title: 3D Shape Measurement of Moving Objects for Industrial Applications

authors: Charleston, Sean Andrew

subjects: Time-of-flight

abstract: Three dimensional (3D) cameras provide distance measurements to objects, allowing computers and instruments to interact with their environment. The applications are wide-ranging, from human gesture control to industrial processing. Time-offlight cameras measure the distance to the scene by measuring the flight time of a modulated light source. Sequential captures are required to produce the depth map, hence time-of-flight cameras are vulnerable to depth errors from motion blur in dynamic scenes. This is a major hindrance for industrial applications, where accurate results are required when reconstructing objects. The fruit grading industry is of particular interest for this work, where significant advancements can be made using 3D cameras. The produce moves at a constant velocity, providing an ideal case for initial work into industrial motion correction.

The SR4000 from Mesa Imaging is an industrial grade time-of-flight camera with a high quality factory calibration, and is used throughout this work. When applying custom algorithms (such as motion correction), the camera is run in ‘raw mode’ where the sequential captures can be individually manipulated, however the factory calibration set is lost. The first part of this work investigates calibrations in time-of-flight cameras, where the factory calibration set in the SR4000 is extracted from the camera to be used on the ‘raw mode’ data in custom algorithms. The factory calibrated data is compared to both the ‘raw mode’ data, as well as data acquired using the extracted calibration set. The key results show a root mean squared error (RMSE) of 62.4 mm for ‘raw mode’ data, while using the extracted calibrations shows an RMSE of 6.1 mm.

The effects of motion blur on time-of-flight cameras are then investigated. The technique from Hussmann et al. (2011) provides a good first attempt at motion correction, however fails to implement a number of calibrations. The improvements presented in this thesis on the motion correction technique manipulates the demodulation of time-of-flight cameras so that these additional calibrations are incorporated, resulting in a more robust motion correction algorithm. To test these improvements, a controlled experiment is setup to image a moving spherical object, and a stationary reference image of the same object is captured for comparison. Without motion correction the RMSE is 75.9 mm. Using the naive correction technique from Hussmann et al. (2011) gives an RMSE of 58.7 mm, and finally applying the suggested improvements reduces the RMSE to 4.3 mm.

text: 3D Shape Measurement of Moving Objects for Industrial Applications Three dimensional (3D) cameras provide distance measurements to objects, allowing computers and instruments to interact with their environment. The applications are wide-ranging, from human gesture control to industrial processing. Time-offlight cameras measure the distance to the scene by measuring the flight time of a modulated light source. Sequential captures are required to produce the depth map, hence time-of-flight cameras are vulnerable to depth errors from motion blur in dynamic scenes. This is a major hindrance for industrial applications, where accurate results are required when reconstructing objects. The fruit grading industry is of particular interest for this work, where significant advancements can be made using 3D cameras. The produce moves at a constant velocity, providing an ideal case for initial work into industrial motion correction.

The SR4000 from Mesa Imaging is an industrial grade time-of-flight camera with a high quality factory calibration, and is used throughout this work. When applying custom algorithms (such as motion correction), the camera is run in ‘raw mode’ where the sequential captures can be individually manipulated, however the factory calibration set is lost. The first part of this work investigates calibrations in time-of-flight cameras, where the factory calibration set in the SR4000 is extracted from the camera to be used on the ‘raw mode’ data in custom algorithms. The factory calibrated data is compared to both the ‘raw mode’ data, as well as data acquired using the extracted calibration set. The key results show a root mean squared error (RMSE) of 62.4 mm for ‘raw mode’ data, while using the extracted calibrations shows an RMSE of 6.1 mm.

The effects of motion blur on time-of-flight cameras are then investigated. The technique from Hussmann et al. (2011) provides a good first attempt at motion correction, however fails to implement a number of calibrations. The improvements presented in this thesis on the motion correction technique manipulates the demodulation of time-of-flight cameras so that these additional calibrations are incorporated, resulting in a more robust motion correction algorithm. To test these improvements, a controlled experiment is setup to image a moving spherical object, and a stationary reference image of the same object is captured for comparison. Without motion correction the RMSE is 75.9 mm. Using the naive correction technique from Hussmann et al. (2011) gives an RMSE of 58.7 mm, and finally applying the suggested improvements reduces the RMSE to 4.3 mm.

year: 2015

title: The viability of waste copper chromium and arsenic treated timber reinforced polypropylene as a sustainable building material

authors: Nelson, Jacob Martin Bruton

subjects: Natural fibre composites

abstract: The aim of this thesis was to investigate the viability of wood-plastic composites (WPCs) produced from wood flour and fibre derived from waste copper chromium and arsenic (CCA) treated timber for use as a sustainable material in the construction sector.

The research included an assessment of mechanical properties and the leaching of heavy metals from the wood-plastic composites, and the results were compared to material requirements in the building sector provided through literature and New Zealand building standards. Mechanical and chemical methods were used to prepare wood flour and fibre samples from waste CCA treated timber for use in wood-plastic composites. Composites were produced through compounding using a twin screw extruder or a custom sigma blade compounder and then injection moulded for material testing. Composites produced using an extruder with 40 wt.% bleached fibres and 4 wt.% MAPP, increased tensile strength (TM) from 18.5 MPa for the polypropylene used for the matrix to 27.6 MPa; Young's modulus (YM) was increased from 0.84 GPa to 2.33 GPa.

Comparison of mechanical performance with commercial WPC properties suggests that waste CCA treated timber could be used as a raw material to produce WPC for semi-structural applications. The modulus (2.33 GPa, in the highest performing composites) was roughly three times lower than commonly used commercial timbers used in structural applications. The creep performance was not measured for a time frame long enough to be indicative of the 50 years required for structural application. Therefore, further research is required to investigate whether the low modulus and creep performance of the WPC is acceptable for a structural material in the construction sector.

