Aidong Xu

Research on deterministic communication of industrial wireless based on WLAN

The shortages of WLAN applied to the field of industrial control are given by analyzing the communication mechanism of WLAN. In this article, it presents a new communication method with deterministic scheduler in order to satisfy requirement of industrial wireless communication. It selects beacon interval as communication macro cycle, and pre-selects a station as the coordinated station that is responsible for the maintenance accurate clock synchronization function within the BSA. In data link layer, packets from user layer are divided into periodic packets and non-periodic packets. In terms of devices configured information beforehand, the periodic packets would be sent by fixed time clock, while the non-periodic packets would be sent when it is polled by the coordinated station, herein, we selected polling algorithm with good performance in the aspect of adaptive. This is called deterministic scheduling. The deterministic scheduling mechanism put forward in this paper provides foundation for applying WLAN to the field of industrial control, and its deterministic communication methods is compatible with other commercial WLAN well.

Avoiding the babbling idiot failure in a communication system based on flexible time division multiple access: A bus guardian solution

In a safety-critical real time system it is important to prevent the babbling idiot failure (BIF), which is characterized by a faulty node transmitting arbitrary messages at random points in time. However, existing communication systems based on flexible time division multiple access (FTDMA), whose development was driven explicitly by the new needs of future in-car control applications involving safety-critical functions, do not provide any efficient solution to avoid the BIF. Therefore, a bus guardian (BG) solution is presented to avoid the BIF in a FTDMA based communication system in this paper. The supervision algorithm of the proposed BG is presented along with the node architecture necessary for implementing the presented technique. Results of performance evaluation show that the proposed BG can enforce the error containment in the time domain of FTDMA based systems and help to make them appropriate for safety-critical applications.

SIL verification for SRS with diverse redundancy based on system degradation using reliability block diagram

Safety integrity level (SIL) verification is a critical step in safety lifecycle of safety-related systems (SRS). Introducing redundancy into SRS raises two issues: voting group configuration and common cause failures (CCF). In order to minimize CCF, diverse redundancy is widely adopted by SRS. However, in the past, almost all attention of SIL verification has been paid to identical redundancy, this is reflected in IEC 61508, ISA-TR84.00.02 and scientific literatures. Therefore, a novel method for SIL verification of SRS with diverse redundancy based on system degradation is proposed. Key idea of the method is to calculate average probability of dangerous failure on demand (PFDG) at each stage of system degradation, which is caused by failures of redundant channels. To validate proposed method, it has been applied on safety shutdown system of Nuclear Power Control Test Facility, and numerical result is compared with FTA and FRANTIC model. Sensitivity studies and comparison of numerical results indicate that the method has very good consistency with FTA and FRANTIC model. Moreover, two sets of general formulae for PFDG of any MooN(D) group with diverse redundancy are provided. From engineering practice point of view, it makes SIL verification process simpler.

A hardware-in-the-loop simulator for demand response energy management in industrial facilities

Demand response (DR) used in smart grid (SG) can enhance the reliability of the power system as well as reduce the energy costs for customers. One of the major consumers of electrical energy is industry. In this study, we develop a hardware-in-the-loop (HIL) simulator to demonstrate how to practically implement DR in industrial facilities. The HIL simulator includes an energy management system (EMS), a monitoring and control system (MCS), an industrial Ethernet backbone network based on RAPIEnet protocol, and a wireless field network based on ISA100.11a protocol. The results show that the electricity demand of industrial facilities can be shifted from peak to off-peak demand periods to improve the reliability of the electrical grid.

Implementation of wireless industrial networks for industrial smart grids

Though industry is one of the major consumers of electricity but Demand Response (DR) research in the industrial sector is relatively immature. The use of wireless technologies as a part of demand response infrastructure in industry has benefits, including increased flexibility of operation and reduced installation and maintenance costs. In this study, a demonstration system of the infrastructure for demand response in industries is developed using two independent (and competing) standards for industrial wireless networks: WirelessHART and ISA100.11a. The demonstration system is tested by controlling the electrical loads using industrial wireless networks and obtaining the energy consumption data of the electrical loads on a host application for demand response.

A homogeneous group bargaining algorithm in a smart grid

In this paper, we consider a smart grid incorporating numerous devices. In order to manage the energy distribution, we propose an algorithm that employs the group bargaining concept of game theory to efficiently allocate electricity resources among these devices. First, we divide the devices into non-overlapping groups, and allow devices to bargain both within and across groups. Second, we regard each group as homogeneous, so that the bargaining authority can be delegated to a representative device. Thus, the bargaining problem involves only the representatives, each of which bargains with other representatives on behalf of the group it belongs to. Third, we compare various bargaining results via a utility function that indicates the satisfaction level of a representative in terms of the bargaining result. Finally, the algorithm determines the optimal resource distribution pattern by maximizing the aggregated utilities of all representatives. Simulation results show that the proposed algorithm can reduce the complexity of energy distribution by distinguishing between inter- and intra-group bargaining processes, and can efficiently allocate resources to various devices according to their actual requirements.

Industrial wireless deterministic communication based on WLAN: Design, implementation and analysis

In this article, it presents the status of wireless communication being applied in industrial environment, and points out its deterministic communication issue existed in control network. According to this issue, a kind of industrial wireless deterministic communication mechanism and method based on WLAN is put forward. Afterwards, the main part is to describe the process of design, implementation and test programs. Depending on test results, some analysis is set out to indicate that the parameters performance of IWLAN with deterministic scheduling mechanism is better than commercial WLAN. At the end of this article, simulation result is supplied as the reference of actual IWLAN parameters performance.

Enforcing Fail-Silence in the Entire FlexRay Communication Cycle

It is desirable that the nodes exhibit fail-silent behavior when designing distributed fault-tolerant systems. Bus Guardian (BG) is adopted to enforce the fail-silence property of the node in the FlexRay communication system. However, the BG is effective only in the static segment while in the dynamic segment it does not provide any protection. Therefore, a novel BG is proposed in this paper. The mechanisms of the novel BG are presented along with the node architecture necessary for implementing the presented technique. Mathematical analysis results show that the novel BG can effectively enforce fail-silence property in the entire FlexRay communication cycle.

A Novel Method of Fault Detection for Solenoid Valves Based on Vibration Signal Measurement

Solenoid valves are vital pieces of equipment which have been widely used in a variety of industries. Fault detection methods of solenoid valves play important role for improving their reliability and maintenance efficiency due to their high failure rates in the field. Therefore, a novel method of fault detection for solenoid valves based on vibration signal measurement is proposed in this paper. The vibration sensor is place on the top of the solenoid valve and the vibration signal is collected by Labview SignalExpress system. The amplitude of the signal is extracted by denoising algorithm based on Wavelet and analyzed to detect the working state with the help of health index. The method is not interfered by the power supply system, and the method enhance the ability to resist interference. Experimental platform was set up to validate the proposed method by injecting faults into the solenoid valve. Experimental results show that the method proposed can provide not only indications of whether or not the valve is functioning, but also the information of how well the valve is functioning, thus empowering condition-based maintenance operations.

Research on the sensor calibration of pressure transmitter based on the least square method

The accuracy of capacitance pressure sensor is easily disturbed by work environment. In order to improve the accuracy of pressure sensor, the paper researches on the sensor calibration of pressure transmitter based on the least square method. The measurement circuit is designed to convert the output of sensor from the capacitance value to the cycle value. Working quadric surface is fitted with the value of environmental temperature, the output of pressure sensor and setting pressure by the least square method. The pressure transmitters can accurately measure at different temperatures by the experiment.