title: An Integrated Whole-Body Planning Framework for Locomotion in Challenging Terrain with Different Types of Tracked Robots
Creators: name: Oehler, Martin Sven
Publisher: name: UNSPECIFIED
Year: 2025

description: Mobile rescue robots can provide valuable support for first responders in disaster scenarios by entering hazardous environments to search for victims or perform other critical tasks. In these scenarios, traversing debris and rough terrain is often inevitable for the robot to successfully complete its mission. However, the risk of vehicle tip-over poses a significant challenge, threatening mission success. Similar conditions are found in related fields such as construction. Autonomous mobile robots can reliably monitor and document the construction progress which is essential for identifying structural errors early. However, as the building is still in an unfinished state, the robot needs to safely overcome obstacles such as steep stairs, high steps, or obstructive building materials.

Tracked robots, equipped with active flippers and a manipulator arm, can overcome these obstacles by efficiently utilizing all joints. Active flippers keep contact with the ground, while the robot can maintain stability by using the arm joints to shift its center of mass. Yet, executing these maneuvers through conventional teleoperation demands expert skill, leading to a high mental load and slow, error-prone operation. Previous research on preventing vehicle tip-over in unstructured terrain has been limited to robotic systems with few degrees of freedom or specific kinematic assumptions, resulting in solutions that are not generally applicable. 

This thesis introduces a novel whole-body planning approach that enables different types of tracked robots to autonomously traverse obstacles and rough terrain safely. Using a 3D environment model, the approach generates a whole-body motion plan by optimizing the trajectory of each joint. Central to this method is the formulation as an optimization problem that incorporates cost functions grounded in general mechanical principles applicable across a wide range of tracked robot platforms. The combination of spatial and temporal planning ensures a coordinated movement between the robot’s base and joints, leading to a smooth traversal of difficult terrain.

Given the dynamic nature of rescue missions, characterized by a high complexity and uncertainty, fully autonomous operation is often infeasible. In this thesis, multiple assistance capabilities are proposed that support the operator with a flexible level of autonomy. Moreover, a framework is described that integrates these capabilities into a cohesive control concept for remote operation, allowing for seamless transitions between autonomy levels.

The developed methods were validated in experiments on two distinct mobile robot platforms, in both simulated and real-world environments. Laboratory experiments demonstrate the ability of the developed approaches to overcome highly challenging obstacles at the robot platforms’ operational limits. In a comparative case study with operators of varying prior experience, the proposed autonomous whole-body planning outperformed teleoperation in terms of locomotion smoothness and completion time. Moreover, the study further highlights the importance of autonomous assistance functions for real-world applications by indicating a considerable decrease in cognitive load and a reduced training time. Additionally, the successful application in the locomotion benchmarks of the Rescue Robot League at the RoboCup World Championship demonstrates the method’s reliability and robustness, serving as an independent evaluation in an international competition. For the first time, two of the challenging mobility arenas were completed autonomously, bridging the gap towards an application in real-world scenarios.