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Rapid Manufacturing of Lightweight Drone Frames Using Single-Tow Architected Composites

arXiv.org Artificial Intelligence

The demand for lightweight and high-strength composite structures is rapidly growing in aerospace and robotics, particularly for optimized drone frames. However, conventional composite manufacturing methods struggle to achieve complex 3D architectures for weight savings and rely on assembling separate components, which introduce weak points at the joints. Additionally, maintaining continuous fiber reinforcement remains challenging, limiting structural efficiency. In this study, we demonstrate the lightweight Face Centered Cubic (FFC) lattice structured conceptualization of drone frames for weight reduction and complex topology fabrication through 3D Fiber Tethering (3DFiT) using continuous single tow fiber ensuring precise fiber alignment, eliminating weak points associated with traditional composite assembly. Mechanical testing demonstrates that the fabricated drone frame exhibits a high specific strength of around four to eight times the metal and thermoplastic, outperforming other conventional 3D printing methods. The drone frame weighs only 260 g, making it 10% lighter than the commercial DJI F450 frame, enhancing structural integrity and contributing to an extended flight time of three minutes, while flight testing confirms its stability and durability under operational conditions. The findings demonstrate the potential of single tow lattice truss-based drone frames, with 3DFiT serving as a scalable and efficient manufacturing method.


Exploring Stiffness Gradient Effects in Magnetically Induced Metamorphic Materials via Continuum Simulation and Validation

arXiv.org Artificial Intelligence

Magnetic soft continuum robots are capable of bending with remote control in confined space environments, and they have been applied in various bioengineering contexts. As one type of ferromagnetic soft continuums, the Magnetically Induced Metamorphic Materials (MIMMs)-based continuum (MC) exhibits similar bending behaviors. Based on the characteristics of its base material, MC is flexible in modifying unit stiffness and convenient in molding fabrication. However, recent studies on magnetic continuum robots have primarily focused on one or two design parameters, limiting the development of a comprehensive magnetic continuum bending model. In this work, we constructed graded-stiffness MCs (GMCs) and developed a numerical model for GMCs' bending performance, incorporating four key parameters that determine their performance. The simulated bending results were validated with real bending experiments in four different categories: varying magnetic field, cross-section, unit stiffness, and unit length. The graded-stiffness design strategy applied to GMCs prevents sharp bending at the fixed end and results in a more circular curvature. We also trained an expansion model for GMCs' bending performance that is highly efficient and accurate compared to the simulation process. An extensive library of bending prediction for GMCs was built using the trained model.


Vision-Based Defect Classification and Weight Estimation of Rice Kernels

arXiv.org Artificial Intelligence

Rice is one of the main staple food in many areas of the world. The quality estimation of rice kernels are crucial in terms of both food safety and socio-economic impact. This was usually carried out by quality inspectors in the past, which may result in both objective and subjective inaccuracies. In this paper, we present an automatic visual quality estimation system of rice kernels, to classify the sampled rice kernels according to their types of flaws, and evaluate their quality via the weight ratios of the perspective kernel types. To compensate for the imbalance of different kernel numbers and classify kernels with multiple flaws accurately, we propose a multi-stage workflow which is able to locate the kernels in the captured image and classify their properties. We define a novel metric to measure the relative weight of each kernel in the image from its area, such that the relative weight of each type of kernels with regard to the all samples can be computed and used as the basis for rice quality estimation. Various experiments are carried out to show that our system is able to output precise results in a contactless way and replace tedious and error-prone manual works.


Spiral Zipper Creates Robot Arm Out of a Strip of Plastic

IEEE Spectrum Robotics

As useful as robot arms are, they tend to be heavy, bulky things that need a bunch of support and structure to get them to work properly. If you need precision and speed, this may be unavoidable, but if all you're looking for is long reach, a high-strength to weight ratio, and very low cost (which, admittedly, are a lot of things to be looking for), another option was presented at ICRA today by researchers from the University of Pennsylvania: an arm made out of a strip of plastic that zips together with itself, creating an extendable cylinder that can be paired with winches and cables and used for manipulation. This concept is similar in principle to some commercially available systems like the Zippermast and Spiralift, but both of those designs are heavier and significantly more complicated. The spiral zipper uses a single band that's made of very lightweight plastic, with a relatively simple meshing mechanism that meshes the teeth on the bottom edge of one wrap with the teeth on the top of the wrap below to create a cylinder that has a very high strength to weight ratio, with exceptionally good compressive performance. And changing the length of the arm is as simple as zipping or unzipping the band: it's completely reversible, and you can stow the arm almost entirely in a very small volume consisting of the plastic band spooled around the zipping mechanism.


Learning to Reject Sequential Importance Steps for Continuous-Time Bayesian Networks

AAAI Conferences

Applications of graphical models often require the use of approximate inference, such as sequential importance sampling (SIS), for estimation of the model distribution given partial evidence, i.e., the target distribution. However, when SIS proposal and target distributions are dissimilar, such procedures lead to biased estimates or require a prohibitive number of samples. We introduce ReBaSIS, a method that better approximates the target distribution by sampling variable by variable from existing importance samplers and accepting or rejecting each proposed assignment in the sequence: a choice made based on anticipating upcoming evidence. We relate the per-variable proposal and model distributions by expected weight ratios of sequence completions and show that we can learn accurate models of optimal acceptance probabilities from local samples. In a continuous-time domain, our method improves upon previous importance samplers by transforming an SIS problem into a machine learning one.