Questions tagged [geometry]

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Which data structure/library to handle set of points within distance bounds from target?

I have a problem where I have to position a camera (mounted on a robot manipulator) at an optimal location from a 3D target defined as a (convex) polyhedron. The camera must maintain a minimum ...
Srijal's user avatar
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Probabilistic Robotics by Thurn: Velocity motion model. Detailed derivation for eq. 18

In the book, The equation for finding center of circle is denoted in eq. 5.17, which is as $$\begin{pmatrix} x^* \\ y^* \end{pmatrix} = \begin{pmatrix} x \\ y\end{pmatrix} + \begin{pmatrix} -\lambda \...
unwantednoise's user avatar
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Why is the angle of the wheels in this ackermann steering system so low?

I am trying to implement Ackermann Steering in Fusion 360. However, I am unsure why the maximum angle of my wheels is capped at such a low turning angle. Are there any issues with my design or with ...
Aditya S's user avatar
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how can i get geomid from all unnamed subnodes

i have a problem. In tutorial you have said, "Note that each dot (.) can be substituted by any number of named or unnamed nodes". But if I use dWebotsGetBodyFromDEF(defname.), I can only get ...
Haolei Tong's user avatar
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DVL as a ranging sensor

I am trying to use a Doppler Velocity Log (DVL) as a ranging sensor. The DVL has four acoustic beams with known poses and ranges. This makes it possible to estimate 3D points on the seabed (if the ...
Apo's user avatar
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1 answer
41 views

Get approach vector from Mano hand model

I'm trying to get approach vector/normal from Mano hand parameters that I get from my network. Because the hand parameters are dependent on how it picks an object, I am interested in getting the ...
Abhinav Kaushal Keshari's user avatar
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1 answer
53 views

Body angle of a centre-articulated robot

Wondering if anyone can help me out with this one, or point me in the right direction. I am working on a centre-articulated robot, which is steered via a push-pull chain drive. The chain drive is ...
Alec Gurman's user avatar
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1 answer
28 views

Explanation of the epipolar constraint in stereo imaging

I am watching this video, in which the epipolar constraint is defined as $x_l \cdot (x_l \times t)=0$ It means that the vector $x_l$ that passes through the observed point and the left camera origin ...
noam steiner's user avatar
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1 answer
47 views

How to find mathematical model of a wheeled robot (to compute robot's trajectory at given time steps) including its kinematic

I would like to learn, how to find proper kinematic model of robot in mathematical form. For example: I would like to create a model of a car, from which I could compute its position and rotation at ...
veronika_cz's user avatar
2 votes
2 answers
186 views

How can I draw a line using rotation of two circles?

I’m building a drawbot with a self imposed constraint that it’s method of motion is just two rotating disks. One holding the paper and one holding the pen. However, the math to calculate the right ...
VexedPanda's user avatar
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1 answer
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given current position and Quaternion and target local rotations (α, β, γ, in radians), how to calculate the new Quaternion

Say we have an object (e.g., end-effector of a robot) that is defined in a general coordinate system by a Cartesian position and Quaternion. since the Quaternion is with respect to a general and fixed ...
Alejandro's user avatar
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2 answers
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What is the idea behind calling configuration space a metric space?

In my robotics textbook 1 , the configuration space has been defined configuration space the following way: A configuration space is a metric space compromising of all given configuration of a ...
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1 answer
368 views

Bearing landmark localization

I am trying to initialize the position of a set of landmarks using only bearing observations. Each robot pose, described by position (x,y) and orientation (theta), observes a small set of landmarks. ...
R.Go's user avatar
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3 votes
1 answer
219 views

given position and orientation of two coordinate frames, how to transfer a vector from one to another

given position and orientation of two coordinate frames, how can transfer a vector from one frame to another. The position is given in Cartesian space and the orientations in quaternion or Euler ...
Alejandro's user avatar
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152 views

How to calculate twist and wrench in local and global frames [closed]

I am rather new to screw theory and also lost in robotics books' formulas. we have a simulator of a robot arm within Mujoco physics engine and I'm wondering how I can calculate wrench and twist in the ...
Alejandro's user avatar
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2 votes
1 answer
589 views

relationship between geometric twist jacobian and wrench

I read the robot textbook of Peter Corke and Richard M. Murray, in Peter’s, chapter 8 about jacobian, there are two jacobian, one is geometric jacobian $^0J$ from math, other is world coordinate frame ...
lumw's user avatar
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Finding orientation angles of end-effector from the DH parameter table and transformation matrices

Let's say we have a manipulator with the following DH parameter table: and transformation matrices: $$A_{01}= \begin{bmatrix} \cos(q_1) & \sin(q_1) & 0 & 95\cos(q_1)\\ \sin(q_1) & -\...
A6EE's user avatar
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1 answer
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Transform PointCloud2 doesn't work as expected

I tried to transform my pointcloud2 in python like stated here. But somehow the result is not correct. I am not able to visualize the pointcloud I get as a result in rviz. This is why I tried to just ...
user avatar
0 votes
1 answer
346 views

Do I need to use Inverse Kinematics if I have the coordinates of all joints?