One of the largest concerns with using waste CCA treated timber as a reinforcement material in WPC was the inclusion of heavy metals and the potential for leaching. Arsenic was considered the most toxic of the heavy metals in the CCA treated timber. Processing of the waste CCA treated timber to obtain fibre was found to reduce arsenic concentration by up to 99.94 % in the best scenario. Furthermore, arsenic in leachate from composites was found to decrease from 41.29 to 0.07 ppb when comparing wood flour composites to digested and bleached fibre composites. The concentration of copper, chromium, and arsenic in leachate from composites produced with chemically obtained fibre was found to be significantly lower than the maximum allowable drinking levels in New Zealand. Therefore, indicating the application of composites produced with wood fibre from waste CCA treated timber can be regarded as safe even in scenarios that involve human contact with the material.

A life cycle analysis study found that the use of an alkali digestion process to obtain fibre significantly increased the environmental impact compared to the processing required to obtain wood flour. In a study of a potential commercial scale process, ultrasonic treatment and hydrogen peroxide bleaching as secondary fibre treatments were the largest contributors to environmental impact in the preparation of wood fibre. Thus, the results suggest that chemical treatments should only be employed to produce wood fibre when the highest mechanical performance or lowest leaching levels are required for the application of the wood-plastic composites.

text: The viability of waste copper chromium and arsenic treated timber reinforced polypropylene as a sustainable building material The aim of this thesis was to investigate the viability of wood-plastic composites (WPCs) produced from wood flour and fibre derived from waste copper chromium and arsenic (CCA) treated timber for use as a sustainable material in the construction sector.

The research included an assessment of mechanical properties and the leaching of heavy metals from the wood-plastic composites, and the results were compared to material requirements in the building sector provided through literature and New Zealand building standards. Mechanical and chemical methods were used to prepare wood flour and fibre samples from waste CCA treated timber for use in wood-plastic composites. Composites were produced through compounding using a twin screw extruder or a custom sigma blade compounder and then injection moulded for material testing. Composites produced using an extruder with 40 wt.% bleached fibres and 4 wt.% MAPP, increased tensile strength (TM) from 18.5 MPa for the polypropylene used for the matrix to 27.6 MPa; Young's modulus (YM) was increased from 0.84 GPa to 2.33 GPa.

Comparison of mechanical performance with commercial WPC properties suggests that waste CCA treated timber could be used as a raw material to produce WPC for semi-structural applications. The modulus (2.33 GPa, in the highest performing composites) was roughly three times lower than commonly used commercial timbers used in structural applications. The creep performance was not measured for a time frame long enough to be indicative of the 50 years required for structural application. Therefore, further research is required to investigate whether the low modulus and creep performance of the WPC is acceptable for a structural material in the construction sector.

One of the largest concerns with using waste CCA treated timber as a reinforcement material in WPC was the inclusion of heavy metals and the potential for leaching. Arsenic was considered the most toxic of the heavy metals in the CCA treated timber. Processing of the waste CCA treated timber to obtain fibre was found to reduce arsenic concentration by up to 99.94 % in the best scenario. Furthermore, arsenic in leachate from composites was found to decrease from 41.29 to 0.07 ppb when comparing wood flour composites to digested and bleached fibre composites. The concentration of copper, chromium, and arsenic in leachate from composites produced with chemically obtained fibre was found to be significantly lower than the maximum allowable drinking levels in New Zealand. Therefore, indicating the application of composites produced with wood fibre from waste CCA treated timber can be regarded as safe even in scenarios that involve human contact with the material.

A life cycle analysis study found that the use of an alkali digestion process to obtain fibre significantly increased the environmental impact compared to the processing required to obtain wood flour. In a study of a potential commercial scale process, ultrasonic treatment and hydrogen peroxide bleaching as secondary fibre treatments were the largest contributors to environmental impact in the preparation of wood fibre. Thus, the results suggest that chemical treatments should only be employed to produce wood fibre when the highest mechanical performance or lowest leaching levels are required for the application of the wood-plastic composites.

year: 2022

title: A step into the light: developing a culturally appropriate research prcoess to study Maori Rangatahi perspectives of leisure in one setting.

authors: Harvey, Geraldine

subjects: research -- methodology

abstract: There is little knowledge of Maori peoples' leisure understandings, experiences and participation. This article reports on the development of a culturally appropriate research process that investigated the leisure participation, perspectives, and experiences of five Rotorua Maori Rangatahi in one research setting'. Within this exploration there is a focus on the need to conduct leisure research with Maori people in culturally appropriate ways. This research approach incorporates focus group methodology within a Kaupapa Maori research framework which addresses issues of research for Maori. The research process revealed that focus group methodology can be adapted into a Kaupapa Maori research framework and that this research approach could be an important tool when conducting research with Maori Rangatahi, including in educational contexts.

text: A step into the light: developing a culturally appropriate research prcoess to study Maori Rangatahi perspectives of leisure in one setting. There is little knowledge of Maori peoples' leisure understandings, experiences and participation. This article reports on the development of a culturally appropriate research process that investigated the leisure participation, perspectives, and experiences of five Rotorua Maori Rangatahi in one research setting'. Within this exploration there is a focus on the need to conduct leisure research with Maori people in culturally appropriate ways. This research approach incorporates focus group methodology within a Kaupapa Maori research framework which addresses issues of research for Maori. The research process revealed that focus group methodology can be adapted into a Kaupapa Maori research framework and that this research approach could be an important tool when conducting research with Maori Rangatahi, including in educational contexts.

year: 2002