From: Jeff S. <jef...@gm...> - 2007-07-23 19:19:36
|
I was thinking the device would know when it is being dropped and could deploy spring loaded shock absorbing arms or something :-) |
From: Craig H. <cr...@gu...> - 2007-07-23 19:48:56
|
On Jul 23, 2007, at 12:19 PM, Jeff Sadowski wrote: > I was thinking the device would know when it is being dropped and > could deploy spring loaded shock absorbing arms or something :-) Actually, it can be programmed to trigger an interrupt when it detects that the device is in free-fall (I guess when it's accelerating in any direction at 9.8m/s^2 or something). C |
From: Black, M. <Michael.Black@EssexCorp.com> - 2007-07-23 20:06:28
|
Actually an accelerometer will show 1G at rest and 0G during free-fall. Just one change occurs from rest to free-fall (i.e. 1G...0G). And you need to be sure that you have the vertical axis being measured -- otherwise you need a 2 or 3 axis accelerometer. You're not actually accelerating during free-fall (your acceleration is constant) -- but your velocity is increasing. Here's some good info on the math... http://www2.usfirst.org/2005comp/Manuals/Acceler1.pdf ___________________ Michael D. Black -----Original Message----- From: gum...@li... [mailto:gum...@li...] On Behalf Of Craig Hughes Sent: Monday, July 23, 2007 2:49 PM To: General mailing list for gumstix users. Subject: Re: [Gumstix-users] use of an accelerometer. On Jul 23, 2007, at 12:19 PM, Jeff Sadowski wrote: > I was thinking the device would know when it is being dropped and > could deploy spring loaded shock absorbing arms or something :-) Actually, it can be programmed to trigger an interrupt when it =20 detects that the device is in free-fall (I guess when it's =20 accelerating in any direction at 9.8m/s^2 or something). C ------------------------------------------------------------------------ - This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ gumstix-users mailing list gum...@li... https://lists.sourceforge.net/lists/listinfo/gumstix-users =20 =20 =20 =20 =20 =20 =20 This electronic message and any files transmitted with it contain = information which may be privileged and/or proprietary. The information = is intended for use solely by the intended recipient(s). If you are not = the intended recipient, be aware that any disclosure, copying, = distribution or use of this information is prohibited. If you have = received this electronic message in error, please advise the sender by = reply email or by telephone (301-939-7000) and delete the message. |
From: Craig H. <cr...@gu...> - 2007-07-23 20:28:47
|
On Jul 23, 2007, at 1:06 PM, Black, Michael wrote: > Actually an accelerometer will show 1G at rest and 0G during free- > fall. > Just one change occurs from rest to free-fall (i.e. 1G...0G). > And you need to be sure that you have the vertical axis being measured > -- otherwise you need a 2 or 3 axis accelerometer. This is a 3-axis accelerometer. > You're not actually accelerating during free-fall (your > acceleration is > constant) -- but your velocity is increasing. > Here's some good info on the math... > http://www2.usfirst.org/2005comp/Manuals/Acceler1.pdf You are actually accelerating during free-fall, at a constant 9.8m/ s^2. Your velocity cannot change unless you're accelerating. The accelerometer is not really measuring your acceleration, it's measuring strain on a MEMS crystal; when you're at rest, the crystal is being tugged on by gravity, but the table or whatever you're sitting on is countering that force, and thereby creates strain in the crystal. When you're in free-fall, you're accelerating at the same speed as the crystal, so there's no strain in the crystal, and so it measures 0. C |
From: <48...@la...> - 2007-07-23 20:37:03
|
A really cool application for the accelerometer is relative position calculation. Combine this with the GPS and you can achieve relatively high resolution position data. The potential robotics appications are tasty. See the datasheet link at the bottom of this page: http://docwiki.gumstix.org/Frequently_asked_questions/Goliath_boards James > > On Jul 23, 2007, at 1:06 PM, Black, Michael wrote: > >> Actually an accelerometer will show 1G at rest and 0G during free- >> fall. >> Just one change occurs from rest to free-fall (i.e. 1G...0G). >> And you need to be sure that you have the vertical axis being measured >> -- otherwise you need a 2 or 3 axis accelerometer. > > This is a 3-axis accelerometer. > >> You're not actually accelerating during free-fall (your >> acceleration is >> constant) -- but your velocity is increasing. >> Here's some good info on the math... >> http://www2.usfirst.org/2005comp/Manuals/Acceler1.pdf > > You are actually accelerating during free-fall, at a constant 9.8m/ > s^2. Your velocity cannot change unless you're accelerating. The > accelerometer is not really measuring your acceleration, it's > measuring strain on a MEMS crystal; when you're at rest, the crystal > is being tugged on by gravity, but the table or whatever you're > sitting on is countering that force, and thereby creates strain in > the crystal. When you're in free-fall, you're accelerating at the > same speed as the crystal, so there's no strain in the crystal, and > so it measures 0. > > C > > ------------------------------------------------------------------------- > This SF.net email is sponsored by: Splunk Inc. > Still grepping through log files to find problems? Stop. > Now Search log events and configuration files using AJAX and a browser. > Download your FREE copy of Splunk now >> http://get.splunk.com/ > _______________________________________________ > gumstix-users mailing list > gum...@li... > https://lists.sourceforge.net/lists/listinfo/gumstix-users > |
