title: Prismatic axis, differential-drive robotic kiwifruit harvester for reduced cycle time

authors: Barnett, Josh

subjects: robotics

abstract: The New Zealand kiwifruit industry is currently worth over NZD 2 billion in annual sales revenue, this is forecast to double within the next 5-10 years due to a significant increase in production volume. The industry is already experiencing a prevalent shortage of labour which is indicative of a global trend. The objective for this study was to define important metrics for the robotic harvesting of kiwifruit and to propose a hardware configuration which could improve on the current kiwifruit harvesting module (KHM) developed by the Multipurpose Orchard Robotics (MOR) project. The research scope was focused to establishing whether a prismatic axis kinematic structure was more effective than a rotational axis kinematic structure for the multiple-robot harvesting of kiwifruit. KPI's (key performance indicators) were defined as evaluation and design measures - these included fruit damage, harvestability and nominal harvest cycle time. An equation specific to the KHM was derived for the latter which included measures of fruit per harvesting phase, time between fruit and a proposed work distribution constant W_D. A prismatic axis, linear rail constrained, kiwifruit harvesting robot (LHR) with two robot-arms was developed, built and tested. It was found to be exponentially beneficial to locate mass proximal to the X axis carriage centres which is achieved with a differential-drive of the YZ axis'. The prismatic axis kinematic structure of the LHR allowed for an 88% greater work distribution constant W_D, a 40% greater harvestable taskspace volume V_h and 2.5 times greater overall workspace efficiency when compared to the KHM. The nominal harvest cycle time was identical for both of these systems. However, the LHR and the developed `x-rank' registry algorithm were capable of maintaining W_D value despite a two-fold increase in robot-arm density. Therefore, in non-collision scenarios the LHR can operate with four robot-arms without compromising performance. In this scenario where both systems have four robot-arms, the LHR had a 44% reduction in harvest cycle time. Further study would need to be done into manipulability measures, scheduling methods and the effects on work distribution to establish whether a prismatic axis structure remains favourable if an orientation structure is implemented for end-effector dexterity.

text: Prismatic axis, differential-drive robotic kiwifruit harvester for reduced cycle time The New Zealand kiwifruit industry is currently worth over NZD 2 billion in annual sales revenue, this is forecast to double within the next 5-10 years due to a significant increase in production volume. The industry is already experiencing a prevalent shortage of labour which is indicative of a global trend. The objective for this study was to define important metrics for the robotic harvesting of kiwifruit and to propose a hardware configuration which could improve on the current kiwifruit harvesting module (KHM) developed by the Multipurpose Orchard Robotics (MOR) project. The research scope was focused to establishing whether a prismatic axis kinematic structure was more effective than a rotational axis kinematic structure for the multiple-robot harvesting of kiwifruit. KPI's (key performance indicators) were defined as evaluation and design measures - these included fruit damage, harvestability and nominal harvest cycle time. An equation specific to the KHM was derived for the latter which included measures of fruit per harvesting phase, time between fruit and a proposed work distribution constant W_D. A prismatic axis, linear rail constrained, kiwifruit harvesting robot (LHR) with two robot-arms was developed, built and tested. It was found to be exponentially beneficial to locate mass proximal to the X axis carriage centres which is achieved with a differential-drive of the YZ axis'. The prismatic axis kinematic structure of the LHR allowed for an 88% greater work distribution constant W_D, a 40% greater harvestable taskspace volume V_h and 2.5 times greater overall workspace efficiency when compared to the KHM. The nominal harvest cycle time was identical for both of these systems. However, the LHR and the developed `x-rank' registry algorithm were capable of maintaining W_D value despite a two-fold increase in robot-arm density. Therefore, in non-collision scenarios the LHR can operate with four robot-arms without compromising performance. In this scenario where both systems have four robot-arms, the LHR had a 44% reduction in harvest cycle time. Further study would need to be done into manipulability measures, scheduling methods and the effects on work distribution to establish whether a prismatic axis structure remains favourable if an orientation structure is implemented for end-effector dexterity.

