In the transporting method in which a strip road is used by a forwarder, the operational efficiency decreases as the strip road length increases. To solve this problem, we designed a method for driving two or more vehicles alone. At the present time, an operator drives the lead vehicle, and the following vehicles are driven automatically. In this report, we experimented with a vehicle equipped with prototype sensors, and examined the factors that influenced the control. The control of following vehicles was made possible by attaching two ultrasonic wave speakers to the back of the lead vehicle and two ultrasonic wave mikes to the front of the following vehicle. When traveling around a curve, the following vehicle went too far inside when the distance between the lead vehicle and following vehicle was set too high. However, if the distance between the two vehicles was set too low, as the travel speed increased, the follow control became unstable. Thus, setting the proper distance between two vehicles was important. It is possible to travel strip roads that are only about 1.4 times the width of the vehicle if they are straight line. However, it is necessary to widen curved parts up to 1.6 times.

View full abstract

We developed a rail type base machine to mechanize forest work on steep slopes. This machine runs on a rail way. It is composed of two vehicles: a power truck and a work truck. The power truck can run safely on slopes with inclinations of ±45 degrees. The work truck is equipped with four-leg type outriggers which are operate with a remote control device, a crane tilt mechanism in which the angle of the crane's central pillar can be adjusted within the range of ±35 degrees, and a grapple crane (reach: 8m) with a winch for the logging and wood loading work. It can work even on inclinations of 30 degrees. As a result of a logging experiment, the work efficiency was found to be 1.37m^3/hr (8.2m^3/day). Thus, we will be able to mechanize forest work on steep slopes further by applying this machine and technology.

View full abstract

In this study, we developed and tested a pair of new yarding cable carriages with an automatic load exchanging mechanism driven with an endless cable. As a result, we found that the switch back and loading mechanisms operated smoothly during both loaded and non-loaded moving experiments. Thus the basic structure and the movement principle of the new carriages were verified. Load exchanging mechanism with 150kg mass could operate over a 0.08sag distance ratio. Furthermore, a theoretical formula for estimating the roll angle of cable carriages, was derived and compared with measured values. The results for 90kg and 150kg masses showed that the theoretical values were similar to the measured values. Thus, this theoretical approach was judged to be applicable for design optimization of new carriages. In addition, during the course of the experiments, safety and other improvements we made, such as enhancing of the visibility of the carriages, and adding an endless cable guide mechanism to reduce rolling.

View full abstract

To enable the auto-landing of log, we have improved the auto-landing mechanism that is an integral part of automatic operation of self-propelled carriages. Measurements were taken of differential pressures that occurred in the hydraulic motor of the hoisting winch drive while log of 10m and 4m in length were being landed. The results clearly showed that there was a temporary but considerable decrease in differential pressure soon after touchdown when the log was lifted up at a certain point away from the center of gravity. This occurred due to slackening of the hoisting cable because the cable momentarily fell faster than the log that was being lodged. On several occasions, the simulation misinterpreted the temporary pressure decrease to mean that landing was completed, so we revised the control program to prevent such misinterpretation. We also created a control program to arrange log in the direction of the skyline by alternately dropping the hoisting cable falling and moving the carriage. When the auto-landing operation was tested using log, automatic operation was accurate and log was arranged in the direction of the skyline according to the plan. Auto-landing operation for the log had been achieved. As a result, it became possible to have automatic operation from transportation to turning back through landing by integrating the auto-landing technique with the auto-traveling technique which had previously been developed.

View full abstract

To understand the course of growth of lower-story trees damaged by upper-story thinning in a multi-storied stand, we examined the condition of lower-story Hinoki (Chamaecyparis obtusa) trees five growth periods that had been damaged in a multi-storied stand in Suwa City, Nagano Prefecture. In addition to assessing the viability of lower-story Hinoki trees, we also investigated the recovery of lodged Hinoki trees and the occurrence of abnormalities in trees with broken trunks or tops. At the same time, we felled specimen trees to examine if staining occurred from the area of decortication as well as if eccentric growth or tension wood occurred in leaning trees. As a result, we found that lodged Hinoki trees, and approximately 30% of leaning trees, did not recover. Many of the trees with broken tops or trunks showed an "S-shaped" or a "broom-shaped" growth from the damaged region. Eccentric growth and tension wood were seen in the curved sections of these "S-shaped" and "broom-shaped" growths. Staining also occurred in the areas of damage among Hinoki trees with broken tops or trunks. However, staining did not spread upward, and downward spread was not extensive. Many of the Hinoki trees with more than 25% of their branches broken were leaninng. Those with decortication of bark showed staining from the area of decortication. The extent of staining was minor in most trees, but wood deterioration was progressive when the decortication was substantial.

View full abstract

We compared the forestry operations, location, and topography of four local authority management areas in the Higashimikawa Forest Planning Area, Japan. The target road density was calculated for each local authority area by considering the public, forest, and strip roads and five basic forestry operations conducted from 1991 to 2000. Forestry operations generally decreased over the study period, especially in the upper-stream area. The mean access distance to worksites, which affected forestry operations more than did topography, was greatest in the mid-stream area, followed in order by the upper- and lower-stream areas. In 1997, the worksite access distance in the upper-stream area began to decrease dramatically as the price of domestic timber declined, while the difference between the mean entire-forest access distance and the mean local worksite access distance tended to increase. In the mid-stream area, the mean worksite access distance generally held steady, whereas the difference between the average entire-forest and local worksite access distances tended to decrease because of new road construction. In the lower-stream area, the mean worksite access distance also tended to decrease, although the difference between the mean entire-forest access distance and mean local worksite access distance was the smallest among the areas studied. The mid-stream area had the lowest target road density, followed by the upper- and lower-stream areas. Road improvements in the upper- and mid-stream areas are needed to improve forest management efficiency. In the lower-stream area, where the road network is already sufficient, extension activity to improve forest management is more important.

View full abstract