From: Jeff S. <jef...@gm...> - 2007-07-23 20:56:03
|
ooh you could also have it deploy a parachute :-P On 7/23/07, 48...@la... <48...@la...> wrote: > A really cool application for the accelerometer is relative position > calculation. Combine this with the GPS and you can achieve relatively > high resolution position data. > > The potential robotics appications are tasty. > > See the datasheet link at the bottom of this page: > http://docwiki.gumstix.org/Frequently_asked_questions/Goliath_boards > > James > > > > > On Jul 23, 2007, at 1:06 PM, Black, Michael wrote: > > > >> Actually an accelerometer will show 1G at rest and 0G during free- > >> fall. > >> Just one change occurs from rest to free-fall (i.e. 1G...0G). > >> And you need to be sure that you have the vertical axis being measured > >> -- otherwise you need a 2 or 3 axis accelerometer. > > > > This is a 3-axis accelerometer. > > > >> You're not actually accelerating during free-fall (your > >> acceleration is > >> constant) -- but your velocity is increasing. > >> Here's some good info on the math... > >> http://www2.usfirst.org/2005comp/Manuals/Acceler1.pdf > > > > You are actually accelerating during free-fall, at a constant 9.8m/ > > s^2. Your velocity cannot change unless you're accelerating. The > > accelerometer is not really measuring your acceleration, it's > > measuring strain on a MEMS crystal; when you're at rest, the crystal > > is being tugged on by gravity, but the table or whatever you're > > sitting on is countering that force, and thereby creates strain in > > the crystal. When you're in free-fall, you're accelerating at the > > same speed as the crystal, so there's no strain in the crystal, and > > so it measures 0. > > > > C > > > > ------------------------------------------------------------------------- > > This SF.net email is sponsored by: Splunk Inc. > > Still grepping through log files to find problems? Stop. > > Now Search log events and configuration files using AJAX and a browser. > > Download your FREE copy of Splunk now >> http://get.splunk.com/ > > _______________________________________________ > > gumstix-users mailing list > > gum...@li... > > https://lists.sourceforge.net/lists/listinfo/gumstix-users > > > > > ------------------------------------------------------------------------- > This SF.net email is sponsored by: Splunk Inc. > Still grepping through log files to find problems? Stop. > Now Search log events and configuration files using AJAX and a browser. > Download your FREE copy of Splunk now >> http://get.splunk.com/ > _______________________________________________ > gumstix-users mailing list > gum...@li... > https://lists.sourceforge.net/lists/listinfo/gumstix-users > |
From: Rob B. <ro...@gm...> - 2007-07-23 23:41:22
|
I think an angular accelerometer would be more useful. With an angular accelerometer you could determine which direction the device is pointing (landscape or vertical). The GPS can then be used to determine position. -RobB On 7/23/07, 48...@la... <48...@la...> wrote: > > A really cool application for the accelerometer is relative position > calculation. Combine this with the GPS and you can achieve relatively > high resolution position data. > > The potential robotics appications are tasty. > > See the datasheet link at the bottom of this page: > http://docwiki.gumstix.org/Frequently_asked_questions/Goliath_boards > > James > > > > > On Jul 23, 2007, at 1:06 PM, Black, Michael wrote: > > > >> Actually an accelerometer will show 1G at rest and 0G during free- > >> fall. > >> Just one change occurs from rest to free-fall (i.e. 1G...0G). > >> And you need to be sure that you have the vertical axis being measured > >> -- otherwise you need a 2 or 3 axis accelerometer. > > > > This is a 3-axis accelerometer. > > > >> You're not actually accelerating during free-fall (your > >> acceleration is > >> constant) -- but your velocity is increasing. > >> Here's some good info on the math... > >> http://www2.usfirst.org/2005comp/Manuals/Acceler1.pdf > > > > You are actually accelerating during free-fall, at a constant 9.8m/ > > s^2. Your velocity cannot change unless you're accelerating. The > > accelerometer is not really measuring your acceleration, it's > > measuring strain on a MEMS crystal; when you're at rest, the crystal > > is being tugged on by gravity, but the table or whatever you're > > sitting on is countering that force, and thereby creates strain in > > the crystal. When you're in free-fall, you're accelerating at the > > same speed as the crystal, so there's no strain in the crystal, and > > so it measures 0. > > > > C > > > > > ------------------------------------------------------------------------- > > This SF.net email is sponsored by: Splunk Inc. > > Still grepping through log files to find problems? Stop. > > Now Search log events and configuration files using AJAX and a browser. > > Download your FREE copy of Splunk now >> http://get.splunk.com/ > > _______________________________________________ > > gumstix-users mailing list > > gum...@li... > > https://lists.sourceforge.net/lists/listinfo/gumstix-users > > > > > ------------------------------------------------------------------------- > This SF.net email is sponsored by: Splunk Inc. > Still grepping through log files to find problems? Stop. > Now Search log events and configuration files using AJAX and a browser. > Download your FREE copy of Splunk now >> http://get.splunk.com/ > _______________________________________________ > gumstix-users mailing list > gum...@li... > https://lists.sourceforge.net/lists/listinfo/gumstix-users > |
