Developing tools and methods for object-oriented mechatronics

Thesis (Ph. D.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. [161]-166).The digital revolution has fundamentally changed our lives by giving us new ways to express ourselves through digital media. For example, accessible multimedia content creation tools allow people to instantiate their ideas and share them easily. However, most of these outcomes only exist on-screen and online. Despite the growing accessibility of digital design and fabrication tools the physical world and everyday objects surrounding us have been largely excluded from a parallel explosion of possibilities to express ourselves. Increasingly, webbased services allow professional and non-professional audiences to access computer-aided manufacturing (CAM) tools like 3D-printing and laser-cutting. Nonetheless, there are few (if any) design tools and methods for creating complex mechanical assemblies that take full advantage of CAM systems. Creating unique mechatronic artifacts or "originalMachines" requires more specific and sophisticated design tools than exist today. "Object-Oriented Mechatronics" is a parametric design approach that connects knowledge about mechanical assemblies and electronics with the requirements of digital manufacturing processes. Parametric instances like gears, bearing and servos are made available as objects within a CAD environment which can then be implemented into specific projects. The approach addresses the missing link between accessible rapid-manufacturing services and currently available design tools thereby creating new opportunities for self-expression through mechatronic objects and machines. The dissertation matches mechanical components and assemblies with rapid manufacturing methods by exploring transferability of conventional manufacturing techniques to appropriate rapid manufacturing tools. I rebuild various gearing and bearing principles like four-contact point bearings, cross roller bearings, spur and helical gears, planetary gears, cycloidal and harmonic gear reducers using the laser cutter, the CNC-mill and the 3D-printer. These explorations lead to more complex assemblies such as the PlywoodServo, 3DprintedClock and 3-DoF (Degree of Freedom) Head. The lessons from these explorations are summarized in a detailed "cook book" of novel mechatronic assemblies enabled by new fabrication tools. Furthermore, I use the results to develop a CAD tool that brings together several existing software packages and plug-ins including Rhino, Grasshopper and the Firefly experiments for Arduino, which will allow animation, fabrication and control of original machines. The tool is an example of an object-oriented design approach to mechatronic assemblies. A user calls a DoF (Degree of Freedom) object (parametric servo) with specific parameters like gearing and bearing types, motor options and control and communication capabilities. The DoF object then creates the corresponding geometry which can be connected and integrated with other actuators and forms. A group of roboticists and designers participated in a workshop to test the tool and make proposals for original machines using the tool. The dissertation has contributions on multiple levels. First, the actuator assembly examples and parametric design tool present a body of novel work that illustrates the benefits of going beyond off-the-shelf actuator assemblies and kit-of-parts for robotic objects. Second, this tool and the accompanying examples enable the design of more original machines with custom actuator assemblies using the latest digital fabrication tools. Finally, these explorations illustrate how new CAD/ CAM tools can facilitate an exchange between more design-oriented users and more engineering-oriented users.by Peter Schmitt.Ph.D

Mechanical Engineering

The book substantially offers the latest progresses about the important topics of the "Mechanical Engineering" to readers. It includes twenty-eight excellent studies prepared using state-of-art methodologies by professional researchers from different countries. The sections in the book comprise of the following titles: power transmission system, manufacturing processes and system analysis, thermo-fluid systems, simulations and computer applications, and new approaches in mechanical engineering education and organization systems

Transmission error in spur gears: Static and dynamic finite-element modeling and design optimization

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University, 07/10/2010.The gear noise problem that widely occurs in power transmission systems is typically characterised by one or more high amplitude acoustic signals. The noise originates from the vibration of the gear pair system caused by transmission error excitation that arises from tooth profile errors, misalignment and tooth deflections. This work aims to further research the effect of tooth profile modifications on the transmission error of gear pairs. A spur gear pair was modelled using finite elements, and the gear mesh was simulated and analysed under static conditions. The results obtained were used to study the effect of intentional tooth profile modifications on the transmission error of the gear pair. A detailed parametric study, involving development of an optimisation algorithm to design the tooth modifications, was performed to quantify the changes in the transmission error as a function of tooth profile modification parameters as compared to an unmodified gear pair baseline. The work also investigates the main differences between the static and dynamic transmission error generated during the meshing of a spur gear pair model. A combination of Finite-Element Analysis, hybrid numerical/analytical methodology and optimisation algorithms were used to scrutinise the dynamic behaviour of the gear pairs under various operating conditions

Dynamic analysis of the cutting forces in gear hobbing

The work reported in this thesis has been developed to predict and measure the cutting forces in the gear hobbing process. A review of past research in this area has highlighted the need to adopt a different approach to modelling the process in order to predict the cutting forces. The hobbing process has been described using six different co-ordinate systems and the kinematic relationships between these systems established. A single rack profile has been used to represent the profile of a single cutting tooth from the hob which was then extended to simulate the hob itself. When the hob gashes pass through the cutting region surfaces are generated which, if mapped on a regular grid can give the basis to estimate the depth of cut, i.e. the instantaneous chip thickness produced by that particular tooth. The instantaneous cutting forces generated by that tooth then can be estimated by using the concept of a specific cutting force of the workpiece material. The estimation of cutting forces acting on a single tooth space was used to predict the cutting forces produced during machining of a full gear, by assuming that the forces acting in a particular tooth space are equal to those acting on the adjacent tooth space at an equivalent instant in the cutting cycle. In order to validate predicted results, a Churchill PH1612 hobbing machine was retrofitted with a CNC control system at Newcastle University, utilising a programmable multi axis controller (PMAC). A specially made single toothed gear, and a full gear were machined, and cut on this machine, and the cutting forces measured in real time using a 3-axis dynamometer. The force signals produced by the dynamometer were measured utilising a 12-bit ADC card. Code, written in C, was developed to perform the many functions needed for the overall control of the machine, but additionally was used to capture both the cutting forces and axis position data. The results of the simulation and modelling have shown very good agreement with those obtained experimentally.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Transmission error in spur gears : static and dynamic finite-element modeling and design optimization

