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21 – 30 of over 22000Xiao Tu, Yunfei Zhou, Pu Zhao and Xin Cheng
This paper aims to present a method for improving the state estimation of a robot in the presence of noise measurement, which can improve the performance of the robot controller.
Abstract
Purpose
This paper aims to present a method for improving the state estimation of a robot in the presence of noise measurement, which can improve the performance of the robot controller.
Design/methodology/approach
In this work, a novel nonlinear tracking differentiator (NTD) was formulated to solve the problems of phase lag, low stability and amplitude attenuation faced by traditional tracking differentiators, which can be used for the state estimation of a robot. Based on the user-defined function stu() with linear and nonlinear characteristics, the authors establish a new acceleration function of NTD and confirm its global asymptotic stability by using the Lyapunov method and the system equivalence method. Phase plane analysis shows that the origin is its stable nodal point or focus point and uncovers the basic constraint conditions for parameter regulation. In addition, the convergence property and robustness performance against noises are studied by describing function method.
Findings
Comparative simulations, robot state estimation experiments and joint trajectory tracking experiments have indicated that NTD proposed integrates tracking rapidness, accuracy and transitional stability and has high approximation and filtering effects on generalized derivatives of the signal, which contribute to an excellent performance of robot controller in stability and response speed in practice.
Originality/value
The main contribution of this paper lies in the design of a novel NTD, which successfully improves the state estimation of a robot joint in noisy surroundings, the tracking performance of robot controller and the stability of the system.
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Keywords
To design a reduced‐order controller with loosing little accuracy.
Abstract
Purpose
To design a reduced‐order controller with loosing little accuracy.
Design/methodology/approach
Singular perturbation approach by quasi‐steady state approximation and by Matrix block diagonalization technique is used.
Findings
It is shown that few errors occur between the uncorrected and corrected solutions for the fast subsystems while a few errors occur between the two kinds of solutions for the slow subsystems. The uncorrected solution is admissible for most dynamics. If not, it is recommended that the corrected solution be used.
Research limitations
Proportional feedback control gain is obtained by Pole placement method, which may produce an unwanted overshoot in the response.
Originality/value
This paper shows that the corrected controller is successfully applied in the aircraft dynamics and control.
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Keywords
The purpose of this paper is to describe the implementation of discrete singular convolution (DSC) method to steady seepage flow while presenting one of the possible uses of DSC…
Abstract
Purpose
The purpose of this paper is to describe the implementation of discrete singular convolution (DSC) method to steady seepage flow while presenting one of the possible uses of DSC method in geotechnical engineering. It also aims to present the implementation of DSC to the problems with mixed boundary conditions.
Design/methodology/approach
Second order spatial derivatives of potential and stream functions in Laplace's equation are discretized using the DSC method in which the regularized Shannon's delta kernel is used as an approximation to delta distribution. After implementation of boundary conditions, the system of equations is solved for the unknown terms.
Findings
The results are compared with those obtained from the finite element method and the finite difference method.
Originality/value
The method is applied to the flow problem through porous medium for the first time.
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Joris Claessens, Claudia Díaz, Caroline Goemans, Jos Dumortier, Bart Preneel and Joos Vandewalle
With the worldwide growth of open telecommunication networks and in particular the Internet, the privacy and security concerns of people using these networks have increased. On…
Abstract
With the worldwide growth of open telecommunication networks and in particular the Internet, the privacy and security concerns of people using these networks have increased. On the one hand, users are concerned about their privacy, and desire to anonymously access the network. On the other hand, some organizations are concerned about how this anonymous access might be abused. This paper intends to bridge these conflicting interests, and proposes a solution for revocable anonymous access to the Internet. Moreover, the paper presents some legal background and motivation for such a solution. However, the paper also indicates some difficulties and disadvantages of the proposed solution, and suggests the need for further debate on the issue of online anonymity.
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YiFan Hou, Murat Uzam, Mi Zhao and ZhiWu Li
Deadlock is a rather undesirable phenomenon and must be well solved in flexible manufacturing systems (FMS). This paper aims to propose a general iterative deadlock control method…
Abstract
Purpose
Deadlock is a rather undesirable phenomenon and must be well solved in flexible manufacturing systems (FMS). This paper aims to propose a general iterative deadlock control method for a class of generalized Petri nets (GPN), namely, G-systems, which can model an FMS with assembly and disassembly operations of multiple resource acquisition. When given an uncontrolled G-system prone to deadlocks, the work focuses on the synthesis of a near-optimal, non-blocking supervisor based on reachability graph (RG) analysis.
