Xu L.-X.,Tianjin University of Technology and Education |
Li Y.-G.,Tianjin University of Technology and Education
Robotics and Computer-Integrated Manufacturing | Year: 2014
In this study, the effects of joint clearance on the dynamic performance of a planar 2-DOF pick-and-place parallel manipulator are investigated. The parallel manipulator is modeled by multi-body system dynamics. The contact effect in revolute joints with clearance is established by using a continuous analysis approach that is combined with a contact force model considering hysteretic damping. The evaluation of the contact force is based on Hertzian contact theory that accounts for the geometrical and material properties of the contacting bodies. Furthermore, the incorporation of the friction effect in clearance joints is performed using a modified Coulomb friction model. By numerical simulation, variations of the clearance joint's eccentric trajectory, the joint reaction force, the input torque, the acceleration, and trajectory of the end-effector are used to illustrate the dynamic behavior of the mechanism when multiple clearance revolute joints are considered. The results indicate that the clearance joints present two obvious separation leaps in a complete pick-and-place working cycle of the parallel manipulator, following a collision. The impact induces system vibration and thus reduces the dynamic stability of the system. The joint clearances affect the amplitudes of the joint reaction force, the input torque, and the end-effector's acceleration, additionally the joint clearances degrade the kinematic and dynamic accuracy of the manipulator's end-effector. Finally, this study proposes related approaches to decrease the effect of joint clearances on the system's dynamic properties for such parallel manipulator and prevent "separation-leap-impact" events in clearance joints. © 2013 Published by Elsevier Ltd. All rights reserved.
Xu L.X.,Tianjin University of Technology and Education
Multibody System Dynamics | Year: 2016
Contact impact has been widely found in the operation of various mechanical systems. These mechanical systems include the type of mechanism typically characterised by circular–non-circular geometric contact. They consist of the mechanisms of the cam with a roller follower, a Geneva wheel with intermittent motion, a cog belt drive with circular-arc teeth, a cycloidal-pin wheel gear, and a roller chain drive. For the two components in contact, one component needs to have an ideal circular shape, while the other is characterised by its non-circular geometry, that is, the contact shape may present varying radii of curvature. Taking this kind of contact mechanical system as a research object, this work proposes a general method for analysing the problems concerning contact impact on this circular–non-circular geometry. This method discretises continuous non-circular geometries to acquire a series of discrete points. Then, the contact areas of components are determined by repeatedly judging the relationships between the positions for various discrete points and the circular geometric centres thereof. In the contact areas, the maximum depth of the contact is measured, and the positions of the contact points between components, in a direction along the maximum contact depth, are determined. Finally, the normal contact force and tangential friction force between contacting components are established at the contact points. This method can be applied to analyse the problems concerning single contact and multi-point contact among various contact components. To verify the validity of this method, this work takes an offset translational roller follower disc cam mechanism (with a single contact) and a cycloidal-pin wheel gear mechanism (with multi-point contact) as examples and investigates the dynamic characteristics of the contact impact for the aforementioned mechanical systems, respectively. © 2016 Springer Science+Business Media Dordrecht
Chen J.,Tianjin University of Technology and Education
Proceedings of the World Congress on Intelligent Control and Automation (WCICA) | Year: 2016
In this paper, a self-organizing cerebellar instrumental learning algorithm (SOCILA) is proposed for a self-balancing robot to achieve the balance control based on the counter-propagation network (CPN), which combined unsupervised and supervised learning. Due to the cerebellar contributions to instrumental learning, the instrumental learning algorithm is designed to change the weights from competitive layer to output layer of CPN, while the clustering to input state is implemented by fuzzy self-organizing map layer (from input layer to competitive layer)of CPN. In order to save the learning results, curiosity parameter is introduced, which is useful to instrumental learning and simulate the biological learning process. Simulations on balance learning of a two-wheeled self-balancing robot is given to illustrate the performance and applicability of the proposed learning scheme, and, as a result, progressive learning process of balance can be achieved using the proposed SOCILA method. Finally, in order to compare the learning performances we choose different number of rules to test the learning performance in balance learning. © 2016 IEEE.
Mei Q.,Whirlpool Corp. |
Shan M.,General Electronics |
Liu L.,Tianjin University of Technology and Education |
Guerrero J.M.,University of Barcelona
IEEE Transactions on Industrial Electronics | Year: 2011
Maximum power point (MPP) tracking (MPPT) techniques are widely applied in photovoltaic (PV) systems to make PV array generate peak power which depends on solar irradiation. Among all the MPPT strategies, the incremental-conductance (INC) algorithm is widely employed due to easy implementation and high tracking accuracy. In this paper, a novel variable step-size incremental-resistance MPPT algorithm is introduced, which not only has the merits of INC but also automatically adjusts the step size to track the PV array MPP. Compared with the variable step-size INC method, the proposed scheme can greatly improve the MPPT response speed and accuracy at steady state simultaneously. Moreover, it is more suitable for practical operating conditions due to a wider operating range. This paper provides the theoretical analysis and the design principle of the proposed MPPT strategy. Simulation and experimental results verify its feasibility. © 2010 IEEE.
