X.P. Liu

Jiangnan University, Wuxi, Jiangsu Sheng, China

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Publications (10)8.57 Total impact

  • H. Wang, X.P. Liu
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    ABSTRACT: This paper presents a new adaptive servo-level shared control scheme for a mobile assistive robot that aims at assisting senior and disabled people to transport heavy objects in a complex environment with obstacles. Several technical problems and challenges related to the assistive robotic system and the shared controller are addressed. Specifically, a nonlinear tracking controller is developed for the robot to follow the user. An obstacle avoidance controller is developed based on the deformable virtual zone principle for the robot to avoid obstacles. The adaptive servo-level shared controller utilizes the tracking controller and the obstacle avoidance controller’s outputs to generate a new shared control output to command the robot. Experiments show that the user can guide the movement of the robot safely and smoothly in the complex environment with the developed controllers.
    IEEE/ASME Transactions on Mechatronics 01/2014; 19(6):1725-1736. · 3.14 Impact Factor
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    ABSTRACT: Some diabetic patients experience difficulties in modulating the grip force magnitude when they manipulate objects using their hands. This difficulty is caused by the sensory loss at the fingertips that impairs the feedback loop between the brain and the aforementioned sensors. In this paper, we present a sensory substitution system called “F-Glove”, which is aimed at helping diabetic patients to manipulate objects more efficiently by using appropriate forces. This is achieved by substituting the force felt at the fingertips when grip an object with an audio feedback displayed through the earphones of a mobile phone. The patient wears a glove integrated with pressure sensors mounted on the fingertips, and the sensors' pressure signals are conditioned and wirelessly transmitted to a mobile phone interface to display an audio with a volume linearly proportional to the pressure applied by the fingers of patients.
    Haptic Audio Visual Environments and Games (HAVE), 2013 IEEE International Symposium on; 01/2013
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    Huanran Wang, X.P. Liu
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    ABSTRACT: This paper presents a prototype of noval assistive robotic system, for which the user can interact with a mobile robot using a haptic interface, for senior and disabled people. The system consists of a nonholonomic PeopleBot mobile robot and a Phantom Omni haptic interface. Several technical problems related to the system are addressed and solved. Specifically, a nonlinear tracking algorithm is developed for the robot to follow the user. To preserve the safety operation of the haptic device, a safety control algorithm is applied. Besides, a simple haptic rendering algorithm is designed to generate the haptic feedback based on the position error. Experiments show that the user can guide the movement of the robot quite safely and smoothly using the haptic interface.
    Virtual Environments Human-Computer Interfaces and Measurement Systems (VECIMS), 2012 IEEE International Conference on; 01/2012
  • Huanran Wang, X.P. Liu
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    ABSTRACT: Haptic shared control (HSC) has been widely used in human-robot interaction systems, such as car driving and assistive robots. However, the stability analysis of HSC is not well investigated in current literature, especially for the nonlinear systems. In this paper, the stability of HSC for nonlinear systems is analyzed based on the set theory and convex analysis. The authority weight calculation and haptic rendering algorithm of HSC are developed based on the stability analysis. Then, we apply these algorithms to our assistive robot system. Experimental results show the stable operation of the assistive robot and the effectiveness of the haptic rendering algorithm.
    Haptic Audio Visual Environments and Games (HAVE), 2012 IEEE International Workshop on; 01/2012
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    ABSTRACT: This technical note studies identification problems for dual-rate sampled-data linear systems with noises. A hierarchical least squares (HLS) identification algorithm is presented to estimate the parameters of the dual-rate ARMAX models. The basic idea is to decompose the identification model of a dual-rate system into several sub-identification models with smaller dimensions and fewer parameters. The proposed algorithm is more computationally efficient than the recursive least squares (RLS) algorithm since the RLS algorithm requires computing the covariance matrix of large sizes, while the HLS algorithm deals with the covariance matrix of small sizes. Compared with our previous work, a detailed study of the HLS algorithm is conducted in this technical note. The performance analysis and simulation results confirm that the estimation accuracy of the proposed algorithm are close to that of the RLS algorithm, but the proposed algorithm retains much less computational burden.
    IEEE Transactions on Automatic Control 12/2011; · 2.72 Impact Factor
  • Huanran Wang, X.P. Liu
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    ABSTRACT: This paper presents a novel human-robot interaction system for which haptic interaction is involved. The system consists of a nonholonomic mobile robot and a Phantom Omni haptic device. The tracking problem on the 2D plane is analyzed and the backstepping technique is used for designing the tracking algorithm for the nonholonomic mobile robot. A haptic rendering algorithm is designed to generate the haptic feedback based on the position error information. Experiments show that the user can guide the movement of the robot quite easily and smoothly.
    Haptic Audio-Visual Environments and Games (HAVE), 2010 IEEE International Symposium on; 11/2010
  • Feng Ding, Guangjun Liu, X.P. Liu
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    ABSTRACT: This technical note addresses identification problems of non-uniformly sampled systems. For the input-output representation of non-uniform discrete-time systems, a partially coupled stochastic gradient (C-SG) algorithm is proposed to estimate the model parameters with high computational efficiency compared with the standard stochastic gradient (SG) algorithm. The analysis indicates that the partially C-SG algorithm can give more accurate parameter estimates than the SG algorithm. The parameter estimates obtained using the partially C-SG algorithm converge to their true values as the data length approaches infinity.
    IEEE Transactions on Automatic Control 09/2010; · 2.72 Impact Factor

Publication Stats

84 Citations
8.57 Total Impact Points

Institutions

  • 2010
    • Jiangnan University
      • School of Communication and Control Engineering
      Wuxi, Jiangsu Sheng, China
    • Carleton University
      • Department of Systems and Computer Engineering
      Ottawa, Ontario, Canada