SPIBOT: A Drone-Tethered Mobile Gripper for Robust Aerial Object Retrieval in Dynamic Environments

2024-09-24

arXiv.org

AI Summary

Aerial grasping by UAVs frequently fails under strong winds, oscillating decks, and heavy payload disturbances. Method: This paper introduces SPIBOT—a spider-inspired tethered mobile manipulator—that employs a lightweight hexapod robot to autonomously descend along a tethered cable, adhere to, and stably grasp targets, thereby overcoming the limitations of conventional onboard grippers subject to aerodynamic disturbances and payload constraints. Contribution/Results: We propose a novel air-ground cooperative tethered architecture integrating a foldable hexapod structure (enabling UAV carriage), multimodal state estimation (fusing IMU, vision, and tactile sensing), and a real-time hierarchical action decision-making algorithm that jointly incorporates environmental perception and task progress. Experiments demonstrate SPIBOT’s high robustness in dynamic terrains—including lake-floating platforms, grasslands, and coastal sandy areas—achieving reliable grasping of 1-kg objects. It significantly mitigates initial pose errors and sensor noise, markedly improving task success rate.

Technology Category

• Intelligent Robots: Manipulation
• Humans and AI: Human-Aware Planning and Behavior Prediction
• Planning, Routing, and Scheduling: Replanning and Plan Repair

Application Category

• Responsible Web: Machine-in-the-loop, human agency and autonomy
• Systems and Infrastructure for Web, Mobile and WoT: Experiences and lessons learnt from Web-based algorithms and system deployments
• Search and Retrieval-Augmented AI: Assisted, interactive, and conversational search

Abstract

In real-world field operations, aerial grasping systems face significant challenges in dynamic environments due to strong winds, shifting surfaces, and the need to handle heavy loads. Particularly when dealing with heavy objects, the powerful propellers of the drone can inadvertently blow the target object away as it approaches, making the task even more difficult. To address these challenges, we introduce SPIBOT, a novel drone-tethered mobile gripper system designed for robust and stable autonomous target retrieval. SPIBOT operates via a tether, much like a spider, allowing the drone to maintain a safe distance from the target. To ensure both stable mobility and secure grasping capabilities, SPIBOT is equipped with six legs and sensors to estimate the robot's and mission's states. It is designed with a reduced volume and weight compared to other hexapod robots, allowing it to be easily stowed under the drone and reeled in as needed. Designed for the 2024 MBZIRC Maritime Grand Challenge, SPIBOT is built to retrieve a 1kg target object in the highly dynamic conditions of the moving deck of a ship. This system integrates a real-time action selection algorithm that dynamically adjusts the robot's actions based on proximity to the mission goal and environmental conditions, enabling rapid and robust mission execution. Experimental results across various terrains, including a pontoon on a lake, a grass field, and rubber mats on coastal sand, demonstrate SPIBOT's ability to efficiently and reliably retrieve targets. SPIBOT swiftly converges on the target and completes its mission, even when dealing with irregular initial states and noisy information introduced by the drone.

Problem

• Addresses challenges in aerial grasping in dynamic environments.
• Develops a drone-tethered gripper for stable object retrieval.
• Enables robust target retrieval on moving ship decks.

Innovation

• Drone-tethered mobile gripper for stable retrieval
• Six-legged design with sensors for mobility and grasping
• Real-time action selection algorithm for dynamic environments