A new approach to anti-sway system design problem

We suggest a new type of swing motion control system for a crane system in which a small auxiliary mass is installed on the spreader. The actuator reacting against the auxiliary mass applies inertial control forces to the spreader of the container crane to reduce the swing motion in the desired manner. In this paper, as the basic and first step, we apply theH _∞, control approach to anti-sway control system design problem. And, it will be shown that the proposed control strategy is useful and it can be easily applicable to the real world. So, in this study, we investigate usefulness of the proposed anti-sway system and evaluate system performance through simulation and experimental studies.     

A hybrid approach to supervisory control of discrete event systems coupling RW supervisors to Petri nets

In this paper a hybrid approach is proposed for supervisory control of discrete event systems (DES) subject to forbidden states. Assuming that an uncontrolled bounded Petri net (PN) model of a (plant) DES and a set of forbidden state specifications are given, the proposed approach computes a maximally permissive and nonblocking closed-loop hybrid model. The first step is to simplify the given PN model by means of PN reduction rules. The simplified model and the specifications are then represented as buffers, and supervisory control theory (SCT) is applied to obtain a Ramadge–Wonham (RW) supervisor in the form of an automaton. After reduction of the latter’s state size by a ‘control congruence’, the simplified RW supervisor is represented by a so-called auto-net and coupled to the given uncontrolled PN plant model by means of inhibitor arcs to represent the disabling actions. The plant model and supervisor auto-net run concurrently, synchronizing on shared events. This procedure provides a maximally permissive and nonblocking ‘hybrid’ (mixed PN/automaton) closed-loop controlled system. The method is straightforward logically, graphically, and technologically. Its applicability is shown by two examples, one of them a workcell from the PN control literature.     

A new approach for pulsating torque minimization of BLDC motor

Torque ripple control of brushless DC motor has long been the main issue of the servo drive systems in which the speed fluctuation, vibration and acoustic noise need to be minimized. The vast majority of the methods for suppressing the torque ripple require the Fourier series analysis and either the iterative or least mean square minimization. In this paper, a novel approach based on thed-q-o reference frame that achieves ripple-free torque control with maximum efficiency is presented. The proposed method optimizes the reference phase current waveforms including even the case of 3-phase unbalanced condition, and the motor winding currents are controlled to track the optimized current waveforms by the delta modulation technique. As a result, the proposed approach provides a simple and yet effectine means for obtaining the optimal motor excitation currents. The validity and applicability of the proposed control scheme are verified through simulations and experimental investigations.     

Closed-loop control of constrained discrete event systems: application to a networked automation system

In this paper, we are interested in the design of closed-loop control laws to satisfy a set of temporal constraints in discrete event systems modeled by timed event graphs (TEGs). The dynamic behavior of the TEG is represented by a system of linear equations in Max-Plus algebra. Temporal constraints are imposed on some paths of the TEG and are expressed by a set of Max-Plus linear inequalities. The proposed approach is applied to the control of a networked automation producer/consumer system under a temporal constraint. The temporal constraint to be satisfied is imposed on the response time of the considered networked automation system (NAS). The calculated control laws are causal feedbacks and can be represented by monitor places connected to the NAS model.     

Discrete event control system design using automation Petri nets and their ladder diagram implementation

As automated manufacturing systems become more complex, the need for an effective design tool to produce both high-level discrete event control systems (DECS) and low-level implementations becomes more important. Petri nets represent the most effective method for both the design and implementation of DECSs. In this paper, automation Petri nets (APN) are introduced to provide a new method for the design and implementation of DECSs. The APN is particularly well suited to multiproduct systems and provides a more effective solution than Grafcet in this context. Since ordinary Petri nets do not deal with sensors and actuators of DECSs, the Petri net concepts are extended, by including actions and sensor readings as formal structures within the APN. Moreover, enabling and inhibitor arcs, which can enable or disable transitions through the use of leading-edge, falling-edge and level of markings, are also introduced. In this paper, the methodology is explained by considering a fundamental APN structure. The conversion of APNs into the IEC1131-3 ladder diagrams (LD) for implementation on a PLC is also explained by using the token passing logic (TPL) concept. Finally, an illustrative example of how APNs can be applied to a discrete manufacturing problem is described in detail.     

A new approach to PLC software design

This paper presents a model-based approach to PLC software development. The essence of this approach is the introduction of a new procedural modeling language called ProcGraph. In contrast to commonly used methods, ProcGraph deals with the procedural aspect of the control system and allows software specification at a higher level of abstraction. The modeling language has been supported with the development of a software tool which facilitates graphical model design and automatic code generation. The specification notation has been tested in the development of software for industrial applications. The supporting tool has been tested in a laboratory environment.     

