62 research outputs found
Linear actuators for locomotion of microrobots
University of Technology, Sydney. Faculty of Engineering.The successful development of the miniaturisation techniques for electronic components
and devices has paved the way for the miniaturisation in other technological fields. In
the past two decades, the research achievements in micromechatronics have spurred fast
development of micro machines and micro robotic systems. Miniature or micro
actuators are the critical components to make these machines more dexterous, compact
and cost effective.
The main purpose of this dissertation is to develop micro actuators suitable for the
locomotion of an in-pipe or endoscopic microrobot. The content of the thesis covers the
selection of the actuation principle, robotic system design, actuator design and prototype
construction, performance analysis, and design, analysis, and implementation of the
appropriate drive control system.
Among different types of actuation principles, piezoelectric and electromagnetic
actuators are the two major candidates for the micro robotic systems. In order to find a
suitable actuation principle for the desired robotic application, a comparative study was
conducted on the scaling effects, attainable energy density, and dynamic performances
of both types of actuators. Through the study, it was concluded that the electromagnetic
actuator is more suitable for the endoscopic microrobot.
Linear actuators are the common design used for the locomotion of microrobots due to
many advantages compared to their rotational counterparts. Through a thorough review
and comparison of the electromagnetic linear actuator topologies, a moving-coil tubular
linear actuator was chosen as the first design due to its simplest structure. Via the
magnetic circuit analysis and numerical magnetic field solutions, the actuator was
designed for optimum force capability, and the electromagnetic force and the machine
parameters of the actuator were predicted. According to the results obtained from the
magnetic field analysis, the dynamic model of the actuation system with a driving
control scheme was established and used in the actuation performance analysis of the
robotic system.
Based on the experience achieved through the first design, a new moving-magnet
tubular linear actuator was designed. The methodology developed in the design and
analysis of the moving-coil linear actuator was adopted for the moving-magnet actuator
design. However, the optimal design is more complicated due to the multi-pole and
multi-phase structure of the moving-magnet actuator. The electromagnetic force of the
actuator was analysed under the condition of different excitation methods. An enhanced
parameter computation method is proposed for predicting the actuator parameters.
Based on the results of magnetic field analysis, a comprehensive dynamic model of the
actuator was developed. Through the coupled field-circuit analysis, this model can
predict accurately the dynamic performance of the actuator. The characteristics analysis
shows that the performance of the moving-magnet actuator is much better than that of
the moving-coil actuator.
Two prototypes of the moving-magnet tubular linear actuator with different dimensions
were constructed to verify the performance and the scaling theory. Various precision
machining techniques were employed during the fabrication. The performances and
parameters of the two different prototypes were measured and the results agree
substantially with the theory.
The brushless DC drive method was chosen for the driving control of the proposed
linear actuator because of the compact circuit topology and simple implementation,
which are two essential factors for micro applications. A sensorless control scheme
based on the back EMF was developed as physical position sensors are not permitted in
such a micro system. The control scheme was then applied to the locomotion control of
the proposed microrobot. The system simulation shows that the control performances of
both the actuator and microrobot are satisfactory.
A dSPACE prototyping system based driving control hardware was designed and
implemented to experimentally verify the control design. The experimental results agree
substantially with the theoretical work
Study on Magnetic Control Systems of Micro-Robots
Magnetic control systems of micro-robots have recently blossomed as one of the most thrilling areas in the field of medical treatment. For the sake of learning how to apply relevant technologies in medical services, we systematically review pioneering works published in the past and divide magnetic control systems into three categories: stationary electromagnet control systems, permanent magnet control systems and mobile electromagnet control systems. Based on this, we ulteriorly analyze and illustrate their respective strengths and weaknesses. Furthermore, aiming at surmounting the instability of magnetic control system, we utilize SolidWorks2020 software to partially modify the SAMM system to make its final overall thickness attain 111 mm, which is capable to control and observe the motion of the micro-robot under the microscope system in an even better fashion. Ultimately, we emphasize the challenges and open problems that urgently need to be settled, and summarize the direction of development in this field, which plays a momentous role in the wide and safe application of magnetic control systems of micro-robots in clinic
Modeling and design of an electromagnetic actuation system for the manipulation of microrobots in blood vessels
Tese de mestrado integrado em Física, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2015A navegação de nano/microdispositivos apresenta um grande potencial para aplicações biomédicas, oferecendo meios de diagnóstico e procedimentos terapêuticos no interior do corpo humano. Dada a sua capacidade de penetrar quase todos os materiais, os campos magnéticos são naturalmente adequados para controlar nano/microdispositivos magnéticos em espaços inacessíveis. Uma abordagem recente é o uso de um aparelho personalizado, capaz de controlar campos magnéticos. Esta é uma área de pesquisa prometedora, mas mais simulações e experiências são necessárias para avaliar a viabilidade destes sistemas em aplicações clínicas.
