Feedforward element design using learning controller for precision control of linear synchronous motor with nonlinear characteristics

This study presents a time-invariant feedforward (FF) element design for the high-speed and high-precision tracking control of an ultrahigh-acceleration, high-velocity linear synchronous motor (LSM). The linear motor can generate an acceleration greater than 70 G (= 686 m/s²) and move at a velocity above 10 m/s. To take advantage of this performance and realize high response, the design and usage of suitable FF elements is crucial. However, as the LSM includes highly nonlinear characteristics, it is difficult to provide an exact dynamic model for FF design. To overcome this problem, a control system with a learning controller (LC) as the FF element has been designed previously, demonstrating high-precision and high response motion. However, the motion performance can be achieved only with sufficient pre-learned motions. The integrator and the disturbance observer that were effective in suppressing disturbances were removed from the control system. In addition, the control system has some FF time-invariant elements along with the LC. This study proposes a design method for easy design of all FF elements using an LC. The designed FF elements are time invariant and are used with an integrator and a disturbance observer, without pre-learning. Using the proposed method, two sets of time-invariant FF elements are designed. The performances of two control systems, which include a set of time-invariant FF elements for each, and a simple disturbance observer are experimentally examined and compared with two previously designed control systems. Experimental results demonstrate that the performance of one of the control systems with a set of time-invariant FF elements designed in this study and a disturbance observer is good and almost comparable with that of the previously designed control system with high-precision and high response motion.     

Un dispositif pour la caractérisation des propriétés amortissantes de matériaux viscoélastiques non-linéaires en cisaillement

Viscoelastic materials are widely used in passive antivibration mounting design. In order to optimize their use, designers have to take into account the non-linearities caused by the large strain amplitudes these systems are subjected to. In this paper we present an apparatus designed to characterize the mechanical behavior of some viscoelastic materials used for this application. Simple shear deformation under sinusoidal load is used. The results are displayed as an extension of the complex moduli linear concept. The highly non-linear behaviour of the samples is underlined. A large scale of frequency and strain amplitude can be studied using this apparatus, without any restrictive assumption regarding the material model. This apparatus was designed in order to validate the design of an aerospace antivibration equipment.     

An easy instrument and a methodology for the monitoring and the diagnosis of a rail

Nowadays, there are no systematic methodologies for evaluating life assessment of the rail, and few systems provide the measures of vertical and lateral forces that train exchanges with the rail. These systems are quite expensive and require the substitution of a portion of the track. In the present paper is presented a simple transducer (MPQY) for measuring, at the same time, the vertical and lateral forces. The easy installation and use of this instrument are its main characteristics. It is sufficient to put it in a hole, made in the rail web in the concurrence of the drilling axis, and connect it to the transmitting station for measuring for each convoy the vertical and lateral forces induced by each wheel. It can be also used for analysing speed and mass of trains and the specific derailment ratio. In addition, by using a damage model, it is possible to estimate the residual life of a rail. In order to do this, a linear model of rolling contact fatigue damage is implemented and tested with same experimental acquisitions. Another application of this transducer can be identified in the variation of the mechanical behaviour of ballast. In fact, by using the information coming from the MPQY and comparing it with the flexural moment measurement, it is possible to evaluate the variation of ballast behaviour with respect to time and set new parameters for ballast maintenance and train safety.     

Le roulement : limites du domaine de fonctionnement et mécanismes de dégradation

After a brief summary of the history of friction, an analysis of the causes of friction are made. The purpose is to improve the behaviour of mechanical systems and to reduce costs. In order to better predict fatigue life, the physical basis of a computation model taking into account the behaviour of the material submitted to Hertzian pressure is presented. The fields where improvements of technical and economical performances of bearings are possible are described. Parameters on which designers can work to enhance the performance without increasing costs are, for example, easy assembly, material quality, heat-treatment, machine techniques.     

