Massey Documents by Type

Permanent URI for this communityhttps://mro.massey.ac.nz/handle/10179/294

Browse

Subject: search.filters.subject.Manipulators (Mechanism)

Search Results

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Learning-based robotic manipulation for dynamic object handling : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Mechatronic Engineering at the School of Food and Advanced Technology, Massey University, Turitea Campus, Palmerston North, New Zealand
    (Massey University, 2021) Janse van Vuuren, Jacobus Petrus
    Recent trends have shown that the lifecycles and production volumes of modern products are shortening. Consequently, many manufacturers subject to frequent change prefer flexible and reconfigurable production systems. Such schemes are often achieved by means of manual assembly, as conventional automated systems are perceived as lacking flexibility. Production lines that incorporate human workers are particularly common within consumer electronics and small appliances. Artificial intelligence (AI) is a possible avenue to achieve smart robotic automation in this context. In this research it is argued that a robust, autonomous object handling process plays a crucial role in future manufacturing systems that incorporate robotics—key to further closing the gap between manual and fully automated production. Novel object grasping is a difficult task, confounded by many factors including object geometry, weight distribution, friction coefficients and deformation characteristics. Sensing and actuation accuracy can also significantly impact manipulation quality. Another challenge is understanding the relationship between these factors, a specific grasping strategy, the robotic arm and the employed end-effector. Manipulation has been a central research topic within robotics for many years. Some works focus on design, i.e. specifying a gripper-object interface such that the effects of imprecise gripper placement and other confounding control-related factors are mitigated. Many universal robotic gripper designs have been considered, including 3-fingered gripper designs, anthropomorphic grippers, granular jamming end-effectors and underactuated mechanisms. While such approaches have maintained some interest, contemporary works predominantly utilise machine learning in conjunction with imaging technologies and generic force-closure end-effectors. Neural networks that utilise supervised and unsupervised learning schemes with an RGB or RGB-D input make up the bulk of publications within this field. Though many solutions have been studied, automatically generating a robust grasp configuration for objects not known a priori, remains an open-ended problem. An element of this issue relates to a lack of objective performance metrics to quantify the effectiveness of a solution—which has traditionally driven the direction of community focus by highlighting gaps in the state-of-the-art. This research employs monocular vision and deep learning to generate—and select from—a set of hypothesis grasps. A significant portion of this research relates to the process by which a final grasp is selected. Grasp synthesis is achieved by sampling the workspace using convolutional neural networks trained to recognise prospective grasp areas. Each potential pose is evaluated by the proposed method in conjunction with other input modalities—such as load-cells and an alternate perspective. To overcome human bias and build upon traditional metrics, scores are established to objectively quantify the quality of an executed grasp trial. Learning frameworks that aim to maximise for these scores are employed in the selection process to improve performance. The proposed methodology and associated metrics are empirically evaluated. A physical prototype system was constructed, employing a Dobot Magician robotic manipulator, vision enclosure, imaging system, conveyor, sensing unit and control system. Over 4,000 trials were conducted utilising 100 objects. Experimentation showed that robotic manipulation quality could be improved by 10.3% when selecting to optimise for the proposed metrics—quantified by a metric related to translational error. Trials further demonstrated a grasp success rate of 99.3% for known objects and 98.9% for objects for which a priori information is unavailable. For unknown objects, this equated to an improvement of approximately 10% relative to other similar methodologies in literature. A 5.3% reduction in grasp rate was observed when removing the metrics as selection criteria for the prototype system. The system operated at approximately 1 Hz when contemporary hardware was employed. Experimentation demonstrated that selecting a grasp pose based on the proposed metrics improved grasp rates by up to 4.6% for known objects and 2.5% for unknown objects—compared to selecting for grasp rate alone. This project was sponsored by the Richard and Mary Earle Technology Trust, the Ken and Elizabeth Powell Bursary and the Massey University Foundation. Without the financial support provided by these entities, it would not have been possible to construct the physical robotic system used for testing and experimentation. This research adds to the field of robotic manipulation, contributing to topics on grasp-induced error analysis, post-grasp error minimisation, grasp synthesis framework design and general grasp synthesis. Three journal publications and one IEEE Xplore paper have been published as a result of this research.
  • Thumbnail Image
    Item
    Development of a compliant micro gripper : a thesis submitted in partial fulfillment for the degree of Masters of Engineering in the School of Engineering and Advanced Technology, Massey University
    (Massey University, 2019) Lofroth, Matthew
