Browsing by Author "B.M., Kunar"

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Performance of a Boost Multi Level Inverter for Mining Applications
(National Institute of Technology Karnataka, Surathkal., 2023) N.V.V., Prudhvi Krishna B; B.M., Kunar; Ch.S.N., Murthy
In recent, much advancement has been witnessed in the field of drive systems. Electrical variable speed drives (VSDs) are integral to mineral processing and mining. VSDs are widely used in mining, drilling, traction, air compressors, water pumps, and conveyors. In fact, drives are back bone for any application, In the field of mining, drilling, traction systems drives are the only important parts of the entire control units. In this regard, the inner structure of drive i.e., inverter is key unit for the same. In the present study a novel inverter structure is designed for different mining, traction and conveyor applications. Although applications are plenty but still the proposed inverter is capable to meet the aforesaid applications. The back ground of drives system is that, for many years DC motors were used in mining applications. Steadily those motors are being replaced with AC motors due to several advancements in the AC drive technology. In addition to better control, AC motors require less maintenance than DC motors. Thus, controlling AC motors with drive system is a challenging issue. This aspect is key for new research and developments in the field of drives. Although voltage control and current control drives exists, still VSD’s have their own functions and features in terms of utilization. Traditionally VSDs are the part of the drive systems, VSD’s are mainly based on the conventional voltage source inverters (VSIs). Nevertheless, the conventional VSIs suffer from the barriers like output voltage limitations, harmonics, and control complexities. Since the loads are variable in the mining applications, continuous and reliable power converters are much needed. Multilevel inverters (MLIs) have become a promising alternative to conventional VSIs due to efficiency, ample power capacity, high-quality injected currents, and less complexity. Most of the available MLIs possess unity or stepped-down voltage feature. In such cases, a front-end boosting stage or step-up transformer at the output is used to meet the voltage requirement. Using MLIs with inherent boosting ability in such a scenario is more logical. Capacitor-based MLIs with boosting ability and self-voltage balancing are termed switched capacitor MLIs (SC-MLIs). Likewise, MLI topologies presented in this thesis amplify the voltage level using a single dc source. These units can be cascaded to produce higher levels by considering a proper choice of the magnitude of the multiple dc sources. The motivation of this research work is to emanate a novel switched-capacitor-based boost MLI for mining and drilling applications. In particular, the proposed inverter is designed for v nine-levels by using two capacitors as virtual sources. To support the proposed configurations, detailed operating principles, modulation, and real time results are presented. The Proposed MLIs is capable to generate large number of levels with a single source if it extended further. However, to achieve nine levels only 11 switches and 2 capacitors are used and this enables the proposed topology in compact and efficient manner.
Predictive Assessment of Postural Risk and Biomechanical Analysis of Musculoskeletal Disorder Related Problems of Dump Truck Operators in Indian Surface Metal Mines
(National Institute of Technology Karnataka, Surathkal., 2024) Kar, Mohith Bekal; M., Aruna; B.M., Kunar
This study aimed to determine the postural risk among dumper operators working in Indian surface metal mines. An epidemiological study was conducted to determine the association between driving posture and Work-Related Musculoskeletal Disorders (WRMSDs). A customized self-reported questionnaire was developed to collect personal, habitual, and work related data from the selected sample. The raw data was pre-processing and analysed using Machine Learning (ML) models, such as Random Forest (RF), Support Vector Machine (SVM), Decision Tree (DT), Gradient Boosting Machine (GBM), and Logistic Regression (LR). The performance of these models was evaluated using metrics, such as accuracy, precision, recall, F1 score, and Receiver Operating Characteristic (ROC) curve. The findings of the performance study indicated that the RF model offers better results over SVM, DT, GBM, and LR models with an accuracy of 0.71, precision of 0.75, recall score of 0.78, and F1 score of 0.76. Furthermore, the study revealed that age of the dumper operators had a significant association with WRMSDs, followed by awkward driving posture, work experience, job demand, alcohol consumption, smoking, work design, and marital status. In overall, the epidemiology study proved that the role of awkward driving posture contributes to the WRMSDs among dumper operators. Consequently, a thorough analysis of sitting posture of dumper operators was conducted using the observation method (i.e. fuzzy RULA method). The findings showed that over 80% of dumper operators exhibited a fuzzy RULA score corresponding to 'action level two', indicating the necessity for further investigation. To investigate deeper, a study of operator’s sitting posture with respect to various job cycles (i.e. loading, hauling with load, unloading, and empty travel) was undertaken. The detailed analysis revealed relatively consistent fuzzy RULA scores ranging from 3.5 to 4.25 during dynamic operations. Conversely, during static operations, the fuzzy RULA scores fluctuated more widely, ranging from 3.25 to 4.5. This reveals that operators maintained nearly identical postures during dynamic operations, whereas their sitting postures varied more during static operations. The Fuzzy RULA method do not consider operator’s height and weight, which is important factors contributing to WRMSDs. Therefore, a comprehensive biomechanical analysis of dumper operators was conducted using the "opensim" software package and Gait2354 human model. In this study the load on the spine, muscles, and tendons during primary climb, main v haul, right incline traverse, left incline traverse, and final climb tasks was determined. The outcome of the study showed that the load on the spinal was varying with the job cycle, with maximum load occurring during main haul (335.74N), followed by primary climb (324.30N), final climb (324.30N), right incline traverse (314.43N), and left incline traverse (304.29N). The biomechanical analysis also indicated that the muscle and tendon forces vary with job cycle. During right incline traverse, the right ERCSPN, right EXTOBL, and right INTOBL muscles experienced relatively high total forces (i.e. 41.76N, 59.99N, and 39.21N, respectively). Similarly, during left incline traverse, the left ERCSPN, left EXTOBL, and left INTOBL muscles experienced high total forces (i.e. 47.34N, 70.05N, and 51.33N, respectively). The tendon which joins the muscles with the bone also showed the same trend. The tendons attached to the right ERCSPN, right EXTOBL, and right INTOBL muscles experienced high total force of 41.76N, 59.99N, and 39.21N, respectively during right inclined transverse. Similarly, the tendons attached to the left ERCSPN, left EXTOBL, and left INTOBL muscles experienced high total force of respectively 47.34N, 70.05N, and 51.33N when the dumper operator were performing left inclined transverse. In general, this study showed that muscles suffers significant tensile forces when operators perform right and left inclined transverse movements. During the field study, it was observed that the operators were not wearing seat belts while operating dumpers. Because of this when navigating corners, operators encountered centripetal forces, prompting them to lean their bodies and consequently shifting the center of gravity (COG) from the center to the side. This change in COG led to tensile forces acting on the muscles and tendons connected to the spine. Hence, this study recommends for the mandatory use of seat belts by operators while operating. Similarly, this study also disclosed that the spine undergoes significant compressive forces during the main hauling operation (i.e. the movement of the dumper between loading and unloading points). The compressive load on the spine increases with increase in Body Mass Index (BMI) of the operators. However, considering operators with lower BMIs may not be feasible due to potential recruitment bias. Hence, this study suggests to incorporate regular breaks for operators during work to mitigate ill effects on their health.