Improved Fibre Availability
Front Arms
The arms resemble claws with retractable chainsaws. The will have four independent joints using the same technology as described in the legs. The claws have the ability to open and close to clamp onto a range of log diameters.
Introduction
During the research stage it was identified that fibre availability for the pulp industry was challenged by;
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Potential biological threats
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Converting existing plantation land to farming
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Demand from export market
The threat from viruses or pests to our plantation stock was evaluated to have a low probability of occurrence, (due to strong bio security processes) but could potentially cause large amounts of damage to plantation forestry. The severity depended on; the type of biological threat, time before detection, the current climate and the required vectors for transition (Sathyapala, 2004). The threat from changing land use is fueled by dairy and meat prices, however it’s uncertain if deforestation will continue to occur at such a rate with more of a global focus on carbon tax. The demand from foreign markets for logs has been increasing rapidly since 2008 and is driving up the cost for logs. Although sawmills are also competing for logs they end up selling their chip to pulp mills so are not as big a threat as the current export demand.
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Core Concepts
Harvester Design
Legs
The design utilises six independent legs to dramatically improve stability and make it possible to climb steeper and un-level terrains. Each leg has four independent joints (fig 6) which will either utilise hydraulic motors or electric motors with absolute encoders to provide current positional feedback to a motion controller responsible for the joint.
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The decision to go electric or hydraulic will depend on
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The availability and ruggedness of the technology by prototyping stage
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The power source used to drive the harvester
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By utilising absolute rotary encoders the current position isn’t lost in the event of loss of power so the axis/joint won’t require referencing like an incremental rotary encoder when the machine is running again.
The base of the leg will have a solid rod which can be pushed into the ground (either using hydraulic or pneumatic force) for more stability when harvesting tree.
Chassis
The chassis will be designed with strength being a focus over weight. It will house the power source which will either be diesel or electric which will be decided on during early development/ research stage of the timeline. In the event of diesel motor it will either drive a generator to supply electric power to joints and controls. Or a hydraulic power pack to power joints and a small generator to supply electric power to controls.
The chassis will also house a controllable moving ballast to distribute the centre mass and improve stability in conjunction with the legs. It will utilise gyroscopic sensors and load cells to work out the best place for the centre of mass distribution whilst harvesting
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Rear Arm
The function of the rear arm is to stabilise and drop logs when harvesting without aerial support. It has four independent joints using the same technology as described in the legs. And also has a claw as described in the arms without the chainsaw. Two of the main members will also act as telescopic arms to increase the reach of the ream arm.
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To address this challenge, pulp mills will look at investing in scrubland that currently isn't used for forestry due to the steepness of the terain. This land is also undesirable for dairy farming so there is alot less demand for the land. The next stage is utilising two types of unmanned vehicles, a harvester and UAV (Un-manned Aerial Vehicle) to harvest logs in terrain that is too dangerous for conventional log felling methods. Both will be controlled from a control room built in a portcom to allow this solution to work on multiple sites. By owning the plantation stock pulp mills can significantly reduce thier running cost as the log cost would be just the running costs of the harvester setup. Design development and building of the harvester and portacom will be done in house however the UAV will be developed by speacilist Avionics companies as initially this solution is not being developed to be mass produced it would be infeasible to invest in the workshop facilities required to build it.
Cab
The initial design was a single cab using reinforced glass and a safety frame. The next iteration of the design was to replace the glass with plate steel and line the exterior with cameras that then display visuals at real time on the inside of the cab, greatly increasing the safety of the occupant. The final iteration was to remove the operator from the cab altogether and feed the information back to a remote user who would control the harvester from a portable office building near the harvesting site. As well as displaying visuals it would also display:
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Waypoints and map data
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Machine status information, include current fuel levels, gyroscopic information and any warnings
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Location of other harvesting gear and personal
The final solution keeps the cab as a failsafe so the harvester can be driven back in the event that the communications to headquarters fail.
Written by: James Batchelar