Praktična sinteza regulatora za precizno pozicioniranje sustava pomične podloge

This paper presents a practical feedback controller design of a ball screw-driven table system for the microdisplacement positioning. Friction of the mechanism in the micro-displacement region has nonlinear elastic properties, unlike Coulomb and/or viscous friction in the macro-displacement, resulting in different positioning responses and frequency characteristics of the plant depending on the regions. In this paper, at first, a numerical simulator with a rolling friction model is adopted to reproduce the positioning behaviors in the micro-displacement region. Based on the simulator, the stability condition of positioning in the region is clarified on the basis of frequency characteristics and, then, appropriate parameters of feedback controller are practically designed to satisfy the required positioning performance. Effectiveness of the proposed design has been verified by a series of experiments using a prototype of ball screw-driven table positioning device.U radu je prikazana sinteza regulatora s povratnom vezom u sustavu za precizno linearno pozicioniranje pomične podloge pomoću kugličnih ležajeva. Za razliku od uobičajenih modela Coulombova i/ili viskoznog trenja, trenje razmatranog sustava ima izrazito nelinearna svojstva u području mikro-pomaka, što za posljedicu ima različite odzive pozicioniranja i frekvencijski karakteristike, ovisno o radnom području. U radu je prvo razvijeno numeričko simulacijsko okruženje zasnovano na modelu trenja kotrljanja u svrhu simuliranja ponašanja sustava pozicioniranja u području mikropomaka. Potom je, zasnivajući se na simulacijskom okruženju, pomoću frekvencijske karakteristike razjašnjen problem stabilnosti sustava u promatranom radnom području te su odabrani odgovarajući parametri regulatora koji poštuju uvjet stabilnosti i zadovoljavaju željenu kvalitetu odziva. Sinteza regulatora provedena je vodeći računa o praktičnoj primjenjivosti postupka. Učinkovitost predložene sinteze potvr.ena je nizom eksperimenata na prototipu sustava za precizno linearno pozicioniranje pomične podloge pomoću kugličnih ležajeva

Feasibility study of electromechanical cylinder drivetrain for offshore mechatronic systems

Currently, there is an increasing focus on the environmental impact and energy consumption of the oil and gas industry. In offshore drilling equipment, electric motors tend to replace traditionally used hydraulic motors, especially in rotational motion control applications. However, force densities available from linear hydraulic actuators are still typically higher than those of electric actuators. Therefore, usually the remaining source of hydraulic power is thereby the hydraulic cylinder. This paper presents a feasibility study on the implementation of an electromechanical cylinder drivetrain on an offshore vertical pipe handling machine. The scope of this paper is to investigate the feasibility of a commercial off-the-shelf drivetrain. With a focus on the motion performance, numerical modeling and simulation are used when sizing and selecting the components of the considered electromechanical cylinder drivetrain. The simulation results are analyzed and discussed together with a literature study regarding advantages and disadvantages of the proposed solution considering the design criteria of offshore drilling equipment. It is concluded that the selected drivetrain can only satisfy the static motion requirements since the required transmitted power is higher than the recommended permissible power of the transmission screw. Consequently, based on the recommendation of the manufacturer, avoidance of overheating cannot be guaranteed for the drivetrain combinations considered for the case study presented in this paper. Hence, to avoid overheating, the average speed of the motion cycle must be decreased. Alternatively, external cooling or temperature monitoring and control system that prevents overheating could be implemented

Influence of controller parameters on the life of ball screw feed drives

The ball screws are the machine component most frequently used for transforming rotational into linear motion of a feed drive, to position the machine tool components carrying the cutting tool to the desired location. A failure of the ball screw usually leads to a total breakdown of the axis; therefore, the attainable life of this component is an important issue concerning the availability and productivity of modern machine tools. This article presents an approach to evaluate the influence of control parameters on the fatigue life of ball screws based on simulation, by means of a numerical model of a machine tool servo-axis. Ball screw life was evaluated with different conditions, varying the position loop main proportional gain and the kinematic limit conditions for trajectory generation. Furthermore, the mathematical model was used to evaluate optimal control gain and trajectory conditions for a machine tool based on the achievable life span of the ball screw feed drive system, with regard to the desirable performances, such as position accuracy, promptness, and cutoff frequency

