In paper, the supervisory control of a Discrete Event System (DES) is analyzed to construct autonomous package delivery system. The delivery system includes legged robot in order to autonomously navigate uneven indoor terrain and a conveyor belt for transporting the package to the legged robot. The aim of the paper is using theory of supervisory control of DES to supervise and control machine’s state and event and ensure robots autonomously collaborate. By applying the theory, we show collaboration of two individual robots to deliver goods in multi-floor environment The obtained results from the theory of supervisory control is implemented and verified in simulation environment. In this code, four legged robot Aliengo and a conveyor belt are implemented in Gazebo environment to collaborate and deliver goods in destinated area. We implement Theory of Supervisory Control of Discrete Events-States (DES) using ROS-Smach library.

• State Machine library (Smach) is obtained from https://github.com/ros/executive_smach

• Aliengo Gazebo is obtained from https://github.com/unitreerobotics/aliengo_ros and https://github.com/unitreerobotics/laikago_ros

• Aliengo's Gait generator and Balancing Control is obtained from https://github.com/chvmp/champ.git

• Note that at this branch, local awarness framework doesnt use in stair climbing application,instead CHAMP lib is used to generate foot placement for climbing (even though it may not be safe for real application). For more information about local awarness for safe foot placement, you can check out elevation mapping and traversability analysis.

Requirements:

• Ubuntu 16.04 or 18.04
• ROS kinetic or melodic
• Gazebo8 or above

ros-melodic-gazebo8-ros
ros-melodic-gazebo8-ros-control
ros-melodic-gazebo8-ros-pkgs
ros-melodic-gazebo8-ros-dev

ROS related packages for simulation

sudo apt-get install ros-melodic-controller-manager ros-melodic-ros-control ros-melodic-ros-controllers ros-melodic-joint-state-controller ros-melodic-effort-controllers ros-melodic-velocity-controllers ros-melodic-position-controllers ros-melodic-robot-controllers ros-melodic-robot-state-publisher

make a workspace folder (for example: aliengo_delivery_ws) and copy src file into here.

• mkdir ~/aliengo_delivery_ws/src
• cd ~/aliengo_delivery_ws/src

compile

• catkin_make

if compiling gives error, to make sure all ros related packages are installed, go to learning_ws

• source devel/setup.bash
• rosdep install --from-path src -yi
  

Proposed delivery framework which includes three main block; DES, Conveyor Belt and Legged Robot

• Framework of our DES implementation on Autonomus Package Delivery

Visualization of multi-floor environment and two collaborative robots

• Simulation Environment in Gazebo: (Up-Left) indoor-unevenenvironment which includes stair, (Bottom Left) Quadrupedal robot which a package carrier is mounted on it’s back, (Bottom Right) Conveyor belt which moves box to robot’s back

includes foot placement controller

includes configs of gaits

includes 2D path planing algorithm (move_base)

including mesh, urdf and xacro files of quadrupedal robot named Aliengo A1

Spawns aliengo robot, conveyor belt and a box in Gazebo enviornment (normal_aliengo.launch)

Laikago's default joint controller, subscribes joint commands via topics

Laikago's default msgs

Open first terminal; (opens gazebo and rviz while spawning Aliengo, conveyor and a box)

• roslaunch aliengo_gazebo normal_aliengo.launch

Open third terminal; (opens state machine)

• rosrun aliengo_state_mach state_machine.py

Open fourth terminal; (opens state-event controller) and press s to start

• rosrun aliengo_delivery aliengo_delivery.py

Additionally to visualize states and events

• rosrun smach_viewer smach_viewer.py

Gazebo Snapshots of Autonmous Delivery Scenario

• Snapshot of Autonomous Package Delivery Scenario:(Up-Right)initial Position , (Up-Left) first goal reached, (Bottom-Left) climbing to thestairs, (Bottom-Right) second goal reached

State Machine Snapshots of Autonmous Delivery Scenario (DES is obtained from Theory of Supervisory Control)

• States and Events in ROS-Smach Implementation

Robot is able to pick-up package and delivery one floor above by climbing stair.

• Video Result of Implemening State Machine considering all CONTRALLABLE states and events

Robots are able to return initial starting state if robot is falling or box is falling.

• Video Result of Implemening State Machine considering all UNCONTRALLABLE states and events

Haddeler, G. (2021). The Analysis of Discrete-Event System in Autonomous Package Delivery using Legged Robot and Conveyor Belt. arXiv preprint arXiv:2101.12347.