Zhang J.,Tianjin University of Technology and Education
Gait and Posture | Year: 2012
A gait analysis method based on continuous wave (CW) radar is proposed in this paper. Time-frequency analysis is used to analyze the radar micro-Doppler echo from walking humans, and the relationships between the time-frequency spectrogram and human biological gait are discussed. The methods for extracting the gait parameters from the spectrogram are studied in depth and experiments on more than twenty subjects have been performed to acquire the radar gait data. The gait parameters are calculated and compared. The gait difference between men and women are presented based on the experimental data and extracted features. Gait analysis based on CW radar will provide a new method for clinical diagnosis and therapy. © 2012 Elsevier B.V.
Ren N.,Tianjin University of Technology and Education
Proceedings - 2016 8th International Conference on Measuring Technology and Mechatronics Automation, ICMTMA 2016 | Year: 2016
In order to make a research on arrangement for yoga movement, we consider universities as our research groups, and use yoga principle selected from principles in yoga movement, with principles being, respectively, integrity principle, principle of gradual and orderly progress, principle of scientific rationality, interesting principle, yoga principle, as a criterion layer of algorithm. We discuss the arrangement of yoga movement via three distinct factors: the season, the crowd and the site, and regard the last factor as a result layer. Quantitative analysis of weights based on the AHP model has been made, from which for considersion to be able to reasonably adjusted the arrangement of college yoga movement in time. © 2016 IEEE.
Li Z.,Tianjin University of Technology and Education |
Zhao X.,Tianjin University of Technology and Education
Nonlinear Analysis: Real World Applications | Year: 2011
Combining adaptive control theory with an antisymmetric structure, an extended adaptive controller which is more generalized and simpler than some existing controllers is designed. Under the controller, generalized function projective synchronization of two different uncertain hyperchaotic systems is achieved, and the unknown parameters are also estimated. In numerical simulations, the scaling function factors discussed in this paper are more complicated, and they have not been discussed in other papers. Corresponding simulation results are presented to show that the controller works well. © 2011 Elsevier Ltd. All rights reserved.
Jian C.,Tianjin University of Technology and Education
Journal of Networks | Year: 2013
Due to the weaknesses of the generalization capability and diagnostic accuracy of identification of the improve extension neural network, we have found the method, Shadowed Sets, to improve the ENN. We can get the algorithm description through analyzing the Shadowed Sets and extension neural network system structure, making a comparison on a variety of extension neural network classifier performance, and detailed analyzing the Shadowed Sets of training data selection method. Finally, we can make a detailed experimental comparison through improved extension neural network (IENN) and traditional extension neural network (ENN), and at the same time get the results of the experiments by the Steam Turbine Power Generation Set Vibration Diagnostic tests. The experiments show that: we can use the shadow data set selection method and obtain high-quality training sample to enhance and improve the performance of ENN; selecting the nuclear data and boundary data as training ENN training data is a scientific and reliable; the improved extension neural network has been improved not only in the accuracy of classification, but the generalization ability. © 2013 ACADEMY PUBLISHER.
Dai Y.,Tianjin University of Technology and Education
Zhongguo Jixie Gongcheng/China Mechanical Engineering | Year: 2011
A reliability evaluation test plan of NC machine tools based on exponent distribution was investigated. At first the evaluation test plan type was confirmed as timing censored lifetime test with replacement, secondly the minimum failure number was discussed to get certain confidence interval, and then the condition that the product of machine tool number and censored time should satisfied was analyzed to get the minimum failure number. At last, the optimum plan about machine tool number and censored time were put forward.
Gu Q.,Tianjin University of Technology and Education |
Gao T.,Nankai University
Digital Signal Processing: A Review Journal | Year: 2013
Reversible watermarking can be applied to the protection for important digital media, such as medical and military image, it allows the watermark to be extracted and the original image to be restored completely, but reversible watermarking with stronger robustness is seldom discussed in existing literature. In this paper, a novel reversible watermarking algorithm based on chaotic system is proposed; chaotic system is not only used to search space of reversibility of the scheme, but also used to randomly select the position of watermarking embedding. Consequently, the proposed scheme achieves larger threshold space of reversibility and better performance of security. For some specific thresholds, the proposed algorithm is not only reversible, but also has stronger robustness against image compression. The experimental results show that the ergodicity and sensitivity to initial values of chaotic system play an important role in reversible watermarking algorithm, and the proposed scheme can achieve balance between reversibility and robustness with the help of chaotic system. © 2012 Elsevier Inc. All rights reserved.