HAND-ARM VIBRATION IN DIFFERENT OPERATING CONDITIONS WITH A CHAINSAW

The mechanization of forest harvesting is a trend in Brazil. However, small and medium-sized companies in the forestry sector, even today, opt for semi-mechanized harvesting, using chainsaws for the harvesting and sectioning of trees. Despite technological advances, when operated continuously, chainsaws may cause damage to the operator’s body, acting as a stressor, and vibration excess is responsible for numerous health disorders, among them the Raynaud syndrome. In this sense, this study aimed to determine the vibration levels to which a chainsaw operator is subjected, during the transversal cut (tracing) of the wood, in different forest species and cutting sets. The treatments consisted of three forest species (Eucalyptus grandis, Eucalyptus dunnii and Acacia mearnsii De Wild) and two cutting sets, consisting of square tooth chains of the semi-chisel and chisel types. The vibration assessment was based on the criteria established by the Regulatory Standards NR15, NHO10 and ISO 2631-4. The results of vibration levels were higher than the reference limits established by ISO 2631-4, and, for both cutting sets, the highest vibration levels occurred on the “x” axis. After the data processing, the acceleration values resulting from the normalized exposure to hand-arm vibrations showed significant differences for the “y” and “z” axes. Therefore, it can be inferred that the chainsaw operation is a stressor, potentially capable of causing damage to workers' health.

Analyzing the Vibration Exposure to the Safety and Health at Workplace: A Case in the Urea Granulation Unit of the Fertilizer Factory

This study aims to evaluate the vibration exposure experienced by workers in the Urea Granulation Screen Unit (UGSU) at the fertilizer factory in Aceh, Indonesia. This study involved 30 labors in charge as operators, mechanical maintenance officers, electrical maintenance officers, instrument maintenance officers, and inspectors. The measurement of vibration was carried out using a Triaxial Accelerometer with Integral Magnet and shows that the vibration exposure on the factory floor of the urea granulation screen unit occurs vertically with a minimum value of 0.298 m/s2 and a maximum of 1.630 m/s2. According to ISO 2631-1:1997, the maximum vibration values that occur are categorized as a likely health risk zone and result in uncomfortable reactions to the workers. Furthermore, this study analyzes the effect of vibrations on musculoskeletal problems using a Nordic Body Map (NBM) questionnaire. It reveals that the average score of musculoskeletal complaints is 71.6, which defines a high degree of pain. The results of the NBM questionnaire also showed that the vulnerable part of the body which experienced musculoskeletal complaints is the knee. The result of vibration exposure on this body part shows the highest value of 3.437 m/s2. To minimize occupational diseases and accidents, it is necessary to manage a working system that takes into account legal standards, ideal working time, and working shifts in the work area.

Conceptual design recommendations to improve seakeeping of small high-speed craft providing interisland transportation in Galápagos

To reduce the negative effects on passengers of the high-speed craft motions in Galapagos inter islands service, an optimization procedure at conceptual design level is developed. First, time histories of vertical acceleration of midship and forward end are first measured and analyzed. Weighted acceleration signals are compared with those from well-known experimental tests and are also used to evaluate the index of motion sickness with ISO 2631 standard to determine the number of persons affected by craft motion. The report from the sea trials includes the number of persons vomiting and those experienced dizziness because of the motions during the two-hour inter islands trip. Then, an optimization procedure using feasible directions is implemented with a combination of resistance and CG acceleration of the vessel to be minimized. Both functions were evaluated using well-known empirical formulations. The results show that increasing length and deadrise angle, and moving LCG forward, it is possible to reduce the acceleration by 20% while obtaining a 4% reduction in resistance.

Limites de vibração de corpo inteiro no mundo

O presente artigo realizou uma análise técnica dos limites e metodologias adotados para avaliação de vibração ocupacional de corpo inteiro em 56 países. O artigo também discute as metodologias e justificativas adotadas no Brasil para avaliar a vibração de corpo inteiro que difere da maioria dos países. A vibração constitui um fator de risco para a saúde nos ambientes ocupacionais se dá de forma total, ou seja, é transferida para todo o corpo. Devido aos diversos efeitos à saúde, atualmente 29% países possuem limites legais para a vibração de corpo inteiro. Quase a totalidade dos países adotam as metodologias e procedimentos da ISO 2631-1, mas não necessariamente adotam os valores do guia de orientação à saúde adotado em 1997. Os valore limites adotados mundialmente 67% estão acima do limite superior da zona de cautela para o método Root mean square (rms) que é o utilizado por 100% dos países, enquanto método adicional VDV é adotado por menos de 11%. A aceleração do pior eixo para avaliar o rico à saúde conforme determina o padrão ISO é adotado por 96,6% dos países. O Brasil adota a metodologia resultante que é a soma quadrática dos três eixos, mas não foram encontrados evidencias que embasem tão escolha. Conclui-se que o Brasil deve revisar os limites adotados atualmente que são mais restritivos, mais não constitui maior proteção, pois os efeitos da vibração dependem de múltiplos fatores, que incluem, por exemplo, fatores ergonômicos da atividade laboral.