From: Dave H. <dhy...@gm...> - 2007-07-24 00:05:21
|
Hi Rob, On 7/23/07, Rob Barnes <ro...@gm...> wrote: > I think an angular accelerometer would be more useful. With an angular > accelerometer you could determine which direction the device is pointing > (landscape or vertical). The GPS can then be used to determine position. So actually, there are 3 common types of sensors for doing all this. 1 - accelerometer 2 - gyro (which I think is what you meant) 3 - magnetometer The accelerometer will tell you if you're in landscape or portrait, provided the screen is vertical (and not laif flat on a table). The gyro will track rotations, but they have a tendency to drift over time, and require some type of reference. Typically an accelerometer/gyro pair is used since the accelerometer won't drift, but the accelerometer is subject to accelerations. So if you're in your car and you hit the gas, the aceelerometers notion of down will change, Whereas a gyro would detect that you weren't realling rotating at all. Magentometers are neat, because they have an absolute notion of where the field lines are, but they can't detect rotations about the axis if the field line. In my part of the world (near the Canada US border), the z axis component of the magnetic field is about twice as strong as the X & Y components. Magenetomers are also influenced by nearby soft iron and other magnetic things. Put all 3 together, and you have a pretty neat IMU. There is a nifty one produced by Analog Devices, which incorporates and calibrates a 3-axis acclerometer and a 3-axis gyro in the same package: <http://www.analog.com/en/prod/0%2C2877%2CADIS16350%2C00.html> -- Dave Hylands Vancouver, BC, Canada http://www.DaveHylands.com/ |
From: Alex M. <amo...@gm...> - 2007-07-24 06:20:13
|
On 7/23/07, Dave Hylands <dhy...@gm...> wrote: > > There is a nifty one produced by Analog Devices, which incorporates > and calibrates a 3-axis acclerometer and a 3-axis gyro in the same > package: > <http://www.analog.com/en/prod/0%2C2877%2CADIS16350%2C00.html> Assuming your device is reasonably large, you could put 3 of the significantly cheaper accelerometers at or near the corners of the device, and, with a bit of math (ok, maybe a lot of math), get the same results, unless you expect to be in freefall for long periods of time (no skydiving robots). Even 2 accelerometers should get you decent results except in the case of spinning on the axis described by the two units. You would still need to rely on a GPS unit to give you a reference point once in a while, to compensate for drift. If you only needed direction and orientation (and not location), one of these could work as a reference as well: http://www.electronicproducts.com/ShowPage.asp?FileName=hlcn1.jan2006.html |
From: Albert D. <al...@da...> - 2007-07-26 22:24:35
|
Hi all, Is it also possible to calculate the m/s from a car with the accelerometer, if the GPS is not available? Regards, Albert On Jul 24, 2007, at 8:20 AM, Alex Montgomery wrote: > > > On 7/23/07, Dave Hylands <dhy...@gm...> wrote: > > There is a nifty one produced by Analog Devices, which incorporates > and calibrates a 3-axis acclerometer and a 3-axis gyro in the same > package: > < http://www.analog.com/en/prod/0%2C2877%2CADIS16350%2C00.html> > > > Assuming your device is reasonably large, you could put 3 of the > significantly cheaper accelerometers at or near the corners of the > device, and, with a bit of math (ok, maybe a lot of math), get the > same results, unless you expect to be in freefall for long periods > of time (no skydiving robots). Even 2 accelerometers should get you > decent results except in the case of spinning on the axis described > by the two units. > > You would still need to rely on a GPS unit to give you a reference > point once in a while, to compensate for drift. > > If you only needed direction and orientation (and not location), > one of these could work as a reference as well: http:// > www.electronicproducts.com/ShowPage.asp?FileName=hlcn1.jan2006.html > ---------------------------------------------------------------------- > --- > This SF.net email is sponsored by: Splunk Inc. > Still grepping through log files to find problems? Stop. > Now Search log events and configuration files using AJAX and a > browser. > Download your FREE copy of Splunk now >> http://get.splunk.com/ > _______________________________________________ > gumstix-users mailing list > gum...@li... > https://lists.sourceforge.net/lists/listinfo/gumstix-users |
From: Jeff S. <jef...@gm...> - 2007-07-26 22:37:32
|
