Problem
Research questions and friction points this paper is trying to address.
mobile manipulator
long-term plant monitoring
open-source robotics
sensor occlusion
arm reachability
ALFRED: Requirement-driven development of an open-source mobile manipulator for long-term plant monitoring
🤖 AI Summary
This study addresses the challenges of enclosed robot designs, limited manipulator reachability, and sensor occlusion in long-term plant monitoring by proposing an open-source mobile manipulation platform built from commercial off-the-shelf components. Through quantitative analysis of structural impacts on reachability, the manipulator workspace and perceptual field of view are iteratively optimized. The system integrates an Ackermann-steering chassis, a six-degree-of-freedom manipulator, LiDAR/RGB-D multimodal sensing, and a containerized ROS software stack to achieve a durable, reproducible, and modular design. Experimental results demonstrate that the effective reachable pose ratio increases to 66.1% while completely eliminating LiDAR occlusion. Furthermore, the platform successfully completed 528 monthly forest surveys with zero missed measurements, validating its reliability for year-round outdoor field operations.
📝 Abstract
Tracking seasonal change in crops and forests requires observing the same plants repeatedly. Ground robots can do this at close range, and a manipulator gives their sensors more viewpoints. Yet the robots behind long-term field datasets are rarely released with their design files, and how a robot's own structure limits arm reach and occludes its sensors is seldom compared between builds. We present ALFRED, an open-source mobile manipulator built from commercially available components. It carries a six-degree-of-freedom arm, LiDAR, RGB-D cameras, RTK GNSS and an IMU on an Ackermann-steered base, all mounted on a reconfigurable aluminium strut frame, and runs containerised ROS software. It was developed through four builds against six requirements for repeated outdoor deployment: durability, modularity, repairability, sensing reach, endurance and reproducibility. Model-based analysis of the last three builds shows the usable share of the arm's reachable poses rising from 34.0% to 60.0% and then 66.1%, and ray casting shows that only the final build keeps the frame-mounted LiDAR's horizontal view clear both forwards and backwards. ALFRED completed a year of monthly forest surveys (528 traversals) without missing a scheduled collection. This was despite battery degradation, reconfiguration for another researcher's study, and the parallel development of ALFRED 2.0 for autonomous crop-row operation, with each switch between builds taking about six hours. The deployment also showed that mechanical modularity is only as dependable as the robot description that tracks it.
Innovation
Methods, ideas, or system contributions that make the work stand out.
mobile manipulator
open-source robotics
long-term plant monitoring
modularity
ray casting
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