Publications

2023

1. ICRA 2024

   How Does Perception Affect Safety: New Metrics and Strategy

   Xiaotong Zhang, Jinger Chong , and Kamal Youcef-Toumi

   arXiv preprint arXiv:2312.07744, 2023

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   Perception plays a pivotal role in enhancing the functionality of autonomous agents. However, the intricate relationship between robotic perception metrics and actuation metrics remains unclear, leading to ambiguity in the development and fine-tuning of perception algorithms. In this paper, we introduce a methodology for quantifying this relationship, taking into account factors such as detection rate, detection quality, and latency. Furthermore, we introduce two novel perception metrics for Human-Robot Collaboration safety predicated upon basic perception metrics: Critical Collision Probability (CCP) and Average Collision Probability (ACP). To validate the utility of these metrics in facilitating algorithm development and tuning, we develop an attentive processing strategy that focuses exclusively on key input features. This approach significantly reduces computational time while preserving a similar level of accuracy. Experimental findings demonstrate that integrating this strategy into an object detector results in a notable maximum reduction of 30.09% in inference time and 26.53% in total time per frame. Additionally, the strategy lowers the CCP and ACP in a baseline model by 11.25% and 13.50%, respectively.

   @article{zhang2023does,
     title = {How Does Perception Affect Safety: New Metrics and Strategy},
     author = {Zhang, Xiaotong and Chong, Jinger and Youcef-Toumi, Kamal},
     journal = {arXiv preprint arXiv:2312.07744},
     year = {2023},
   }

2. arXiv

   Enhanced Human-Robot Collaboration using Constrained Probabilistic Human-Motion Prediction

   Aadi Kothari , Tony Tohme , Xiaotong Zhang, and 1 more author

   2023

   Abs arXiv Bib

   Human motion prediction is an essential step for efficient and safe human-robot collaboration. Current methods either purely rely on representing the human joints in some form of neural network-based architecture or use regression models offline to fit hyper-parameters in the hope of capturing a model encompassing human motion. While these methods provide good initial results, they are missing out on leveraging well-studied human body kinematic models as well as body and scene constraints which can help boost the efficacy of these prediction frameworks while also explicitly avoiding implausible human joint configurations. We propose a novel human motion prediction framework that incorporates human joint constraints and scene constraints in a Gaussian Process Regression (GPR) model to predict human motion over a set time horizon. This formulation is combined with an online context-aware constraints model to leverage task-dependent motions. It is tested on a human arm kinematic model and implemented on a human-robot collaborative setup with a UR5 robot arm to demonstrate the real-time capability of our approach. Simulations were also performed on datasets like HA4M and ANDY. The simulation and experimental results demonstrate considerable improvements in a Gaussian Process framework when these constraints are explicitly considered.

   @misc{kothari2023enhanced,
     title = {Enhanced Human-Robot Collaboration using Constrained Probabilistic Human-Motion Prediction},
     author = {Kothari, Aadi and Tohme, Tony and Zhang, Xiaotong and Youcef-Toumi, Kamal},
     year = {2023},
     eprint = {2310.03314},
     archiveprefix = {arXiv},
     primaryclass = {cs.RO},
   }

2022

1. TMECH

   Magnetohydrodynamic energy harvester for low-power pipe instrumentation

   Xiaotong Zhang, and Kamal Youcef-Toumi

   IEEE/ASME Transactions on Mechatronics, 2022

   Awareded Abs Bib PDF

   2023 Best Paper Award of TMECH

   Smart pipes can be adopted as a solution to problems in water distribution systems. However, the real application of such a system is usually constrained by power delivery. In this article, a magnetohydrodynamic (MHD) energy harvester for low-power pipe instrumentation is developed. A theoretical model of the maximum power output containing parameters of water conductivity, flow velocity, magnetic flux density, and water channel volume is derived. To enhance the magnetic flux density, a magnetic concentrator is designed and carefully tuned to arrange the magnetic flux as we desire and magnify the magnetic flux density within the channels. A spiral flow diverter is proposed to reconfigure the original pipe flow pattern and divert the flow into the surrounding channels to enhance the flow velocity. After integrating the proposed improvements from different fields and globally optimizing the power output, a final design is prototyped and tested in the lab, which achieves a maximum power output of 87.47 nW with a 2-m/s pipe inlet velocity. To the best of our knowledge, this is the first MHD energy harvester for low-power sensor networks. Its great potential is demonstrated, and several potential enhancements to the power output are proposed and analyzed.

