using an accelerometer to measure distance
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Posts: 46,084
the calculation is
x(next)=x(initial)+v(now)*t+(1/2)*A(now)*t^2
I've done it with op-amps. Not too bad. However, the programming solution
would be my 1st attempt to solve the problem.
Richard
Original Message
From: "Rory MacKean" <mackean@c...>
To: <basicstamps@yahoogroups.com>
Sent: Monday, August 06, 2001 11:19 AM
Subject: [noparse][[/noparse]basicstamps] using an accelerometer to measure distance
> Heya,
>
> So I have this project I've been working on, and I figured I'd toss it
> out there and see what you guys think, or have any flashes of insight
> for me...
>
> I want to build a relatively cheap, portable way of measuring the
> distance a boat has travelled. I think an accelerometer is the way to
> go, and I have the AXL202EB (or whatever--the 2g one with pwm on the
> evaluation board), and I also have one of Analog's normal (analog output
> proportional to acceleration) accelerometers.
>
> I remember some of the other ideas that came up in a similar situation,
> but I think this is the best way to go about it. The device has to be
> portable, and can't add any drag...
>
> My idea was to continuously find the acceleration, and then calculate
> the velocity and distance travelled since the last reset.
>
> I'll give you the way I've been working on, and then one other way I've
> thought of...
>
> I'm using a 555 to give me a 20 Hz signal, with a duty cycle of 67%.
> When the output is high, I'm running a loop to sample the accelerometer
> as fast as possible, and calculate the average for this cycle on the fly
> (using the sum of (sample/(# of samples)) method). Then, once the 555
> goes low, I enter my housekeeping mode, where I use the average
> acceleration, multiply it by the time that's elapsed (1/20 of a second),
> and then I get the instantaneous velocity. Then, using the last
> velocity reading, I can calculate the distance travelled in that step.
> I output this to a serial LCD, and then write the data to the EEPROM so
> I can look at the data later.
>
> So, this is pretty much what I've been doing so far. But I remember
> from my intro to Electronics class that I can use an op-amp as an
> integrator. It would seem that this would be an easier way to do it,
> and cut down on my calculations. Instead of trying to calculate the
> velocity, I could just use an A/D and sample the values. But, I'm not
> sure where to start--how do I go about picking capacitor values and
> things like that? Anyone used the circuit before?
>
> I've been working on this in my spare time, and just wanted to see if
> the way I'm doing it was the best way, or see if you guys had any other
> ideas...
>
> Thanks!
> Rory
>
> To UNSUBSCRIBE, just send mail to:
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>
>
x(next)=x(initial)+v(now)*t+(1/2)*A(now)*t^2
I've done it with op-amps. Not too bad. However, the programming solution
would be my 1st attempt to solve the problem.
Richard
Original Message
From: "Rory MacKean" <mackean@c...>
To: <basicstamps@yahoogroups.com>
Sent: Monday, August 06, 2001 11:19 AM
Subject: [noparse][[/noparse]basicstamps] using an accelerometer to measure distance
> Heya,
>
> So I have this project I've been working on, and I figured I'd toss it
> out there and see what you guys think, or have any flashes of insight
> for me...
>
> I want to build a relatively cheap, portable way of measuring the
> distance a boat has travelled. I think an accelerometer is the way to
> go, and I have the AXL202EB (or whatever--the 2g one with pwm on the
> evaluation board), and I also have one of Analog's normal (analog output
> proportional to acceleration) accelerometers.
>
> I remember some of the other ideas that came up in a similar situation,
> but I think this is the best way to go about it. The device has to be
> portable, and can't add any drag...
>
> My idea was to continuously find the acceleration, and then calculate
> the velocity and distance travelled since the last reset.
>
> I'll give you the way I've been working on, and then one other way I've
> thought of...
>
> I'm using a 555 to give me a 20 Hz signal, with a duty cycle of 67%.
> When the output is high, I'm running a loop to sample the accelerometer
> as fast as possible, and calculate the average for this cycle on the fly
> (using the sum of (sample/(# of samples)) method). Then, once the 555
> goes low, I enter my housekeeping mode, where I use the average
> acceleration, multiply it by the time that's elapsed (1/20 of a second),
> and then I get the instantaneous velocity. Then, using the last
> velocity reading, I can calculate the distance travelled in that step.
