On Thu, 03 May 2012 12:57:27 +0000, Jukka Marin wrote:
> On 2012-04-30, Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> wrote:
>> I noticed when driving a new car in Europe that the nav system managed
>> to track fairly well through long tunnels. Makes sense that they would
>> stick an accelerometer and/or gyros in there for when the GNSS
>> satellite signal is not available- tunnels and urban driving between
>> tall buildings. Even a lousy MEMS gyro won't drift that many degrees in
>> a few minutes.
>
> Those systems also use the speed/distance information from the wheel
> sensors, so the can be pretty accurate. A bit like a hi-tech device
> called odometer ;-)
>
> -jm
If you can be pretty sure that there's no skidding going on, an odometer
and a steering-position sensor should be able to mostly or completely
replace gyros, accelerometers, etc.
Of course, the more sensors, the merrier.
--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?
Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com
Reply by Jukka Marin●May 3, 20122012-05-03
On 2012-04-30, Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> wrote:
> I noticed when driving a new car in Europe that the nav system managed
> to track fairly well through long tunnels. Makes sense that they would
> stick an accelerometer and/or gyros in there for when the GNSS
> satellite signal is not available- tunnels and urban driving between
> tall buildings. Even a lousy MEMS gyro won't drift that many degrees
> in a few minutes.
Those systems also use the speed/distance information from the wheel
sensors, so the can be pretty accurate. A bit like a hi-tech device
called odometer ;-)
-jm
Reply by Jan Panteltje●May 1, 20122012-05-01
On a sunny day (Mon, 30 Apr 2012 13:36:14 -0600) it happened hamilton
<hamilton@nothere.com> wrote in <jnmpjg$hvk$1@dont-email.me>:
On Mon, 30 Apr 2012 16:02:07 -0500, Tim Wescott <tim@seemywebsite.com>
wrote:
>On Mon, 30 Apr 2012 11:09:49 -0700, linnix wrote:
>
>
>>> I'm nearly 100% sure that if you want to do credible dead reckoning you
>>> need accelerometers and gyros, not just one or the other. �Gyros don't
>>> mean much when you don't know the acceleration, and accelerometers
>>> don't mean much when you don't know the vehicle direction.
>>
>> Why can't you figure out the direction with 2D accelerometers?
>
>Because without a gyro or some other angular reference you don't know
>what direction they're pointed.
>
>I suppose that if you were really cost-conscious you could assume no
>skidding and take sideways acceleration to be an indication of turning
>rate -- but that's a pretty tenuous connection to reality.
Yes, it's definitely one of those "works in theory but..." applications.
But in theory, it would work. ;-) In practice, it could be good enough
to work thorough the "urban canyon" effect for brief GPS outages,
although the addition of a simple fluxgate compass would help
tremendously.
--
Rich Webb Norfolk, VA
Reply by Jan Panteltje●May 1, 20122012-05-01
On a sunny day (Mon, 30 Apr 2012 16:31:37 -0400) it happened Spehro Pefhany
<speffSNIP@interlogDOTyou.knowwhat> wrote in
<3kttp79uni4e3gm3e18u06ji5f2rclponv@4ax.com>:
>On Mon, 30 Apr 2012 16:42:21 GMT, Jan Panteltje
><pNaonStpealmtje@yahoo.com> wrote:
>
>>On a sunny day (Mon, 30 Apr 2012 00:07:14 -0400) it happened Spehro Pefhany
>><speffSNIP@interlogDOTyou.knowwhat> wrote in
>><bo3sp7dfd9qhdsrac7d3fp31bpn7pfrorb@4ax.com>:
>>
>>
>>
>>>GlobalSat or U-blox modules with SiRF III etc. are around $15 shipped.
>>>
>>>Eg.
>>>http://www.dealextreme.com/p/eb-365-gps-engine-board-module-with-sirf-star-iii-chipset-80045?item=4
>>
>>Do those modules come with any sort of datasheet?
>
>Check the manufacturer website, I doubt DX will give yo anything more
>than a padded envelope marked "gift".
OK
The FM modules for Hongong I have, at least had a pin connection diagram...
