Master_Thesis

This repository contains the code developed during my master thesis period at the Humanoid and Human Centered Mechatronic department of the Istituto Italiano di Tecnologia in Genova. The objective of this work was to develop a control strategy for the lower part of the quadruped robot CENTAURO to execute wheeled locomotion on uneven and rough terrain.

Introduction

This thesis proposes the design of two controllers for the wheel-on-leg robot CENTAURO, developed in the laboratory of Humanoid and Human-Centered Mechatronics at the Istituto Italiano di Tecnologia. The existing real-time framework was expanded by two modules: a Cartesian Impedance Controller and an Attitude Controller for each leg. The purpose of the former is to handle all the disturbances coming from the environment in a compliant way. When deviating from the reference values, this controller will generate a force to counteract the movement, following a mass-spring-damper dynamics. Tuning the parameters of the controller will change the behavior of the robot to better match the condition of the terrain. The latter has been developed with the intent to dynamically change the reference values of the Cartesian impedance controller to control the roll and pitch angle of the base, maintaining the robot base parallel to the ground. The modified framework is then tested on both real and simulated scenarios to validate the effectiveness of the controllers.

documentation

The complete master thesis and a short summury are reported in the documentation folder.

File System Structure

• /CMakeFiles contain the file generated by CMake
• /CentauroConfig is the folder containing all the configuration file (.yaml) employed in the code for quick setup of the controllers as well as the Xbot2 and CartesI/O framework configuration
• /documentation present the PDFs of the thesis, both summury and complete master thesis, which serves as a theoretical documentation for the implementation of the two controllers
• /include contains the header files for the created classes
• /msg is the folder containing all the custom messages created for ROS, which are needed for the data log in real-time
• /src is the heart of this repository, since it contains all the source files with the implementation of the controllers

Configuration Files

This section present a description of each configuration files created for the setup of the complete framework.

new_centauro_config.yaml

This configuration file is used to set up the Xbot2 framework, following the guidelines outlined in its documentation. Of particular importance here is the addition of the impedance_control plugin, which integrates the Cartesian Impedance Controller into Xbotcore. The plugin receives parameters such as stack_path, which is the path to the stack of problem configuration files (to be further analyzed), stab_controller_path for inserting the path to the Attitude Controller configuration file, and a boolean parameter stab_control_enable to quickly enable or disable the presence of the Attitude Controller in the control strategy.

roll_pitch_controller_config.yaml

Each controlled chain, in this case each leg, is linked to an Attitude Controller, which compute the new references of the Cartesian Impedance Controller such that the base of the robot remain parallel to the ground. In this file, the proportional gain of each controller is specified along with the damping ratio, both for the roll and pitch control laws. Furthermore, other parameters are specified: