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- Bergsten, Eva L., 1969-, et al.
(författare)
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Physical and psychosocial work conditions among baggage handlers in six Swedish airports
- 2012
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Konferensbidrag (refereegranskat)abstract
- Introduction Flight baggage handlers are mainly engaged in sorting luggage or cargo, loading and unloading it to and from the airplanes. The Vocational Training and Working Environment Council, TYA - formed by employer’s and employee’s organizations in the transportation sector - initiated a scientific study in 2009 to investigate the prevalence of musculoskeletal disorders and their suspected determinants in six Swedish airports involving a total of about 1000 handlers in 14 cargo- and handling companies. Encouraged by an initial literature review, the present field study was designed to contain qualitative, questionnaire-based, and observational surveys of working conditions, as well as extensive direct measurements of postures using full-shift inclinometry. This paper reports the design and results of the questionnaire part of the study.MethodAll baggage handlers working at least half-time (n=1044) were encouraged to fill in an extensive questionnaire handed out at the workplace by a research team member. In general the researcher collected the questionnaires at the same occasion. The questionnaire addressed general health, work capacity and physical exposures in relevant handling tasks. It also included a modified version of the Copenhagen Psychosocial Questionnaire (COPSOQ), the Nordic Council of Minister’s Questionnaire (NMQ) on disorders, and the SOFI-questionnaire measuring perceived fatigue.ResultsThe response rate was 73%. The prevalence of musculoskeletal disorders in the back, shoulders and wrists during the last 12 months was 70%, 60% and 45%. Positive effects of devices used for reducing perceived physical load were confirmed. The handlers expressed a low confidence in the leadership, and insufficient feedback, information and influence at work. Fatigue particularly occurred in the dimensions lack of energy and physical discomfort.DiscussionThe observed prevalence of low back pain (70%) is high, and in parity with results among nurses in Sweden (64%; Josephson et al. 1997) and China (56%; Smith et al. 2004). Further examination of questionnaires, interviews and direct posture measurements will identify determinants to consider for intervention to reduce the prevalence of disorders among the baggage handlers.Josephson M, et al. Occup Environ Med 1997;54:681-685.Smith DR, et al. Occup Med 2004;54:579-582
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| 3. |
- Jakobsson, Erik, et al.
(författare)
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Automated Usage Characterization of Mining Vehicles For Life Time Prediction
- 2020
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Ingår i: IFAC PAPERSONLINE. - : ELSEVIER. - 2405-8963. ; , s. 11950-11955
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Konferensbidrag (refereegranskat)abstract
- The life of a vehicle is heavily influenced by how it is used, and usage information is critical to predict the future condition of the machine. In this work we present a method to categorize what task an earthmoving vehicle is performing, based on a data driven model and a single standalone accelerometer. By training a convolutional neural network using a couple of weeks of labeled data, we show that a three axis accelerometer is sufficient to correctly classify between 5 different classes with an accuracy over 96% for a balanced dataset with no manual feature generation. The results are also compared against some other machine learning techniques, showing that the convolutional neural network has the highest performance, although other techniques are not far behind. An important conclusion is that methods and ideas from the area of Human Activity Recognition (HAR) are applicable also for vehicles. Copyright (C) 2020 The Authors.
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| 4. |
- Jakobsson, Erik, 1987-, et al.