> I output this to a serial LCD, and then write the data to the EEPROM so
> I can look at the data later.
>
> So, this is pretty much what I've been doing so far. But I remember
> from my intro to Electronics class that I can use an op-amp as an
> integrator. It would seem that this would be an easier way to do it,
> and cut down on my calculations. Instead of trying to calculate the
> velocity, I could just use an A/D and sample the values. But, I'm not
> sure where to start--how do I go about picking capacitor values and
> things like that? Anyone used the circuit before?
>
> I've been working on this in my spare time, and just wanted to see if
> the way I'm doing it was the best way, or see if you guys had any other
> ideas...
>
> Thanks!
> Rory
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
Comments
So I have this project I've been working on, and I figured I'd toss it
out there and see what you guys think, or have any flashes of insight
for me...
I want to build a relatively cheap, portable way of measuring the
distance a boat has travelled. I think an accelerometer is the way to
go, and I have the AXL202EB (or whatever--the 2g one with pwm on the
evaluation board), and I also have one of Analog's normal (analog output
proportional to acceleration) accelerometers.
I remember some of the other ideas that came up in a similar situation,
but I think this is the best way to go about it. The device has to be
portable, and can't add any drag...
My idea was to continuously find the acceleration, and then calculate
the velocity and distance travelled since the last reset.
I'll give you the way I've been working on, and then one other way I've
thought of...
I'm using a 555 to give me a 20 Hz signal, with a duty cycle of 67%.
When the output is high, I'm running a loop to sample the accelerometer
as fast as possible, and calculate the average for this cycle on the fly
(using the sum of (sample/(# of samples)) method). Then, once the 555
goes low, I enter my housekeeping mode, where I use the average
acceleration, multiply it by the time that's elapsed (1/20 of a second),
and then I get the instantaneous velocity. Then, using the last
velocity reading, I can calculate the distance travelled in that step.
I output this to a serial LCD, and then write the data to the EEPROM so
I can look at the data later.
So, this is pretty much what I've been doing so far. But I remember
from my intro to Electronics class that I can use an op-amp as an
integrator. It would seem that this would be an easier way to do it,
and cut down on my calculations. Instead of trying to calculate the
velocity, I could just use an A/D and sample the values. But, I'm not
sure where to start--how do I go about picking capacitor values and
things like that? Anyone used the circuit before?
I've been working on this in my spare time, and just wanted to see if
the way I'm doing it was the best way, or see if you guys had any other
ideas...
Thanks!
Rory
using accelerometers only, a 747 could fly from Dallas to Hawaii and the
autopilot would be off course <1 mile at the end of that 4000 mile flight
!!!
just useless info that is somewhat related to this thread
Richard
Original Message
From: "Alex Sulkowski" <asulkowski@a...>
To: <basicstamps@yahoogroups.com>
Sent: Monday, August 06, 2001 12:32 PM
Subject: RE: [noparse][[/noparse]basicstamps] using an accelerometer to measure distance
> Why not use the output from a GPS to determine distance traveled. This is
> portable and requires no contact with the water. I am interested if
someone
> has a good solution using the accelerometer because the GPS solution does
> not work well in areas with tall buildings. (Since you are in a boat, this
> should not be a problem for you.)
>
>
Original Message
> From: Rory MacKean [noparse]/noparse]SMTP:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=uIshmfZNR4EqQe3Ok9LLsOxaiZQzBZxiE58SmGPDUj7xWu-CeF8h3Vt6kAzvsmaMdA0LQQh4zJd4UQ]mackean@c...[/url
> Sent: Monday, August 06, 2001 12:20 PM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] using an accelerometer to measure
> distance
>
> Heya,
>
> So I have this project I've been working on, and I figured I'd toss
> it
> out there and see what you guys think, or have any flashes of
> insight
> for me...
>
> I want to build a relatively cheap, portable way of measuring the
> distance a boat has travelled. I think an accelerometer is the way
> to
> go, and I have the AXL202EB (or whatever--the 2g one with pwm on the
> evaluation board), and I also have one of Analog's normal (analog
> output
> proportional to acceleration) accelerometers.
