Screw-Propelled Omni-Directional Robot: Automation of Waypoint Navigation and Control System Integration

Abstract

Helix-25 is a screw-propelled mobile robot designed by Copperstone Technologies® to survey hazardous ponds and fields. Currently this robot is manually operated, which may not be feasible during various circumstances. The control strategies for screw propelled robots have been limited, with a small element of control and they are all focussed on modelling. This project is a first pass effort to automate the movement of Helix -25 through waypoint navigation. A preliminary attempt to implement PID controller for automation of Helix is made as a first pass method, as dwelling into other sophisticated controllers may depend on dynamics of the terrain. In this project, GPS and IMU sensors are integrated into the Helix rover and the sensor data is fused using EK3 filter provided in-built by Pixhawk unit to get the pose estimate, and the ROS drivers provided by Copperstone Technologies® are used to send feedback-controlled commands to the motors based on PID errors. PID algorithms for roll, scroll and omni-directional modes were simulated in Gazebo using ZM robot and Helix model before being applied on field tests. Robots were made to follow preprogrammed Square, Hexagon and Circle trajectories to validate the robustness of control algorithm in various modes. A trial field test was conducted on beach sand in a volleyball court, and it was found that Helix needs a cohesive medium to exhibit scroll and omnidirectional movement. Based on the inference, field testing is moved to hard surface medium to automate way point navigation in roll mode using the PID control on field test and the Helix is made to follow a 10 m x 10 m square trajectory successfully to prove the appropriate working of the automation controller interface. Later, a refinement in the robotic system and electronic design is suggested based on the field test learnings. Further, this proof of concept and mechatronic system integration builds a pathway for expanding research as well as facilitating tests of more sophisticated autonomous controller development on Helix -25.