Current Issue : January - March Volume : 2015 Issue Number : 1 Articles : 7 Articles
In this paper, an arbitrary finite-time tracking\ncontrol (AFTC) method is developed for magnetic\nlevitation systems with uncertain dynamics and external\ndisturbances. By introducing a novel augmented slidingmode\nmanifold function, the proposed method can\neliminate the singular problem in traditional terminal\nsliding-mode control, as well as the reaching-phase\nproblem. Moreover, the tracking errors can reach the\nreference value with faster convergence and better\ntracking precision in arbitrarily determined finite time. In\naddition, a fuzzy-arbitrary finite-time tracking control (FAFTC)\nscheme that combines a fuzzy technique with\nAFTC to enhance the robustness and sliding performance\nis also proposed. A fuzzy logic system is used to replace\nthe discontinuous control term. Thus, the chattering\nphenomenon is resolved without degrading the tracking\nperformance. The stability of the closed-loop system is\nguaranteed by the Lyapunov theory. Finally, the\neffectiveness of the proposed methods is illustrated by\nsimulation and experimental study in a real magnetic\nlevitation system....
The purpose of this study is to prove the\nconvergence of the simultaneous estimation of the optical\nflow and object state (SEOS) method. The SEOS method\nutilizes dynamic object parameter information when\ncalculating optical flow in tracking a moving object within\na video stream. Optical flow estimation for the SEOS\nmethod requires the minimization of an error function\ncontaining the object�s physical parameter data. When\nthis function is discretized, the Euler-Lagrange equations\nform a system of linear equations. The system is arranged\nsuch that its property matrix is positive definite symmetric,\nproving the convergence of the Gauss-Seidel iterative\nmethods. The system of linear equations produced by\nSEOS can alternatively be resolved by Jacobi iterative\nschemes. The positive definite symmetric property is not\nsufficient for Jacobi convergence. The convergence of\nSEOS for a block diagonal Jacobi is proved by analysing\nthe Euclidean norm of the Jacobi matrix. In this paper,\nwe also investigate the use of SEOS for tracking individual\nobjects within a video sequence. The illustrations provided\nshow the effectiveness of SEOS for localizing objects\nwithin a video sequence and generating optical flow\nresults....
For natural human-robot interaction, the location\nand shape of facial features in a real environment\nmust be identified. One robust method to track facial\nfeatures is by using a particle filter and the active\nappearance model. However, the processing speed of\nthis method is too slow for utilization in practice. In\norder to improve the efficiency of the method, we\npropose two ideas: (1) changing the number of particles\nsituationally, and (2) switching the prediction model\ndepending upon the degree of the importance of each\nparticle using a combination strategy and a clustering\nstrategy. Experimental results show that the proposed\nmethod is about four times faster than the conventional\nmethod using a particle filter and the active appearance\nmodel, without any loss of performance....
In day to day life human friendly mobile robots are achieving great popularity. As these robots are making human life easier, their demand is increasing day by day. There are many kind of indoor mobile robots developed which are used in different sectors like hotels, hospitals, airports and for the household work. To obey any further instructions or to move smoothly into given environment a mobile robot must know its current location. So this paper mainly focuses on finding indoor mobile robot’s location. For this purpose a RFID (Radio frequency identification) technique is being used. Basically this technique is identification technique but due to its enormous features, from last ten years this technique has been used for the localization purpose also. Again indoor environment may contain different obstacles that must be avoided by the robot while roaming. So for this purpose infrared sensors are used which will detect the obstacle and avoid collision by changing its path....
Biped robots have better mobility than\nconventional wheeled robots. The bio-inspired method\nbased on a central pattern generator (CPG) can be\nused to control biped robot walking in a manner like\nhuman beings. However, to achieve stable locomotion,\nit is difficult to modulate the parameters for the neural\nnetworks to coordinate every degree of freedom of the\nwalking robot. The zero moment point (ZMP) method\nis very popular for the stability control of biped robot\nwalking. However, the reference trajectories have low\nenergy efficiency, lack naturalness and need significant\noffline calculation. This paper presents a new method\nfor biped real-time walking generation using a hybrid\nCPG-ZMP control algorithm. The method can realize a\nstable walking pattern by combining the ZMP criterion\nwith rhythmic motion control. The CPG component is\ndesigned to generate the desired motion for each robot\njoint, which is modulated by phase resetting according\nto foot contact information. By introducing the ZMP\nlocation, the activity of the CPG output signal is adjusted\nto coordinate the limbs� motion and allow the robot to\nmaintain balance during the process of locomotion. The\nnumerical simulation results show that, compared with\nthe CPG method, the new hybrid CPG-ZMP algorithm\ncan enhance the robustness of the CPG parameters\nand improve the stability of the robot. In addition, the proposed algorithm is more energy efficient than the\nZMP method. The results also demonstrate that the\ncontrol system can generate an adaptive walking pattern\nthrough interactions between the robot, the CPG and the\nenvironment....
This paper presents a framework for tracking\na mobile ground target (MGT) using a fixed-wing\nunmanned aerial vehicle (UAV). Challenges from pure\ntheories to practical applications, including varying\nillumination, computational limits and a lack of clarity are\nconsidered. The procedure consists of four steps, namely:\ntarget detection, target localization, states estimation and\nUAV guidance. Firstly, the MGT in the wild is separated\nfrom the background using a Laplacian operator-based\nmethod. Next, the MGT is located by performing\ncoordinate transformations with the assumption that the\naltitude of the ground is invariant and known. Afterwards,\na Kalman filter is used to estimate the location and velocity\nof the MGT. Finally, a modified guidance law is developed\nto guide the UAV to circle and track the MGT. The\nperformance of our framework is validated by simulations\nand a number of actual flight tests. The results indicate\nthat the framework is effective and of low computational\ncomplexity, and in particular our modified guidance law\ncan reduce the error of the tracking distance by about 75%\nin specified situations. With the proposed framework,\nsuch challenges caused by the actual system can be tackled\neffectively, and the fixed-wing UAV can track the MGT\nstably....
Three-dimensional (3D) object reconstruction is\nthe process of building a 3D model of a real object. This\ntask is performed by taking several scans of an object from\ndifferent locations (views). Due to the limited field of\nview of the sensor and the object�s self-occlusions, it is a\ndifficult problem to solve. In addition, sensor positioning\nby robots is not perfect, making the actual view different\nfrom the expected one. We propose a next best view\n(NBV) algorithm that determines each view to reconstruct\nan arbitrary object. Furthermore, we propose a method\nto deal with the uncertainty in sensor positioning. The\nalgorithm fulfills all the constraints of a reconstruction\nprocess, such as new information, positioning constraints,\nsensing constraints and registration constraints. Moreover,\nit improves the scan�s quality and reduces the navigation\ndistance. The algorithm is based on a search-based\nparadigm where a set of candidate views is generated\nand then each candidate view is evaluated to determine\nwhich one is the best. To deal with positioning uncertainty,\nwe propose a second stage which re-evaluates the views\naccording to their neighbours, such that the best view is\nthat which is within a region of the good views. The results\nof simulation and comparisons with previous approaches\nare presented....
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