一种改进的TPC混合译码算法

为简化Turbo乘积码(Turbo Product Code,TPC)译码处理过程,缩短接收机译码时延,针对航天测控领域应用广泛的子码为扩展汉明码的TPC码,提出一种改进的混合译码算法。改进算法以传统混合译码算法为基础,把SISO和HIHO两种译码器相结合,优化软输入输出(Soft In Soft Out,SISO)中的外信息计算方式,纠正硬输入输出(Hard In Hard Out,HIHO)中的特殊错误图样,并引入切换门限完成SISO到HIHO的自适应切换,实现了基于码字可靠性的智能译码。仿真表明,对于TPC码(64,57)2,误码率为10-5时,改进算法在不减弱译码性能的前提下,复杂度仅为原算法的1/2。改进算法的提出及应用,将有利于航天测控设备小型化和国产化。     

Serial decoding of rateless code over noisy channels

Rateless code usually generates a potentially infinite number of coded packets at the encoder and collects enough packets at the decoder to ensure reliable recovery of multiple information packets.The ...     

A novel QO-STBC scheme with linear decoding

A new quasi-orthogonal space-time block code(QO-STBC)scheme,based on eigen value decomposition(EVD),is explored in this paper.The new scheme can significantly reduce the QO-STBC decoding complexity at receiver and achieves better bit-error rate(BER)performance as well.With EVD manipulations,the detection matrix and the channel matrix can be redefined to remove all interference terms which come from other antennas,and therefore the conventional maximum likelihood(ML)decoding method with less complexity can b...     

A compliant surgical robotic instrument with integrated IPMC sensing and actuation

Robotic assisted surgery is becoming widely adopted by surgeons for a number of reasons, which include improved instrumentation control and dexterity as well as faster patient recovery times and cosmetic advantages. Robotic assisted surgery is currently one of the fastest growing applications in robotics. Although the traditional robotic actuators which are currently used have advanced performance which can, in some aspects, surpass that of humans, they simply do not have the capabilities and diversity required to meet the demand for new applications in robotic surgery. Novel transducers which have advanced capabilities and which allow safe operation in delicate environments are needed. Ionic polymer–metal composites (IPMCs) have extensive desirable characteristics when compared with traditional actuators and as their transduction mechanisms can mimic biological muscle they have much potential for future advanced biomedical and surgical robotics. In this research, a complete two degree-of-freedom (2DOF) surgical robotic instrument has been developed, which with the attachment of surgical tools (scalpel, etc.) has the ability to undertake surgical procedures. The system integrates an IPMC sensor and actuator at each joint. A gain scheduled (GS) controller, which is tuned with an iterative feedback tuning (IFT) algorithm, has been developed to ensure an accurate and adaptive response. The main advantages of this device over traditional devices are the improved safety through a natural compliance of the joints as well as the mechanical simplicity which ensures ease of miniaturisation for minimally invasive surgery (MIS). The components of the system have been tested and shown to have the capabilities required to operate the device for certain surgical procedures, specifically a device work envelope of 1600 mm², compliance of 0.0668 m/N while still maintaining enough force to cut tissue, IPMC sensor accuracy between 3–22% and a control system which has shown to guarantee zero steady state error.     

A common setting for the design of iterative learning and repetitive controllers with experimental verification

Previous work has shown that the structure of repetitive control (RC) and that of iterative learning control (ILC) differ only in the location of an internal model of the disturbance. In this paper, it is shown how this common setting permits derivation of controllers in one domain based on an existing controller in the other. This is illustrated using the following case studies: 1) an RC scheme using a state feedback structure is derived based on an existing ILC scheme, which also uses state feedback (the underlying structure is first extended to comprise both current‐error feedback and previous‐error feedforward implementations); and 2) an ILC scheme using an output injection structure is developed based on an existing RC scheme, which uses state feedback, but differs from 1) by containing only a single internal model representation. All controllers are shown to have similar equivalent representations, with parameters derived by using linear quadratic regulator analysis. This correspondence enables comparison of the effect of the structure (ILC or RC, state feedback or output injection), number of internal models, and use of error (feedback or feedforward) on subsequent performance. This is undertaken using experimental results obtained using a gantry robot. Copyright © 2012 John Wiley & Sons, Ltd.     

