ROS robotic arm

MoveIt installation

Since I am here on Ubuntu 20.04, the noetic version of the package will be installed

sudo apt install ros-noetic-moveit

If Ubuntu 18.04, run

sudo apt install ros-melodic-moveit

Installation here takes a little while.

After the installation is complete, enter

moveit_version

There is an output indicating that the installation is successful, and my output here is

1.1.13

install ccd

Download the source code from https://github.com/danfis/libccd , unzip it and enter the src in the main folder, compile

cd src

Modify the Makefile, the modified content is as follows

CFLAGS += -I. -fvisibility=hidden -fPIC

continue to execute

make
sudo make install

Install the fcl library

Download the source code from https://github.com/flexible-collision-library/fcl , unzip it and enter the main folder for compilation and installation

mkdir build
cd build
cmake ..
make
sudo make install

Create a robotic arm model

URDF modeling principle

Robots are mainly divided into control systems, drive systems, actuators, and sensing systems.

1. Control system: It is equivalent to the human brain, realizes the processing of tasks and information, and outputs control command signals.
2. Drive system: equivalent to human muscles and meridians, it is responsible for driving the actuator and converting the commands issued by the control system into the signals required by the actuator.
3. Executing mechanism: Equivalent to human hands and feet, a mechanical device that works directly.
4. Sensing system: equivalent to human senses and nerves, complete signal input and feedback, including internal sensing system (perceiving the internal state of the robot, such as attitude sensor, odometer) and external sensing system (perceiving the external environment, such as laser radar ).

The modeling mentioned here refers to modeling the actuator (mechanical device).

URDF: A robot model file described in XML format.

For the robotic arm in the above picture, it is divided into a large arm, a small arm, and a joint in the middle. Whether it is a big arm or a small arm, we call it a rigid body link ( links ), and the joint in the middle is called a joint . Include in the model file

1. Links: Coordinate system and geometric relationship.
2. Joints: The connection relationship between Links.

URDF can not only model the robotic arm, but also model the external scene. For example, the table in the picture above is actually a rigid body part, so it is also a link.

<link>

1. Describe the appearance and physical properties of a rigid body part of the robot;
2. Describe the connecting rod size (size), color (color), shape (shape), inertia matrix (inertial matrix), collision parameters (collsion properties), etc.;
3. Each Link will become a coordinate system

<link name="link_4">
    <visual>
        <geometry>
             <mesh filename="link_4.stl" />
        </geometry>
    </visual>
    <collision>
        <geometry>
            <cylinder length="0.5" radius="0.1" />
        </geometry>
        <origin xyz="0 0 -0.05" rpy="0 0 0" />
    </collision>
</link>

MoveIt core functionality and Rivz controls

Execute in a different command line window

roscore
rosrun moveit_setup_assistant moveit_setup_assistant

A window will pop up with two buttons - Create New MoveIt Configuration Package (create a new package), Edit Existing MoveIt Configuration Package (edit an existing package).

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