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Optimization of the levels of grip force, stroke rotation, frequency and grip span for a torqueing task

Bano F., Mallick Z., Khan A. A.

International Journal of Occupational Safety and Ergonomics

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2015

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Vol. 21, No. 1

94--104

EN

This study was to investigate the effects of grip force, frequency, stroke rotation and grip-span on discomfort and obtain best posture for hand tool users. Fifteen male participants volunteered in this study. Participants performed combined gripping with torqueing exertions for 5 min for two levels of frequency (10 and 20 exertions/min) at two levels of grip force (50 and 70 N), two levels of stroke rotation (30° and 60°) and three levels of grip-span (4.7, 6 and 7.3 cm). Therefore, a 2×2×2×3 full factorial design was used. The analysis of variance (ANOVA) showed that frequency, stroke rotation and grip-span were significant on discomfort score. Minimum discomfort and comfortable posture was found to be 90 N grip force with 10 exertions/min for 60° stroke rotation at 6-cm grip-span. The grip force, frequency and stroke rotation were found significant on EMG activity of forearm muscles using multivariate analysis of variance (MANOVA). The extensor muscles were found more activated than flexor muscles during the given task.

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A Study on the Combined Effect of Noise and Vibration on the Performance of a Readability Task in a Mobile Driving Environment by Operators of Different Ages

Khan I. A., Mallick Z., Khan Z. A., Muzammil M.

International Journal of Occupational Safety and Ergonomics

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2009

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Vol. 15, No. 3

277--286

EN

This study investigated the combined effect of noise and vibration on the performance of a readability task in a mobile driving environment by operators of different ages. Subjects performed a readability task on a laptop computer in a sitting posture without their backs supported under varying levels of noise and vibration. Data in terms of a mean number of characters read per minute were collected and statistically analyzed. Results showed that the individual effects of noise, vibration, and operators’ age as well as the interaction between operators’ age and vibration were statistically significant. However, the combined effect of noise and vibration was not found to be statistically significant. Results also indicated that the operators’ age was statistically significant at all levels of vibration and vibration was statistically significant at all levels of operators’ age.

3

Evaluation and Optimization of Handle Design Parameters of a Grass Trimming Machine

Mallick Z.

International Journal of Occupational Safety and Ergonomics

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2008

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Vol. 14, No. 3

343–-349

EN

The grass trimming machine is a widely used agricultural machine for cutting grass by the roadside and in other areas in Malaysia. Hand–arm vibration (HAV) syndrome is very common among workers operating power tools and performing similar work for extended periods. Grass trimming involves the use of a motorized cutter spinning at high speed, resulting in high levels of HAV among its operators. The existing D-shape handle causes HAV-related stress and operational load in operators. This research proposes a new design of a handle of the grass trimming machine. When this new design was compared with the old one, it was found that the new handle resulted in 18% lower HAV. To find the lowest HAV, 3 critical parameters of the new handle (length, angle and material of the cap of the handle) were optimized using the Taguchi quality tool. Appropriately selected parameters of the new handle significantly reduced the occurrence of HAV among grass trimmers.

4

Investigating Data Entry Task Performance on a Laptop Under the Impact of Vibration: The Effect of Color

Mallick Z.

International Journal of Occupational Safety and Ergonomics

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2007

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Vol. 13, No. 3

291--303

EN

The last 20 years have seen a tremendous growth in mobile computing and wireless communications and services. An experimental study was conducted to explore the effect of text/background color on a laptop computing system along with variable environmental vibration on operators’ data entry task performance in moving automobiles. The operators’ performance was measured in terms of the number of characters entered per minute without spaces (NCEPMWS) on a laptop computing system. The subjects were divided into 3 categories, namely, Novices, Intermediates and Experts. Findings suggest a re-evaluation of existing laptop designs taking ergonomics into consideration. It appears that proper selection of text/background color on the laptop coupled with controlled vehicular speed could result in a better quality of interaction between human and laptops and it could also resolve the problem of poor data entry task performance.

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A Study on the Combined Effect of Noise and Vibration on Operators’ Performance of a Readability Task in a Mobile Driving Environment

Khan I. A., Mallick Z., Khan Z. A.

International Journal of Occupational Safety and Ergonomics

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2007

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Vol. 13, No. 2

127--136

EN

This paper presents a study in which the main objective was to investigate the combined effect of noise and vibration on the performance of a readability task in a mobile driving environment. Subjects performed a readability task on a laptop computer in a sitting posture with their backs supported with a backrest under varying levels of noise and vibration. The data in terms of the mean number of characters read per minute were collected and statistically analyzed. Results showed that the individual effect of noise, vibration, and the operators’ gender as well as the interaction between gender and noise, and gender and vibration were statistically significant. However, the combined effect of noise and vibration was not found to be statistically significant. Results also indicated that gender was statistically significant at all levels of noise as well as vibration, and noise and vibration were statistically significant at both levels of gender.