Use of measured accelerations from a passenger rail car to evaluate ride quality and track roughness – A case study

Increasing traffic and speeds on passenger rail lines, and a short season for maintenance work, have motivated the industry to find new methods to assess the condition of existing infrastructure and determine where upgrades are required. In this study, acceleration data from the car body and axle boxes of a revenue car over 92 km of a Canadian passenger rail route in Ontario were collected for two purposes: first, to apply weighted filtering method according to ISO 2631-1997 standard as a technique to determine the locations which highly impact the ride quality and to investigate the effect of type of track features and speed on the ride quality; second, a new analytical method called the envelope of acceleration was applied to use the recorded accelerations to evaluate the alignment and surface roughness along the track. Since the alignment and surface roughness values are always positive and are calculated over a specified length (e.g. 9.5 m, 18.9 m, 38 m) an envelope technique was employed which uses spline interpolations over local maxima of the absolute magnitude of accelerations at every separated n samples corresponding to best fit with track roughness. The regression analysis between the envelope of accelerations and alignment and surface roughness presented a meaningful correlation and showed the applied method is a promising analytical technique to indicate rough sections of the track. The limitations to the application of envelope of acceleration are also discussed.

Path Planning Based on Obstacle-Dependent Gaussian Model Predictive Control for Autonomous Driving

Path planning research plays a vital role in terms of safety and comfort in autonomous driving systems. This paper focuses on safe driving and comfort riding through path planning in autonomous driving applications and proposes autonomous driving path planning through an optimal controller integrating obstacle-dependent Gaussian (ODG) and model prediction control (MPC). The ODG algorithm integrates the information from the sensors and calculates the risk factors in the driving environment. The MPC function finds vehicle control signals close to the objective function under limited conditions, such as the structural shape of the vehicle and road driving conditions. The proposed method provides safe control and minimizes vehicle shaking due to the tendency to respond to avoid obstacles quickly. We conducted an experiment using mobile robots, similar to an actual vehicle, to verify the proposed algorithm performance. The experimental results show that the average safety metric is 72.34%, a higher ISO-2631 comport score than others, while the average processing time is approximately 14.2 ms/frame.

Impact Assessment of Whole Body Vibration and Physiological Stress Factors on Dumper Operator during Different Phases of Operating Cycle as per ISO 2631-1

Introduction: In the mining industry, the dumper vehicle plays a vital role in material handling tasks. During the various operations, the dumper operators are subjected to Whole-Body Vibrations(WBV) which also affects their physiological factors. The present study investigates the dumper operator discomfort during various dumper operations such as Material-Loading(ML), Loaded-Travel(LT), Material-Unloading(MU) and Unloaded-Travel(UT). Methodology: The experimental study is carried out in iron ore opencast mine with a 25 number of operators volunteered to participate in this ergonomic assessment, and the evaluation is performed as per ISO 2631:1 Results: During the ML, and MU task, the measured crest factor value is greater than the recommended values. However, the measured aw(8) and VDV(8) magnitude are within the HGCZ limit. In the LT, it is observed that the VDV is within the limit of HGCZ, although the measured value is 4.08 times greater than MU task. The maximum WBV is observed during the UT, and the measured value of VDV falls above the HGCZ limit, and experience a greater amplification of source vibration at 1.6Hz. Moreover, the demand for the operation cycle increases the risk of neck pain and back pain among the study population. Further, operators immediately after the WBV exposure showed a significant increase in Heart Rate by 2.04 bpm. Whereas, no significant influence on the increase in blood pressure (SYS/DIA: 1.56/0.72 mmHg) and a decrease in oxygen saturation level (SpO2) by 1% was observed. Conclusion: Therefore, the present study reveals that the prolonged sitting and constant experience of WBV force the operator to change the posture more frequent. The combined effect of WBV with asymmetric posture can lead to musculoskeletal disorders. Practical Applications: The experimental findings support the health and safety officer to make a productive work plan for labour workforce to reduce health-related risk from WBV exposures.

An extended model of the ISO-2631 standard to objectify the ride comfort in autonomous driving

BACKGROUND: With the development of autonomous driving, the occupants’ comfort perception and their activities during the drive are becoming increasingly the focus of research. Especially in one of the first applications, a drive on a motorway, vertical dynamics play a major role. OBJECTIVE: To be able to robustly objectify ride comfort, better models need to be developed. Initial studies have shown, that the current ISO-2631 standard creates good results in the objectification and can be regarded as benchmark. METHODS: To increase the accuracy in objectification, an extended model with the occupants’ head as additional measuring point is introduced. Instead of the known frequency filters, weighting (k-factors) is used to differentiate possible excitations. For comparing the model with the ISO-2631, a simulator study with 5 excitations and 50 inattentive subjects is carried out. RESULTS: Evaluating the study with the ISO-2631, 3 out of 5 excitations indicate a significant difference between the occupant’s impression and the calculated comfort value. In comparison the extended model has no significant difference. CONCLUSION: The results further show, that inattentive occupants move their heads significantly more. By measuring accelerations of the head, the extended model creates equivalent or more accurate comfort values than the ISO-2631.

Analysis of bio-dynamic model of seated human subject and optimization of the passenger ride comfort for three-wheel vehicle using random search technique

Ride comfort is the major concern to the roadway vehicle passengers, travelling in as it affects their health and efficiency to work. In the present study, a 9 DoF model of a three-wheel vehicle is developed with Lagrangian approach to investigate its ride behavior when subjected to random surface irregularities. The irregularities of the track are measured with a three-wheeled setup equipped with profilometer known as opto-coupler. The present model is validated in two ways, first by comparing the vertical-lateral PSD acceleration received from simulation and actual testing and second by comparing vertical seat to head transmissibility obtained from analysis (VSTH) with past reported studies. A 7 DoF bio-dynamic model of the seated human subject is formulated and integrated with the vehicle model, ride comfort of the vehicle and human body segments are assessed based on ISO specifications. Passenger Ride Comfort is optimized through non-linear optimization using Random Search Technique. The modified values of vehicle suspension parameters are presented to obtain optimum passenger comfort based on ISO-2631-1 criteria.