Reply by Jan Panteltje●May 1, 20122012-05-01
On a sunny day (Mon, 30 Apr 2012 13:36:14 -0600) it happened hamilton
<hamilton@nothere.com> wrote in <jnmpjg$hvk$1@dont-email.me>:
Thanks!
I have downloaded the pdfs, maybe I buy one just for fun,
could be an other PIC project, and combine with my fluxgate compass...
Years of fun ahaead...
Maybe needs a more powerful computah, one of those recent Linux based boards
perhapds (display maps on LCD etc).
;-)
I would not use FAT filesystem ....
Reply by krw...@att.bizzzzzzzzzzzz●May 1, 20122012-05-01
>Tim Wescott wrote:
>
>> On Sun, 29 Apr 2012 21:30:43 -0700, miso wrote:
>>
>>> On 4/29/2012 6:32 PM, Spehro Pefhany wrote:
>>>> On Sun, 29 Apr 2012 17:24:36 -0700, the renowned Mark Borgerson
>>>> <mborgerson@comcast.net> wrote:
>>>>
>>>>> In article<apsqp7lbsvqv9jrrleaoqpgurqg900t0e8@4ax.com>,
>>>>> nospam@nospam9876.com says...
>>>>>>
>>>>>> I am looking at a project which requires a simple GPS receiver (not
>>>>>> waas/egnos) and a low grade solid state gyro (not a "level") like the
>>>>>> ones you get in smartphones.
>>>>>>
>>>>>> The build volumes will be initially a batch of 100 and later perhaps
>>>>>> thousands, but not more than that.
>>>>>>
>>>>>> What would be the currently recommended GPS module or chip, and a
>>>>>> solid state gyro component?
>>>>>>
>>>>>> There is a lot of stuff on the market...
>>>>>>
>>>>>> One requirement is reasonably low power - milliamps rather than 10s
>>>>>> of milliamps. I have no idea if that is possible.
>>>>> I have not yet found a GPS solution that can give 1HZ updates and draw
>>>>> less than about 20mA. There are some that can go into a low-power
>>>>> sleep mode and wake up on command to give a fix. However, when awake,
>>>>> they still draw 20 to 30mA. To get the overall power down, you need a
>>>>> fairly low duty cycle.
>>>>>>
>>>>>> Ideally the two items can be obtained for under $20-30.
>>>>>
>>>>> The low end for GPS chips that I've used is about $30 qty 1.
>>>>
>>>> GPS module + chip antenna should be around $17 quantity one.
>>>>
>>>> Cost of gyros and translational accelerometers depends a lot on their
>>>> performance, from a few dollars up to serious dollars/euros for
>>>> military grade stuff.
>>>>
>>>>>> Any pointers would be much appreciated.
>>>>>
>>>>> Mark Borgerson
>>>>
>>>>
>>>> Best regards,
>>>> Spehro Pefhany
>>>
>>> The GPSs in cars (built in units) have accelerometers. It makes the user
>>> experience better since it can sense a turn before differential
>>> waypoints can sense it. I don't think they have to be very good to do
>>> that task.
>>>
>>> They can also do dead reckoning fairly well, but I've never been out of
>>> GPS contact for more than a few miles.
>>>
>>> There is a usenet group on gps.
>>>> sci.geo.satellite-nav
>>
>> I'm nearly 100% sure that if you want to do credible dead reckoning you
>> need accelerometers and gyros, not just one or the other. Gyros don't
>> mean much when you don't know the acceleration, and accelerometers don't
>> mean much when you don't know the vehicle direction.
>>
>> If there's no skidding going on, a good odometer and a steering position
>> sensor may work better than an IMU, though.
>>
>
>How about a compass module for orientation? That'll probably work OK for 2D
>navigation tasks between GPS fixes. Not sure what the OP needs.
That's all the automotive GPS units I've seen have.
Reply by Paul Hovnanian P.E.●April 30, 20122012-04-30
Tim Wescott wrote:
> On Sun, 29 Apr 2012 21:30:43 -0700, miso wrote:
>
>> On 4/29/2012 6:32 PM, Spehro Pefhany wrote:
>>> On Sun, 29 Apr 2012 17:24:36 -0700, the renowned Mark Borgerson
>>> <mborgerson@comcast.net> wrote:
>>>
>>>> In article<apsqp7lbsvqv9jrrleaoqpgurqg900t0e8@4ax.com>,
>>>> nospam@nospam9876.com says...