混联仿生机器狗构型研究

仿生机器人研究是机器人学研究的热点之一,由于多年的进化,生物的各关节运动一般难以用机械结构完全实现。为克服目前仿生机器人普遍存在的刚度低、肢体功能弱等不足,以机器狗为研究对象,结合狗的基本行为特征和各关节的生理结构,将各关节的主要功能进行排序,并提出重要性/权重法作为机器狗设计中简化各运动关节的依据;据此分别运用并联双自由度转动机构RGRR-Ⅰ、RGRR-Ⅱ以及单自由度转动机构设计机器狗的各关节,并构造出24自由度的混联机器狗。所设计的混联机器狗具有结构简单、制造容易、刚度强、控制便捷、肢体运动灵活等优点。此研究思路和方法,对其他类型的仿生机器人设计有借鉴作用。     

Characterization of an electrostatic filter prototype for bioaerosol flowmetering for INTA Investigation Aerial Platforms

The characterization of the airborne microorganisms at different altitudes of the atmosphere is usually conducted by means of aerial platforms. It is very interesting to know the biological processes in the atmosphere. However, there are problems associated to the fact that sampling systems are embarked on an aircraft and the low presence of microorganisms at high altitude. A prototype of a new electrostatic filter for bioaersol flowmetering dedicated to biology investigations has been developed. This prototype was designed to be installed on board in aerial platforms of INTA. The experimental characterization of the aerodynamic flow was performed in order to investigate the behaviour of the filter when different air intake widths and different mechanical deflectors are employed. A combination of these impactor with the filters based on industrial electrostatic precipitator technology have been studied. Non-intrusive Particle Image Velocimetry technique has been used to measure the flow field inside the filter when it was running under controlled conditions in laboratory. This study is a first investigation on the flow field of filter for bioaerosol flowmetering to be embarked on an aircraft. The results show the influence of each parameter in the flow field that could be used for further investigations and designs.     

Alarm system optimization for increasing operations productivity

While it is widely recognized that total quality is a cost problem for production systems, it is less well recognized that alarm system efficiency is also an important cost problem. Practically, a well-designed alarm system is an essential tool in to maintain effective plant operations. Poorly designed alarm systems cause unnecessary disturbances, a waste of resources, and decreased plant operability. All of these adversely impact product quality and cost efficiency. Ongoing production system changes and enhancements typically increase the number of potential alarms. They are added to the existing alarm trip points, which are usually kept originally designed. This causes an ever-increasing number of alarms to be generated. On the other hand, the number of operators is usually kept the same or is even reduced for the requirements of the cost control. This results in an increasing number of alarms for each operator to handle, thereby worsening total productivity. It is important to evaluate repeatedly how operators react to the alarms. Alarm system efficiency can be evaluated by capturing when, where, and how frequently alarm messages are generated, and by comparing how operators respond to them. It is also important to analyze statistically the efficiency for each part of a facility or each product in order to optimize a better alarm system.     

The compression of crossed layers of thin tubes

The behaviour of orthogonal layers of aluminium and mild steel tubes under lateral compression is considered. The results for each material are presented separately in Parts I and II of the paper. In all the tests the initial separation of tubes in the same layer is sufficiently large to preclude contact being established between adjacent tubes as they deform.Part I: Aluminium systems are examined and two principal categories of behaviour are identified. As well as providing basic load-deflection data in a suitably non-dimensionalised form, certain particular features of the modes of deformation of individual tubes in the systems are examined in detail.Part II: This presents data and observations concerning mild steel systems. Of especial interest is the difference between the behaviour of as-received tubes, which develop cracks in the regions of greatest deformation, and that of annealed mild steel tubes which show similar characteristics to those of the aluminium systems.     

The peeling of flexible probabilistic fasteners

Probabilistic fasteners are attachment devices consisting of two elements each of which is covered by an array of outgrowths or protuberances which interact or interlock with those on the opposing surface to form a bond which can be made and detached many times. A number of peel tests are described in which the behaviour of such bonds, specifically those formed by Velcro® hooks and loops and Dual Lock®, has been explored. The value of the specific energy of detachment of such mechanically latched systems can be related to the geometry and material properties of the individual fixing elements. Similar arguments can be applied, both qualitatively and quantitatively, to some natural systems such as the spines on some cacti.     

