Jiajun Xu

Nanjing University of Aeronautics and Astronautics

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Linsen Xu

Hohai University

Jinfu Liu

Fujian Agriculture and Forestry University

Shouqi Chen

University of Science and Technology of China

Gaoxin Cheng

University of Science and Technology of China

Aihong Ji

Nanjing University of Aeronautics and Astronautics

Guanghui Gao

Advanced Institute of Materials Science

Hong Xu

Xi'an Jiaotong University

Jia Shi

Ruijin Hospital

Youfu Li

City University of Hong Kong

Xingcan Liang

Hefei Institutes of Physical Science

Cooperative Institutions

Nanjing University of Aeronautics and Astronautics

Chinese Academy of Sciences

University of Science and Technology of China

Jilin University

Hefei Institutes of Physical Science

Yunnan Agricultural University

Zhejiang University

Shanghai Jiao Tong University

Tongji University

Tsinghua University

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Distributed Hovering Formation Method based on Multi-objective Trajectory Optimization for UAVs

Jiajun Xu Chaofang Hu Didi Wang

Trajectory Optimization

10.23919/ccc63176.2024.10661391

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Citations (0)

Laboratory investigation of the relationship between electrical resistivity and geotechnical properties of phosphate tailings

Measurement (2018)

Yulong Chen Zuoan Wei Muhammad Irfan Jiajun Xu Yonghao Yang

Consolidation

Oedometer test

Cohesion (chemistry)

Direct shear test

Shear Strength

10.1016/j.measurement.2018.05.095

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Citations (27)

A Multi-Mode Biomimetic Wall-Climbing Robot

2022 IEEE 18th International Conference on Automation Science and Engineering (CASE) (2018)

Jiajun Xu Linsen Xu Jinfu Liu Xiaohu Li Xuan Wu

In this paper, a multi-mode biomimetic wall-climbing robot is represented, which employs spiny wheels, adhesive treads, spiny treads and a suction cup, and it can switch different modes with self-adapting to different terrains. The robot employs spiny wheels and spiny treads while meeting with rough surfaces and employs adhesive treads while encountering smooth surfaces. And a suction cup is applied all the time for assistive adhesive function. The adhesion property of the adhesive materials is analyzed, and their high reliability is proved. Moreover, the prototype of the robot is manufactured, and some experiments are completed.

Climbing

Suction cup

Mode (computer interface)

10.1109/coase.2018.8560382

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Citations (4)

Robotic mirror therapy system for lower limb rehabilitation

Industrial Robot the international journal of robotics research and application (2020)

Gaoxin Cheng Linsen Xu Jiajun Xu Jinfu Liu Jia Shi

Purpose This paper aims to develop a robotic mirror therapy system for lower limb rehabilitation, which is applicable for different patients with individual movement disability levels. Design/methodology/approach This paper puts forward a novel system that includes a four-degree-of-freedom sitting/lying lower limb rehabilitation robot and a wireless motion data acquisition system based on mirror therapy principle. The magnetorheological (MR) actuators are designed and manufactured, whose characteristics are detected theoretically and experimentally. The passive training control strategy is proposed, and the trajectory tracking experiments verify its feasibility. Also, the active training controller that is adapt to the human motor ability is designed and evaluated by the comparison experiments. Findings The MR actuators produce continuously variable and compliant torque for robotic joints by adjusting excitation current. The reference limb joint position data collected by the wireless motion data acquisition system can be used as the motion trajectory of the robot to drive the affected limb. The passive training strategy based on proportional-integral control proves to have great trajectory tracking performance through experiments. In the active training mode, by comparing the real-time parameters adjustment in two phases, it is certified that the proposed fuzzy-based regulated impedance controller can adjust assistance torque according to the motor ability of the affected limb. Originality/value The system developed in this paper fulfills the needs of robot-assisted mirror therapy for hemiplegic patients.

10.1108/ir-06-2020-0112

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Citations (7)

A Soft Supernumerary Robotic Limb with Fiber-Reinforced Actuators

Journal of Intelligent & Robotic Systems (2024)

Jiajun Xu Tianyi Zhang Kaizhen Huang Mengcheng Zhao Xuyan Hou

Abstract Supernumerary robotic limbs (SRLs) have great potentials to assist human in daily activities and industrial manufacturing by providing extra limbs. However, current SRLs have heavy and rigid structures that may threaten the operator safety; moreover, their limited degrees of freedom and movement modes are not suitable for complicated tasks. Although soft SRLs have exhibited advantages in structure compliance and flexible manipulation to address these problems, it remains challenging to accurately design the geometrical parameters to adapt to specific tasks, and accurate control is also required to realize the expected movement. Inspired by the biological characteristics of the octopus arm muscle fibers, fiber-reinforced actuators (FRAs) are employed to realize various motions, including extension, expansion, bending, and twisting; multiple FRAs are assembled to implement the SRL to achieve complex movement trajectories. The analytic model of the FRA is established to reveal the relationship between its deformation and geometrical parameters as well as input air pressures, which is validated with finite element simulation. Trajectory and payload optimization algorithms are proposed to optimally design the SRL and its control strategy with meeting the prescribed requirement of movement trajectory and payload capacity. Finally, experiments are conducted to validate the proposed robotic system.