(författare)
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Data driven modeling and estimation of accumulated damage in mining vehicles using on-board sensors
- 2017
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Ingår i: PHM 2017. Proceedings of the Annual Conference of the Prognostics and Health Management Society 2017, St. Petersburg, Florida, USA, October 2–5, 2017. - : Prognostics and Health Management Society. - 9781936263264 ; , s. 98-107
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Konferensbidrag (refereegranskat)abstract
- The life and condition of a MT65 mine truck frame is to a large extent related to how the machine is used. Damage from different stress cycles in the frame are accumulated over time, and measurements throughout the life of the machine are needed to monitor the condition. This results in high demands on the durability of sensors used. To make a monitoring system cheap and robust enough for a mining application, a small number of robust sensors are preferred rather than a multitude of local sensors such as strain gauges. The main question to be answered is whether a low number of robust on-board sensors can give the required information to recreate stress signals at various locations of the frame. Also the choice of sensors among many different locations and kinds are considered. A final question is whether the data could also be used to estimate road condition. By using accelerometer, gyroscope and strain gauge data from field tests of an Atlas Copco MT65 mine truck, coherence and Lasso-regression were evaluated as means to select which signals to use. ARX-models for stress estimation were created using the same data. By simulating stress signals using the models, rain flow counting and damage accumulation calculations were performed. The results showed that a low number of on-board sensors like accelerometers and gyroscopes could give enough information to recreate some of the stress signals measured. Together with a linear model, the estimated stress was accurate enough to evaluate the accumulated fatigue damage in a mining truck. The accumulated damage was also used to estimate the condition of the road on which the truck was traveling. To make a useful road monitoring system some more work is required, in particular regarding how vehicle speed influences damage accumulation.
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| 5. |
- Jakobsson, Erik, et al.
(författare)
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Fault Identification in Hydraulic Rock Drills from Indirect Measurement During Operation
- 2021
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Ingår i: IFAC PAPERSONLINE. - : ELSEVIER. - 2405-8963. ; , s. 73-78
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Konferensbidrag (refereegranskat)abstract
- This work presents a method for on-line condition monitoring of a hydraulic rock drill, though some of the findings can likely be applied in other applications. A fundamental difficulty for the rock drill application is discussed, namely the similarity between frequencies of internal standing waves and rock drill operation. This results in unpredictable pressure oscillations and superposition, which makes synchronization between measurement and model difficult. To overcome this, a data driven approach is proposed. The number and types of sensors are restricted due to harsh environmental conditions, and only operational data is available. Some faults are shown to be detectable using hand-crafted engineering features, with a direct physical connection to the fault of interest. Such features are easily interpreted and are shown to be robust against disturbances. Other faults are detected by classifying measured signals against a known reference. Dynamic Time Warping is shown to be an efficient way to measure similarity for cyclic signals with stochastic elements from disturbances, wave propagation and different durations, and also for cases with very small differences in measured pressure signals. Together, the two methods enables a step towards condition monitoring of a rock drill, robustly detecting very small changes in behaviour using a minimum amount of sensors. Copyright (C) 2021 The Authors.
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| 6. |
- Lapkin, Igor, 1963, et al.
(författare)
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Dual Band MM-Wave Receiver for Onsala 20 m Antenna
- 2014
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Ingår i: Proceedings of the TWENTY-FIFTH INTERNATIONAL SYMPOSIUM ON SPACE TERAHERTZ TECHNOLOGY, April 27-30, 2014, Moscow, Russia. ; , s. 132-
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Konferensbidrag (refereegranskat)abstract
- We present the design and the first light results for the new dual band receiver (4 mm and 3 mm bands) for Onsala Observatory 20 m antenna. For single dish operation, the receiver uses innovative on-source/off-source optical switch. Within the same optical layout, the switch, in combination with additional optical components, provides 2 calibration loads and sideband measurements possibilities. The optics layout of the receiver uses offset elliptical cold mirrors for both channels whereas the on-off switch employs flat mirrors only. The 3 mm channel employs 2SB dual polarization receiver with OMT, 4-8 GHz IF, x 2pol x (USB+LSB). The cryostat has 4 optical widows made of HDPE with anti-reflection corrugations, two for the signal and two for each frequency band cold load. The cryostat employs a two stage cryocooler RDK 408D2 and uses anti-vibration suspension of the cold-head to minimize impact of the vibrations on the receiver stability. The LO system is based on Gunn oscillator with PLL and two mechanical tuners for broadband operation, providing independently tunable LO power for each polarization. At the conference, we will present details on the receiver optics, cryostat design and the result of the first on-sky observations.
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