well think physics we know v=a*s you could get a rough estimate. I wouldn't rely on it too much though. I'm not sure how often you can take readings on the accelerometer. and how accurate it is. it would almost certainly need to be reset a lot there would be no good way for it to get good info without a gps reading. On 7/26/07, Albert Dahan <al...@da...> wrote: > Hi all, > > Is it also possible to calculate the m/s from a car with the accelerometer, > if the GPS is not available? > > Regards, > Albert > > > On Jul 24, 2007, at 8:20 AM, Alex Montgomery wrote: > > > > On 7/23/07, Dave Hylands <dhy...@gm...> wrote: > > > > There is a nifty one produced by Analog Devices, which incorporates > > and calibrates a 3-axis acclerometer and a 3-axis gyro in the same > > package: > > < > http://www.analog.com/en/prod/0%2C2877%2CADIS16350%2C00.html> > > > Assuming your device is reasonably large, you could put 3 of the > significantly cheaper accelerometers at or near the corners of the device, > and, with a bit of math (ok, maybe a lot of math), get the same results, > unless you expect to be in freefall for long periods of time (no skydiving > robots). Even 2 accelerometers should get you decent results except in the > case of spinning on the axis described by the two units. > > You would still need to rely on a GPS unit to give you a reference point > once in a while, to compensate for drift. > > If you only needed direction and orientation (and not location), one of > these could work as a reference as well: > http://www.electronicproducts.com/ShowPage.asp?FileName=hlcn1.jan2006.html > ------------------------------------------------------------------------- > This SF.net email is sponsored by: Splunk Inc. > Still grepping through log files to find problems? Stop. > Now Search log events and configuration files using AJAX and a browser. > Download your FREE copy of Splunk now >> > http://get.splunk.com/_______________________________________________ > gumstix-users mailing list > gum...@li... > https://lists.sourceforge.net/lists/listinfo/gumstix-users > > ------------------------------------------------------------------------- > This SF.net email is sponsored by: Splunk Inc. > Still grepping through log files to find problems? Stop. > Now Search log events and configuration files using AJAX and a browser. > Download your FREE copy of Splunk now >> http://get.splunk.com/ > _______________________________________________ > gumstix-users mailing list > gum...@li... > https://lists.sourceforge.net/lists/listinfo/gumstix-users > > |
From: Dave H. <dhy...@gm...> - 2007-07-26 23:28:20
|
Hi Albert, > Is it also possible to calculate the m/s from a car with the accelerometer, > if the GPS is not available? You can integrate to get speed (I think). But if you're moving along at a constant speed, the accelerometer will just read 0, regardless of what speed you're moving with. -- Dave Hylands Vancouver, BC, Canada http://www.DaveHylands.com/ |
From: Albert D. <al...@da...> - 2007-07-27 00:21:29
|
Hi Dave, Thanks for making that clear. Any idea how I can read the distance if the GPS isn't available? I need to determine the kilometers made by a car without using a pulse or can solution, is that possible? Regards, Albert On Jul 27, 2007, at 1:28 AM, Dave Hylands wrote: > Hi Albert, > >> Is it also possible to calculate the m/s from a car with the >> accelerometer, >> if the GPS is not available? > > You can integrate to get speed (I think). But if you're moving along > at a constant speed, the accelerometer will just read 0, regardless of > what speed you're moving with. > > -- > Dave Hylands > Vancouver, BC, Canada > http://www.DaveHylands.com/ > > ---------------------------------------------------------------------- > --- > This SF.net email is sponsored by: Splunk Inc. > Still grepping through log files to find problems? Stop. > Now Search log events and configuration files using AJAX and a > browser. > Download your FREE copy of Splunk now >> http://get.splunk.com/ > _______________________________________________ > gumstix-users mailing list > gum...@li... > https://lists.sourceforge.net/lists/listinfo/gumstix-users |
From: Christopher G. <mo...@gm...> - 2007-07-27 18:43:57
|
These problems are all solvable with a little bit of calculus. Provided that your accelerometer will read negative with you slow down, keeping a log of accelerometer readings should be enough. Let's say you have a graph of your accelerometer readings. The area under the curve (between it rather, because it will drop negative as well) will be your difference in speed between any two intervals. By starting at a known speed, you can then accurately (as far as numbers are concerned) form a graph of your speed. Taking a look at this second graph, the area under the curve will be the total distance traveled. 2007/7/26, Albert Dahan <al...@da...>: > > Hi Dave, > > Thanks for making that clear. > > Any idea how I can read the distance if the GPS isn't available? > > I need to determine the kilometers made by a car without using a > pulse or can solution, is that possible? > > Regards, > Albert > > On Jul 27, 2007, at 1:28 AM, Dave Hylands wrote: > > > Hi Albert, > > > >> Is it also possible to calculate the m/s from a car with the > >> accelerometer, > >> if the GPS is not available? > > > > You can integrate to get speed (I think). But if you're moving along > > at a constant speed, the accelerometer will just read 0, regardless of > > what speed you're moving with. > > > > -- > > Dave Hylands > > Vancouver, BC, Canada > > http://www.DaveHylands.com/ > > > > ---------------------------------------------------------------------- > > --- > > This SF.net email is sponsored by: Splunk Inc. > > Still grepping through log files to find problems? Stop. > > Now Search log events and configuration files using AJAX and a > > browser. > > Download your FREE copy of Splunk now >> http://get.splunk.com/ > > _______________________________________________ > > gumstix-users mailing list > > gum...