Stability and parking cross distance adapter mechanism for electric vehicle

Due to the actual vehicle dimensions, low occupancy rates and the increase of world population, a trend to develop new vehicle concepts with smaller dimensions is seen. The objective of this trend is to reduce traffic congestion and park ability related issues in overpopulated areas. Not only footprint reduction is necessary, but also maintaining actual vehicle safety and comfort metrics is a must. Therefore, first of all, a mechanism to reduce wheel track to the third of the space required for a conventional car for low speed and parking situations is designed and developed. Once the track variation mechanism is completely defined, several suspensions and steering mechanism are analysed, concluding with a design of an unconventional front independent suspension and steering systems which are detailed in the present manuscript. By using MBS (Multi-body System) model, loads transmitted from tyre through mechanism joints to the vehicle chassis are computed. Special attention has been paid to the maximum peak loads that mechanism will suffer from road irregularities in extreme conditions. These load values are also used to evaluate the components that compose the track variation mechanism. Continuing with the actuation of the system, an electronic control strategy is created and virtually tested, with what vehicle track position and vehicle speed and acceleration conditions are instantaneously controlled and related with the wheel track variation system. Finally, the complete track width variation mechanism is manufactured, assembled and tested in a test rig

Lightweight design of a suspension arm by friction stir welding

The research seeks initially to investigate why a greater shift to lightweight technologies for suspension design has not occurred already over the mass market vehicle sector. It outlines the 'knock-on' benefits of lightweight design and identifies roadblocks which hinder progress. Recent annual metrics of vehicle performance related to mass are investigated. Focusing on individual areas of the suspension, benchmarking identifies the best practice amongst current designs. Manufacturing and process engineering strategies are proposed to support the development of lightweight products with considerably improved environmental acceptability.MIG (Metal Inert Gas) welding, universally accepted as the default joining technology in this field, was found to be restrictive to progress due primarily to detrimental effects on metallurgical, dimensional and process variation on both steel and aluminium products. The latest construction materials were reviewed for suspension application, but the focus remained on proposing light weighting solutions for material generically available in economic volumes today, but with new joining technologies to overcome current restrictions in using less of these materials for each component. Following a full review of the joining technologies available for automotive suspension construction, friction stir welding (FSW) was proposed as an alternative joining technology, with FSW replacing MIG in conjunction with extruded aluminium materials. This removed the barriers incumbent in the use of MIG, which demands a more conservative, heavier design to ensure adequate service lifetime. Design concepts were engineered to take maximum advantage of the strategy of aluminium, extrusions, assembled with friction stir welding. Several viable designs were conceived, from which two were developed and compared. The optimum design was then carried forward into a manufacturing feasibility stage. The extrusions were developed for ease of manufacture, and friction stir welding trials progressed on coupons (plain plates) to ensure that the process was viable. Aluminium in the soft and hardened conditions in different thicknesses and joint configurations were successfully friction stir welded during the trial. Future work would develop the extruded aluminium arm further, into the prototype phase, with sample extrusions being manufactured, FSW welded and assembled. Prototypes would then be rig tested to ensure mechanical and durability performance prior to vehicle trials. There are also possibilities in developing high strength thin wall multi-phase steel solutions, utilising Friction Stir Spot Welding (FSSW). This welding technology enhances the selection of high strength steels, as minimal strength is sacrificed during the joining operation

Automation and robotic control of a multi-sensor medical device platform

Biocompatibility testing is a complex and time-consuming process that can create significant delays when new medical devices and systems are brought to market. This thesis summarises work performed when automating a platform that incorporates new technologies to speed up the test protocol.As part of the H2020 project PANBioRa, several partners within the consortium have developed sensing technologies for cytotoxicity and cytokine analysis which are intended for inclusion in a multi-test platform. This platform is designed for use in the medical device industry and for use in hospitals, where tests on individuals will provide personal biocompatibility results. Dublin City University has been tasked with integrating the novel sensing methods to determine cell health and to design the system so that it is contained in a user-friendly bench-top unit. The thesis is focused on the design of an autofocusing microscope that will be used to identify cells, test for confluency within cell chambers, and determine cell health throughout the testing process by implementing image processing algorithms. The microscope is designed to obtain approximately 10x magnification and to have a physical size that allows it to move and operate as an end effector of a robotic system, meaning it can navigate to various cell locations. The objective of this project was therefore to design, construction, and validation of a high precision multi-axis robot to control the position and focus of the microscope, while in addition meeting the cost and size demands of the project. With the system being capable of moving the microscope assembly into various positions where cells were present, while with the desired level of accuracy. Continuing to autofocus on cells and collect Images of cells to a level where the desired characteristics could be determined

A novel haptic model and environment for maxillofacial surgical operation planning and manipulation

This paper presents a practical method and a new haptic model to support manipulations of bones and their segments during the planning of a surgical operation in a virtual environment using a haptic interface. To perform an effective dental surgery it is important to have all the operation related information of the patient available beforehand in order to plan the operation and avoid any complications. A haptic interface with a virtual and accurate patient model to support the planning of bone cuts is therefore critical, useful and necessary for the surgeons. The system proposed uses DICOM images taken from a digital tomography scanner and creates a mesh model of the filtered skull, from which the jaw bone can be isolated for further use. A novel solution for cutting the bones has been developed and it uses the haptic tool to determine and define the bone-cutting plane in the bone, and this new approach creates three new meshes of the original model. Using this approach the computational power is optimized and a real time feedback can be achieved during all bone manipulations. During the movement of the mesh cutting, a novel friction profile is predefined in the haptical system to simulate the force feedback feel of different densities in the bone

Design and Implement Towards Enhanced Physical Interactive Performance Robot Bodies

In this thesis, it will introduce the design principle and implement details towards enhanced physical interactive performance robot bodies, which are more specically focused on under actuated principle robotic hands and articulated leg robots. Since they both signicantly function as the physical interactive robot bodies against external environment, while their current performance can hardly satisfy the requirement of undertaking missions in real application. Regarding to the enhanced physical interactive performances, my work will emphasis on the three following specific functionalities, high energy efficiency, high strength and physical sturdiness in both robotics actuation and mechanism. For achieving the aforementioned targets, multiple design methods have been applied, rstly the elastic energy storage elements and compliant actuation have been adopted in legged robots as Asymmetrical Compliant Actuation (ACA), implemented for not only single joint but also multiple joints as mono and biarticulation congurations in order to achieve higher energy effciency motion. Secondly the under actuated principle and modular nger design concept have been utilized on the development of robotic hands for enhancing the grasping strength and physical sturdiness meanwhile maintaining the manipulation dexterity. Lastly, a novel high payload active tuning Parallel Elastic Actuation (PEA) and Series Elastic Actuation (SEA) have been adopted on legged robots for augmenting energy eciency and physical sturdiness. My thesis contribution relies on the novel design and implement of robotics bodies for enhancing physical interactive performance and we experimentally veried the design effectiveness in specic designed scenario and practical applications

Performance and manufacturing considerations for series elastic actuators

Robots are becoming an integral part of our lives. We are already physically connected with them through many robotic applications such as exoskeletons in military, orthosis devices in health care, collaborative robots in industry, etc. While the integration of robots improves the quality of human life, it still poses a safety concern during the physical human-robot interaction. Series Elastic Actuators (SEAs) play an important role in improving the safety of human-robot interaction and collaboration. Considering the fast expansion of robotic applications in our lives and the safety benefits of SEAs, it is conceivable that SEAs are going to play an important role in robotic applications in every aspect of human life. This dissertation focuses on reducing the cost, simplifying the use and improving the performance of SEAs. The first research focus in this dissertation is to reduce the cost of SEAs. Robots are successful in reducing production and service costs when used but the capital cost of robot installations are very high. As robotics research shifts to safe robotic applications, reducing the cost of SEAs will greatly help to deploy this technology in more robotic applications and to increase their accessibility to a broader range of researchers and educators. With this motivation, I present a case study on reducing the cost of a SEA while maintaining high force and position control performance and industrial grade service life. The second research focus in this dissertation is to simplify the laborious gain selection process of the cascaded controllers of SEAs. In order to simplify the gain selection process of the impedance controllers of SEAs, an optimal feedback gain selection methodology was developed. Using this method, the feedback gains of the cascaded PD-type impedance controllers of SEAs can easily be calibrated. The developed method allows the users to find the highest feedback gains for a desired phase-margin. Beyond the low-cost realization and simple controller tuning of SEAs, performance improvements on SEAs are possible utilizing the series elasticity in these actuators. As the third research focus in this dissertation, a sequential convex optimization-based motion planning technique is developed in order to improve the joint velocity capabilities of SEAs with nonlinearities. By using this method, higher joint velocities, that are not achievable with the rigid counterparts of SEAs can be achievedMechanical Engineerin