The gear noise problem that widely occurs in power transmission systems is typically characterised by one or more high amplitude acoustic signals. The noise originates from the vibration of the gear pair system caused by transmission error excitation that arises from tooth profile errors, misalignment and tooth deflections. This work aims to further research the effect of tooth profile modifications on the transmission error of gear pairs. A spur gear pair was modelled using finite elements, and the gear mesh was simulated and analysed under static conditions. The results obtained were used to study the effect of intentional tooth profile modifications on the transmission error of the gear pair. A detailed parametric study, involving development of an optimisation algorithm to design the tooth modifications, was performed to quantify the changes in the transmission error as a function of tooth profile modification parameters as compared to an unmodified gear pair baseline. The work also investigates the main differences between the static and dynamic transmission error generated during the meshing of a spur gear pair model. A combination of Finite-Element Analysis, hybrid numerical/analytical methodology and optimisation algorithms were used to scrutinise the dynamic behaviour of the gear pairs under various operating conditions.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Wireless capsule endoscope for targeted drug delivery

The diagnosis and treatment of pathologies of the gastrointestinal (GI) tract are performed routinely by gastroenterologists using endoscopes and colonoscopes, however the small intestinal tract is beyond the reach of these conventional systems. Attempts have been made to access the small intestines with wireless capsule endoscopes (WCE). These pill-sized cameras take pictures of the intestinal wall and then relay them back for evaluation. This practice enables the detection and diagnosis of pathologies of the GI tract such as Crohn's disease, small intestinal tumours such as lymphoma and small intestinal cancer. The problems with these systems are that they have limited diagnostic capabilities and they do not offer the ability to perform therapy to the affected areas leaving only the options of administering large quantities of drugs or surgical intervention. To address the issue of administering therapy in the small intestinal tract this thesis presents an active swallowable microrobotic platform which has novel functionality enabling the microrobot to treat pathologies through a targeted drug delivery system. This thesis first reviews the state-of-the-art in WCE through the evaluation of current and past literature. A review of current practises such as flexible sigmoidoscopy, virtual colonoscopy and wireless capsule endoscopy are presented. The following sections review the state-of-the-art in methods of resisting peristalsis, drug targeting systems and drug delivery. A review of actuators is presented, in the context of WCE, with a view to evaluate their acceptability in adding functionality to current WCEs. The thesis presents a novel biologically-inspired holding mechanism which overcomes the issue of resisting natural peristalsis in the GI tract. An analysis of the two components of peristaltic force, circumferential and longitudinal peristaltic contractions, are presented to ensure correct functionality of the holding mechanism. A detailed analysis of the motorised method employed to deploy the expanding mechanism is described and a 5:1 scale prototype is presented which characterises the gearbox and validates the holding mechanism. The functionality of WCE is further extended by the inclusion of a novel targeting mechanism capable of delivering a metered dose of medication to a target site of interest in the GI tract. A solution to the problem of positioning a needle within a 360 degree envelope, operating the needle and safely retracting the needle in the GI tract is discussed. A comprehensive analysis of the mechanism to manoeuvre the needle is presented and validation of the mechanism is demonstrated through the evaluation of scale prototypes. Finally a drug delivery system is presented which can expel a 1 ml dose of medication, stored onboard the capsule, into the subcutaneous tissue of the GI tract wall. An analysis of the force required to expel the medication in a set period of time is presented and the design and analysis of a variable pitch conical compression spring which will be used to deliver the medication is discussed. A thermo mechanical trigger mechanism is presented which will be employed to release the compressed conical spring. Experimental results using 1:1 scale prototype parts validate the performance of the mechanisms.Open Acces

Tool Wear Characterisation and Parameter Optimisation in Micro-manufacturing Processes

Increases in demand for miniaturised static parts, actuators and devices has presented challenges in machining; requiring fast advancement in the field. This work examines two processes: Wire Electrical Discharge Machining (WEDM), and micro-milling. While very different processes, both of these have in common the fact that their behaviour and the phenomena seen differ from those seen in conventional subtractive machining. Capability of machine tools has increased to allow highly intricate parts to be produced, but there are significant challenges in achieving excellent surface finish, geometrical accuracy and tool life. WEDM is appropriate for cutting complex shapes without long set-up times, but cutting very thin workpieces represents difficulties in achieving stable machining, while the process results in a recast layer which can affect wear and transmission. This work focuses on investigating optimal parameters for machining micro-gears. This has traditionally been challenging because the limited area for spark generation between wire and workpiece leads to unstable machining, resulting in poor machining rate and surface finish. Investigations into significant machining parameters have taken place, followed by a feasibility study cutting brass gears of 0.3 mm thickness. The results indicate that the depth of the recast layer can be minimised while maintaining an acceptable Material Removal Rate (MRR), by considering gear geometry. This work suggests that WEDM is a valuable tool in prototyping miniature gears. Micro-milling allows small, accurate parts to be produced, but micro-tools wear quickly and unpredictably, therefore tool wear is difficult to measure. This results in a high rate of tool changes and reduced productivity. A protocol for measuring tool wear has been produced to allow a common method to be used across research institutes. This presents a method for analysing and reporting micro-mill tool wear which will allow transfer between research institutions and industry, to extend tool life and improving process efficiency. This protocol has then been used to investigate tool coatings on the micro scale, and compare the tribological processes seen on micro-tools to their macro counterparts. This work has resulted in extended tool life for industrial micro-mills and has been applied to industrial situations