A new hybrid approach to discrete multiple facility location problem

Locating certain facilities in predetermined sites is named the multiple facility location problems (MFLP). The objective of these kinds of problems is locating facilities to serve a given set of customers so that candidate sites and requirements are known. When the new facility sites have to be selected from a given set of candidate sites, the mentioned location problem becomes a discrete multiple facility location problem (DMFLP). In this paper, a special approach of DMFLP is considered where different multiple facilities have to be placed (location decision) and also customers have to be assigned to these facilities (allocation or assignment). The mathematical model of the proposed problem is developed, and with respect to the complexity of solving the mathematical model, especially in large scale, a new hybrid approach is proposed based on tabu search algorithm to solve the problem at each scale. Computational results on several randomly generated problems in comparison with a new proposed lower bound obtained from Lagrangian relaxation indicate that the proposed hybrid approach is both accurate and efficient.     

A new approach to design of a dynamic output feedback stabilizing control law for LTI systems

We present a new state-space approach to construct a dynamic output feedback controller which stabilizes a class of linear time invariant systems All the states of the given system are not measurable and only the output is used to design the stabilizing control law In the design scheme, however, we first assume that the given system can be stabilized by a feedback law composed of the output and its derivatives of a certain order Beginning with this assumption, we systematically construct a dynamic system which removes the need of the derivatives The mam advantage of the proposed controller is regarding the controller order, which may be smaller than that of conventional output feedback controller Using a simple numerical example, it is shown that the order of the proposed controller is indeed smaller than that of reduced-order observer based output feedback controller     

A new continuous sliding mode control approach with actuator saturation for control of 2-DOF helicopter system

The 2-degree of freedom (DOF) helicopter system is a typical higher-order, multi-variable, nonlinear and strong coupled control system. The helicopter dynamics also includes parametric uncertainties and is subject to unknown external disturbances. Such complicated system requires designing a sophisticated control algorithm that can handle these difficulties. This paper presents a new robust control algorithm which is a combination of two continuous control techniques, composite nonlinear feedback (CNF) and super-twisting control (STC) methods. In the existing integral sliding mode (ISM) based CNF control law, the discontinuous term exhibits chattering which is not desirable for many practical applications. As the continuity of well known STC reduces chattering in the system, the proposed strategy is beneficial over the current ISM based CNF control law which has a discontinuous term. Two controllers with integral sliding surface are designed to control the position of the pitch and the yaw angles of the 2- DOF helicopter. The adequacy of this specific combination has been exhibited through general analysis, simulation and experimental results of 2-DOF helicopter setup. The acquired results demonstrate the good execution of the proposed controller regarding stabilization, following reference input without overshoot against actuator saturation and robustness concerning to the limited matched disturbances.     

单机型人脸识别门禁系统的设计

本文在介绍智能IC卡门禁系统的功能及结构组成的基础上,结合人脸识别技术的最新发展,采用一种新型的人脸特征提取和识别算法,设计了单机型人脸识别门禁系统。将人脸识别的高安全性、便携性,难以伪造等优点用于门禁系统的身份认证,使门禁系统更安全,更易被人接受。实验证明该系统能够起到很好的实际应用效果。     

一种嵌入式多工位压力机送料机构控制系统

本文设计了一种嵌入式多工位压力机送料机构控制系统.基于总线式和模块化设计方法,分别建立了基于ARM的主控制器、手控盒以及基于FPGA的运动控制器等子单元.该系统具有易于维护、扩展性好、抗干扰能力强、结构紧凑等优点.     

A new approach for polymer composite gear design

A new design method for polymer composite gear has been proposed in the current paper. This design method is based on the link between polymer gear wear rate and its surface temperature. It has been found from the tests that the polymer (acetal) gear wear rate will be increased dramatically when the load reaches a critical value for a specific geometry. The gear surface will wear slowly with a low specific wear rate if the gear is loaded below the critical one. The possible reason of the sudden increase in wear rate is due to the gear operating temperature reaching the material melting point under the critical load condition. Gear surface temperature has been then investigated in detail through three components: ambient, bulk and flash temperatures. Through extensive experimental investigations and modelling on gear surface temperature variations, a general relation has been built up between gear surface temperature and gear load capacity. The method has been related to test results under different operating ambient temperature and gear geometries. Good agreement has been achieved between the proposed method predictions and experimental test results. Experimental investigation on polymer composite (glass fibre reinforced nylon with PTFE as internal lubricant) gears have also been carried out and two forms of failure have been found, root and pitch fractures.     

A computer-aided system for an optimal moulding conditions design using a simulation-based approach

Moulding conditions design refers to parameter settings of moulding conditions such as melt temperature, mould temperature and injection time. They are important factors in plastic injection moulding design. The determination of these parameters is a highly skilled job and has largely been dependent on injection moulding engineers' experience and intuitiveness. In this paper, the authors present a flexible computer-aided system to assist the designers by using simulation-based technology. One of the most prominent characteristics of the system is that it allows the designers to specify their intended quality measuring criteria such as minimum cavity pressure and shear stress, a uniform distribution of cooling time, end-of-fill temperature and volumetric shrinkage. The system uses weighted criteria as an objective function to determine optimal moulding conditions when multiple criteria are specified. Moldflow simulation results are used to compare different designs. A two-step exhaustive search strategy (from coarse to refined) is used to search for a near-optimal design.     

