Bruce Talbot

Assessing the Utility of Two Integrated Harvester-Forwarder Machine Concepts Through Stand-Level Simulation

Abstract The relative performance of two integrated machine concepts (combined harvesting / forwarding capabilities) was assessed against a conventional harvester / forwarder CTL system in a simulated thinning regime. Multiple-regression based on the simulation output was used in deriving time-consumption functions at the systems and machine level. Descriptive stand variables could be reduced to; harvest volume (m3/ha), stem volume (m3), lead distance (m) and object volume (m3/stand) while maintaining acceptable statistical rigour (R2 > 0.95). The ability of one of the integrated machines to process logs directly onto the bunk provided it with an advantage that more than compensated for its reduced harvesting efficiency. Both integrated machine systems show a competitive advantage in forest structures with low object volumes and long or frequent relocations. Factors negatively affecting forwarding productivity (e.g. long lead distances) favour the conventional two- machine system. A break-even economic analysis showed that integrated machines could present a feasible alternative to contemporary mechanised CTL systems.

Operator performance improvement through training in a controlled cable yarding study

This paper provides evidence of improvement in cable yarder operator proficiency through initial training on a controlled site. Five subjects were included in the study: one expert (as control), two with limited experience in operating similar machines, and two with no experience. A 1:3 scale tower-yarder modeled on the Owren 400 was used as a test rig. A wireless control with two joysticks, used individually and in combination, covered all yarder and carriage functionality. The time taken to individually yard five logs was measured and repeated six times over two days for each subject. Cable tension in the system was simultaneously monitored as an indicator of operating consistency. Evidence of a distinct learning curve was obtained through statistical analysis by applying mixed-effects models. The standard deviations of times and tensions of the limited-experience group rapidly emulated the profiles of the expert, and subjects in the no-experience group were comfortable with the operation of the yarder controls after the six trial replications. A reduction in initial large fluctuations in cable tension demonstrated the usefulness of training. On-the-job training with full-scale machines under similar conditions could have led to system failure, with possible breakage of the tail spar, guy lines or mainline and potential material loss and human injury.

Applicability of the GRASP metaheuristic method in designing machine trail layout

The ground-based harvesting system consisting of a harvester and a forwarder is the dominant harvesting system in parts of the world, due to its high productivity. Both machines usually operate along extraction trails, and are equipped with cranes that can reach some distance from the extraction trail. In this work we optimize the layout of an extraction trail network by considering how terrain topography influences the cost of forwarding. Given the complexity of finding optimal machine trails for terrain transportation, traditional optimization methods might be limited due to the problem size. In this study, the optimization is done with a greedy constructive heuristic and a Greedy Randomized Adaptive Search Procedure (GRASP) metaheuristic, and the results of the two solution techniques are compared. Both the greedy heuristic and the GRASP metaheuristic were examined for a semi-random terrain and a smooth cone-shaped terrain, and provided useable extraction trail layouts in terms of how a forest machine operates on slopes. The objective value of the solution found by the GRASP metaheuristic was 5.6% better than the greedy heuristic in the semi-random terrain, and 2.3% better in the cone-shaped terrain. The result of this study showed that the GRASP metaheuristic is useful for finding feasible routes in the terrain, increasing efficiency. The method could be useful for planning feasible routes in the terrain, thereby increasing efficiency, or for acquiring a better estimate of the cost of terrain transport in price setting.

Extracting and chipping hardwood crowns for energy.

Abstract This study investigated the feasibility of extracting and chipping hardwood crowns for energy after motor-manual thinning in stands of common beech. Large crowns were extracted and chipped from stands where only sawlogs had been produced, while small crowns were extracted and chipped from stands where sawlogs and firewood had been harvested. The fuel chip yield was 15 ha–1 when extracting and chipping large crowns, while it was 8 ha–1 when extracting and chipping small crowns. The productivity for extracting and chipping large crowns was 8.5 per workplace hour, and for small crowns was 5.9 per workplace hour. Extracting and chipping large crowns gave a net income of €167 ha–1 (€11 ), while extracting and chipping small crowns gave a lower net income of €23 ha–1 (€3 ). The study showed that extracting and chipping large hardwood crowns is feasible and can make a substantial contribution to woody biomass feedstocks. Four product-mix alternatives were considered, but the marginal differences in outcome led the authors to recommend that in addition to sawlogs only one product, firewood or chips, should be produced in each stand.

Biomass Harvesting and Logistics

This chapter provides an introduction into the harvesting and supply of biomass from timber plantations. It considers the main sources of utilizable biomass and their properties and discusses harvesting equipment, machinery and systems that could potentially be applied for moving these resources to a landing and eventually the conversion plant. Important supply processes such as storage and drying, quality assurance, transport and simple trade models are also presented. Management of feedstock supply is discussed and illustrated with two examples integrating concepts included in this chapter. This chapter will provide the reader with an overview of the techno-economic factors to be considered for biomass procurement, how these interact with each other, and how they can be applied in developing supply models to provide strategic insight into the harvesting and transport of woody biomass.