A ratio control scheme decoupling disturbance response from set-point response

In this paper a novel ratio control scheme is proposed for stable and unstable processes with time delay. The proposed ratio control system consists of two control loops with two-degrees-of-freedom control structure, which decouples the set-point response of each loop from its disturbance response. Two ratio controllers separately for the set-point and load disturbance changes are introduced between the two control loops, in order to achieve improved ratio control performance during the transients caused by the set-point and disturbance changes and to decouple the set-point response of the whole ratio control system from its disturbance response. For easy understanding and tuning, all the controllers in the ratio control system are designed analytically. As a result, the set-point and load disturbance responses of the ratio control system can be independently and conveniently tuned by a single control parameter. In addition, the proposed ratio control scheme can provide quantitative performance estimation. Simulation examples are included to illustrate the effectiveness of the proposed method.     

Multi-objective optimal design of high frequency probe for scanning ion conductance microscopy

Scanning ion conductance microscopy(SICM) is an emerging non-destructive surface topography characterization apparatus with nanoscale resolution. However, the low regulating frequency of probe in most existing modulated current based SICM systems increases the system noise, and has difficulty in imaging sample surface with steep height changes. In order to enable SICM to have the capability of imaging surfaces with steep height changes, a novel probe that can be used in the modulated current based hopping mode is designed. The design relies on two piezoelectric ceramics with different travels to separate position adjustment and probe frequency regulation in the Z direction. To further improve the resonant frequency of the probe, the material and the key dimensions for each component of the probe are optimized based on the multi-objective optimization method and the finite element analysis. The optimal design has a resonant frequency of above 10 kHz. To validate the rationality of the designed probe, microstructured grating samples are imaged using the homebuilt modulated current based SICM system. The experimental results indicate that the designed high frequency probe can effectively reduce the spike noise by 26% in the average number of spike noise. The proposed design provides a feasible solution for improving the imaging quality of the existing SICM systems which normally use ordinary probes with relatively low regulating frequency.     

带有摩擦的机器人鲁棒控制

根据机械系统中摩擦力的特性,把有关标量情况下摩擦力的结论推广到矢量空间中,使机器人系统中的外部随机干扰控制问题具体化。首先利用反馈控制技术,把基于拉格朗日方程的机器人动力学模型转化成一个线性状态方程,并详细介绍这一转化过程。然后基于此线性状态方程,应用李雅普诺夫函数稳定性理论,针对摩擦力的一般特性,设计鲁棒补偿控制器来抑制摩擦力对机器人控制系统的影响,以使机器人实际运动轨迹能够全局渐近收敛于所给定的期望轨迹。所设计的控制器具有理论清晰、设计简单、鲁棒性好等优点。给予完整的理论证明,最后以两关节机器人为例,给出仿真试验结果。通过对比采用不同控制器所得出的不同仿真结果,可以看出所提出的鲁棒控制器具有较好的实用效果。     

灰色PID控制在航空发动机中的应用研究

对于航空发动机这样复杂的系统,经典的PID算法难以对其实现良好控制。灰色系统理论是处理不确定量的一种有效途径。它需要信息少,通用性好,计算方便。针对航空发动机难于建立精确数学模型的特点,采用灰色控制理论与PID控制相结合,实现对PID参数的最佳整合。并且对某型航空发动机进行了全包线内的数字仿真。仿真结果证明了其在航空发动机控制中的可能性。     

Dominant pole placement with fractional order PID controllers: D-decomposition approach

Dominant pole placement is a useful technique designed to deal with the problem of controlling a high order or time-delay systems with low order controller such as the PID controller. This paper tries to solve this problem by using D-decomposition method. Straightforward analytic procedure makes this method extremely powerful and easy to apply. This technique is applicable to a wide range of transfer functions: with or without time-delay, rational and non-rational ones, and those describing distributed parameter systems. In order to control as many different processes as possible, a fractional order PID controller is introduced, as a generalization of classical PID controller. As a consequence, it provides additional parameters for better adjusting system performances. The design method presented in this paper tunes the parameters of PID and fractional PID controller in order to obtain good load disturbance response with a constraint on the maximum sensitivity and sensitivity to noise measurement. Good set point response is also one of the design goals of this technique. Numerous examples taken from the process industry are given, and D-decomposition approach is compared with other PID optimization methods to show its effectiveness.     