Soft Robotics

10.1007/s10846-024-02102-6

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Citations (1)

A Multi-Channel Reinforcement Learning Framework for Robotic Mirror Therapy

IEEE Robotics and Automation Letters (2020)

Jiajun Xu Linsen Xu Youfu Li Gaoxin Cheng Jia Shi

In the letter, a robotic framework is proposed for hemiparesis rehabilitation. Mirror therapy is applied to transfer therapeutic training from the patient's function limb (FL) to the impaired limb (IL). The IL mimics the action prescribed by the FL with the assistance of the wearable robot, stimulating and strengthening the injured muscles through repetitive exercise. A master-slave robotic system is presented to implement the mirror therapy. Especially, the reinforcement learning is involved in the human-robot interaction control to enhance the rehabilitation efficacy and guarantee safety. Multi-channel sensed information, including the motion trajectory, muscle activation and the user's emotion, are incorporated in the learning algorithm. The muscle activation is expressed via the skin surface electromyography (EMG) signals, and the emotion is shown as the facial expression. The reinforcement learning approach is realized by the normalized advantage functions (NAF) algorithm. Then, a lower extremity rehabilitation robot with magnetorheological (MR) actuators is specially developed. The clinical experiments are carried out using the robot to verify the performance of the framework.

Transfer of learning

10.1109/lra.2020.3007408

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Citations (27)

Design and study of a biomimetic wall-climbing robot with spine wheels and a vacuum suction cup

2022 IEEE International Conference on Real-time Computing and Robotics (RCAR) (2019)

Jinfu Liu Linsen Xu Shouqi Chen Hong Xu Gaoxin Cheng

Wall-climbing robots can be widely applied in search and rescue, nuclear power plant maintenance, pressure pipeline inspection and so on, as a kind of special robots in extreme environment. However, the traditional single motion mode can not ensure the stable adhesion of the robot on complex wall surfaces. Inspired by the structure characteristics of flies and clingfish, a biomimetic flexible spine wheel and an eddy suction cup mechanism are proposed. Then, based on the law of mechanism configuration synthesis, a novel wall-climbing locomotion mechanism is developed by equipping these above biomimetic mechanisms. With the elastic mechanics theory of finite element, the original stiffness matrix of a single spine wheel at different stiffness is deduced. Based on the transformation mechanism of rotation matrix and the original stiffness matrix of the spine wheel, an innovative contact model is set up to analyze the forces acting on a single spine wheel. Beyond that, mechanical analysis model between suction force and load is also presented, and the simulation results show that the mechanical model is effective and reasonable in the selection of vacuum component. Finally, we fabricated the wall-climbing robot adopting the technology of 3D printing and precision machining to verify its climbing performance. Meanwhile, experiment results present the robot could climb stably on the 0-360° wall surfaces.

Climb

10.1109/rcar47638.2019.9044028

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Citations (1)

Cartilage-inspired hydrogel strain sensors with ultrahigh toughness, good self-recovery and stable anti-swelling properties

Journal of Materials Chemistry A (2019)

Jiajun Xu Rining Jin Xiuyan Ren Guanghui Gao

Conventional hydrogels inevitably “swell” under liquid or physiological conditions, which drastically destroys their mechanical properties, severely limiting their practical applicability.

Strain (injury)

10.1039/c9ta09170j

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Citations (135)

Human-in-the-Loop Modeling and Bilateral Skill Transfer Control of Soft Exoskeleton

Sensors (2024)

Jiajun Xu Kaizhen Huang Mengcheng Zhao Jinfu Liu

Soft exoskeletons (exosuits) are expected to provide a comfortable wearing experience and compliant assistance compared with traditional rigid exoskeleton robots. In this paper, an exosuit with twisted string actuators (TSAs) is developed to provide high-strength and variable-stiffness actuation for hemiplegic patients. By formulating the analytic model of the TSA and decoding the human impedance characteristic, the human-exosuit coupled dynamic model is constructed. An adaptive impedance controller is designed to transfer the skills of the patient's healthy limb (HL) to the bilateral impaired limb (IL) with a mirror training strategy, including the movement trajectory and stiffness profiles. A reinforcement learning (RL) algorithm is proposed to optimize the robotic assistance by adapting the impedance model parameters to the subject's performance. Experiments are conducted to demonstrate the effectiveness and superiority of the proposed method.

Soft Robotics

Human-in-the-loop

10.3390/s24237845

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Citations (0)

Ultrastretchable Wearable Strain and Pressure Sensors Based on Adhesive, Tough, and Self-healing Hydrogels for Human Motion Monitoring

ACS Applied Materials & Interfaces (2019)

Jiajun Xu Guangyu Wang Yufan Wu Xiuyan Ren Guanghui Gao

Currently, flexible wearable hydrogel-based sensors have attracted considerable attention due to their promising applications in a variety of fields. However, concurrently integrating toughness, adhesiveness, self-healing ability, and conductivity into the hydrogel is still a great challenge. Here, casein sodium salt from bovine milk (sodium casein, SC) and polydopamine (PDA, inspired by mussels) were successfully introduced into the polyacrylamide (PAAm) hydrogel system to fabricate a tough and adhesive SC-PDA hydrogel. The hydrogel exhibits splendidly reversible adhesive behavioral bonding toward various materials and even human skin. Moreover, based on the dynamic cross-linking of SC and PDA in the system, the hydrogel has superstretching ability, excellent fatigue resistance, and rapid self-healing ability. In addition, the existence of sodium ions also endowed the SC-PDA hydrogel with sensitive deformation-dependent conductivity to act as a flexible strain and pressure sensor for directly monitoring large-scale human motions (e.g., joint bending) and tiny physiological signals (e.g., speaking and breathing). Therefore, the strategy would broaden the path of a new generation of hydrogel-based sensors for wide applications.

Human motion

10.1021/acsami.9b08369

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Citations (188)