A new history-independent modeling approach for feature-based design

The majority of current feature-based modeling systems employ model history to store feature creation operations and re-execute them sequentially after each modification, which is called history-based modeling. Due to the static feature creation order, history-based modeling causes some problems during the reevaluation of the model, such as the evaluated model does not correspond to its specification, the operation can only refer to the boundary entities created by the previous operations, high computation cost, etc. In this research work, a new history-independent modeling approach is proposed. For the “remove feature” operation, only boundary faces originating from the feature being removed, and the intersecting features are modified for updating the resulting BRep model. For the “modify feature” operation, the feature being modified is first removed from the product model and then re-added with the new specifications, thus its creation step in the model history is changed. As a result, some of the problems caused by the static feature creation order are solved. During the reevaluation, the computation time is dependent solely on the execution of the feature and its intersecting features being edited. The computational complexity of the boundary evaluation using the proposed method for three representative models has been analyzed based on Open CASCADE. A case model was studied in a proof-of-concept prototype system to demonstrate the proposed modeling approach.     

Synthesis of feedback control elements for discrete event systems using Petri net models and theory of regions

This paper describes a method for constructing a Petri-net-based controller for a discrete event system (DES) modelled by a Petri net. Assuming that an uncontrolled Petri net model of the DES and a set of forbidden state specifications are given, feedback control elements, i.e. a set of places and related transitions, with initial marking, are computed using the theory of regions, which is a formal synthesis technique for deriving Petri nets from automaton-based models. When feedback control elements are added to the uncontrolled Petri net model, the controlled (closed-loop) Petri net model of the system is obtained. The controlled Petri net model obtained is maximally permissive while guaranteeing that forbidden states do not occur. The proposed method is computationally efficient and does not suffer from the state explosion problem. Two examples are provided to show the applicability of the proposed method.     

A new approach to motion control of torque-constrained manipulators by using time-scaling of reference trajectories

We introduce a control scheme based on using a trajectory tracking controller and an algorithm for on-line time-scaling of the reference trajectories. The reference trajectories are time-scaled according to the measured tracking errors and the detected torque/acceleration saturation. Experiments are presented to illustrate the advantages of the proposed approach.     

一种用于pH值控制的非线性系统的实现

分析了pH值曲线的非线性特点,对PID控制和前馈控制中的非线性控制因素分别采用非线性增益和模糊控制的方法来实现,并在实际运用中取得了较好的效果。     

A new approach to detection of vortices using ultrasound

The measurement principle of vortex flowmeter is based on von Karman vortex shedding phenomenon. Frequency of vortices, behind the bluff body, is proportional to the mean flow velocity. There are different ways of detection of vortices, and different sensors are used (presser sensors, capacitive sensors, thermo-resistance sensors, ultrasonic sensors, etc.). Proposed method to vortex identification, presented in this paper is based on simultaneous detection of pair of vortices with opposite circulation, by means of two pairs of ultrasonic transducers. A beam of ultrasound, from ultrasonic transmitter to ultrasonic receiver is transmitted perpendicularly to the vortex street. The received ultrasonic signal is amplitude and phase modulated. Frequency of demodulated signal is equal to the frequency of vortices. This technique allows a number of advantages comparing to conventional solutions: reduction, or elimination of noises caused by installation vibration and disturbances in the flow, higher sensor sensitivity, which as a result leads to a possibility of a reduction of the bluff body size, i.e. reduction of the pressure drop on the flow meter, increase of the measurement range in the low flow region, the possibility of redundant operation of the flow meter, reduced measurement uncertainty, instrument technology improvements, improved reliability of the instrument, assured improved statement of complete uncertainty contributions, improved metrology of the equipment as such and calibration procedures that contribute to measuring capabilities etc. For experimental testing a prototype vortex flowmeter of a nominal inner diameter (ID) 50 mm is developed. A cylindrical bluff body for vortex shedding is used. Ultrasonic transducers based on piezo-crystal PZT-5A, inserted in the wall of the vortex meter casing are utilized. The testing of prototype ultrasonic vortex flowmeter is realized on the calibration station on the water. The results at the testing point to the possibility of measuring flow of liquid fluids at velocities less than 0.5 m/s, with an uncertainty better than ±1%.     

液压系统故障诊断的实用方法探析

针对现今广泛应用的液压传动系统故障诊断的困难性,提出一种简便、实用的故障诊断方法。此法通过对系统参数的定量检测和逻辑分析,大大提高了系统故障诊断的科学性、快速性和准确性,降低了对维修人员的技术水平要求。大量实验表明,此法较传统的故障诊断方法效率大大提高,装拆工作量大大减少,具有较高的实用推广价值。