    Manipulating micro objects simply and effectively has been a widely discussed and challenging task in recent literature for many reasons. Limitations in complex micro fabrication techniques mean creating extremely small tools at the micro scale is very difficult. Adhesion forces also dominate at this scale, causing anything and everything to stick together. This means that even when these tiny structures are created and introduced to the micro world, they quickly become polluted with contaminants and struggle to pick and place particles without said particle adhering to the tool. Indirect methods for micro manipulation exist, however these can be damaging to biological material such as cells, due to unseen forces being focused into a small point. Having the ability to safely manipulate and separate these objects from a culture is crucial to understanding their individual characteristics. Therefore a safe and reliable method for micro manipulation needs to be developed. This project focuses on investigating the current methods used for micro manipulation in order to identify any possible routes towards developing a simple and yet effective means for manipulating micro objects. A modular micro gripping mechanism is proposed in this report, capable of manipulating many different types of objects such as spherical, non spherical or other arbitrary shapes. The proposed micro gripper combines traditional machining techniques with a complex micro fabrication process to produce a modular mechanism consisting of a sturdy, compliant aluminium base in which replaceable silicon and borosilicate glass end effectors are attached. This creates an easily customisable solution for micro manipulation with an array of different micro tips for different applications. A kinematic analysis for the gripper has been provided which predicts the workspace of the gripper given an input actuation. Design parameters of the gripper have also been optimised through various techniques such as FEA (finite element analysis) simulation and the effects of altering individual flexure beam lengths. The gripper is operated by a piezo actuator with a total capable expansion of 19 mm when 150 VDC is applied. This expansion is then amplified by a factor of 8.1 to a maximum tip displacement of approximately 154 mm. Displacement amplification is achieved by incorporating bridge and lever amplifying techniques into the compliant design. The complete micro gripper is then used to demonstrate manipulation tasks on several different target object types including silica micro beads (spherical and non spherical), a human eyelash and a grain of pollen. These tests are performed to investigate the effect of adhesion forces and also to demonstrate the large size range of capable pick and place objects (6 mm to 500 mm).
  • Thumbnail Image
    Item
    Mathematical modelling and control of a robotic manipulator : a thesis presented in partial fulfilment of the requirements of the degree of Masters of Technology at Massey University
    (Massey University, 1996) Yee, Nigel
    Control system engineering strives to alter a systems performance to suit the objectives of the user. This requires pre-requisite knowledge of the system behaviour. This is often in the form of mathematical models of the system. These models can then be used to simulate the system and obtain a sound understanding of the systems operation, these can then be used in controller design. Every real world physical system has its own unique characteristics. These must be modelled to develop a simulation of the system. The uniqueness of a real world system necessitates the use of experimental practices and procedures to obtain information about the system. This information is then used to form models representing the system. A simulation of the system can then be based on these models. In this project a robotic system comprising of a link structure, a pneumatic driving system and a valve regulating system, is investigated. Mathematical models describing each component of the robotic system are investigated. Mathematical models describing the dynamic interactions of the link structure are developed and implemented in a fashion to facilitate control of the robot mechanism. The equations are in an explicit form which do not require the use of a numerical method for development of state space equations used in controller development. The pneumatic muscle used as the desired actuator for the robot structure is analysed. Analytical models obtained from the available literature are examined and new models are developed to describe the characteristics of the pneumatic muscle. A proto-type valve specially developed for supplying air to the pneumatic muscle is investigated. Experiments are conducted on this valve to characterise the valves behaviour. A model of the valves behaviour is then developed. A selection of controllers are then applied to the valve pneumatic muscle system. The investigation of alternative actuation systems proposes a new rotary pneumatic muscle design. Analytical models for the rotary pneumatic muscle are developed, a prototype is constructed as part of a feasibility study.
  • Thumbnail Image
    Item
    Multiple configuration shell-core structured robotic manipulator with interchangeable mechatronic joints : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Engineering in Mechatronics at Massey University, Turitea Campus, Palmerston North, New Zealand
    (Massey University, 2017) Janse van Vuuren, Jacques J P
    With the increase of robotic technology utilised throughout industry, the need for skilled labour in this area has increased also. As a result, education dealing with robotics has grown at both the high-school and tertiary educational level. Despite the range of pedagogical robots currently on the market, there seems to be a low variety of these systems specifically related to the types of robotic manipulator arms popular for industrial applications. Furthermore, a fixed-arm system is limited to only serve as an educational supplement for that specific configuration and therefore cannot demonstrate more than one of the numerous industrial-type robotic arms. The Shell-Core structured robotic manipulator concept has been proposed to improve the quality and variety of available pedagogical robotic arm systems on the market. This is achieved by the reconfigurable nature of the concept, which incorporates shell and core structural units to make the construction of at least 5 mainstream industrial arms possible. The platform will be suitable, but not limited to use within the educational robotics industry at high-school and higher educational levels and may appeal to hobbyists. Later dubbed SMILE (Smart Manipulator with Interchangeable Links and Effectors), the system utilises core units to provide either rotational or linear actuation in a single plane. A variety of shell units are then implemented as the body of the robotic arm, serving as appropriate offsets to achieve the required configuration. A prototype consisting of a limited number of ‘building blocks’ was developed for proof-of-concept, found capable of achieving several of the proposed configurations. The outcome of this research is encouraging, with a Massey patent search confirming the unique features of the proposed concept. The prototype system is an economic, easy to implement, plug and play, and multiple-configuration robotic manipulator, suitable for various applications.