How to Shake Trees with Aerial Manipulators? a Theoretical and Experimental Study
Antonio Gonzalez-Morgado, Eugenio Cuniato, Guillermo Heredia, Anibal Ollero, Roland Siegwart, Marco Tognon
AI summary
Problem
Existing aerial manipulator tree-shaking methods only exploit translational forces, leaving the choice between translational and rotational strategies undefined for specific contact points.
Approach
The authors integrate a hybrid pose-shaking controller with a Rayleigh-Ritz tree model to derive closed-loop dynamics for both strategies, analyzing how platform mass versus rotational inertia dictates oscillation amplitude and frequency.
Key results
- Generalized shaking controller supporting both translational and rotational interactions
- Theoretical proof that platform mass dominates translation effectiveness while rotational inertia dominates rotation effectiveness
- Closed-form criteria to select the optimal strategy based on platform characteristics for a fixed interaction point
- Experimental validation using a fully-actuated aerial manipulator and a handmade bamboo tree
Why it matters
Provides a practical decision framework for agricultural and environmental robotics to optimize remote tree shaking and flexible structure interaction.
Abstract
Aerial manipulators are advancing beyond tra- ditional inspection roles to enable complex interactions with flexible structures. Applications such as structural health mon- itoring, and especially agricultural tasks like fruit harvest- ing or environmental monitoring, require inducing controlled vibrations into flexible elements. However, current solutions for controlled shaking of trees with aerial manipulators are limited to push and pull forces applied through translational movements, without exploiting the fully-capabilities of aerial platforms. This paper introduces a controlled shaking strategy that enables interaction with trees using both linear movements generated by forces (translation strategy) and rotational move- ments generated by torques (rotation strategy) thus exploiting the different interaction capabilities of the platform. These two strategies open a previously unexplored question: which strategy is more effective given a specific interaction point? To address this, the two interaction strategies are integrated with the Rayligh-Ritz model of the tree, obtaining the closed-loop dynamics of the system during the vibration. These closed-loop dynamics are then analyzed for the two shaking strategies, deriving which one is better for achieving higher oscillation amplitudes or frequencies. This analysis shows that, for a given interaction point of the tree trunk, this decision depends only on the platform’s physical characteristics, such as mass and inertia. Finally, the theoretical analysis is experimentally validated with a hand-made bamboo tree and a fully-actuated platform through indoors flights.