On 1/1/22 12:40 PM, Pito Salas wrote:
> I think something that's been missing for me in this thread is "why do
> you want odometry"? In my experience (like has been said) odometry is
> quite inaccurate by itself. But it does give some information. And
> combined with the IMU it is even better. But how are you going to use
> this odometry data?
>
> Is it for navigation? Getting to a certain destination given a known
> starting point? Without more information (a map and coordinate system)
> the best you could do is to drive in a straight line from where you
> (think you) are to where you want to be, without regards to anything else.
>
> If not for navigation, how else are you planning to use it? I think we
> need to settle on that before worrying too much about how accurate it is
> or isn't. I don't think we can think of odometry as a way to localize
> the robot over longer distances.
>
> In our case we are using odometry in combination with the IMU and the
> Lidar to create a map and then use it for navigtation (classic SLAM).
> But we are experimenting with RTK GPS which is supposed to give us
> centimeter precision (but only within range of the GPS signal, i.e.
> outdoors.) In that case there's a real question whether we will need
> odometry at all.
Even GNSS RTK is not working well everywhere:-( In the shadow of tall
buildings or under tree cover, ... it's not good. There, you want to
have other sensors.
An IMU works ok on flat ground. But when the route gets bumpy, it will
record a lot of 'noise', which you you have to compensate with other
sensors.
The UBlox ZED-F9R is a combination of GNSS RTK + IMU (
https://www.sparkfun.com/products/16344 ) But even that would expect a
relatively smooth ride of a full size car, not the 1:10th, we normally
think in.
-- Marco
>
> Pito
>
>
> Pito Salas
> Faculty, Computer Science
> Brandeis University
>
>> On Dec 31, 2021, at 2:53 PM, Michael Wimble <
mwi...@gmail.com
>> <mailto:
mwi...@gmail.com>> wrote:
>>
>> The problem with odometry is the problem of all closed loop systems.
>> Attempting odometry with an open loop system is likely to be useless
>> after a small driving distance. A closed loop system can work well,
>> but only against what the loop entails. If your closed loop is based
>> upon wheel encoders, then all you know is how the wheels spun. Which
>> has only a casual relationship with how the robot moved on a surface.
>>
>> You can use visual odometry with cameras, as I do with my T265 camera
>> and it can work fairly well. You can even do optical odometry with
>> just a LIDAR, which works, for example, in one of the hector-SLAM
>> packages. Just choose a loop system which is measuring what you want,
>> such as where you are in a room, not how the wheels spun.
>>
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