@li... > > https://lists.sourceforge.net/lists/listinfo/gumstix-users > > > ------------------------------------------------------------------------- > This SF.net email is sponsored by: Splunk Inc. > Still grepping through log files to find problems? Stop. > Now Search log events and configuration files using AJAX and a browser. > Download your FREE copy of Splunk now >> http://get.splunk.com/ > _______________________________________________ > gumstix-users mailing list > gum...@li... > https://lists.sourceforge.net/lists/listinfo/gumstix-users > -- Christopher Gilbert B.S., Computer Science University of Maine 2006 http://motomastyle.com |
From: Rob B. <ro...@gm...> - 2007-08-01 00:39:15
|
Here is a real world example of how to use an accelerometer to monitor the speed of your car: http://forums.vwvortex.com/zerothread?id=3362586 This guy actually uses the accelerometer embedded in the Wiimote. -RobB On 7/27/07, Christopher Gilbert <mo...@gm...> wrote: > > These problems are all solvable with a little bit of calculus. > > Provided that your accelerometer will read negative with you slow down, > keeping a log of accelerometer readings should be enough. > > Let's say you have a graph of your accelerometer readings. The area under > the curve (between it rather, because it will drop negative as well) will be > your difference in speed between any two intervals. By starting at a known > speed, you can then accurately (as far as numbers are concerned) form a > graph of your speed. Taking a look at this second graph, the area under the > curve will be the total distance traveled. > > > > 2007/7/26, Albert Dahan <al...@da...>: > > > > Hi Dave, > > > > Thanks for making that clear. > > > > Any idea how I can read the distance if the GPS isn't available? > > > > I need to determine the kilometers made by a car without using a > > pulse or can solution, is that possible? > > > > Regards, > > Albert > > > > On Jul 27, 2007, at 1:28 AM, Dave Hylands wrote: > > > > > Hi Albert, > > > > > >> Is it also possible to calculate the m/s from a car with the > > >> accelerometer, > > >> if the GPS is not available? > > > > > > You can integrate to get speed (I think). But if you're moving along > > > at a constant speed, the accelerometer will just read 0, regardless of > > > what speed you're moving with. > > > > > > -- > > > Dave Hylands > > > Vancouver, BC, Canada > > > http://www.DaveHylands.com/ > > > > > > ---------------------------------------------------------------------- > > > > > --- > > > This SF.net email is sponsored by: Splunk Inc. > > > Still grepping through log files to find problems? Stop. > > > Now Search log events and configuration files using AJAX and a > > > browser. > > > Download your FREE copy of Splunk now >> http://get.splunk.com/ > > > _______________________________________________ > > > gumstix-users mailing list > > > gum...@li... > > > https://lists.sourceforge.net/lists/listinfo/gumstix-users > > > > > > ------------------------------------------------------------------------- > > > > This SF.net email is sponsored by: Splunk Inc. > > Still grepping through log files to find problems? Stop. > > Now Search log events and configuration files using AJAX and a browser. > > Download your FREE copy of Splunk now >> http://get.splunk.com/ > > _______________________________________________ > > gumstix-users mailing list > > gum...@li... > > https://lists.sourceforge.net/lists/listinfo/gumstix-users > > > > > > -- > Christopher Gilbert > B.S., Computer Science > University of Maine 2006 > http://motomastyle.com > ------------------------------------------------------------------------- > This SF.net email is sponsored by: Splunk Inc. > Still grepping through log files to find problems? Stop. > Now Search log events and configuration files using AJAX and a browser. > Download your FREE copy of Splunk now >> http://get.splunk.com/ > _______________________________________________ > gumstix-users mailing list > gum...@li... > https://lists.sourceforge.net/lists/listinfo/gumstix-users > > |
From: Sean R. <rei...@cs...> - 2007-08-01 12:13:35
|
has anyone actually implemented this ? I think that this only works for very small amounts of time (seconds max) as the error from the accelerometer quickly becomes too big, its also why its very hard to determine distance from accelerometers (the double integral) Sean Christopher Gilbert wrote: > These problems are all solvable with a little bit of calculus. > > Provided that your accelerometer will read negative with you slow > down, keeping a log of accelerometer readings should be enough. > > Let's say you have a graph of your accelerometer readings. The area > under the curve (between it rather, because it will drop negative as > well) will be your difference in speed between any two intervals. By > starting at a known speed, you can then accurately (as far as numbers > are concerned) form a graph of your speed. Taking a look at this > second graph, the area under the curve will be the total distance > traveled. > > > > 2007/7/26, Albert Dahan <al...@da... <mailto:al...@da...