Robust clustering approach for the shortest path problem on finite capacity fuzzy queuing network

This paper introduces a new model in the field of fuzzy queuing networks based on the clustering and finite capacity concepts. The proposed model includes fuzzy queuing systems which are located at the nodes of the network. Arc lengths, interarrival times, and service times are all fuzzy triangular fuzzy numbers. In order to find the shortest path on this network, queuing systems should be transformed to waiting times. The waiting times of each system are calculated by a conditional transformation. On the other hand, a robust fuzzy method is proposed for clustering of the arriving customers to the network. Robustness of this method prevents noisy data to affect results. Outputs of the clustering reduce shortest path calculations drastically. Based on a simulation process, the fuzzy queuing network is reduced to a deterministic network. A robust simulated annealing is designed for this network to find the shortest path. Numerical results showed that the clustering process is successful in eliminating outliers, and could be addressed as an efficient method. The convergence and solution time of the algorithm is reasonably better in comparison with published methods. Several experiments are conducted to compare the proposed method with corresponding researches.     

Review of oil–water through pipes

In oilfield operations, co-current flow of oil–water mixture is very common and can cause significant flow assurance problems during production. Accurate knowledge of behaviour of oil–water in a pipeline flow is crucial to design/optimize production, transportation, and processing facilities. Many researchers have attempted to generalize the liquid–liquid or the two phase flow systems through mechanical models and develop means for predicting the flow patterns, pressure drop, and water holdups. However, the crude oil properties differ and the oil–water system can be operated over various range of operating conditions and subsequently encounter an altered hydrodynamics behaviour in two phase flow system. To worsen the situation, almost all the empirical correlations and mechanical models developed were for low viscosity oil and with majority focused on gas–liquid flow. Thus, comprehensive models still remain unsolved for some of the flow issues especially when involving high viscosity or waxy crude oils. Hence an attempt to generalize liquid–liquid flow in multiphase systems seems impractical. Since conventional light crude oil or easy oil reserves are gradually depleted, thus many research works on high viscosity oil–water flow in pipes have been initiated. Presently, there is limited number of papers on high viscous oil–water flow in open literature which has confined the understanding of the flow behaviour of two-phase flow. In this communication, we report a review on the current state of research on two phase flow oil–water phenomena, highlighting what is so far has been realized and how this knowledge can be applied as a basis to understand better of the more complex cases of gas-crude oil–water three phase flow.     

User Interface for Multitasking on Internet‐Based Embedded Systems

Abstract

User interfaces are designed for particular operating systems (OSs). Designing a user interface for no specific OS is a difficult task. This task becomes increasingly complex when a user interface is needed for multi‐tasking, particularly for Internet‐based embedded systems. Furthermore, storage size is a critical component of resource‐limited systems. This work presents a novel method for writing a very small program that can function as a universal interface for multi‐tasking embedded systems, regardless of which OS is used or whether an OS exists. This study presents a model‐driven approach. Both menu models and item models are designed as programming models. These models are written in C language. The proposed method can be implemented regardless of the hardware and computer language used. The proposed method is implemented in an Internet‐capable data acquisition system with a two‐row LCD display. Implementation results are discussed.     

A modular designed ultra-high-vacuum spin-polarized scanning tunneling microscope with controllable magnetic fields for investigating epitaxial thin films

A room-temperature ultra-high-vacuum scanning tunneling microscope for in situ scanning freshly grown epitaxial films has been developed. The core unit of the microscope, which consists of critical components including scanner and approach motors, is modular designed. This enables easy adaptation of the same microscope units to new growth systems with different sample-transfer geometries. Furthermore the core unit is designed to be fully compatible with cryogenic temperatures and high magnetic field operations. A double-stage spring suspension system with eddy current damping has been implemented to achieve ≤5 pm z stability in a noisy environment and in the presence of an interconnected growth chamber. Both tips and samples can be quickly exchanged in situ; also a tunable external magnetic field can be introduced using a transferable permanent magnet shuttle. This allows spin-polarized tunneling with magnetically coated tips. The performance of this microscope is demonstrated by atomic-resolution imaging of surface reconstructions on wide band-gap GaN surfaces and spin-resolved experiments on antiferromagnetic Mn(3)N(2)(010) surfaces.