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
portable and requires no contact with the water. I am interested if someone
has a good solution using the accelerometer because the GPS solution does
not work well in areas with tall buildings. (Since you are in a boat, this
should not be a problem for you.)
Original Message
From: Rory MacKean [noparse]/noparse]SMTP:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=7JycaNqHDkqzzS4dbe44W_bN72ct36NEgqT9uFAmOFozQoYw2SpAjgSyRZ3POJ4MfFhAu8rqUeSXqfMR]mackean@c...[/url
Sent: Monday, August 06, 2001 12:20 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] using an accelerometer to measure
distance
Heya,
So I have this project I've been working on, and I figured I'd toss
it
out there and see what you guys think, or have any flashes of
insight
for me...
I want to build a relatively cheap, portable way of measuring the
distance a boat has travelled. I think an accelerometer is the way
to
go, and I have the AXL202EB (or whatever--the 2g one with pwm on the
evaluation board), and I also have one of Analog's normal (analog
output
proportional to acceleration) accelerometers.
around $100.000 and a special DOD license.
ACJacques
Richard Friedrich wrote:
>
> inertial navigation was real big in airplanes prior to gps (1970-1980)
> using accelerometers only, a 747 could fly from Dallas to Hawaii and the
> autopilot would be off course <1 mile at the end of that 4000 mile flight
> !!!
>
> just useless info that is somewhat related to this thread
>
> Richard
>
>
Original Message
> From: "Alex Sulkowski" <asulkowski@a...>
> To: <basicstamps@yahoogroups.com>
> Sent: Monday, August 06, 2001 12:32 PM
> Subject: RE: [noparse][[/noparse]basicstamps] using an accelerometer to measure distance
>
> > Why not use the output from a GPS to determine distance traveled. This is
> > portable and requires no contact with the water. I am interested if
> someone
> > has a good solution using the accelerometer because the GPS solution does
> > not work well in areas with tall buildings. (Since you are in a boat, this
> > should not be a problem for you.)
> >
> >
Original Message
> > From: Rory MacKean [noparse]/noparse]SMTP:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=ujsH4GxKxQg-nDTJsPuaF02fgdQo8J3Jaz76csTodOL1Mufnt0HLI3v9cU0-ab1cQdQKM5AyvRb_]mackean@c...[/url
> > Sent: Monday, August 06, 2001 12:20 PM
> > To: basicstamps@yahoogroups.com
> > Subject: [noparse][[/noparse]basicstamps] using an accelerometer to measure
> > distance
> >
> > Heya,
> >
> > So I have this project I've been working on, and I figured I'd toss
> > it
> > out there and see what you guys think, or have any flashes of
> > insight
> > for me...
> >
> > I want to build a relatively cheap, portable way of measuring the
> > distance a boat has travelled. I think an accelerometer is the way
> > to
> > go, and I have the AXL202EB (or whatever--the 2g one with pwm on the
> > evaluation board), and I also have one of Analog's normal (analog
> > output
> > proportional to acceleration) accelerometers.
> >
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@yahoogroups.com
> > from the same email address that you subscribed. Text in the Subject and
> Body of the message will be ignored.
> >
> >
> > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
> >
> >
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and Body
of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
I've been successful measuring boat speed by using a differential pressure
transducer. I've used this to sense the differential pressure across a
piece of delrin which was in the shape of an airplane wing cross-section. I
put this "sensor" on the bottom of a boat at the transom center. This
worked well even at very low speeds.
Original Message
From: Richard Friedrich [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=-hfqT1wQV07EnjMwiwkHuQfbW6SV2Rhm1sG-q624WV8u645vGj5ZW7xdaPTCc4EbiWhNCNzDmMigV4eZDvfrmz6s6g]rfriedrich@a...[/url
Sent: Monday, August 06, 2001 12:48 PM
To: basicstamps@yahoogroups.com
Subject: Re: [noparse][[/noparse]basicstamps] using an accelerometer to measure distance
inertial navigation was real big in airplanes prior to gps (1970-1980)
using accelerometers only, a 747 could fly from Dallas to Hawaii and the
autopilot would be off course <1 mile at the end of that 4000 mile flight
!!!
just useless info that is somewhat related to this thread
Richard
Original Message
From: "Alex Sulkowski" <asulkowski@a...>
To: <basicstamps@yahoogroups.com>
Sent: Monday, August 06, 2001 12:32 PM
Subject: RE: [noparse][[/noparse]basicstamps] using an accelerometer to measure distance
> Why not use the output from a GPS to determine distance traveled. This is
> portable and requires no contact with the water. I am interested if
someone
> has a good solution using the accelerometer because the GPS solution does
> not work well in areas with tall buildings. (Since you are in a boat, this
> should not be a problem for you.)
