This book is a book supplemented by Gu Yueju, a well-known domestic ROS blogger, based on his series of blog posts on the exploration and summary of ROS. It should be said that it is relatively easy for domestic learners to learn.
1. ROS communication mechanism
Topic based (most used) - publish/communication mode, asynchronous communication
Service-based - client/server model, synchronous communication
based on
2. Node relationship diagram
Take the node relationship diagram of the classic turtle function package turtlesim as an example. The oval circles in the box with / are nodes (such as /teleop_turtle, turtlesim), above the oval circles are topics (such as teleop_turtle, turtlesim), and above the arrows are messages ( Such as /turtle/cmd_vel).
3. usb_cam
usb_cam is a ROS driver function package for USB cameras, and the core node is usb_cam_node.
4. joint tag
The joint tag is used to describe the kinematic and dynamic properties of robot joints, including the position and speed limits of joint motion.
Divided into six types: continuous, revolute, prismatic, planar, floating and fixed.
The main function of the joint is to connect two links, namely parent link and child link.
5. Computer vision vs human vision
The light reflected by the object stimulates the photoreceptor cells of the human eye, and the optic nerve forms an image of the object in the brain, so the human eye can see the object.
Computer vision is much simpler. The photosensitive element of the camera converts the light signal into a digital signal and quantifies it into a digital matrix to represent the intensity of the reflected light from the object.
6. Camera calibration
The camera itself has optical distortion, and the camera_calibration function package can be used to achieve calibration of binocular and monocular cameras.