   @article{zhang2022magnetohydrodynamic,
     title = {Magnetohydrodynamic energy harvester for low-power pipe instrumentation},
     author = {Zhang, Xiaotong and Youcef-Toumi, Kamal},
     journal = {IEEE/ASME Transactions on Mechatronics},
     volume = {27},
     number = {6},
     pages = {4718--4728},
     year = {2022},
     publisher = {IEEE},
   }

2. IROS 2022

   Systematic evaluation and analysis on hybrid strategies of automatic agent last-mile delivery

   Xiaotong Zhang, Abdullatif Al Alsheikh , and Kamal Youcef-Toumi

   In 2022 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) , 2022

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   This paper focuses on problems associated with the deployment of automatic agents for last-mile delivery. We propose a framework and methodology to systematically evaluate and compare different hybrid strategies. Performance metrics in agent noise, delivery time, energy consumption, coverage rate, package throughput, and system costs are defined rigorously and modeled mathematically. Using the methodology, we conduct a case study in the city of Boston for four agent delivery strategies, including a hybrid strategy proposed in this paper. The proposed strategy utilizes available space in public transits’ cabins during off-peak hours to relocate the agent traveling start locations. Simulations and analyses show that hybrid strategies outperform the Agent-Only delivery strategy in terms of noise exposure, energy consumption, and coverage rate. The performance of hybrid strategies highly depends on the characteristics of the ground transportation methods accompanying agents. Thus, the methods of ground transportation should carefully be examined and selected for each case and strategy in real-world applications.

   @inproceedings{zhang2022systematic,
     title = {Systematic evaluation and analysis on hybrid strategies of automatic agent last-mile delivery},
     author = {Zhang, Xiaotong and Al Alsheikh, Abdullatif and Youcef-Toumi, Kamal},
     booktitle = {2022 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)},
     pages = {2733--2740},
     year = {2022},
     organization = {IEEE},
   }

2021

1. Mechatronics

   A modular low-cost atomic force microscope for precision mechatronics education

   Fangzhou Xia , James Quigley , Xiaotong Zhang, and 3 more authors

   Mechatronics, 2021

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   Precision mechatronics and nanotechnology communities can both benefit from a course centered around an Atomic Force Microscope (AFM). Developing an AFM can provide precision mechatronics engineers with a valuable multidisciplinary hands-on training experience. In return, such expertise can be applied to the design and implementation of new precision instruments, which helps nanotechnology researchers make new scientific discoveries. However, existing AFMs are not suitable for mechatronics education due to their different original design intentions. Therefore, we address this challenge by developing an AFM intended for precision mechatronics education.This paper presents the design and implementation of an educational AFM and its corresponding precision mechatronics class. The modular educational AFM is low-cost (4,000) and easy to operate. The cost reduction is enabled by new subsystem development of a buzzer-actuated scanner and demodulation electronics designed to interface with a myRIO data acquisition system. Moreover, the use of an active cantilever probe with piezoresistive sensing and thermomechanical actuation significantly reduced experiment setup overhead with improved operational safety. In the end, the developed AFM capabilities are demonstrated with imaging results. The paper also showcases the course design centered around selected subsystems. The new AFM design allows scientific-method-based learning, maximizes utilization of existing resources, and offers potential subsystem upgrades for high-end research applications. The presented instrument and course can help connect members of both the AFM and the mechatronics communities to further develop advanced techniques for new applications.

