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Piskunov Maxim, Prof.

Investigation of Structure of Technology Cycle Time of Hydraulic Manipulators in the Process of Loading Forwarders with Logs

volume: 42, issue:

In the practice of using cut-to-length technology, hydraulic manipulators are widely used. Understanding manipulator cycle is important for improving existing logging technologies and developing new machine designs. The paper analyzes structure of technological cycle and operating time of manipulator in the process of loading forwarder on skid trails. Twenty-one loading processes were investigated. In the structure of technological cycle, the following elements were considered: empty movements, loaded movements, movements of manipulator links when performing operations inside load space of forwarder and special techniques such as re-grabbing logs and pulling of an incompletely closed log grip through the logs when the ends of the grabbed logs tilt and abut against the ground used during loading movement. Statistical processing of data showed that median values of samples consisting of time intervals of empty movements are in trange from 3.8 to 6 seconds, the median of samples of loaded movements is 6–16 seconds and median of samples of a pair of movements 5–9 seconds. With a 95% degree of probability, under the studied production conditions, the time of one loaded movement falls within the range of 4–14 seconds; one empty movement – in the range of 3–7 seconds. Total time of empty movements takes a share from 20 to 45% of the total loading time (on average 30%), the total time of loading movements is from 51 to 72% (on average 63%), the time of operations inside the load space is from 0 to 18% (on average 7%). Time of loaded movements, including use of special techniques, is from 13% to 64% of total time of loaded movements (or 10–53% of total number of loaded movements). The time, consisting of a pair of movements: empty and loaded, is somewhat influenced by forwarder size. Duration of one loaded movement is significantly affected by use of special techniques by the operator. Number and duration of loaded movements with these techniques is significantly influenced by: average size of loaded assortments and number of assortments carried in the grapple during one loaded movement. No significant influence of average size of assortments, number of assortments in grapple and size of the machine on empty movements was found. However, some influence on empty movements of number of loaded movements performed from one forwarder parking lot was observed. Duration and frequency of operations within the load space are weakly correlated with the size of assortments and forwarder size.

Influence of Stump-Root System of Trees on Rut Formation During Forwarder Operation on Peat Soils

volume: 44, issue:

To explain the soil deformation processes under the influence of logging machines, average values of various indicators are often used. One of these indicators is the rut depth formed during tractor passages. The average values do not fully describe the consequences of passages on the skidding trails, for example, the rut depth varies along the track. This variability includes both random and regular components. The stump-root systems of trees located on the skidding trail and along its border act as a factor that introduces a pattern. To determine the degree of influence of stumps on 8 sections of skidding trails with the length of 25 and 50 m, located on peat soils (the average mass fraction of water is 82.3%), the rut depth was measured at intervals of 0.5 m and the locations of stumps were noted. The resulting arrays of vertical marks represent the microprofiles of the experimental sections. Measurements were taken after 2 harvester passages and 2 forwarder passages. The stumps were divided into two groups: located inside the tractor track and outside it. Statistical processing of the data showed a wide spread of the rut dimensions in each array. Average values at the sections (standard deviations) in cm were: 21.6(17.7); 30.6(21.6); 37.7(22.7); 46(20.3); 36.4(15.0); 36(15.4); 30.6(21.0); 34(21.0). The autocorrelation functions, constructed for the series of values, showed surges with moderate correlation coefficients on the lags where stumps were noted. An increase in stumps per a length unit of the skidding trail shows an increase in the number of such surges. A decrease in the rut dimensions, in relation to the places where the influence of the roots was absent, averaged: in points 0.5 m away from the stump – 44% (22.6); 1 m away – 32% (20.4); 1.5 m away – 22% (14.2). The spatial influence factor of the roots explains 21% of the variability of the rut dimensions along the skidding trail. The factor of the stump location relative to the track is 19%. The combined influence of these factors is 25%. Further identification of regularities in the rut formation processes is associated both with the continuation of studies of the root system influence, but with the inclusion of factors of the stump size and variety, and with the study of the variability of the soil physical properties along the skidding trails, analysing how this is found in the microprofile structure.

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Web of Science Impact factor (2022): 3.200
Five-years impact factor: 3.000

Quartile: Q1 - Forestry

Subject area

Agricultural and Biological Sciences

Category/Quartile

Forestry/Q1