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  • 08:55

    jlblancoc on matching-pair-double

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    jlblancoc on matching-pair-double

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DJuego
@DJuego
Hi to all!
I am a absolute newbie in this field. ;-)
I am working in a robotic-based project of Indoor Positioning System.
For this purpose, we are building a robot similar to this: https://www.youtube.com/watch?v=uv2faO7GhXc
First Question: This 4 joints/4 wheels design (or architecture)...
What is its 'formal' denomination?
DJuego
@DJuego
I would like to look for papers or similar that describe or model its kinematics mathematically...
Anyway, we have a ultrasonic indoor "GPS" than promise a +/2cm accuracy.
The challenge is to develop a autonomous drive in order to reach certain coordinates
in the XY plane. Or follow a path as tightly as possible...
What approach can I follow? What family of algorithms solve this kind of problem for mobile robots?
Can MRPT help me?
matrixbot
@matrixbot

bergercookie hey DJuego (Gitter) ,

I'm not sure of the name of this kinematic model. They look very similar to the omni wheels though.
Notice that the wheels themselves are not that special. it's rather the motors above them that rotate them

DJuego
@DJuego
Thanks!
matrixbot
@matrixbot

bergercookie > You could take a look at the mrpt-navigation component

I thinkyou are looking for is the holonomic model

DJuego
@DJuego
@matrixbot Yes. It is holonomic for sure. :-)
matrixbot
@matrixbot

bergercookie https://en.wikipedia.org/wiki/Holonomic_(robotics)

Anyway, there are navigation algorithms in MRPT that can help you navigate from A -> B, given some sensor input. I guess the most popular one would be the reactive navigator: https://www.mrpt.org/tag/reactive-navigation/

bergercookie If you 're using ROS, MRPT also offers ROS wrappers: https://github.com/mrpt-ros-pkg/mrpt_navigation
bergercookie As far as I know though, either the reactive nav2d or the localisation nodes operate using 2D laser scans
DJuego
@DJuego
"reactive navigator". Ok.
Yes. I want to track in real-time. I get the position through a system of ultrasonic beacons.
The promised precision has an estimated +/-2 cm error. The idea is to stay as close as possible to the planned path.
Especially at the destination point.
matrixbot
@matrixbot
bergercookie Well, what's the representation of your planned path though?
DJuego
@DJuego
At the moment I try to avoid ROS. I guess I could change my mind later
matrixbot
@matrixbot
bergercookie is it a black line on a 2D surface?
bergercookie Is it a set of given (x,y) coords?
DJuego
@DJuego
A set of given (x,y) coords sounds good to me.
I want flexibility and versatility.
Actually, the path could have "curves", like the one that can grant a mathematical function (exponential, logarithm, ...).
matrixbot
@matrixbot

bergercookie OK, but how do you reach that (x,y) representation to feed to your algoirthm?

If you have that (x,y) representation and your estimated position from your GPS-like system then you can implement simple PID controllers for the x,y (and theta?) of your robot to follow those waypoints

bergercookie Otherwise you have to "sense" where the line is relative to the robot and have some sort of feedback control loop to follow that line.
Look up path planning algorithms or line following more specifically
DJuego
@DJuego
I understand you. Yes. I hope to have a (X,Y) representation (my desired position) and my "real" position from the sensorial GPS-Like system. I want to minimize the error making the necessary corrections through orders to the 8 actuators (wheels and joints).
DJuego
@DJuego
Well. (X,Y, theta) :-)
Nguyễn Thành Tín
@ngthanhtin
hi everyone
I am a newbie. I have learnt ROS for a few weeks, and I've came across MRPT just a few days ago. I wonder what is the difference between ROS and MRPT. And Are there any resources to learn MRPT. Thank you
Jose Luis Blanco-Claraco
@jlblancoc
Hi!
ROS is a meta-operative system, in charge of allowing modules (nodes) to talk to each other. Then, ROS is used for robotics applications, but it's nowadays a quite general framework for distributed computing
MRPT is a set of C++ libraries, for writing robotics apps or libraries, that could be integrated into ROS, or not...
Hope that helps!
Nguyễn Thành Tín
@ngthanhtin
thank you, are there any books to learn MRPT, because I dont know where to start