   @article{xia2021modular,
     title = {A modular low-cost atomic force microscope for precision mechatronics education},
     author = {Xia, Fangzhou and Quigley, James and Zhang, Xiaotong and Yang, Chen and Wang, Yi and Youcef-Toumi, Kamal},
     journal = {Mechatronics},
     volume = {76},
     pages = {102550},
     year = {2021},
     publisher = {Elsevier},
   }

2019

1. Thesis

   Design and optimization of an MHD energy harvester for intelligent pipe systems

   Xiaotong Zhang

   Massachusetts Institute of Technology , 2019

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   In this thesis, an innovative Magnetohydrodynamic (MHD) energy harvester with the use of the magnetic concentrator is designed and optimized. A theoretical model relating the conductivity of water, magnetic flux density B, flow velocity u and the channel volume to the power output is first established. This leads to the decoupled analysis and simulations of magnetic field and flow field. The prototyped energy harvester without the concentrator achieves a power output of 442 nW, while the power output of the final design with the concentrator is expected to be 718.5 nW. The concept of another MHD energy harvester with a spiral flow diverter is also established with hollow space in the middle of the energy harvester for flow and robots to pass through. It is validated by CFD simulations that the flow velocity in the channel surrounding the hollow area is greatly amplified with the spiral flow diverter. The MHD energy harvester with the concentrators and spiral flow divereter is expected to produce power output of 238.3 nW.

   @phdthesis{zhang2019design,
     title = {Design and optimization of an MHD energy harvester for intelligent pipe systems},
     author = {Zhang, Xiaotong},
     year = {2019},
     school = {Massachusetts Institute of Technology},
   }

2017

1. ISOPE 2017

   Numerical study of oscillatory dual cylinders in tandem arrangement

   Xiaotong Zhang, Dixia Fan , and Decheng Wan

   In ISOPE International Ocean and Polar Engineering Conference , 2017

   Bib

   @inproceedings{zhang2017numerical,
     title = {Numerical study of oscillatory dual cylinders in tandem arrangement},
     author = {Zhang, Xiaotong and Fan, Dixia and Wan, Decheng},
     booktitle = {ISOPE International Ocean and Polar Engineering Conference},
     pages = {ISOPE--I},
     year = {2017},
     organization = {ISOPE},
   }

2. ISOPE 2017

   Drag coefficient enhancement of dual cylinders in oscillatory flow

   Dixia Fan , Xiaotong Zhang, and Michael S Triantafyllou

   In ISOPE International Ocean and Polar Engineering Conference , 2017

   Bib

   @inproceedings{fan2017drag,
     title = {Drag coefficient enhancement of dual cylinders in oscillatory flow},
     author = {Fan, Dixia and Zhang, Xiaotong and Triantafyllou, Michael S},
     booktitle = {ISOPE International Ocean and Polar Engineering Conference},
     pages = {ISOPE--I},
     year = {2017},
     organization = {ISOPE},
   }

3. CJH

   Numerical Study of Wave-current Loads Acting on Foundation of Fixed Offshore Wind Turbine”

   Yao Peng , Xiaotong Zhang, Decheng Wan , and 1 more author

   Chinese Journal of Hydrodynamics A, 2017

   Bib

   @article{Peng2017Numerical,
     title = {Numerical Study of Wave-current Loads Acting on Foundation of Fixed Offshore Wind Turbine”},
     author = {Peng, Yao and Zhang, Xiaotong and Wan, Decheng and Huang, Caiyun},
     journal = {Chinese Journal of Hydrodynamics A},
     number = {1},
     year = {2017},
   }

2016

1. CCSH

   Numerical analysis of the coupling response of a semi-submersible platform with its mooring system

   Xiaotong Zhang, Yao Peng , and Decheng Wan

   2016

   Bib

   @article{zhang2016numerical,
     title = {Numerical analysis of the coupling response of a semi-submersible platform with its mooring system},
     author = {Zhang, Xiaotong and Peng, Yao and Wan, Decheng},
     year = {2016},
   }