The accuracy of measurements in a time study of harvester operations

Abstract

Background: Work time measurements are the starting point for any calculation of unit costs of machine exploitation; therefore, the accuracy of evaluating these costs determines the economic effectiveness of technological solutions employed in forest work. The research aimed to determine the level of measurement error of harvester operation times by means of a chronometric method. Methods: Different methods for measuring the components of the work cycle in cut-to-length harvesting operations were compared. These operations consisted of a thinning and a clear-cut harvesting operation in two Scots pine (Pinus sylvestris L.) stands in central Poland. The average duration of a work cycle was determined from cumulative timing using either the on-board PSION microcomputers or analysis of video footage. Results from these two methods were compared with the standard method used in work study which is snap-back timing (i.e. the timer is reset at the end of each activity within the work cycle, the average time for each activity calculated and then summed to give the average cycle time) using the PSION microcomputer.

The mental workload of harvester operators working in steep terrain conditions

“…In particular, mental workload derives from two main and opposite causes: task complexity -which requires concentration and coordination -and task simplicity characterised by a number of repetitions -which generates a state of reduced alertness as a side effect of the long-term performance of monotonous tasks (Grzywiński and Hołota 2006). Furthermore, due to the highly variable working conditions in forestry, even the seemingly stable job of the harvester operator shows large variability in the length of work cycles and in the workload (Szewczyk et al 2014;Szewczyk and Sowa 2017). These factors cause fatigue, which leads to reduced concentration, difficulty focusing, slower and weaker perception, decreased motivation and emotional disorders (Wykowska 1994;Grzywiński 2007).…”

Using harvester data from on-board computers: a review of key findings, opportunities and challenges

“…Unlike these positive aspects, Szewczyk and Sowa (2017) found out, that snap-back timing was slightly more accurate than the harvester data method. The latter had significantly shorter mean durations of some harvester work cycles (Szewczyk and Sowa 2017).…”

“…Another field that the reviewed articles are addressing is the topic of time and productivity studies is the comparison of manual versus automated methods. For example, time data of a harvester's PSION OBC was used in a work cycle analysis (Szewczyk and Sowa 2017). This cumulative method was compared statistically with cumulative video recording time analysis and the standard snap-back timing method, with the result that snap-back timing was slightly more accurate than the cumulative timing methods.…”

“…Snap-back timing underestimated work cycle time in clearcut operations by 6%, but provided overestimations in thinning operation by approx. 12% (Szewczyk and Sowa (2017).…”

Differences in Timber Volume Estimates Using Various Algorithms Available in the Control and Information Systems of Harvesters

“…To enable the efficient use of any technology, we must study all relevant characteristics connected to it. Several aspects of using the harvester technology were studied, such as the damage to logs by feed roller spikes [20][21][22], the impact of heavy machinery on soil [23], harvester efficiency and performance [24,25], bucking optimization [26], harvester productivity [27][28][29], time consumption analysis [30][31][32] and harvester operators [33]. However, one key aspect of the harvester technology has been largely neglected in the scientific literature: the control and information systems and standards connected with their settings to achieve the most accurate volume estimates of the produced timber.…”