New configurations of the tele-extraction concept

Figures & data

Figure 1. Conceptual illustration of the different configurations of tele-extraction. “Teleload” was simulated in Lundbäck et al. (2022) and Teledrives A and B were simulated in this study, with Full Auto as the ultimate reference point. The width of the box with each work element corresponds to the average productive machine hour (PMH) time for that work element as a share of the total PMH time per forwarder load according to Manner et al. (2016). Red text indicates that the work element was teleoperated.

Figure 2. Approximate location and key figures of the harvest areas included in the study.

Figure 3. Illustration of the main work elements within forwarding in a teleoperation setting (drawings by Mikael Lundbäck, Ola Lindroos, and Skogforsk).

Table 1. Application of probability density functions and their parameters in the simulations (Lundbäck et al. 2022.).

Application	Function	Parameters	Truncation	Visualization	Comment
Driving empty and loaded distances (m)	Exponential distribution	Mean (scale) = de, shift (threshold) = 1	min = de $-\hspace{0.17em}\frac{\sqrt{\text{{{V\_{tot}}}}/\text{{v }}\times 10000}}{2}$ max = de + (de – min) where de= driving empty, v = harvested volume/ha, Vtot = harvest plot total size (m^3)		Example visualization: Extraction distance = 500 m, v = 250 m^3, Vtot = 5 000 m^3
Driving empty speed (km/h)	Normal distribution	Mean = 3.4, Standard deviation = 1	min = 1.44, max = 6.12
Driving while loading speed (km/h)	Normal distribution	Mean = 2.1, Standard deviation = .5	min = 1.04, max = 3.6
Unloading time (minutes)	Erlang distribution (special case of the Gamma distribution)	beta = 2.5, m = 2	min = 3.5
Downtime occurance (minutes)	Exponential distribution	Mean (scale) = 68, shift (threshold) = 0	min = 0, max = 1000
Downtime duration (minutes)	Exponential distribution	Mean (scale) = 10, shift (threshold) = 0	min = 0, max = 450

Table 2. The variation of operator cost and time consumption for automated work elements parameters.

		Sensitivity analysis
Parameter	Unit	Baseline	Min	Max	Step
Operator cost	$/SMH	43.6	21.9	65.6	10.9
	%	100	50	150	25
Time consumption automation	%	100	50	150	25

Table 3. Productivity (m³ sub/SMH) and cost (USD/m³ sub), average with standard deviation in parentheses and median with inter-quartile range (Q3–Q1) in parentheses, for Teledrive A (teleoperated driving between log piles) and Teledrive B at different number of operators on ten forwarders.

	Number of operators	Full Tele (10)	9	8	7	6	5	4	3	2	1	Full Auto (0)
Teledrive A
	North Region
	Productivity average (std. dev.)	30.47 (11.21)	30.44 (11.23)	30.44 (11.20)	30.17 (11.02)	29.23 (10.61)	26.92 (9.53)	22.76 (7.83)	17.02 (5.73)	10.38 (3.36)	4.18 (1.20)	31.44 (10.87)
	Productivity median (IQR)	34.09 (14.86)	34.10 (14.80)	34.06 (14.83)	33.71 (14.63)	32.52 (13.98)	29.53 (12.92)	24.52 (10.92)	18.01 (8.23)	10.81 (4.88)	4.29 (1.71)	34.74 (14.49)
	Cost average (std. dev.)	3.73 (.71)	3.59 (.71)	3.45 (.71)	3.32 (.70)	3.23 (.71)	3.23 (.72)	3.37 (.75)	3.79 (.83)	4.91 (1.08)	9.10 (2.03)	2.25 (.69)
	Cost median (IQR)	3.55 (.80)	3.40 (.79)	3.26 (.79)	3.14 (.79)	3.05 (.80)	3.05 (.82)	3.20 (.88)	3.63 (1.02)	4.77 (1.40)	8.94 (2.73)	2.08 (.77)
Teledrive B
	North Region
	Productivity average (std. dev.)	31.09 (11.13)	31.09 (11.20)	31.04 (11.17)	30.98 (11.21)	30.86 (11.02)	30.24 (10.66)	28.45 (9.66)	24.55 (7.87)	18.03 (5.41)	9.42 (2.70)	31.44 (10.87)
	Productivity median (IQR)	34.57 (14.85)	34.59 (14.87)	34.53 (14.86)	34.50 (14.90)	34.24 (14.62)	33.42 (14.14)	30.94 (13.14)	26.10 (11.00)	18.74 (7.75)	9.66 (3.88)	34.74 (14.49)
	Cost average (std. dev.)	3.67 (.70)	3.53 (.70)	3.39 (.70)	3.26 (.70)	3.12 (.70)	3.01 (.70)	2.96 (.70)	3.04 (.72)	3.40 (.77)	4.80 (1.05)	2.25 (.69)
	Cost median (IQR)	3.49 (.78)	3.35 (.78)	3.21 (.78)	3.07 (.79)	2.94 (.78)	2.83 (.78)	2.79 (.79)	2.87 (.82)	3.26 (.93)	4.68 (1.38)	2.08 (.77)

Figure 4. Average utilization of machines and operator pool for different number of operators (x-axis) and different configurations (Teledrive A and Teledrive B) with Full Auto as reference (*). North region.

Figure 5. Average forwarder cost (USD/m³ sub) per cost category with varying number of teleoperators (x-axis) and different configurations (Teledrive A and Teledrive B) with Full Auto as reference. North region.

Figure 6. Simulated potential cost reductions for tele-extraction compared to standard forwarding, north region, with varying number of teleoperators (x-axis), relatively adjusted extraction distances, and different configurations (Teledrive A and Teledrive B) with Full Auto as reference (*). Most lines continue below the x-axis when number of operators decreases, spiking again for Full Auto (black stars).

Figure 7. Sensitivity analyses of the parameters “Operator cost” and “Time consumption for automated work elements compared to their teleoperated equivalents”.

Figure 8. High-resolution visualization of a one-hour output of the Teledrive A simulation with five operators, black = busy and green = idle. The gray zones in the green areas indicate very short time windows for driving between log piles (operator busy) and loading (operator idle).

Lundbäck M, Häggström C, Fjeld D, Lindroos O, Nordfjell T. 2022. The economic potential of semi-automated tele-extraction of roundwood in Sweden. Int J For Eng. 33(3):1–18. doi: 10.1080/14942119.2022.2103784.

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Manner J, Palmroth L, Nordfjell T, Lindroos O. 2016. Load level forwarding work element analysis based on automatic follow-up data. Silva Fenn. 50(3):1–19. doi: 10.14214/sf.1546.

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