A Collision-Free Sway Damping Model Predictive Controller for Safe and Reactive Forestry Crane Navigation
Marc-Philip Ecker, Christoph Froehlich, Johannes Huemer, David Gruber, Bernhard Bischof, Tobias Glück, Wolfgang Kemmetmueller
AI summary
Problem
Existing forestry crane controllers treat sway damping and collision avoidance separately, relying on predefined paths that fail when encountering unforeseen obstacles or external disturbances in dynamic environments.
Approach
A unified Model Predictive Controller that directly integrates online LiDAR-based Euclidean distance fields into its optimization loop to simultaneously enforce collision constraints and dampen payload sway.
Key results
- Effective real-time payload sway damping under external disturbances
- Successful reactive replanning around unforeseen quasi-static obstacles
- Guaranteed safe stopping when no collision-free path exists
- Robust collision avoidance compensating for tracking inaccuracies in narrow passages
Why it matters
Provides a foundational step toward autonomous forestry operations by enhancing safety and reducing dependency on highly skilled operators in cluttered, dynamic workspaces.
Abstract
Forestry cranes operate in dynamic, unstructured outdoor environments where simultaneous collision avoidance and payload sway control are critical for safe navigation. Existing approaches address these challenges separately, either focusing on sway damping with predefined collision-free paths or performing collision avoidance only at the global planning level. We present the first collision-free, sway-damping model predictive controller (MPC) for a forestry crane that unifies both objectives in a single control framework. Our approach integrates LiDAR-based environment mapping directly into the MPC using online Euclidean distance fields (EDF), enabling real-time environmental adaptation. The controller simulta- neously enforces collision constraints while damping payload sway, allowing it to (i) replan upon quasi-static environmental changes, (ii) maintain collision-free operation under distur- bances, and (iii) provide safe stopping when no bypass exists. Experimental validation on a real forestry crane demonstrates effective sway damping and successful obstacle avoidance. A video can be found at https://youtu.be/tEXDoeLLTxA.