High-pruning of European beech (Fagus sylvatica L.) and pedunculate oak (Quercus robur L.): work efficiency for target pruning as a function of tree species, pruning height, branch characteristics, pole saw type and operator

ABSTRACT The objective of this study was to establish an operational model of productive work time per tree (work efficiency) for high-pruning of young European beech and pedunculate oak depending on tree species, pruning height, branch characteristics, pole saw type and operator. The final model included all of these independent variables with branch characteristics specified in terms of number of live branches and cross-sectional area of the thickest branch at the cut. Work time increased with increasing values of each of the three numeric variables. For a given pruning height the size of the largest branch was for all practical purposes more influential than the number of live branches. Beech took 28% longer to prune than oak. The German Ergo-Schnitt saw was 21% slower than the Japanese Silky Hayauchi saw. The variation in worker performance within our study was larger than that attributed to tree species and pruning equipment.

An operational UAV-based approach for stand-level assessment of soil disturbance after forest harvesting

ABSTRACT The effectiveness of generating virtual transects on unmanned aerial vehicle-derived orthomosaics was evaluated in estimating the extent of soil disturbance by severity class. Combinations of 4 transect lengths (5–50 m) and five sampling intensities (1–20 transects per ha) were used in assessing traffic intensity and the severity of soil disturbance on six post-harvest, cut-to-length (CTL) clearfell sites. In total, 15% of the 33 ha studied showed some trace of vehicle traffic. Of this, 63% of was categorized as light (no visible surface disturbance). Traffic intensity varied from 787 to 1256 m ha−1, with a weighted mean of 956 m ha−1, approximately twice the geometrical minimum achievable with CTL technology under perfect conditions. An overall weighted mean of 4.7% of the total site area was compromised by severe rutting. A high sampling intensity, increasing with decreasing incidence of soil disturbance, is required if mean estimation error is to be kept below 20%. The paper presents a methodology that can be generally applied in forest management or in similar land-use evaluations.

Automatic recognition of work phases in cable yarding supported by sensor fusion

ABSTRACT Cable yarding is a semi-mechanized timber harvesting system that relies on human machine interaction where a considerable share of the work is done by forest workers. The system is used in mountain forests around the world. Automation of one or more functions could contribute to increased productivity, reduced physical workloads and improved safety conditions. This paper presents a method for sensor data fusion in order to automatically distinguish work phases using Partial Least Squares Discriminant Analysis (PLS-DA). The Robot Operation System (ROS) is implemented to allow for real-time data processing with a maximum latency of 0.16 s. Global Positioning System (GPS), Inertial Measurement Unit (IMU) and camera integration provided a robust solution for 78% correct process segmentation. These results provide a basis for further development from which there is a possibility of expanding this approach for semi-automation, remote control, and autonomous operation.

Selecting an appropriate excavator-based yarder concept for Norwegian conditions through the analytic hierarchy process

Preference data on 10 important machine functions pertaining to excavator-based yarders were gathered from five categories of respondents, including contractors, pre-contractors, operations managers, forestry authorities, and research and extension professionals. The analytic hierarchy process was used in ranking four representative excavator-based yarders in accordance with the preferences expressed and the ranked ability of each of the machines to meet them. The criteria being evaluated were accrued to three categories: economics, versatility, and productivity. The pre-contractor and contractor groups tended to express a similar ranking of preferences, as did the other three groups. At the individual-criterion level, the predominant preference was for a tower, followed by processing capability and extra stability. Initial capital outlay was the criterion of lowest common importance for all response groups. Matching the preference matrix with the machine performance matrix allowed for a direct ranking of contestant machines, where a larger tracked machine concept including a boom-mounted tower, long-range skyline, and fixed bucket was the most popular outcome (four of five groups), while the boom-tip-mounted integrated tower and winch was the least popular for all five groups.

Reverting urban exotic pine forests to Macchia and indigenous forest vegetation, using cable-yarders on the slopes of Table Mountain, South Africa

Synopsis This paper discusses some ofthe issues faced during the initial phases of a 12-year long project, which will ultimately result in the transformation of 53 ha of urban pine forests to a more diverse natural vegetation cover. Public sentiment, harvesting procedures and future management practices are addressed. The forests are currently managed for recreation and arc a heavily utilised public amenity. Efforts have been made at every opportunity, to minimise disturbances to the recreational and biological capacity of the forest area. Public participation was encouraged at all stages, from a local to a national level. Harvesting operations were planned to make the transition from high open pine forest to mixed scrub Macchia and moist indigenous high forest as gradual, though complete, as possible within the given time frame. An aerial cable extraction system with a fixed skyline was applied in extracting the timber to minimise site impacts. Successful marketing of the timber together with the application of industrial harvesting technology meant that the project could be self-financing, which was an important prerequisite. Both public and vegetational response has been encouraging, and the inevitable, unforeseen problems and compromises, that have had to be met since project inception have been dealt with in an open and constructive participatory forum.