Performance and robustness of block constraint preconditioners in finite element coupled consolidation problems

Block constraint preconditioners are a most recent development for the iterative solution to large‐scale, often ill‐conditioned, coupled consolidation problems. A major limitation to their practical use, however, is the somewhat difficult selection of a number of user‐defined parameters (at least 4) in a more or less optimal way. The present paper investigates the robustness of three variants of the block constraint preconditioning in relation to the above parameters. A theoretical analysis of the eigenspectrum of the preconditioned matrix provides relatively simple bounds of the eigenvalues as a function of these parameters. A number of test problems used to validate the theoretical results show that both the mixed constraint preconditioner (MCP) combined with the symmetric quasi‐minimal residual (SQMR) solver and the MCP triangular variant (T‐MCP) combined with the bi‐conjugate gradient stabilized (Bi‐CGSTAB) are efficient and robust tools for the solution to difficult Finite Element‐discretized coupled consolidation problems. Moreover, the practical selection of the user‐defined parameters is relatively easy as a stable behavior is observed for a wide range of fill‐in degree values. The theoretical bounds on the eigenspectrum of the preconditioned matrix may help to suggest the most appropriate parameter combination. Copyright © 2009 John Wiley & Sons, Ltd.     

Some iterative algorithms for the obstacle problems

In this paper we propose some iterative algorithms for the obstacle problems discretized by the finite difference method. We rewrite the obstacle problem to an equivalent complementarity problem. We use the regularization trick to non-smooth absolute function. Then we apply the Newton's method to obtain an iterative algorithm. Some other two algorithms based on this algorithm are derived. Numerical experiments show the effective of the algorithm.     

Dynamics of a fifth-order iterative method

In this paper, we study the dynamical behaviour of a two-point iterative method with order of convergence five to solve nonlinear equations in the complex plane. In fact, we complement the dynamical study started in previous works with a more systematic analysis for polynomials with at most two different roots and different multiplicities. In addition, we characterize some polynomials of degree greater or equal to 4, such that the related methods are not generally convergent. We also analyse the degrees of the rational functions associated with two-point methods when they are applied to polynomials of degree n, showing their dependence on n ² and how this fact considerably complicates the dynamical study.     

Frequency domain analysis of acoustic wave propagation in heterogeneous media considering iterative coupling procedures between the method of fundamental solutions and Kansa's method

Acoustic wave propagation in heterogeneous media is a topic of significant interest in many areas of science and engineering, including aeroacoustics and sound propagation in oceans. In the present work, numerical frequency domain models based on the joint use of the method of fundamental solutions and of the radial basis function collocation method (also known as Kansa's method) are discussed. In this context, the method of fundamental solutions is used to model the homogeneous part of the propagation domain, while Kansa's method is employed to model the presence of heterogeneities. The coupling between the two parts of the propagation domain is performed iteratively, allowing independent spatial discretization between the different subdomains of the model (i.e. matching collocation points at common surfaces are not necessary). Additionally, an optimised algorithm, based on the use of a varying relaxation parameter, is employed to speed up and/or to ensure the convergence of the iterative coupling process. At the end of the paper, numerical results illustrate the applicability and potentialities of the proposed formulations. Copyright © 2011 John Wiley & Sons, Ltd.     

Precise disturbance modeling for improvement of positioning performance

This paper presents a modeling methodology for unknown disturbances in mechatronics systems, based on disturbance estimation using an iterative learning process. In disturbance modeling, nonlinear frictions are specially handled as disturbances in the mechanisms, which mainly degrade trajectory control performance. Friction can be mathematically modeled by using learned estimation data as a function of the displacement, velocity. acceleration, and jerk of the actuator. This model has the distinctive feature that friction compensation can be achieved with a generalization capability for different conditions. The proposed positioning control approach with disturbance modeling and compensation has been verified by experiments using a table drive system on a machine stand. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(2): 31–39, 2010; Published online in Wiley InterScience ( www. interscience.wiley.com ). DOI 10.1002/eej.20928