Fuzzy Sliding Mode Control for logitudinal motion of underground mining electric vehicles

Cost and safety are always the most important factors for personnel transport and mining vehicles in mining industry. That is why the development of underground mining electrical vehicles (UMEVs) becomes more and more attractive in undergrounds mines. However, a stable, reliable and robust controller for the UMEV is also a critical condition due to the safety requirements. Sliding Mode Control (SMC) is able to deal with system uncertainties and external disturbances, but it cannot achieve smooth performance during the transition between different subspaces in the state space. This paper first presents the modeling of an UMEV for acceleration, braking and speed maintenance, and a global fuzzy model will be developed based on that. Then, a Fuzzy Sliding Mode Controller (FSMC) of the UMEV will be proposed. The comparison of the simulation results for both the proposed FSMC controller and an SMC controller shows that the proposed FSMC controller has a better performance when the system switches in different subspaces in the state space

Full-size testing to determine stress concentration factors of dragline tubular joints

This paper describes the determination of stress concentration factors (SCFs) of dragline tubular joints through laboratory testing of four full-size dragline tubular joints. Strip gauges are installed both outside and inside the footprint of the joints to measure stress distribution at the weld toe and weld root. Measurements for SCF are carried out for two load cases, i.e. tension or compression forces in the main chord alone and tension or compression forces in the vertical bracings alone with reaction forces in the inclined braces. The relationship of the SCF between the corresponding weld toes and weld roots are presented in the paper. The weld profile and weld root gaps that have been measured using the silicon imprint technique and feeler gauges, provide valuable information for future FE simulation and weld root failure study using the effective notch stress approach

Clustering LiFePO4 cells for battery pack based on neural network in EVs

Power sources of electric vehicles (EVs) are integrated by hundreds of cells connected in series and parallel. Due to slight differences in the manufacturing process and various operating conditions of the individual cell in a battery pack in EVs, the characteristics of the individual cell to cell can be non-uniform in the battery pack, which affects the available capacity and the life of the battery pack. This paper investigates the neural network (NN) based method to sort lithium iron phosphate (LiFePO4) cells so that the cells can be as consistant as possible before these cells form a battery pack. All cells used in the sorting process are LiFePO4 Cells. A clustering NN tool of self-organizing map (SOM) is adopted to classify the cells based on the experimental data of all cells. The cell temperature and capacity are used in the trained SOM to classify the cells. The cells in the same category are connected in series to form a sorted battery pack whereas the randomly chosen cells are connected in series to form the unsorted battery pack. The comparison between the sorted battery pack and the unsorted battery pack has been conducted to verify the clustering methods and the consistency of the cells in the battery pack

Self-organising map based classification of LiFePO4 cells for battery pack in EVs

This paper presents a self-organising map (SOM) based classification of lithium iron phosphate cells for a battery pack in EVs. The experimental data of the cells have been obtained to train the SOM. The temperature variation, internal resistance and available capacity of the cells are used as the inputs of the SOM, and the output of the SOM classifies the cells into three groups with the similar characteristics in terms of its input parameters. Then, the cells in the same group are connected in series to build a sorted battery pack whereas the randomly chosen cells are connected in series to build an unsorted battery pack. The comparison of the consistency between these two battery packs under different discharging conditions has demonstrated the effectiveness of the proposed classification method. In addition, the experimental results show that state of charge based approaches for cell balancing are more effective than voltage based approaches

Structural health monitoring of a dragline cluster using the hot spot stress method

'Hot spot stress' is an approach often used to consider fatigue loadings in heavily welded tubular joints. This article reports the determination of hot spot stresses in mining dragline booms, which are often ≥100 m in length, using strain gage measurements and finite element analysis (FEA) modeling as part of a structural health monitoring concept. Strain gages were installed on a typical A11 cluster for estimating hot spot stresses, as recommended in the existing fatigue design guidelines by the International Institute of Welding (IIW) and the International Committee for the Development and Study of Tubular Construction (CIDECT). The results from the experimental measurements and the FEA were found to be comparable to a large measure. It was concluded that while hot spot stresses were high enough at the weld toes to cause cracking, they could not explain the cracking that occurs at the welds in the main chords on their own. Issues in comparing theoretical and experimental measurements are discussed

Cumulative damage analysis for fatigue life in dragline clusters

Stresses close to the weld toes in a dragline cluster were measured for a dragline under service conditions. Hot spot stresses were determined at the weld toes in the cluster using the linear extrapolation method as recommended by existing fatigue design guidelines. A rainflow counting analysis was carried out on the resultant hot spot stress-time histories for strain gauges located in the main chord and the lacing members. Existing fatigue design curves are used to estimate the fatigue life in the main chord and the lacing members using cumulative damage analysis. A comparison of fatigue life estimates from the cumulative damage analysis and average lives observed in the field is used as a basis for rec:ommending a modified method for cumulative damage analysis of the chord members. This investigation focuses on a cluster that is close to the boom foot and in which compressive stresses are significant in service. The findings in this investigation are compared to previous research

Notch stress factor of welded thick-walled tubular dragline joints by effective notch stress method

In Australia, draglines are used extensively in the coal mining industry. The tubular booms of the dragline are susceptible to fatigue cracking due to the large number of cycles they are subjected to during operation. Fatigue cracks may occur at either weld toe or weld root of the dragline joints. This paper acts as the first attempt to use the effective notch stress (ENS) method to determine the notch stress factors (NSFs) of the dragline joints. Only simplified 2D finite element analysis (FEA) was carried out at this stage. It was found that the NSF at the weld toe is higher than the NSF at the weld root for LC(I), the NSF at the weld root is in general higher than the NSF at the weld toe. The NSF results obtained are also used to compare with those obtained by using ENS method in the literature