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Pose Estimation Demo: Part 1

In this first part of the tutorial, we will start by downloading and installing the Unity Editor. We will install our project's dependencies: the Perception, URDF, and TCP Connector packages. We will then use a set of provided prefabs to easily prepare a simulated environment containing a table, a cube, and a working robot arm.

Table of Contents

Requirements
Create a New Project
Download the Perception, the URDF and the TCP connector Packages
Setup the Ground Truth Render Feature
Setup the Scene

Requirements

To follow this tutorial you need to clone this repository even if you want to create your Unity project from scratch.

Note For Windows users: You need to have a software enabling you to run bash files. One option is to download GIT. During installation of GIT, add GIT Bash to windows context menu by selecting its option. After installation, right click in your folder, and select GIT Bash Here.

Open a terminal and put yourself where you want to host the repository.

git clone https://github.com/Unity-Technologies/Unity-Robotics-Hub.git

Then we need to be in the Unity-Robotics-Hub/tutorials/pose_estimation folder and generate the contents of the universal_robot, moveit_msgs, ros_tcp_endpoint, and the robotiq folders.

cd Unity-Robotics-Hub/tutorials/pose_estimation
./submodule.sh

Install Unity 2020.2.*.

Create a New Project

When you first run Unity, you will be asked to open an existing project, or create a new one.

Open Unity and create a new project using the Universal Render Pipeline. Name your new project Pose Estimation Tutorial, and specify a desired location as shown below.

Download the Perception, the URDF and the TCP connector Packages

Once your new project is created and loaded, you will be presented with the Unity Editor interface. From this point on, whenever we refer to the "editor", we mean the Unity Editor.

How to install packages

We will need to download and install several packages. In general, packages can be installed in Unity with the following steps:

From the top menu bar, open Window -> Package Manager. As the name suggests, the Package Manager is where you can download new packages, update or remove existing ones, and access a variety of information and additional actions for each package.
Click on the + sign at the top-left corner of the Package Manager window and then choose the option Add package from git URL....
Enter the package address and click Add. It will take some time for the manager to download and import the package.

Installing the different packages may take some time (few minutes).

Install Dependencies

Install the following packages with the provided git URLs:

Perception package - com.unity.perception@0.7.0-preview.1
- This will help us collect training data for our machine learning model.
URDF Importer package - https://github.com/Unity-Technologies/URDF-Importer.git#v0.1.2
- This package will help us import a robot into our scene from a file in the Unified Robot Description Format (URDF).
TCP Connector package - https://github.com/Unity-Technologies/ROS-TCP-Connector.git#v0.1.2
- This package will enable a connection between ROS and Unity.

Note: If you encounter a Package Manager issue, check the Troubleshooting Guide for potential solutions.

Set up Ground Truth Render Feature

The Hierarchy, Scene View, Game View, Play/Pause/Step toolbar, Inspector, Project, and Console windows of the Unity Editor have been highlighted below for reference, based on the default layout. Custom Unity Editor layouts may vary slightly. A top menu bar option is available to re-open any of these windows: Window > General.

The perception packages relies on a "ground truth render feature" to save out labeled images as training data. You don't need to worry about the details, but follow the steps below to add this component:

The Project tab contains a search bar; use it to find the file named ForwardRenderer, and click on the file named ForwardRenderer.asset as shown below:

Click on the found file to select it. Then, from the Inspector tab of the editor, click on the Add Renderer Feature button, and select Ground Truth Renderer Feature from the dropdown menu:

Set up the Scene

The Scene

Simply put in Unity, a Scene contains any object that exists in the world. This world can be a game, or in this case, a data-collection-oriented simulation. Every new project contains a Scene named SampleScene, which is automatically opened when the project is created. This Scene comes with several objects and settings that we do not need, so let's create a new one.

In the Project tab, right-click on the Assets > Scenes folder and click Create -> Scene. Name this new Scene TutorialPoseEstimation and double-click on it to open it.

The Hierarchy tab of the editor displays all the Scenes currently loaded, and all the objects currently present in each loaded Scene, as shown below:

As seen above, the new Scene already contains a camera (Main Camera) and a light (Directional Light). We will now modify the camera's field of view and position to prepare it for the tutorial.

Still in the Inspector tab of the Main Camera, modify the camera's Position and Rotation to match the values shown below. This orients the camera so that it will have a good view of the objects we are about to add to the scene.

Click on Directional Light and in the Inspector tab, modify the light's Position and Rotation to match the screenshot below.

Adding Tutorial Files

Now it is time to add some more objects to our scene. Before doing so, we need to import some folders containing the required assets.

Download TutorialAssets.zip, and unzip it. It should contain the following subfolders: Materials, Prefabs, RosMessages, Scripts, URDFs.
Drag and Drop the TutorialAssets folder onto the Assets folder in the Project tab.

Your Assets folder should like this:

Using Prefabs

Unity’s Prefab system allows you to create, configure, and store a GameObject complete with all its components, property values, and child GameObjects as a reusable Asset. It is a convenient way to store complex objects.

A prefab is just a file, and you can easily create an instance of the object in the scene from a prefab by dragging it into the Hierarchy panel.

For your convenience, we have provided prefabs for most of the components of the scene (the cube, goal, table, and floor).

In the Project tab, go to Assets > TutorialAssets > Prefabs > Part1 and drag and drop the Cube prefab inside the Hierarchy panel.
Repeat the action with the Goal, Table and the Floor.

Note: If you encounter an issue with the imported prefab materials, check the Troubleshooting Guide for potential solutions.

Importing the Robot

Finally we will add the robot and the URDF files in order to import the UR3 Robot.

In the Project tab, go to Assets > TutorialAssets > URDFs > ur3_with_gripper and right click on the ur3_with_gripper.urdf file and select Import Robot From Selected URDF file. A window will pop up, keep the default Y Axis type in the Import menu and the Mesh Decomposer to VHACD. Then, click Import URDF. These set of actions are showed in the following video.

Note Unity uses a left-handed coordinate system in which the y-axis points up. However, many robotics packages use a right-handed coordinate system in which the z-axis or x-axis points up. For this reason, it is important to pay attention to the coordinate system when importing URDF files or interfacing with other robotics software.

Note: VHACD algorithm produces higher quality convex hull for collision detection than the default algorithm.

Note: If you encounter an issue with importing the robot, check the Troubleshooting Guide for potential solutions.

Setting up the Robot

Select the ur3_with_gripper GameObject and in the Inspector view, go to the Controller script and set the Stiffness to 10000, the Damping to 1000 and the Force Limit to 1000. These are physics properties that control how the robot moves.
In the Hierarchy tab, select the ur3_with_gripper GameObject and click on the arrow on the left, then click on the arrow on the left of world, then on base_link. In the Articulation Body component, toggle on Immovable for the base link. This will fix the robot base to its current position.

10 KiB 原始文件 文件历史