ros_best_practices | Best practices , conventions , and tricks for ROS | Robotics library

This question is related to my final project. In gazebo simulation environment, I am trying to detect obstacles' colors and calculate the distance between robot and obstacles. I am currently identifying their colors with the help of OpenCV methods (object with boundary box) but I don't know how can i calculate their distances between robot. I have my robot's position. I will not use stereo. I know the size of the obstacles. Waiting for your suggestions and ideas. Thank you!

My robot's topics :

• cameras/camera/camera_info (Type: sensor_msgs/CameraInfo)
• cameras/camera/image_raw (Type: sensor_msgs/Image)
• sensors/lidars/points (Type: sensor_msgs/PointCloud2)

I’m a college student and I’m trying to build an underwater robot with my team.

We plan to use stm32 and RPi. We will put our controller on stm32 and high-level algorithm (like path planning, object detection…) on Rpi. The reason we design it this way is that the controller needs to be calculated fast and high-level algorithms need more overhead.

But later I found out there is tons of package on ROS that support IMU and other attitude sensors. Therefore, I assume many people might build their controller on a board that can run ROS such as RPi.

As far as I know, RPi is slower than stm32 and has less port to connect to sensor and motor which makes me think that Rpi is not a desired place to run a controller.

So I’m wondering if I design it all wrong?

In a formation robots are linked with eachother,number of robots in a neighbourhood may vary. If one robot have 5 neighbours how can I find the angle of that one robot with its other neighbour?

Overlapping targetless stereo camera calibration can be done using feautre matchers in OpenCV and then using the 8-point or 5-point algoriths to estimate the Fundamental/Essential matrix and then use those to further decompose the Rotation and Translation matrices.

How to approach a non-overlapping stereo setup without a target?

Can we use visual odometry (like ORB SLAM) to calculate trajectory of both the cameras (cameras would be rigidly fixed) and then use hand-eye calibration to get the extrinsics? If yes, how can the transformations of each trajectory mapped to the gripper->base transformation and target->camera transformation? Or is there another way to apply this algorithm?

If hand-eye calibration cannot be used, is there any recommendations to achieve targetless non-overlapping stereo camera calibration?

As a premise I must say I am very inexperienced with ROS.

I am trying to publish several ros messages but for every publish that I make I get the "publishing and latching message for 3.0 seconds", which looks like it is blocking for 3 seconds.

I'll leave you with an example of how I am publishing one single message:

A c++ novice here! The verbose in the terminal output says the problem is solved successfully, but I am not able to access the solution. What is the problem with the last line?

I'm programming a robot's controller logic. On the controller there is 2 buttons. There is 3 different actions tied to 2 buttons, one occurs when only the first button is being pushed, the second when only the second is pushed, and the third when both are being pushed.

Normally when the user means to hit both buttons they would hit one after another. This has the consequence of executing a incorrect action.

Here is part of the code.

I'm trying to put together a programmed robot that can navigate the room by reading instructions off signs (such as bathroom-right). I'm using the AlphaBot2 kit and an RPI 3B+.

the image processing part works well, but for some reason, the MOTION CONTROL doesn't work. I wrote a simple PID controller that "feeds" the motor, but as soon as motors start turning, the robot turns off.

I have read multiple resources that say the InverseKinematics class of Drake toolbox is able to solve IK in two fashions: Single-shot IK and IK trajectory optimization using cubic polynomial trajectories. (Link1 Section 4.1, Link2 Section II.B and II.C)
I have already implemented the single-shot IK for a single instant as shown below and is working, Now how do I go about doing it for a whole trajectory using dircol or something? Any documentation to refer to?