So I have the positions of all the joints (x,y,z) of a robot arm. I need to calculate the angles of the joints to feed them to another similar robot arm. I cannot get the angles from the robot I need ...
da silva's user avatar
2 votes
1 answer
156 views

Efficient sphere surface area search

As shown in the figure, there are objects of arbitrary shapes placed on the surface of the sphere at arbitrary locations. The problem is to search the surface to locate these objects in most efficient ...
ewaolx's user avatar
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1 vote
0 answers
304 views

How to get RPY(Roll, Pitch, Yaw) from directional cosines from a single vector?

I'm trying to find the pose of an 3D vector in terms of RPY. Let's say the two end points of the vector is P0(x0, y0, z0) and P1(x1, y1, z1). So the centered vector I get is V(Vx, Vy, Vz) = P1 - P0 = (...
paul-shuvo's user avatar
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1 answer
2 views

unable to build geometry package in ROS kinetic

Im trying to install geometry package but im getting this error: ...
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1 vote
1 answer
93 views

Representation of 2D coordinate space with orientation

I wanted to know what is the mathematical representation of 2D coordinate space with orientation in the same plane. 2D coordinate space is represented as $R^{2}$, how do I include orientation in the ...
Ajin2305's user avatar
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1 answer
9 views

tf2_eigen include does not find library Eigen/Geometry

Hi, I want to use tf2_eigen to convert geometry_msgs/Vector3 messages (and further ...
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2 answers
423 views

Vısual sensor.camera lenses with a field of view of more than 180 degree

What kind of camera models can be used for lenses with a field of view of more than 180 degree ? Is ıt possible if not why? Are fisheye lenses suitable for this purpose?
MIRMIX's user avatar
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1 answer
17 views

Please help me understand origin in URDF

Hi folks, I have been following the book Programming Robots with ROS and have been struggling with how the origin tag means in URDF files. In the chapter 18, there is a snippet of URDF as the ...
user avatar
2 votes
1 answer
2k views

Image coordinate to robot coordinate

I am working with a Nao robot. One if the things I want to do is the following: Take an image of geometrical objects in front of the Nao (done) Extract features from the objects in the image, such as ...
JNevens's user avatar
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1 answer
3 views

how to Transform Pointcloud2 with tf

Hi, I tried to run the python code on this link http://answers.ros.org/question/9103/how-to-transform-pointcloud2-with-tf/ and got such an error below : Traceback(most recent call last): File "/...
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1 vote
0 answers
89 views

Which Trajectory representation for optimization

I'm strugling on that problem for a while, so any help is welcome. I need a trajectory representation that is performant for optimization, i.e. I want something that computes quickly. The function I ...
JulesW's user avatar
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2 votes
1 answer
44 views

Recognizing a line from three r-theta ultrasonic distance readings?

Anyone know of sample Python code, or a tutorial, on the polar coordinate math for recognizing that three ultrasonic distance readings form a straight line? ...
Cyclical Obsessive's user avatar
2 votes
0 answers
95 views

Consitent Scale in Monocular pose estimation

I just wanted to know if scale is conserved across multiple images, when doing a process such as monocular odometry. I know in reality the scale tends to drift over time due to accumulation of small ...
edwinem's user avatar
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0 votes
1 answer
3k views

6 axis robot arm with non-perpendicular axes?

Lately I've been thinking about 6 axis robots and noticed that all examples that I've seen on the internet use the same configuration of axes: Vertical axis waist (1), horizontal axis shoulder (2) ...
cube's user avatar
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1 answer
2 views

Which library can I access XmlRpcValue.h file?