>>: > > Hi Dave, > > Thanks for making that clear. > > Any idea how I can read the distance if the GPS isn't available? > > I need to determine the kilometers made by a car without using a > pulse or can solution, is that possible? > > Regards, > Albert > > On Jul 27, 2007, at 1:28 AM, Dave Hylands wrote: > > > Hi Albert, > > > >> Is it also possible to calculate the m/s from a car with the > >> accelerometer, > >> if the GPS is not available? > > > > You can integrate to get speed (I think). But if you're moving along > > at a constant speed, the accelerometer will just read 0, > regardless of > > what speed you're moving with. > > > > -- > > Dave Hylands > > Vancouver, BC, Canada > > http://www.DaveHylands.com/ > > > > > ---------------------------------------------------------------------- > > > --- > > This SF.net email is sponsored by: Splunk Inc. > > Still grepping through log files to find problems? Stop. > > Now Search log events and configuration files using AJAX and a > > browser. > > Download your FREE copy of Splunk now >> http://get.splunk.com/ > > _______________________________________________ > > gumstix-users mailing list > > gum...@li... > <mailto:gum...@li...> > > https://lists.sourceforge.net/lists/listinfo/gumstix-users > > > ------------------------------------------------------------------------- > > This SF.net email is sponsored by: Splunk Inc. > Still grepping through log files to find problems? Stop. > Now Search log events and configuration files using AJAX and a > browser. > Download your FREE copy of Splunk now >> http://get.splunk.com/ > _______________________________________________ > gumstix-users mailing list > gum...@li... > <mailto:gum...@li...> > https://lists.sourceforge.net/lists/listinfo/gumstix-users > > > > > -- > Christopher Gilbert > B.S., Computer Science > University of Maine 2006 > http://motomastyle.com > ------------------------------------------------------------------------ > > ------------------------------------------------------------------------- > This SF.net email is sponsored by: Splunk Inc. > Still grepping through log files to find problems? Stop. > Now Search log events and configuration files using AJAX and a browser. > Download your FREE copy of Splunk now >> http://get.splunk.com/ > ------------------------------------------------------------------------ > > _______________________________________________ > gumstix-users mailing list > gum...@li... > https://lists.sourceforge.net/lists/listinfo/gumstix-users > |
From: Jon H. <jo...@hu...> - 2007-08-01 12:20:56
|
On Wed, 01 Aug 2007 13:13:28 +0100, Sean Reilly <rei...@cs...> = wrote: > has anyone actually implemented this ? I think that this only works for= =20 > very small amounts of time (seconds max) as the error from the=20 > accelerometer quickly becomes too big, its also why its very hard to=20 > determine distance from accelerometers (the double integral) There's a really interesting practical-world page that talks about = odometry and IMUs and such here: http://www.geology.smu.edu/~dpa-www/robo/Encoder/imu_odo/ Later, Jon -------------------------------------------------------------- Jon Hylands Jo...@hu... http://www.huv.com/jon Project: Micro Raptor (Small Biped Velociraptor Robot) http://www.huv.com/blog |
From: Chad R. <cr...@lu...> - 2007-07-27 00:40:19
|
Albert Dahan wrote: > Hi Dave, > > Thanks for making that clear. > > Any idea how I can read the distance if the GPS isn't available? > > I need to determine the kilometers made by a car without using a > pulse or can solution, is that possible? > You can still do it with an accelerometer, it's just harder and will build up error over time. It's called dead reckoning. You need to read the accelerometer VERY fast (this may be beyond the reach of a slow MCU and ADC) and make sure you never accelerate beyond its limits (or you won't know how far beyond the limits you were). Basically, as often as you can, you sample the accelerometer. If it says you're accelerating, you calculate speed by continually adding (or subtracting for negative Gs - slowing down) your acceleration value from your current speed, and you calculate position by adding speed * sample time to old position. You need to be able to sample at least twice as fast as your expected acceleration period. So, you probably won't ever be very good at telling when somebody smacked you with a hammer and knocked you three feet over, but you could be OK at telling that somebody pushed you that same distance if it wasn't so abrupt. Ideally you want some other reference to calibrate this to. It would be MUCH more accurate if you had a speed reading from a wheel, say, or if you could periodically hope that you could sample GPS and update. High-end car GPS units do this so they can get better than the accuracy they get with GPS - they use GPS to get you to within 100ft or whatever the accuracy is at that time, then dead reckoning WITHIN that box. If you want to do this, be prepared for a lot of complexity, code, and frustrating. It takes a LOT of effort and skill to do this accurately, and good dead-reckoning systems for things like submarines and airplanes can cost hundreds of thousands of dollars. Regards, Chad |
From: Albert D. <al...@da...> - 2007-07-27 02:07:21
|
