ROS package for Kobot -- Heteregoneous swarm robot platform.

Kobot package is actively used and tested on RPi 3B+ running Ubuntu Mate 18.04, ROS Melodic and RPi Zero W running Raspbian Buster and ROS Melodic.

Additionally, this repository contains dotfiles (.vimrc, .zshrc, .tmux.conf), shell scripts and plain hardware test scripts that are used by Kobot robots.

Currently, 3 different swarm robots are extended from the Kobot platform:

• Kobot-W (Wheeled robot, equipped with IR floor sensors, 9-Axis IMU, Xbee for local communication) Design Link
• Kobot-F (Flying robot using Ryze Tello as the base) Desing Link
• Kobot-T (Tracked Robot using Zumo from Pololu as the base, equipped with a 2-D.o.F. compliant gripper) [Design Link will be available soon]

SD Card Image of the Kobot-W running Ubuntu Mate 18.04 and ROS Melodic

SD Card Image of the Kobot-F running Raspbian Buster and ROS Melodic Image of the Kobot-T running Raspbian Buster and ROS Melodic (In-progress)

Branches are used for developing extended robot specific features until they are ready to be merged with the main branch. Maintainers and branches are:

• main ([email protected])
• kobot_w ([email protected])
• kobot_f ([email protected],[email protected])
• kobot_t ([email protected])

If you are not using the SD Card images and would like to use kobot_ros package for other purposes, there are quite a few required dependencies which are given below (these are not updated regularly):

• cv_bridge (need to build as a seperate catkin workspace)
• camera_info_manager (required by ROS nodes)
• tf (required by ROS nodes)
• Python 3.6 or later version (not the default interpreter for ROS Melodic)
• opencv-contrib-python (need to build from source for RPi Zero and 3B+)
• mpu9250_jmdev (handling i2c comm. with MPU9255 9-Axis IMU)
• adafruit_neopixel (handling comm. w/ neopixel led ring by using one of the GPIO pins)
• pyserial (handling the serial comm. w/ Xbee RF Module)
• smbus2 (handling all the i2c communication)
• numpy (handling linear algebra)
• RPi.GPIO (handling basic GPIO operations such as digital write, read)

There are no installation instructions for the stand-alone kobot package. The recommended way is using one of the SD Card images.

This repository contains two types of nodes:

• High-level beahvioural nodes to control the swarm behaviour of the robots
  • flocking Paper Link i.e. Swarm members perform alignment, avoidance and cohesion using robot, obstacle detection, range of the objects, heading with resepect to an absolute reference and non-holonomic velocity control Video Link
  • alignment, i.e. modified flocking algorithm where swarm members align their headings w.r.t. a common orientation reference
  • wall_following i.e. modified flocking algorithm where swarm members follow walls instead of avoiding perpendicularly
  • dispersion_avoidance, i.e. modified flocking algorithm where Kobot-F robots disperse in z-axis (altitude), avoid obstacles Video Link
  • beeclust Paper Link i.e. Swarm members aggregate on a cue denoted by high IR reflectivity (other abstractions are possible), avoid obstacles by random walk and wait in the cue when collide with another robot inside cue. Duration is determined by the reflectivity
  • lba (landmark-based aggregation) Paper Link i.e. Extended version of beeclust where swarm members learn and store the paths from landmarks to the cue (landmarks are abstracted by ArUco markers Paper Link detection by OpenCV) Video Link
  • rl_lba (landmark-based aggregation using reinforcement learning), i.e. Extended version of lba exploring, exploiting an action space when a landmark in the environment is detected
• Sub-system driver nodes abstracting the hardware using ROS messages and subscriber/publisher architecture.
  • common nodes for all extended robots
    • range_n_bearing (get angle and range of objects and decide whether robot or obstacle)
    • landmark_pose_estimator (estimate pose of the ArUco marker abstracting landmarks)
    • pose_controller (controller pose of the robot, i.e. x,y,theta)
    • heading (get heading of the robot w.r.t. a common reference)
    • local_communication (broadcast locally using XBee RF module)
    • battery (check battery cell voltages regularly)
  • kobot_w, kobot_t specific nodes
    • teleop_key (tele-operate robot by using keyboard)
    • cmd_vel2motors (convert ROS's cmd_vel msg to seperate velocity commands for motors)
    • differential_driver (set, get controller params., velocity of the motors)
    • odom (collect wheel odometry data from the motors, get robot pose)
    • mpu9255 (get orientation data from IMU)
    • floor_sensor (get IR reflection intensity from floor sensors)
  • kobot_f specific nodes
    • tello_driver (to operate Ryze Tello drone)

Custom ROS messages used by the Kobot sub-systems and behavioural nodes:

• range_n_robot, i.e. reading of an individual sensor of the range and bearing board. Robot field is a boolean which is true for robots and false for all other objects. Range field is the range reading corresponding to the sensor.
• range_n_bearing, i.e. array of all sensor of the range_n_bearing board.
• virtual_sensor, i.e. array of sensor readings.
• floor_sensor, i.e. array of individual IR floor sensor readings.
• landmark_pose, landmarks are abstracted by using Aruco markers,

Three types of parameter files in .yaml format are used to configure the operation of the nodes:

• Behavioural parameters
  • flocking
  • alignment (modified flocking beta=0, u_max=0)
  • wall_following (modified flocking avoid_angle = 90)
  • lba (modified beeclust)
  • beeclust (modified lba d_landmark = 0)
  • rl_lba (modified lba)
• Calibration files, these files are specific to robots and stored locally hence, they are ignored by git.
  • IMU (gyro bias, magnetometer hard-iron, soft-iron biases)
  • Camera (intrinsic parameters, calibrated with a Charuco Board)
  • Odometry (left, right wheel radii and axle distance)
• Controller
  • Velocity Controller (PID gains, velocity limits, control loop frequency)
  • Pose Controller (PID gains, error-window, max. translational velocity)

Launch files are used for running multiple nodes, loading parameters to the ROS's parameter server and handling individual namespaces.

• Sub-system launch files
  • move
  • heading
  • landmark_pose_estimator
  • floor_sensing
• Behaviour launch files
  • flocking
  • alignment
  • wall_following
  • beeclust
  • lba
  • rl_lba
• Calibration launch files
  • calibrate_camera
  • calibrate_imu

• Kobot-T sub-system drivers
• flocking behaviour for Kobot-F
• Kobot-H and Kobot-L (holonomic wheeled and legged swarm robots) conceptual design

MIT License

Copyright (c) 2021 cemoke

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

• kobotMotorController Link
• kobotRangeNBearing Link
• kobot_base Link

• ROMER -- Instuition where Kobot platform is deleoped Webpage
• Kovan Research Lab -- Laboratory where Kobot platform is developed Webpage