year: 2018

title: Hamilton City long-tailed bat survey: Annual monitoring report, 2022

authors: Caskey, Laura

abstract: Deforestation, urbanisation and the introduction of mammalian predators has resulted in a significant decline of New Zealand’s long-tailed bat (Chalinolobus tuberculatus or pekapeka-tou-roa), which is currently classified as threatened, nationally critical. Hamilton City is one of three urban areas with confirmed long-tailed bat populations. Since 2016, annual city-wide surveys have been conducted by Project Echo, a multi-agency advocacy group for Hamilton City bats. The purpose of the annual surveys is to monitor for changes in bat activity and habitat use throughout Hamilton City, this report presents findings from the 2022 survey.

A total of 72 automatic bat monitors (ABMs) were deployed across 20 historically monitored sites and 52 spatially distributed sites, as specified by a Master Sample design. Acoustic bat monitors (Model AR4) were deployed for approximately 3 weeks, however, only 14 ABMs remained operational for the full 3-weeks, with 30 units failing to operate for more than 4 days. ABM failure was ascribed to the use of older rechargeable batteries. Despite this, a total of 6,734 bat passes were detected from 19 sites, compared to detections at 18 sites from 64 deployments in the 2021 city survey. Similar to previous years, most bat activity was recorded in the south of the city, in close association with the Waikato River and the Mangakotukutuku gully system. There were also six passes recorded in the central city (Site 67, Tristram Street) along with multiple detections in the Hillcrest, Fairfield and Melville residential areas. This data supports the continued use of the Master Sample survey design for the selection of survey sites. While it is advantageous to retain a proportion of previously monitored sites (~25%) for continuity of data, the Master Sample design has improved the proportion of habitats surveyed with greater coverage of residential areas and the inclusion of commercial and industrial areas which have rarely been surveyed.

The reduced number of operational ABM nights is likely to have substantially reduced the sensitivity of the survey to identify locations of low bat activity, as well as the magnitude of detections in high activity areas. Therefore, it is recommended that the data be treated with caution if making comparisons to previous or similar surveys. On-going annual city-wide bat surveys will help identify key habitat areas for conservation and enhancement, in addition to helping understand the effects of urban development and intensification. This is of particular importance given the ongoing and proposed future development in the south of the city, which raises concerns for the preservation of current bat habitats and their connectivity to the city.

text: Hamilton City long-tailed bat survey: Annual monitoring report, 2022 Deforestation, urbanisation and the introduction of mammalian predators has resulted in a significant decline of New Zealand’s long-tailed bat (Chalinolobus tuberculatus or pekapeka-tou-roa), which is currently classified as threatened, nationally critical. Hamilton City is one of three urban areas with confirmed long-tailed bat populations. Since 2016, annual city-wide surveys have been conducted by Project Echo, a multi-agency advocacy group for Hamilton City bats. The purpose of the annual surveys is to monitor for changes in bat activity and habitat use throughout Hamilton City, this report presents findings from the 2022 survey.

A total of 72 automatic bat monitors (ABMs) were deployed across 20 historically monitored sites and 52 spatially distributed sites, as specified by a Master Sample design. Acoustic bat monitors (Model AR4) were deployed for approximately 3 weeks, however, only 14 ABMs remained operational for the full 3-weeks, with 30 units failing to operate for more than 4 days. ABM failure was ascribed to the use of older rechargeable batteries. Despite this, a total of 6,734 bat passes were detected from 19 sites, compared to detections at 18 sites from 64 deployments in the 2021 city survey. Similar to previous years, most bat activity was recorded in the south of the city, in close association with the Waikato River and the Mangakotukutuku gully system. There were also six passes recorded in the central city (Site 67, Tristram Street) along with multiple detections in the Hillcrest, Fairfield and Melville residential areas. This data supports the continued use of the Master Sample survey design for the selection of survey sites. While it is advantageous to retain a proportion of previously monitored sites (~25%) for continuity of data, the Master Sample design has improved the proportion of habitats surveyed with greater coverage of residential areas and the inclusion of commercial and industrial areas which have rarely been surveyed.