Design/methodology/approach
The concept of a global idle place (GIP) for an original uncontrolled G-system is presented. To simplify the RG computation of an uncontrolled G-system, a GIP is added temporarily to the net model during monitor computation steps. Starting with one token and then by gradually increasing the number of tokens in the GIP at each iteration step, the related net system is obtained. The minimal-covered-set of all bad markings of the related net system suffering from deadlock can be identified and then removed by additional monitors through an established place-invariant control method. Consequently, all related systems are live, and the GIP is finally removed when the non-blockingness of the controlled system is achieved. Meanwhile, the redundancy of monitors is also checked.
Findings
A typical G-system example is provided to demonstrate the applicability and effectiveness of the proposed method. Experiments show that the proposed method is easy to use and provides very high behavioral permissiveness for G-system. Generally, it can achieve an optimal or a near-optimal solution of the non-blocking supervisor.
Originality/value
In this work, the concept of GIP for G-systems is presented for synthesis non-blocking supervisors based on RG analysis. By using GIP, an effective deadlock control method is proposed. Generally, the proposed method can achieve an optimal or a near-optimal, non-blocking supervisor for an uncontrolled G-system prone to deadlocks.
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Ryosuke Masuda, Kensuke Hasegawa and Wei‐Ting Gong
Various types of sensors such as tactile, proximity and visual, have been developed to give robots flexibility and adaptability. It is argued that for complex tasks the individual…
Abstract
Various types of sensors such as tactile, proximity and visual, have been developed to give robots flexibility and adaptability. It is argued that for complex tasks the individual sensors need to be integrated into a total system. In this article a variety of sensors developed by the authors are presented as modules and a design approach for a total system is discussed.
A linear‐model‐based adaptive control system is developed. Alternative identification techniques are combined with a suboptimal controller. Iterative and recursive algorithms are…
Abstract
A linear‐model‐based adaptive control system is developed. Alternative identification techniques are combined with a suboptimal controller. Iterative and recursive algorithms are applied to produce minimum norm estimates of multivariable models, adequate over a range of plant operation. Parameter estimates are used to update the stage‐by‐stage suboptimal control algorithm. The techniques are applied to control a non‐linear chemical reactor model.
Wen‐Jer Chang, Cheung‐Chieh Ku and Wei Chang
The purpose of this paper is to propose a stability analysis and control synthesis for achieving passivity properties of a class of continuous‐time nonlinear systems. These…
Abstract
Purpose
The purpose of this paper is to propose a stability analysis and control synthesis for achieving passivity properties of a class of continuous‐time nonlinear systems. These nonlinear systems are represented via continuous affine Takagi‐Sugeno (T‐S) fuzzy models, which played an important role in nonlinear control systems. The affine T‐S fuzzy models are more approximate than homogeneous T‐S fuzzy models for modeling nonlinear systems. Using the energy concept of passivity theory with Lyapunov function, the conditions are derived to ensure the passivity and stability of nonlinear systems. Based on the parallel distribution compensation (PDC) technique, this paper proposes a fuzzy controller design approach to achieve the passivity and stability for the continuous affine T‐S fuzzy systems.
Design/methodology/approach
For solving stability and stabilization problems of affine T‐S fuzzy models, the conversion techniques and passive theory are employed to derive the stability conditions. By applying the linear matrix inequality technique, a modified iterative linear matrix inequality algorithm is proposed to determine and update the auxiliary variables for finding feasible solutions of these stability conditions.
Findings
By studying the numerical example, the proposed design technique of this paper is an effectiveness and useful approach to design the PDC‐based fuzzy controller. From the simulation results, the considered nonlinear system with external disturbances driven by proposed design fuzzy controller is stable and strictly input passive.
Originality/value
This paper is interesting for designing fuzzy controller to guarantee the stability and strict input passivity of affine T‐S fuzzy models.
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Raja Ben Mohamed, Hichem Ben Nasr and Faouzi M'Sahli
The purpose of this paper is to present a new concept based on a neural network validity approach in the area of multimodel for complex systems.
Abstract
Purpose
The purpose of this paper is to present a new concept based on a neural network validity approach in the area of multimodel for complex systems.
Design/methodology/approach
The multimodel approach was recently developed in order to solve the modeling problems and the control of complex systems. The strategy of this approach coincides with the usual approach of the engineer which consists in subdividing a complex problem to a set of simple, manageable sub‐problems that can be solved separately. However, this approach still faces some problems in design, especially in determining models and in finding the appropriate method of calculating validities.
Findings
A novel approach based on neural network validity shows very remarkable performances in multimodel for complex systems.
Research limitations/implications
The validity of each model is based on the convergence of each neural network. For a fast convergence the proposed approach can be online to give a good performance in multimodel representation for system with rapid dynamics.
Practical implications
The proposed concept discussed in the paper has the potential to be applied to complex systems.
Originality/value
The suggested approach is implemented and reviewed with a complex dynamic and fast process compared to the residue approach commonly used in the calculation of validities. The results prove to be satisfactory and show a good accuracy.
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