>
>
Original Message
> From: Rory MacKean [noparse]/noparse]SMTP:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=n9NMOqvei1vPAYcphJYDt7n2k9f5e3aGH6ZJZM3B23SfA6WcsK_LephWCvRJb9nDLKr1UN-50VGhHZDw]mackean@c...[/url
> Sent: Monday, August 06, 2001 12:20 PM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] using an accelerometer to measure
> distance
>
> Heya,
>
> So I have this project I've been working on, and I figured I'd toss
> it
> out there and see what you guys think, or have any flashes of
> insight
> for me...
>
> I want to build a relatively cheap, portable way of measuring the
> distance a boat has travelled. I think an accelerometer is the way
> to
> go, and I have the AXL202EB (or whatever--the 2g one with pwm on the
> evaluation board), and I also have one of Analog's normal (analog
> output
> proportional to acceleration) accelerometers.
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
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Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
st poster asked for. You only need the gyro's to generate a signal for the
torque motors to stabilize the inertial platform, especially for the drift
of the earth which is not that easy to measure.
In AGV's, they don't use gyro's as far as I can remember me.
I read once an article of students in Germany which used accelerometers to
measure the speed, lap time etc and also for plotting the track of high
speed go-karts on a race circuit.
Inertial platforms are still used in even the newest airplanes and that will
go on for a while. To determine a position with a GPS, you always need some
satellites (which can be set off any time by the US Army). A INS is an
independent system and calculates his distance where a GPS measures the
distance. For that reason, an INS is much safer for the captain, especially
when he as 3 of it in his cockpit (captain, 1st officer and STBY).
INS is often linked on fixed well known beacons on the ground.
But all of this is no help for our reader I think but perhaps interesting to
know.
Peter.
Belgium.
Oorspronkelijk bericht
Van: A.C.Jacques [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=n6dSkDa6JuulQwY-EbxB90gSueOvGYhjnnNXybV-SAQsn_agrxy0aaPQ5hNsp2ywRs-SRX88-FUvb6YUCi0pYwA]acjacques@i...[/url
Verzonden: maandag 6 augustus 2001 21:51
Aan: basicstamps@yahoogroups.com
Onderwerp: Re: [noparse][[/noparse]basicstamps] using an accelerometer to measure distance
Inertial platforms also uses gyros. To buy one of this kind is needed
around $100.000 and a special DOD license.
ACJacques
Richard Friedrich wrote:
>
> inertial navigation was real big in airplanes prior to gps (1970-1980)
> using accelerometers only, a 747 could fly from Dallas to Hawaii and the
> autopilot would be off course <1 mile at the end of that 4000 mile flight
> !!!
>
> just useless info that is somewhat related to this thread
>
> Richard
>
>
Original Message
> From: "Alex Sulkowski" <asulkowski@a...>
> To: <basicstamps@yahoogroups.com>
> Sent: Monday, August 06, 2001 12:32 PM
> Subject: RE: [noparse][[/noparse]basicstamps] using an accelerometer to measure distance
>
> > Why not use the output from a GPS to determine distance traveled. This
is
> > portable and requires no contact with the water. I am interested if
> someone
> > has a good solution using the accelerometer because the GPS solution
does
> > not work well in areas with tall buildings. (Since you are in a boat,
this
> > should not be a problem for you.)
> >
> >
Original Message
> > From: Rory MacKean [noparse]/noparse]SMTP:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=UktmkFHwkMk3234_MvEYYAISQnA53yHD_OfgC6rBAgbTSeMvdnrVhccVFa6dM6FlDC1p08irfpnclo5jdQ]mackean@c...[/url
> > Sent: Monday, August 06, 2001 12:20 PM
> > To: basicstamps@yahoogroups.com
> > Subject: [noparse][[/noparse]basicstamps] using an accelerometer to measure
> > distance
> >
> > Heya,
> >
> > So I have this project I've been working on, and I figured I'd toss
> > it
> > out there and see what you guys think, or have any flashes of
> > insight
> > for me...