The reduced number of operational ABM nights is likely to have substantially reduced the sensitivity of the survey to identify locations of low bat activity, as well as the magnitude of detections in high activity areas. Therefore, it is recommended that the data be treated with caution if making comparisons to previous or similar surveys. On-going annual city-wide bat surveys will help identify key habitat areas for conservation and enhancement, in addition to helping understand the effects of urban development and intensification. This is of particular importance given the ongoing and proposed future development in the south of the city, which raises concerns for the preservation of current bat habitats and their connectivity to the city.

year: 2022

title: Catchment and lake water quality modelling to assess management options for Lake Tutira

authors: McBride, Chris G.

abstract: Lake Tutira is an important ecological, historical and cultural asset to the Hawke’s Bay. It is a highly utilised trout fishery, a popular recreational destination, and is particularly significant to Ngāti Kahungunu, for its historical eel fishery and rongoa (medicinal) harakeke (flax) beds. The lake and its catchment have been substantially altered from their natural condition, including conversion of forested catchment to pasture, invasion by aquatic macrophytes such as Hydrilla sp., the introduction of grass carp (Ctenopharyngaodon idella) for weed management, and diversion of the largest stream inflow, Papakiri Stream (Sandy Creek), away from the lake and directly to the outflow (Mahiaruhe Stream) in the early 1980s. Lake Tutira’s history of poor water quality dates back decades, with Trophic Level Index (TLI; a metric of overall water quality) values from the 1960s similar to recent years, and blooms of cyanobacteria (blue-green algae) recorded as early as the 1970s. Nevertheless, the years since 2010 have been characterised by very poor water quality and particularly severe blooms, sometimes resulting in near-complete loss of oxygen from surface waters and associated fish kill events. This has attracted media attention and provided impetus from community and stakeholders to assess available management options for restoring more natural conditions and improving water quality in the lake. 
This report examines the drivers of poor water quality and algal blooms the lake, and assesses various management options that have either been specifically proposed for Tutira, or have proven effective for other lakes in New Zealand and globally. Here we report on monitoring undertaken by Hawke’s Bay Regional Council in the catchment (surface inflows) and lake. We also apply state-of-the-art computer models for simulating physical, chemical, and biological processes in the catchment and lake. These simulations are then used to evaluate a range of management ‘scenarios’ to provide guidance on the likely effects of management options tested with the model.

text: Catchment and lake water quality modelling to assess management options for Lake Tutira Lake Tutira is an important ecological, historical and cultural asset to the Hawke’s Bay. It is a highly utilised trout fishery, a popular recreational destination, and is particularly significant to Ngāti Kahungunu, for its historical eel fishery and rongoa (medicinal) harakeke (flax) beds. The lake and its catchment have been substantially altered from their natural condition, including conversion of forested catchment to pasture, invasion by aquatic macrophytes such as Hydrilla sp., the introduction of grass carp (Ctenopharyngaodon idella) for weed management, and diversion of the largest stream inflow, Papakiri Stream (Sandy Creek), away from the lake and directly to the outflow (Mahiaruhe Stream) in the early 1980s. Lake Tutira’s history of poor water quality dates back decades, with Trophic Level Index (TLI; a metric of overall water quality) values from the 1960s similar to recent years, and blooms of cyanobacteria (blue-green algae) recorded as early as the 1970s. Nevertheless, the years since 2010 have been characterised by very poor water quality and particularly severe blooms, sometimes resulting in near-complete loss of oxygen from surface waters and associated fish kill events. This has attracted media attention and provided impetus from community and stakeholders to assess available management options for restoring more natural conditions and improving water quality in the lake. 
This report examines the drivers of poor water quality and algal blooms the lake, and assesses various management options that have either been specifically proposed for Tutira, or have proven effective for other lakes in New Zealand and globally. Here we report on monitoring undertaken by Hawke’s Bay Regional Council in the catchment (surface inflows) and lake. We also apply state-of-the-art computer models for simulating physical, chemical, and biological processes in the catchment and lake. These simulations are then used to evaluate a range of management ‘scenarios’ to provide guidance on the likely effects of management options tested with the model.

year: 2017