A biomimetic approach to inverse kinematics for a redundant robot arm

Redundant robots have received increased attention during the last decades, since they provide solutions to problems investigated for years in the robotic community, e.g. task-space tracking, obstacle avoidance etc. However, robot redundancy may arise problems of kinematic control, since robot joint motion is not uniquely determined. In this paper, a biomimetic approach is proposed for solving the problem of redundancy resolution. First, the kinematics of the human upper limb while performing random arm motion are investigated and modeled. The dependencies among the human joint angles are described using a Bayesian network. Then, an objective function, built using this model, is used in a closed-loop inverse kinematic algorithm for a redundant robot arm. Using this algorithm, the robot arm end-effector can be positioned in the three dimensional (3D) space using human-like joint configurations. Through real experiments using an anthropomorphic robot arm, it is proved that the proposed algorithm is computationally fast, while it results to human-like configurations compared to previously proposed inverse kinematics algorithms. The latter makes the proposed algorithm a strong candidate for applications where anthropomorphism is required, e.g. in humanoids or generally in cases where robotic arms interact with humans.     

Fuzzy goal-driven intelligent control for satellite environmental qualification

This paper reports on the application of Fuzzy Reference Gain-Scheduling Control (FRGS) to control a thermal-vacuum unit that emulates space environmental conditions for satellite and space device qualification. FRGS is a variation of fuzzy control that changes the controller gain surface in accordance to distinct operational conditions established by the reference (goal). This system allows to incorporate the experience of human operators by emulating human decision-making and reasoning, with the advantage of adaptation when parameters are adjusted on-line. The controller gain surface is adapted by modifying the shapes of the membership functions according to piecewise constant reference values. While the goal-driven adjustment is accomplished in a feedforward manner, feedback control technique is used to guarantee dynamical response. The experimental response obtained in the application to the real system has shown the effectiveness and flexibility of this control approach for such a nonlinear system.     

Limits in growing TlGaAs/GaAs quantum-well structures by low-temperature molecular-beam epitaxy

TlGaAs/GaAs multiple-quantum-well (MQW) structures were grown on GaAs substrates at a substrate temperature of 190 °C by molecular-beam epitaxy. The MQW structures were intended to consist of four identical TlGaAs wells, each of which is sandwiched by GaAs barrier layers. X-ray diffraction was used to investigate the limits to Tl content and thickness of the TlGaAs well layer for forming the MQW structures. Successful growth of TlGaAs/GaAs MQW structures having nominal Tl contents of 6, 8, and 9% was confirmed for the three different well thicknesses of about 15, 10, and 5 nm, respectively, while further increase in Tl content resulted in failure in forming MQW structures. The bounds for forming the MQW structures are discussed in terms of the epitaxial thickness of TlGaAs. The effect of the MQW structures on retarding the formation of Tl droplets is pointed out.     

Resource conscious development of middleware for control environments: a case of CORBA-based middleware for the CAN bus systems

While it is imperative to exploit middleware technologies in developing software for distributed embedded control systems, it is also necessary to tailor them to meet the stringent resource constraints and performance requirements of embedded control systems. In this paper, we propose a CORBA-based middleware for Controller Area Network (CAN) bus systems. Our design goals are to reduce the memory footprint and remote method invocation overhead of the middleware and make it support group communication that is often needed in embedded control systems. To achieve these, we develop a transport protocol on the CAN and a group communication scheme based on the publisher/subscriber model by realizing subject-based addressing that utilizes the message filtering mechanism of the CAN. We also customize the method invocation and message passing protocol of CORBA so that CORBA method invocations are efficiently serviced on a low-bandwidth network such as the CAN. This customization includes packed data encoding and variable-length integer encoding for compact representation of IDL data types.We have implemented our CORBA-based middleware using GNU ORBit. We report on the memory footprint and method invocation latency of our implementation.     

