Round wood laser scanning

RESEARCH DATA


Funding: NCCR

Status: Ongoing since 2019

PhD Student: Cheng Chang, Civil engineer, IBOIS

Thesis director: Prof. Yves Weinand, architect and engineer, IBOIS


RESEARCH ABSTRACT

Currently, timber industry is pays particular attention on transforming naturally grown timber to regular, straight and flat elements only to undergo subtractive machining processes. However, tree trunks often have conic, bent or bifurcated shapes, that has no value in today forestry. Only straight trees give an economic profit and the “unfit” trees are mostly exploited as fuel. If the irregularities of wood could be exploited as a building material, what kind of timber processing would it require? Giving a vision to blind-cutting machines for processing irregular timber pieces is a key problem to solve. Currently, object-to-process is most often 3D modelled in CAD software assuming it will be subtracted from already known volume such as engineered timber plate, beam or glue-lam. Irregularities as such are not taken into consideration and a bigger safety factor is used to cut from more larger bounding volumes in order to keep the machines safe.
The aim of this research is to be able to develop a workflow to custom tree shapes and reasonable applying timber irregularities in a structural form with minimal cutting time and maximum exploitation of timber biomass.
Research methodology depends on stock – forest or already cut trees. Before cutting specific trees for construction, a digital library of point clouds has to be made. This requires laser scanning in a forest during winter season or scanning separate trunks in a clear zone. The next step is to register point clouds, clean them from unnecessary noise and gather them in one database. Then the cloud data has to be transformed to low poly geometry by means of making water tight mesh i.e. Poisson reconstruction and central axis of tree i.e. libigl, PCL, CloudCompare, geometry processing algorithms. The following step needs to be coordinated within a group of collaborators to understand the joinery methods and choosing common structural system composed from linear elements such as solid timber slabs, trusses, space-frames or reciprocals. During fabrication, laser scanning has to be equally involved in cutting process to position joinery elements in ever changing cutting setup and developing cutting tool-path.

There is a need to exploit unused timber resources as a building material and there is a means of measuring and processing them. If there is a will to communicate between stakeholders of the timber building sector such as forestry guards, researchers and computer scientists, such study would not only increase the maximum use of biomass, decrease timber processing time but also help to exploit timber in its natural form.