Thanks a lot Chad. I'm going to build a test board and try this one out with one of our developers. Regards, Albert On Jul 27, 2007, at 2:39 AM, Chad Robinson wrote: > Albert Dahan wrote: >> Hi Dave, >> >> Thanks for making that clear. >> >> Any idea how I can read the distance if the GPS isn't available? >> >> I need to determine the kilometers made by a car without using a >> pulse or can solution, is that possible? >> > You can still do it with an accelerometer, it's just harder and will > build up error over time. It's called dead reckoning. You need to read > the accelerometer VERY fast (this may be beyond the reach of a slow > MCU > and ADC) and make sure you never accelerate beyond its limits (or you > won't know how far beyond the limits you were). Basically, as often as > you can, you sample the accelerometer. If it says you're accelerating, > you calculate speed by continually adding (or subtracting for negative > Gs - slowing down) your acceleration value from your current speed, > and > you calculate position by adding speed * sample time to old position. > > You need to be able to sample at least twice as fast as your expected > acceleration period. So, you probably won't ever be very good at > telling > when somebody smacked you with a hammer and knocked you three feet > over, > but you could be OK at telling that somebody pushed you that same > distance if it wasn't so abrupt. > > Ideally you want some other reference to calibrate this to. It > would be > MUCH more accurate if you had a speed reading from a wheel, say, or if > you could periodically hope that you could sample GPS and update. > High-end car GPS units do this so they can get better than the > accuracy > they get with GPS - they use GPS to get you to within 100ft or > whatever > the accuracy is at that time, then dead reckoning WITHIN that box. > > If you want to do this, be prepared for a lot of complexity, code, and > frustrating. It takes a LOT of effort and skill to do this accurately, > and good dead-reckoning systems for things like submarines and > airplanes > can cost hundreds of thousands of dollars. > > > Regards, > Chad > > > ---------------------------------------------------------------------- > --- > This SF.net email is sponsored by: Splunk Inc. > Still grepping through log files to find problems? Stop. > Now Search log events and configuration files using AJAX and a > browser. > Download your FREE copy of Splunk now >> http://get.splunk.com/ > _______________________________________________ > gumstix-users mailing list > gum...@li... > https://lists.sourceforge.net/lists/listinfo/gumstix-users |
From: Erik R. <eri...@ce...> - 2007-07-27 16:12:55
|
Since this topic went into determining distance traveled, you may find this useful if not interesting: http://www.hackaday.com/2006/03/19/codys-robot-optical-motion-sensor/ Erik Rodriguez -----Original Message----- From: gum...@li... [mailto:gum...@li...] On Behalf Of Michael Caughey Sent: Thursday, July 26, 2007 8:14 PM To: General mailing list for gumstix users. Subject: Re: [Gumstix-users] use of an accelerometer. But if you know what speed your at when its zero you know it wont change until the value of acceleration changes. the key is to be able to either=20 determine the zero speed or some known speed then make calculation from=20 that. ----- Original Message -----=20 From: "Dave Hylands" <dhy...@gm...> To: "General mailing list for gumstix users."=20 <gum...@li...> Sent: Thursday, July 26, 2007 7:28 PM Subject: Re: [Gumstix-users] use of an accelerometer. > Hi Albert, > >> Is it also possible to calculate the m/s from a car with the=20 >> accelerometer, >> if the GPS is not available? > > You can integrate to get speed (I think). But if you're moving along > at a constant speed, the accelerometer will just read 0, regardless of > what speed you're moving with. > > --=20 > Dave Hylands > Vancouver, BC, Canada > http://www.DaveHylands.com/ > > ------------------------------------------------------------------------ - > This SF.net email is sponsored by: Splunk Inc. > Still grepping through log files to find problems? Stop. > Now Search log events and configuration files using AJAX and a browser. > Download your FREE copy of Splunk now >> http://get.splunk.com/ > _______________________________________________ > gumstix-users mailing list > gum...@li... > https://lists.sourceforge.net/lists/listinfo/gumstix-users >=20 ------------------------------------------------------------------------ - This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ gumstix-users mailing list gum...@li... https://lists.sourceforge.net/lists/listinfo/gumstix-users |
From: Michael C. <mi...@ca...> - 2007-07-27 03:14:22
|
But if you know what speed your at when its zero you know it wont change until the value of acceleration changes. the key is to be able to either determine the zero speed or some known speed then make calculation from that. ----- Original Message ----- From: "Dave Hylands" <dhy...@gm...> To: "General mailing list for gumstix users." <gum...@li...> Sent: Thursday, July 26, 2007 7:28 PM Subject: Re: [Gumstix-users] use of an accelerometer. > Hi Albert, > >> Is it also possible to calculate the m/s from a car with the >> accelerometer, >> if the GPS is not available? > > You can integrate to get speed (I think). But if you're moving along > at a constant speed, the accelerometer will just read 0, regardless of > what speed you're moving with. > > -- > Dave Hylands > Vancouver, BC, Canada > http://www.DaveHylands.com/ > > ------------------------------------------------------------------------- > This SF.net email is sponsored by: Splunk Inc. > Still grepping through log files to find problems? Stop. > Now Search log events and configuration files using AJAX and a browser. > Download your FREE copy of Splunk now >> http://get.splunk.com/ > _______________________________________________ > gumstix-users mailing list > gum...@li... > https://lists.sourceforge.net/lists/listinfo/gumstix-users > |
