Prerequisites:

Extra software which is used is listed below:

1. Eigen, a C++ template library for linear algebra: matrices, vectors, numerical solvers, and related algorithms.

2. Catkin tools. catkin is the official build system of ROS to generate executables, libraries, and interfaces. Catkin Command Line Tools are used in order to build packages in the workspace.

The required packages (Eigen, catkin tools) can be installed by executing the shell script install_packages.sh.

Installation

• Make sure you have Ubuntu 20.04 installed and running. This framework was developed on ROS Noetic and Gazebo 11, so this version of Ubuntu is necessary.

• Clone the repository in the desired folder using:

git clone [email protected]:csl_legged/legsimulation.git

• Execute the install_packages.sh script, providing a workspace name. e.g:

./install_packages.sh <leg_workspace>

ROS & Gazebo

Argos Leg model

The argos leg model in gazebo consists of the following packages:

leg_description

This package contains:

1. The urdf file for the leg, in a .xacro format: urdf/my_leg.xacro.

The mesh files for the leg are in the meshes folder.

2. A launch file: launch/visual.launch.

It opens the leg in rviz while simultaneously running joint_state_publisher_gui, in order to manually set the joint positions of the leg. The user can view the model in rviz by executing the following command on a new terminal (After sourcing the environment):

roslaunch leg_description visual.launch

3. A static library: leg.

The header files are in include/leg/leg.hpp and the source files in include/leg.cpp. This library contains a leg class with methods for the kinematic calculations (Jacobian, Direct and Inverse Kinematics), for calculating joint angular distances, for calculating the gravity vector for gravity compensation and a method to querry the state of the robot.

* There is a generated .urdf file that was imported in matlab simulation in the urdf folder. There is a rviz configuration file in rvizConfigs folder and the mandatory package.xml and CMakeLists.txt files that are required by the catkin build system

leg_control

This package contains:

1. A launch file: LegFramework.launch.

This file spawns the leg in the gazebo simulation environment, opens up the gui and activates the high-level controller (legHLC), and the contact force tranformation (legContact) nodes. It spawns the leg with initial angular positions q1_0, q2_0, q3_0. Finally, it activates the joint_state_controller in order to publish the states of the robot. It must be noted, that the high level controller loads the Position controllers during its initialization. The user can launch the framework, with the leg in the zero position by executing the following command on a terminal (After sourcing the environment):

roslaunch leg_control LegFramework.launch

The user can launch the framework, with specified initial joint angle positions by executing the following command on a terminal (After sourcing the environment):

roslaunch leg_control LegFramework.launch q1_0:=0.1 q2_0:=0.1 q3_0:=0.1

2. The controller node: legHLC.

This node activates the high level controller for the leg. The update rate is 1ms and it is hardcoded. The source code is in src folder.

3. The source code for the controllers.

The low-level controllers are the following: PositionController, TrajectoryController and Effort Controller. The high level controller is HLC. It switches between the low level ones. The source code for the controllers is in the include folder.

4. Services for sending reference signals to the controller.

The services are in the srv folder. The created services are:

• ControllerSelector: that switcher between low level controllers,

• GoalSet: which sets a desired position, in the world frame, for the position controller (the first argument is a boolen to select whether the target is in cartesian coordinates-> True or joint angles -> False)

• SetEllipse: which sets the ellipse parameters for the TrajectoryController,

• SetEffort: which sets a desired wrench for the effort controller.

5. A contact force tranformation node: legContact

Even though the gazebo_ros_bumper plugin has a <frameName> tag, to specify the frame in which the contact forces will be reported, it does not work. So, this node transforms the contact forces from the end effector reference frame to the world frame.

6. A helper node to make simulations: legSim

Manually create a task, writing c++ code. It was used for the reports.

* There is a rviz configuration file in rvizConfigs folder, a saved rqt_perspective in rqt_perspectives and the mandatory package.xml and CMakeLists.txt files that are required by the catkin build system

Framework GUI

The graphical user interface is presented in the figure below. The user can use the dynamic reconfigure window to change physics (erp, time_step, etc.) and controller parameter (pid gains). Also, they can call the aforementioned services.