磨料水射流切割可视化BP神经网络模型研究

针对磨料水射流切割性能与影响因素间存在复杂的非线性关系,无法用传统数学方法建模的问题,基于BP人工神经网络理论,结合典型材料的切割实验结果,在考虑射流压力、磨料流量、切割靶距、工件厚度、磨料喷嘴直径与切割速度6个因素情况下,建立了磨料水射流切割BP神经网络模型.同时,基于Delphi开发出了可移植的磨料水射流切割速度人工神经网络预测单元,实现了所建网络模型的可视化,为实现网络模型与数控系统的集成提供条件.研究结果表明,该网络模型能快速、准确、可靠地预测切割速度,与数控系统相集成可实现对磨料水射流切割质量的有效控制.     

基于多重判别分析和分形维的数字调制样式自动识别

将不同数字调制样式的通信信号采样重组成为二维数据阵列后,会呈现独特的纹理。根据分形型理论,不同纹理具有不同的多分形维,因此本文提出通过多重分形维区别不同调制样式的方法。首先用离散小波去噪的方法处理含噪声的采样信号,然后计算信号纹理的多重分形维,再将分形维特征向量通过多重判别分辨分析投影到Fisher超平面,最后用最大似然方法分类识别特征向量。用算法对四种数字调制样式的分析获得了正确的分类结果,证明将多重分形维用于识别数字调制样式是可行的。     

电子商务环境下连锁餐饮业供应链运营模型

通过建立基于电子商务的连锁餐饮业供应链运营模型,得到其净利润的优化解法.该模型从成本和利润两方面入手,将连锁餐饮业的供应链特点与电子商务的优点相结合,量化了各种需要考虑的因素,建立了相应的方程,通过仿真实验分析了优化方法及其最优解.与传统连锁餐饮业的供应链相比,电子商务供应链更有利于提高信息传递的效率和准确率.     

Plasma parameters and volume kinetics in Cl<Subscript>2</Subscript>/O<Subscript>2</Subscript> mixtures

We investigated plasma characteristics, plasma mass content and kinetic dependencies of both neutral and charged particle formation and decay in Cl₂/O₂ gas mixture. For these purposes we used a combination of experimental methods (optical emission spectroscopy, Langmuir probe) and a plasma modeling on the base of self-consistent solution of Boltzmann kinetic equation together with balance kinetic equations for neutral and charged particles in a quasi-stationary approximation. It was found that the change of O₂/(Cl₂+O₂) mixing ratio from 0 to 0.2 leads to an increase of electron average energy and electron energy distribution function (EEDF) deformation. The main mechanisms of Cl and O atom formation are the direct electron impact dissociation of corresponding molecules while the contribution of all possible “secondary” processes is not significant in the case of a relatively low O₂ addition.     

下行床内颗粒浓度的电容层析成像测量的研究

利用电容层析成像(electrical capacitance tomography,ECT),以非侵入的方式,对下行床内气固流动情况进行测量研究。针对下行床内固体颗粒浓度低的特点,采用了SIRT图像重建算法,得到了高质量的ECT图像。在颗粒流量和流化风量变化的情况下测量了不同截面固体颗粒体积份额平均值的变化,得到了下行床内气固流动规律。实现了快速的下行床内粉粒体的ECT在线可视化测量,具有较大的工程和学术价值。     

Low rate energy use for heating and in industrial energy supply systems—Some technical and economical aspects

The subject hereof are two typical examples of waste heat and low-temperature heat use and the objective is to evaluate economic effectiveness taking into account various boundary conditions. The first facility considered is an “earth-coupled” heat pump with direct evaporation used as a component of a heating system. The second is an industrial installation, based on a specific project to use waste heat from the cooling process. Alternatively, four different technical options have been considered, including the use of the compression heat pump, absorption heat pump, heat transformer (absorption) and combined system with a gas motor for driving the heat pump compressor. An original simple methodology for economic analysis evaluating uses of low-temperature heat sources as elements of energy supply systems has been developed using input data taken from actual research or industrial projects. The paper also offers a comparison between such energy supply systems operating under different economic conditions of Germany and Poland.