From: Julien L. <305...@st...> - 2007-07-23 21:06:34
|
Quoting Craig Hughes <cr...@gu...>: > This is a 3-axis accelerometer. > > You are actually accelerating during free-fall, at a constant 9.8m/ > s^2. Your velocity cannot change unless you're accelerating. The > accelerometer is not really measuring your acceleration, it's > measuring strain on a MEMS crystal; when you're at rest, the crystal > is being tugged on by gravity, but the table or whatever you're > sitting on is countering that force, and thereby creates strain in > the crystal. When you're in free-fall, you're accelerating at the > same speed as the crystal, so there's no strain in the crystal, and > so it measures 0. > > C The fact that the falling object might be in translation when falling should be considered too, the case where the object simply fall along an axis is a particular case. Parabolic motion is also a free fall is there is only gravity affecting the object, therefore all three axis are involved. I'd check all three axis for motion, the object could also have rotated (and could still be rotating). Julien |
From: Black, M. <Michael.Black@EssexCorp.com> - 2007-07-23 21:18:30
|
All 3 axes will show 0 (or close to it) if it's in free-fall (parabolic or not -- rotating or not). Unless you have some other external force besides gravity acting on it (like wind maybe). Accelerometers do not measure absolute acceleration (though you can compute it from the data) -- it measures relative acceleration (i.e. the force being exerted against external forces). =20 ___________________ Michael D. Black -----Original Message----- From: gum...@li... [mailto:gum...@li...] On Behalf Of Julien Lebot Sent: Monday, July 23, 2007 4:06 PM To: gum...@li... Subject: Re: [Gumstix-users] use of an accelerometer. Quoting Craig Hughes <cr...@gu...>: > This is a 3-axis accelerometer. > > You are actually accelerating during free-fall, at a constant 9.8m/ > s^2. Your velocity cannot change unless you're accelerating. The > accelerometer is not really measuring your acceleration, it's > measuring strain on a MEMS crystal; when you're at rest, the crystal > is being tugged on by gravity, but the table or whatever you're > sitting on is countering that force, and thereby creates strain in > the crystal. When you're in free-fall, you're accelerating at the > same speed as the crystal, so there's no strain in the crystal, and > so it measures 0. > > C The fact that the falling object might be in translation when falling=20 should be considered too, the case where the object simply fall along=20 an axis is a particular case. Parabolic motion is also a free fall is=20 there is only gravity affecting the object, therefore all three axis=20 are involved. I'd check all three axis for motion, the object could also have rotated=20 (and could still be rotating). Julien ------------------------------------------------------------------------ - This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ gumstix-users mailing list gum...@li... https://lists.sourceforge.net/lists/listinfo/gumstix-users =20 =20 =20 =20 =20 =20 =20 This electronic message and any files transmitted with it contain = information which may be privileged and/or proprietary. The information = is intended for use solely by the intended recipient(s). If you are not = the intended recipient, be aware that any disclosure, copying, = distribution or use of this information is prohibited. If you have = received this electronic message in error, please advise the sender by = reply email or by telephone (301-939-7000) and delete the message. |
From: Craig H. <cr...@gu...> - 2007-07-23 21:47:21
|
On Jul 23, 2007, at 2:18 PM, Black, Michael wrote: > All 3 axes will show 0 (or close to it) if it's in free-fall > (parabolic > or not -- rotating or not) Probably depends on how fast it's rotating -- I imagine that if it's spinning rapidly, centripetal force will strain the sensor and lead to a false reading. C |
From: Kevin C. <Ke...@sy...> - 2007-07-23 21:56:17
|
Not really, short of going to the stadium and buying them there. They go on sale Monday July 30 and will probably sell out for the season in a couple hours or less. -----Original Message----- From: gum...@li... [mailto:gum...@li...] On Behalf Of Craig Hughes Sent: Monday, July 23, 2007 2:47 PM To: General mailing list for gumstix users. Subject: Re: [Gumstix-users] use of an accelerometer. On Jul 23, 2007, at 2:18 PM, Black, Michael wrote: > All 3 axes will show 0 (or close to it) if it's in free-fall =20 > (parabolic > or not -- rotating or not) Probably depends on how fast it's rotating -- I imagine that if it's =20 spinning rapidly, centripetal force will strain the sensor and lead =20 to a false reading. C ------------------------------------------------------------------------ - This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ gumstix-users mailing list gum...@li... https://lists.sourceforge.net/lists/listinfo/gumstix-users |