If you put someone like Rodgers on the Bears, you'd have that 16-0 season we haven't seen in 40 years.
I've seen groups detach parachutes at landing, and yes, they used a servo to move something that released it. I wish I had photos, but your problem will be to have the parachute secure enough not to detach under the shock of opening, but still able to be detached by the mere movement of a servo. The best thing is a metal pin that runs through holes in the sides of a metal u-shaped holder, so that all of the forces in the direction the parachute pulls are metal-against-metal, but in the direction of pulling the pin, there's just a smooth unfettered sideways pull. There's probably a name for that, but I don't know it. This is the closest I come:
http://en.wikipedia.org/wiki/Clevis_fastener
Sylvie369;970946 said:
"...the best thing is a metal pin that runs through holes in the sides of a metal u-shaped holder, so that all of the forces in the direction the parachute pulls are metal-against-metal, but in the direction of pulling the pin..."
Sylvie,
You took a 10-mile hike in Wisconsin in January? Weren't you cold? It must have been brisk to say the least. I haven't been able to do much running in months. I've had a nagging ilio-psaos problem for months now and I really miss running. I did get to do a 5K with my son on New Year's Day though, the "Peanut Butter Chip Chase 5K Race"... it rhymes! And they had great cookies too.
I thought about the clevis pin idea too, with the clevis pin being pulled out by a servo somehow. It would have to be a fairly snug fit into the U-shaped piece though. Otherwise the clevis pin might simply slide out of the hole at apogee or during "roll-over".
What about securing a nut to the servo and using a bolt instead of a clevis pin? The servo would unthread the nut from the bolt (then somehow pull the bolt out too...?) I don't have the idea entirely evolved but the clevis pin idea is a start. I'll have the Rocketeers research it; that's how we learned about various ways to deploy parachutes (parachute bags, etc.) We have practice on Sunday.
What other thoughts are rattling around inside your cranium? Did I tell you I was invited to apply for admission into a PhD program in Aerospace Studies? It sounds daunting.
Mark
:cool:
-Jake-
. .
Jake,
This is certainly a creative approach to the problem. Hmmmm.... I'm not sure what to think. So you're saying that the altimeter would activate a motor that pulls the magnets apart? Interesting. It makes me wonder several things:
How is the parachute attached to the magnet(s)? Are the magnets strong enough to hold the parachute (which is attached to the ASP or the robot)? Is the motor strong enough to pull the magnets apart? Will the magnetic field affect the ASP's electronics, especially the altimeter, the shortwave transmitter, and the BOE (the brains of the project)? Where will the magnets be mounted? Is there research on anything like this that's been done before? Is the a simpler way* (*Obie, what was that thing about Ockham's Razor I asked you to look up...?)
You have my interest piqued, Jake. What do others think?
Mr. Kibler
:nerd:
Sorry I haven't talked in a LONG TIME, but I've just been sitting back and reading your posts, and the book Mr. Kibler gave me What's a Microcontroller?. Also I noticed that I never really answered the question if I could make it to the meeting this weekend, but it would be a yes.
Dylan (I think that's who posted about the midweek meeting),
I believe that I can make that meeting, let me just double check. Is it okay if I answer Sunday?
~Steph
P.S. I will try to supply some cookies, too.
Emily
Thank you for confirming that you're coming on Sunday. Are the rest of you coming on Sundsay too... Who would you like to bring cookies this time? Who can bring (healthy) drinks?
.
ALL ROCKETEERS:
.
Practice will BEGIN at 1:00 PM on Sunday as we discussed last time. Consider your team practices the same as those for a varsity sport (it is: ithis is athletics for your brain.) What would a varsity coach think or do if a player rolled in late for practice (no you won't run laps and no, coming late doesn't demonstrate leadership either.)
50 push-ups instead?!
Mr. Kibler
Head Coach, Unity College "Runnin' Rams" cross country team
1996 NSCAA National Champions
Mr. Kibler,
Just confirming that I will be in attendance on Sunday, as I previously mentioned. I would be glad to bring some healthy drinks. Also, I have accomplished a little more with my GPS movement experiment, thanks to the extra EEPROM available on the BS2e Stamp. At the moment, it's still very rudimentary and merely proof of concept, but it is making the possibility of integrating GPS-guided navigation for the rover seem like a possibility. I'll be posting more details on this soon, and will definitely bring the results to our next meeting.
Andrew
I was in my IED class today, (Intro to Engineer Design), and was playing around with a CaD program, (Computer Aided Design). I was thinking about the parachute release mechanism, and I believe I found the most simplistic idea I could think of. I do not have the CaD program here at my house, so I am searching the web for a program that will be able to express my idea properly. I will post it soon if my searches yeild results.
Yes I will be going to the practice/meeting this weekend, can't wait, but I don't think I'll be able to make the Tuesday/Radio Assembly due to syblings Basketball schedules.
Mr. Kibler, sorry I've been so slow about Occam's Razor, I just saw that request today. Occam's Razor is a principle used to simplify matters. Basically if you have multiple answers for the same solution you choose the simplest one. I know why you wanted me to look this up. We have many ideas about how we detach the parachute. So in other words we need to look for the simpliest one and use that because it will be easier to do and still work just as well. Currently, (to my knowledge anyway), we have three or so suggestions.
First: A timer would countdown and detach the parachute upon the end of the countdown
2. We use MAWD to determine when the parachute releases
3. We try to use the Atla spectrometer to determine when its on the ground
4. Use a pressure sensitive piece to realease the parachute
Those are the options unless Dylan can tell me what his idea is. I would say the simpliest of these choices is the MAWD. That's sums it up.
-Obie
Obie,
So now you know Sir William of Ockham's advice, one of the most fundamental of all engineering precepts:
K. I. S. S. ===> Keep It Simple Students. Put differently, "Of all possible solutions, the simplest is usually the best." Sound advice, I think.
Another fundamental engineering principal is "F.F.F." Anyone want to take a guess at what this stands for and what exactly it means, in simple terms...?!
I have two more BOE circuit boards, another BOE-bot robot, and a bunch of new resistors, capacitors, wires, and books on the way from Parallax. Thank you, Parallax! The new kits won't be here in time for Sunday's practice but we will have them to work with. Obie, think about what parts you will need for your independent project.
I've also bought five more RTC chips, 5 more resonator crystals, 10 more SHT chips, and a Parallax book about "Programming the Parallax robot." You, young scientists, must decide what we should do with these new materials. What is our primary mission? What do you think our next step is...?
Keep up the good work,
Mr. Kibler
:cool:
I believe F.F.F. means "Form follows function." In other words, how you design and create something should be based around it's purpose.
That's fantastic news, and very generous of Parallax! I'm sure everything will be put to great use shortly.
Several ideas come to mind to put the parts you've just bought to use, including the most obvious of beginning to assemble a replica of the current ASP-II . However, as you stated Mr. Kibler, we still need to clarify our primary mission goals before we proceed any further.
Team members, in your own opinion, what do you consider our current mission goals to be -- and why? As you have all realized by now, there are many options for our primary mission, some of which are more difficult than others. We need to pick one, that in my opinion is 1) within our abilities (but not necessarily "easy") 2) serves a real purpose. I believe answering these questions will also answer the other questions that Mr. Kibler has proposed.
-- Andrew
Andrew,
The two points you make are spot-on accurate. Thanks for sharing your insights.
Mr. Kibler:cool: