RDA: An Accelerated Collision Free Motion Planner for Autonomous Navigation in Cluttered Environments

Autonomous motion planning is challenging in multi-obstacle environments due to nonconvex collision avoidance constraints. Directly applying numerical solvers to these nonconvex formulations fails to exploit the constraint structures, resulting in excessive computation time. In this paper, we present an accelerated collision-free motion planner, namely regularized dual alternating direction method of multipliers (RDADMM or RDA for short), for the model predictive control (MPC) based motion planning problem. The proposed RDA addresses nonconvex motion planning via solving a smooth biconvex reformulation via duality and allows the collision avoidance constraints to be computed in parallel for each obstacle to reduce computation time significantly. We validate the performance of the RDA planner through path-tracking experiments with car-like robots in both simulation and real-world settings. Experimental results show that the proposed method generates smooth collision-free trajectories with less computation time compared with other benchmarks and performs robustly in cluttered environments. The source code is available at https://github.com/hanruihua/RDA_planner.Comment: Published in: IEEE Robotics and Automation Letters ( Volume: 8, Issue: 3, March 2023) (https://ieeexplore.ieee.org/document/10036019

NeuPAN: Direct Point Robot Navigation with End-to-End Model-based Learning

Navigating a nonholonomic robot in a cluttered environment requires extremely accurate perception and locomotion for collision avoidance. This paper presents NeuPAN: a real-time, highly-accurate, map-free, robot-agnostic, and environment-invariant robot navigation solution. Leveraging a tightly-coupled perception-locomotion framework, NeuPAN has two key innovations compared to existing approaches: 1) it directly maps raw points to a learned multi-frame distance space, avoiding error propagation from perception to control; 2) it is interpretable from an end-to-end model-based learning perspective, enabling provable convergence. The crux of NeuPAN is to solve a high-dimensional end-to-end mathematical model with various point-level constraints using the plug-and-play (PnP) proximal alternating-minimization network (PAN) with neurons in the loop. This allows NeuPAN to generate real-time, end-to-end, physically-interpretable motions directly from point clouds, which seamlessly integrates data- and knowledge-engines, where its network parameters are adjusted via back propagation. We evaluate NeuPAN on car-like robot, wheel-legged robot, and passenger autonomous vehicle, in both simulated and real-world environments. Experiments demonstrate that NeuPAN outperforms various benchmarks, in terms of accuracy, efficiency, robustness, and generalization capability across various environments, including the cluttered sandbox, office, corridor, and parking lot. We show that NeuPAN works well in unstructured environments with arbitrary-shape undetectable objects, making impassable ways passable.Comment: submit to TR

Nanoengineering surface wettability via metal-phenolic networks

© 2019 Shuaijun PanSurface engineering is extensively involved in many industrial processes as well as diverse research applications including the engineering of catalysts, nanoparticles, coatings, membranes, gels, and other materials. In general, the purpose of surface engineering is to alter the physical or chemical surface properties on the molecular, nano-, micro-, or macroscale in order to target desired applications. Surface wetting, a ubiquitous natural interfacial phenomenon, is one of the most important yet least understood surface properties useful for addressing a broad range of practical and scientific issues. Surface wetting is also important for various global challenges such as the emerging energy and environment crises, and various health and safety concerns. One particularly “hot” scientific topic surrounding surface wetting is engineering coatings to render surfaces with tailored wettability, including coatings that are hydrophilic, hydrophobic, oleophobic, responsive, or versatile. Metal-phenolic networks, coordination assemblies between metal ions and polyphenols, are emerging conformal coating materials useful for versatile surface engineering, including the engineering of nanomaterials and bio-interfaces. Polyphenols, which are abundant in natural sources as well as synthetic chemicals, have outstanding physicochemical properties besides metal chelation, such as reactive chemical groups, special interfacial interactions, and controllable bioactivity, and thus provide vast potentials in the field of advanced surface modifications. However, the potential of polyphenols in surface wetting has rarely been investigated, leaving the fundamental understanding necessary for advanced surface design and surface wetting largely unclear and incomplete. Therefore, this thesis aims to provide an overview of the wetting potential of metal-phenolic networks and to provide fundamental understandings for engineering advanced surface wetting. Specifically, this thesis investigates engineering surfaces on the levels of chemical structure, coating composition, and substrate hierarchy. Finally, some emerging applications for metal-phenolic networks with tailored surface wetting are presented. The scope of this thesis is the engineering and exploitation of the surface wetting of metal-phenolic networks. The wetting fundamentals of metal-phenolic networks are first explored through the systematic study of coatings prepared from a wide range of polyphenolic ligands and a collection of metal ions on diverse substrates utilizing a series of coating methods. The intrinsic wetting properties, together with the active surface nature, were then successfully exploited for various applications including catalysis, oil-water separations, air filtration, and self-cleaning. The toolbox applicable building blocks for making metal-phenolic materials was enlarged by introducing the concept of host-guest chemistry—host functionality is incorporated into metal-phenolic networks where guest molecules can specifically bind with the host motifs within the surface coating. In addition to the facile control over surface wetting and specific binding, the host-guest metal-phenolic networks can also potentially help tackle incompatibility problems encountered in the design of materials for advanced interfacial interactions. Finally, dynamic metal-phenolic networks capable of adaptively interacting with a range of liquids were engineered. The resultant adaptive surface wetting, along with the broad wetting potentials of the metal-phenolic networks, is expected to contribute to the engineering of advanced surface coatings and find applications in other fields requiring tunable interactions

In Vivo Evaluation of a Novel Oriented Scaffold-BMSC Construct for Enhancing Full-Thickness Articular Cartilage Repair in a Rabbit Model.

Tissue engineering (TE) has been proven usefulness in cartilage defect repair. For effective cartilage repair, the structural orientation of the cartilage scaffold should mimic that of native articular cartilage, as this orientation is closely linked to cartilage mechanical functions. Using thermal-induced phase separation (TIPS) technology, we have fabricated an oriented cartilage extracellular matrix (ECM)-derived scaffold with a Young's modulus value 3 times higher than that of a random scaffold. In this study, we test the effectiveness of bone mesenchymal stem cell (BMSC)-scaffold constructs (cell-oriented and random) in repairing full-thickness articular cartilage defects in rabbits. While histological and immunohistochemical analyses revealed efficient cartilage regeneration and cartilaginous matrix secretion at 6 and 12 weeks after transplantation in both groups, the biochemical properties (levels of DNA, GAG, and collagen) and biomechanical values in the oriented scaffold group were higher than that in random group at early time points after implantation. While these differences were not evident at 24 weeks, the biochemical and biomechanical properties of the regenerated cartilage in the oriented scaffold-BMSC construct group were similar to that of native cartilage. These results demonstrate that an oriented scaffold, in combination with differentiated BMSCs can successfully repair full-thickness articular cartilage defects in rabbits, and produce cartilage enhanced biomechanical properties

Superomniphobic Surfaces for Effective Chemical Shielding

Superomniphobic surfaces display contact angles >150° and low contact angle hysteresis with essentially all contacting liquids. In this work, we report surfaces that display superomniphobicity with a range of different non-Newtonian liquids, in addition to superomniphobicity with a wide range of Newtonian liquids. Our surfaces possess hierarchical scales of re-entrant texture that significantly reduce the solid–liquid contact area. Virtually all liquids including concentrated organic and inorganic acids, bases, and solvents, as well as viscoelastic polymer solutions, can easily roll off and bounce on our surfaces. Consequently, they serve as effective chemical shields against virtually all liquidsorganic or inorganic, polar or nonpolar, Newtonian or non-Newtonian

Superomniphobic Surfaces for Effective Chemical Shielding

Superomniphobic surfaces display contact angles >150° and low contact angle hysteresis with essentially all contacting liquids. In this work, we report surfaces that display superomniphobicity with a range of different non-Newtonian liquids, in addition to superomniphobicity with a wide range of Newtonian liquids. Our surfaces possess hierarchical scales of re-entrant texture that significantly reduce the solid–liquid contact area. Virtually all liquids including concentrated organic and inorganic acids, bases, and solvents, as well as viscoelastic polymer solutions, can easily roll off and bounce on our surfaces. Consequently, they serve as effective chemical shields against virtually all liquidsorganic or inorganic, polar or nonpolar, Newtonian or non-Newtonian

Superomniphobic Surfaces for Effective Chemical Shielding

Superomniphobic surfaces display contact angles >150° and low contact angle hysteresis with essentially all contacting liquids. In this work, we report surfaces that display superomniphobicity with a range of different non-Newtonian liquids, in addition to superomniphobicity with a wide range of Newtonian liquids. Our surfaces possess hierarchical scales of re-entrant texture that significantly reduce the solid–liquid contact area. Virtually all liquids including concentrated organic and inorganic acids, bases, and solvents, as well as viscoelastic polymer solutions, can easily roll off and bounce on our surfaces. Consequently, they serve as effective chemical shields against virtually all liquidsorganic or inorganic, polar or nonpolar, Newtonian or non-Newtonian

Superomniphobic Surfaces for Effective Chemical Shielding

Superomniphobic surfaces display contact angles >150° and low contact angle hysteresis with essentially all contacting liquids. In this work, we report surfaces that display superomniphobicity with a range of different non-Newtonian liquids, in addition to superomniphobicity with a wide range of Newtonian liquids. Our surfaces possess hierarchical scales of re-entrant texture that significantly reduce the solid–liquid contact area. Virtually all liquids including concentrated organic and inorganic acids, bases, and solvents, as well as viscoelastic polymer solutions, can easily roll off and bounce on our surfaces. Consequently, they serve as effective chemical shields against virtually all liquidsorganic or inorganic, polar or nonpolar, Newtonian or non-Newtonian

Superomniphobic Surfaces for Effective Chemical Shielding

Superomniphobic surfaces display contact angles >150° and low contact angle hysteresis with essentially all contacting liquids. In this work, we report surfaces that display superomniphobicity with a range of different non-Newtonian liquids, in addition to superomniphobicity with a wide range of Newtonian liquids. Our surfaces possess hierarchical scales of re-entrant texture that significantly reduce the solid–liquid contact area. Virtually all liquids including concentrated organic and inorganic acids, bases, and solvents, as well as viscoelastic polymer solutions, can easily roll off and bounce on our surfaces. Consequently, they serve as effective chemical shields against virtually all liquidsorganic or inorganic, polar or nonpolar, Newtonian or non-Newtonian

High-Performance Cathode Material of FeF3·0.33H2O Modified with Carbon Nanotubes and Graphene for Lithium-Ion Batteries

Abstract The FeF3·0.33H2O cathode material can exhibit a high capacity and high energy density through transfer of multiple electrons in the conversion reaction and has attracted great attention from researchers. However, the low conductivity of FeF3·0.33H2O greatly restricts its application. Generally, carbon nanotubes (CNTs) and graphene can be used as conductive networks to improve the conductivities of active materials. In this work, the FeF3·0.33H2O cathode material was synthesized via a liquid-phase method, and the FeF3·0.33H2O/CNT + graphene nanocomposite was successfully fabricated by introduction of CNTs and graphene conductive networks. The electrochemical results illustrate that FeF3·0.33H2O/CNT + graphene nanocomposite delivers a high discharge capacity of 234.2 mAh g−1 in the voltage range of 1.8–4.5 V (vs. Li+/Li) at 0.1 C rate, exhibits a prominent cycling performance (193.1 mAh g−1 after 50 cycles at 0.2 C rate), and rate capability (140.4 mAh g−1 at 5 C rate). Therefore, the electronic conductivity and electrochemical performance of the FeF3·0.33H2O cathode material modified with CNTs and graphene composite conductive network can be effectively improved