Hello ROS users, While installing geometry package for tf, during catkin_make I receive error: 21%] Built target roscpp_generate_messages_cpp [ 21%] Built target roscpp_generate_messages_py [ 22%] ...
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0 votes
1 answer
19 views

how to calculate transform for two geometry_msgs/poseStamped messages

Hi, I am new to ROS and RTT. I want to calculate the transformation (relative position) for two geometry_msgs/poseStamped messages so that I can get the absolute position of my object if the position ...
user avatar
3 votes
2 answers
98 views

Fence avoidance for manually controlled robot

I'm trying to find known techniques for keeping a manually controlled robot within a known polygon fence. More specifically, a pilot controls a robot by issuing desired velocity vectors, and the ...
Daniel Ricketts's user avatar
3 votes
3 answers
2k views

Generalized Voronoi Diagram

I need to compute the Voronoi diagram for a map with some obstacles but I can't find any pseudo-code or example in MATLAB. The "voronoi" function in MATLAB works with points, but in this case the ...
osuarez's user avatar
  • 358
3 votes
1 answer
162 views

Mobile robot algorithm implementation error

I am working in reproducing a robotics paper, first simulating it in MATLAB in order to implement it to a real robot afterwards. The robot's model is: $$\dot{x}=V(t)cos\theta $$ $$\dot{y}=V(t)sin\...
Wobbler28's user avatar
1 vote
0 answers
48 views

How to determine the angles between a UAV and a sphere

I have an UAV modeled in three dimensions with let's say position coordinates $p_{uav} = (x_1,y_1,z_1)$ that is moving in a direction $d = (d_x,d_y,d_z)$ and a moving obstacle modeled as a sphere with ...
Wobbler28's user avatar
2 votes
4 answers
2k views

Most accurate rotation representation for small angles

Assume that I have a rigid body for which I know that it can rotate with respect to a global reference frame (which is considered fixed and already given) for only a few degrees of angle, so I can ...
jpro's user avatar
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1 answer
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URDF Mesh filetypes?

What are all the possible filetypes I can use in the , <mesh ... /> tag? I'm actually trying to use another URDF file as a mesh filetype, but it doesn't seem to be possible. Originally posted ...
user avatar
2 votes
2 answers
241 views

Angle to a circle tangent line

I want to simulate the detection of a moving object by a unicycle type robot. The robot is modelled with position (x,y) and direction theta as the three states. The obstacle is represented as a circle ...
Wobbler28's user avatar
1 vote
1 answer
42 views

Which geo-projection to use for odometry [closed]

I would like to make a little survey regarding the (geo)spatial projection that you use when elaborating your GPS and movement data for the spatial awareness of your robots. Moving all GPS ...
Campa's user avatar
  • 113
7 votes
1 answer
112 views

6D localization with 6 lasers

I have to know where a multi-rotor is, in a rectangular room, via 6 lasers, 2 on each axis. The problem is like this: Inputs : Room : square => 10 meters by 10 meters 6 positions of the lasers : ...
Alexis Paques's user avatar
0 votes
1 answer
305 views

Relative orientation of two robots

Given two robot arms with TCP (Tool Center Point) coordinates in the world frame is: $X_1 = [1, 1, 1, \pi/2, \pi/2, -\pi/2]$ and $X_2 = [2, 1, 1, 0, -\pi/2, 0]$ The base of the robots is at: $...
50k4's user avatar
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0 votes
1 answer
5 views

How to deal with an offset in precise GPS data?

I've got a robot setup with a very precise differential GPS (centimeter level). For technical reasons, I can't attach the GPS directly over the rotational center of the robot, but rather need to make ...
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0 votes
1 answer
2 views

how to: geom calcs in ROS

I'm in the need to do geometry calculations (matrix_by_matrix, vector_by_matrix, scalar_by_vector, and so on). I looked up the documentation but the vector class isn't documented at all, and doing ...
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1 answer
25 views

Could not find tf/transform_listener.h

Hey there, I have a problem with the tf package. In my code I'm using the following includes: ...
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0 votes
2 answers
4 views

Geometry tools for python

I want to perform some basic geometry computations using python, for example calculating the euclidean distance between two points. Of course, implementing that is easy enough, but littering code with ...
Stefan Kohlbrecher's user avatar
0 votes
1 answer
6 views

question about projectpixelto3dray

Hi I have a question about the function projectPixelTo3dRay, according to the API the return value is a 3d ray passing through (u,v). But what does that mean? Why Z is 1? How I can calculate the point ...
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0 votes
1 answer
1 view

Convert coordinates 2d to 3D point, theoretical question

Hi, this is my first post. I am a student and I'm doing a project with ARDrone to follow a red ball. I have a question about robotics and ROS, with ARDrone locate the red ball in the image, which ...
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