>>>>>
>>>>> I am looking at a project which requires a simple GPS receiver (not
>>>>> waas/egnos) and a low grade solid state gyro (not a "level") like the
>>>>> ones you get in smartphones.
>>>>>
>>>>> The build volumes will be initially a batch of 100 and later perhaps
>>>>> thousands, but not more than that.
>>>>>
>>>>> What would be the currently recommended GPS module or chip, and a
>>>>> solid state gyro component?
>>>>>
>>>>> There is a lot of stuff on the market...
>>>>>
>>>>> One requirement is reasonably low power - milliamps rather than 10s
>>>>> of milliamps. I have no idea if that is possible.
>>>> I have not yet found a GPS solution that can give 1HZ updates and draw
>>>> less than about 20mA. There are some that can go into a low-power
>>>> sleep mode and wake up on command to give a fix. However, when awake,
>>>> they still draw 20 to 30mA. To get the overall power down, you need a
>>>> fairly low duty cycle.
>>>>>
>>>>> Ideally the two items can be obtained for under $20-30.
>>>>
>>>> The low end for GPS chips that I've used is about $30 qty 1.
>>>
>>> GPS module + chip antenna should be around $17 quantity one.
>>>
>>> Cost of gyros and translational accelerometers depends a lot on their
>>> performance, from a few dollars up to serious dollars/euros for
>>> military grade stuff.
>>>
>>>>> Any pointers would be much appreciated.
>>>>
>>>> Mark Borgerson
>>>
>>>
>>> Best regards,
>>> Spehro Pefhany
>>
>> The GPSs in cars (built in units) have accelerometers. It makes the user
>> experience better since it can sense a turn before differential
>> waypoints can sense it. I don't think they have to be very good to do
>> that task.
>>
>> They can also do dead reckoning fairly well, but I've never been out of
>> GPS contact for more than a few miles.
>>
>> There is a usenet group on gps.
>>> sci.geo.satellite-nav
>
> I'm nearly 100% sure that if you want to do credible dead reckoning you
> need accelerometers and gyros, not just one or the other. Gyros don't
> mean much when you don't know the acceleration, and accelerometers don't
> mean much when you don't know the vehicle direction.
>
> If there's no skidding going on, a good odometer and a steering position
> sensor may work better than an IMU, though.
>
How about a compass module for orientation? That'll probably work OK for 2D
navigation tasks between GPS fixes. Not sure what the OP needs.
--
Paul Hovnanian mailto:Paul@Hovnanian.com
------------------------------------------------------------------
Leap and the net will appear.
Reply by Tim Wescott●April 30, 20122012-04-30
On Mon, 30 Apr 2012 11:09:49 -0700, linnix wrote:
>> I'm nearly 100% sure that if you want to do credible dead reckoning you
>> need accelerometers and gyros, not just one or the other. Gyros don't
>> mean much when you don't know the acceleration, and accelerometers
>> don't mean much when you don't know the vehicle direction.
>
> Why can't you figure out the direction with 2D accelerometers?
Because without a gyro or some other angular reference you don't know
what direction they're pointed.
I suppose that if you were really cost-conscious you could assume no
skidding and take sideways acceleration to be an indication of turning
rate -- but that's a pretty tenuous connection to reality.
--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?
Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com
Reply by Spehro Pefhany●April 30, 20122012-04-30
On Mon, 30 Apr 2012 16:42:21 GMT, Jan Panteltje
<pNaonStpealmtje@yahoo.com> wrote:
>On a sunny day (Mon, 30 Apr 2012 00:07:14 -0400) it happened Spehro Pefhany
><speffSNIP@interlogDOTyou.knowwhat> wrote in
><bo3sp7dfd9qhdsrac7d3fp31bpn7pfrorb@4ax.com>:
>
>
>
>>GlobalSat or U-blox modules with SiRF III etc. are around $15 shipped.
>>
>>Eg.
>>http://www.dealextreme.com/p/eb-365-gps-engine-board-module-with-sirf-star-iii-chipset-80045?item=4
>
>Do those modules come with any sort of datasheet?
Check the manufacturer website, I doubt DX will give yo anything more
than a padded envelope marked "gift".