> >
> > I want to build a relatively cheap, portable way of measuring the
> > distance a boat has travelled. I think an accelerometer is the way
> > to
> > go, and I have the AXL202EB (or whatever--the 2g one with pwm on the
> > evaluation board), and I also have one of Analog's normal (analog
> > output
> > proportional to acceleration) accelerometers.
> >
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@yahoogroups.com
> > from the same email address that you subscribed. Text in the Subject
and
> Body of the message will be ignored.
> >
> >
> > Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
> >
> >
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
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Body of the message will be ignored.
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planes, submarines or missiles must use gyros AND accelerometers.
"An inertial navigation system (INS) contains two core
components: an inertial measurement unit (IMU) and a
navigation processor (NP). The IMU contains three
accelerometers and three gyros, whose respective input
axes form an orthogonal triad, plus digitization and
digital interface electronics. The accelerometers measure
the specific force that the IMU experiences, comprising
accelerations and gravity with respect to an inertial
reference. The gyros measure the angular rate that the
IMU experiences, comprising its angular rate with respect
to the earth plus the earth’s angular rate with respect to
the inertial reference."
The above text was from:
http://www.applanix.com/pdf/seg_2000.pdf
There are a lot of references about RingLaserGyros found in the 747,
Airbus and other commercial and military aircrafts INS:
http://www.cas.honeywell.com/ats/products/nav.html
A more scientific description:
http://www.imar-navigation.de/download/basicnav.pdf
ACJacques
Daliti wrote:
>
> In my opinion, you don't need gyro's for a position measurement like the 1
> st poster asked for. You only need the gyro's to generate a signal for the
> torque motors to stabilize the inertial platform, especially for the drift
> of the earth which is not that easy to measure.
> In AGV's, they don't use gyro's as far as I can remember me.
> I read once an article of students in Germany which used accelerometers to
> measure the speed, lap time etc and also for plotting the track of high
> speed go-karts on a race circuit.
> Inertial platforms are still used in even the newest airplanes and that will
> go on for a while. To determine a position with a GPS, you always need some
> satellites (which can be set off any time by the US Army). A INS is an
> independent system and calculates his distance where a GPS measures the
> distance. For that reason, an INS is much safer for the captain, especially
> when he as 3 of it in his cockpit (captain, 1st officer and STBY).
> INS is often linked on fixed well known beacons on the ground.
> But all of this is no help for our reader I think but perhaps interesting to
> know.
> Peter.
> Belgium.
>
http://precision3d.org/IGS/
and have researched it in depth. The major limitation of any "strap-down
inertial guidance system" (early jargon meaning on-board sensors and
computers) is drift. Any voltage offsets, when integrated twice from
acceleration to position, will result in systematic drift, which results in
errors in position. Use of MEMS sensors may appear to reduce this problem.
But the (Analog Devices) mfr's notes point out that temperature fluctuations
will change the sensitivity of the device, and a temperature-stabilized oven
may be necessary to maintain an accurate sensitiviy. The link below is
interesting, but appears to be a "work in progress" without an error
analysis based on pilot data. If you have a license to Matlab
(www.mathworks.com), with an access code, download the "Robot Toolbox" for a
useful set of transformation routines.
Practical systems often use positional corrections of the errors in computed
positions, using information based on GPS, fixed stars, or other cues.
There are lessons from animal navigation that we don't fully understand,
such as how giant sea turtles manage to find the Galapagos Islands during
migrations of several hundred miles.
Dennis O'Leary
WSR Inc
Pasadena CA
Original Message
From: Daliti [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=XV79Lh3UQXwgBIR14qjKhPjYNDNUJRXtcXaD6_LkqS8XLl2htOUWuqJvNU2yD7uMZo7RN11-pVOSX4Pw5A9N3Jg5gC6N]peter.christiaen@s...[/url
Sent: Tuesday, August 07, 2001 9:16 AM
To: basicstamps@yahoogroups.com
Subject: RE: [noparse][[/noparse]basicstamps] using an accelerometer to measure distance
One link perhaps
http://precision3d.org/IGS/
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