O objectivo deste projecto foi a simulação e desenho de um sistema de atuação eletromagnética para estudar a locomoção bidimensional de microdispositivos. O primeiro passo foi identificar, através da análise de elementos finitos, usando o software COMSOL, diferentes configurações de bobines que permitiriam o controlo de dispositivos magnéticos em diferentes escalas. Baseado nos resultados das simulações, um protótipo de um sistema de atuação magnética para controlar dispositivos com mais de 100 m foi desenhado e construído de raiz, tendo em conta restrições de custos. O sistema consistiu num par de bobines de Helmholtz e rotacionais e um par de bobines de Maxwell dispostas no mesmo eixo. Além disso, componentes adicionais tiveram de ser desenhados ou selecionados para preencher os requisitos do sistema. Para a avaliação do sistema fabricado, testes preliminares foram realizados. A locomoção do microrobot foi testada em diferentes direções no plano x-y.
As simulações e experiências confirmaram que é possível controlar a força magnética e o momento da força que atuam num microdispositivo através do campos produzidos pelas bobines de Maxwell e Helmholtz, respectivamente. Assim, este tipo de atuação magnética parece ser uma forma adequada de transferência de energia para futuros microdispositivos biomédicos.Navigation of nano/microdevices has great potential for biomedical applications, offering a means for diagnosis and therapeutic procedures inside the human body. Due to their ability to penetrate most materials, magnetic fields are naturally suited to control magnetic nano/microdevices in inaccessible spaces. One recent approach is the use of custom-built apparatus capable of controlling magnetic devices. This is a promising area of research, but further simulation studies and experiments are needed to estimate the feasibility of these systems in clinical applications.
The goal of this project was the simulation and design of an electromagnetic actuation system to study the two dimensional locomotion of microdevices. The first step was to identify, through finite element analysis using software COMSOL, different coil configurations that would allow the control of magnetic devices at different scales. Based on the simulation results, a prototype of a magnetic actuation system to control devices with more than 100 m was designed and built from the ground up, taking into account cost constraints. The system comprised one pair of rotational Helmholtz coils and one pair of rotational Maxwell coils placed along the same axis. Furthermore, additional components had to be designed or selected to fulfil the requirements of the system. For the evaluation of the fabricated system, preliminary tests were carried out. The locomotion of a microdevice was tested along different directions in the x-y plane.
The simulations and experiments confirmed that it is possible to control the magnetic force and torque acting on a microdevice through the fields produced by Maxwell and Helmholtz coils, respectively. Thus, this type of magnetic actuation seems to provide a suitable means of energy transfer for future biomedical microdevices
A review of modeling and control of remote-controlled capsule endoscopes.
INTRODUCTION: The significance of this review lies in addressing the limitations of passive locomotion in capsule endoscopes, hindering their widespread use in medical applications. The research focuses on evaluating existing miniature in vivo remote-controlled capsule endoscopes, examining their locomotion designs, and working theories to pave the way for overcoming challenges and enhancing their applicability in diagnostic and treatment settings. AREAS COVERED: This paper explores control methods and dynamic system modeling in the context of self-propelled remote-controlled capsule endoscopes with a two-mass arrangement. The literature search, conducted at Queen Mary University of London Library from 2000 to 2022, utilized a systematic approach starting with the broad keyword 'Capsule Endoscope' and progressively narrowing down to specific aspects such as 'Capsule Endoscope Control' and 'Self-propelled Capsule Endoscope' using various criteria. EXPERT OPINION: Efficiently driving and controlling remote-controlled capsule endoscopes have the potential to overcome the current limitations in medical technology, offering a viable solution for diagnosing and treating gastrointestinal diseases. Successful control of the remote-controlled capsule endoscope, as demonstrated in this review paper, will lead to a step change in medical engineering, establishing the remote-controlled capsule endoscope as a swift standard in the field
Novel Locomotion Methods in Magnetic Actuation and Pipe Inspection
There is much room for improvement in tube network inspections of jet aircraft. Often, these inspections are incomplete and inconsistent. In this paper, we develop a Modular Robotic Inspection System (MoRIS) for jet aircraft tube networks and a corresponding kinematic model. MoRIS consists of a Base Station for user control and communication, and robotic Vertebrae for accessing and inspecting the network. The presented and tested design of MoRIS can travel up to 9 feet in a tube network. The Vertebrae can navigate in all orientations, including smooth vertical tubes. The design is optimized for nominal 1.5 outside diameter tubes. We developed a model of the Locomotion Vertebra in a tube. We defined the model\u27s coordinate system and its generalized coordinates. We studied the configuration space of the robot, which includes all possible orientations of the Locomotion Vertebra. We derived the expression for the elastic potential energy of the Vertebra\u27s suspensions and minimized it to find the natural settling orientation of the robot. We further explore the effect of the tractive wheel\u27s velocity constraint on locomotion dynamics. Finally, we develop a general model for aircraft tube networks and for a taut tether.
Stabilizing bipedal walkers is a engineering target throughout the research community. In this paper, we develop an impulsively actuated walking robot. Through the use of magnetic actuation, for the first time, pure impulsive actuation has been achieved in bipedal walkers. In studying this locomotion technique, we built the world\u27s smallest walker: Big Foot. A dynamical model was developed for Big Foot. A Heel Strike and a Constant Pulse Wave Actuation Schemes were selected for testing. The schemes were validated through simulations and experiments. We showed that there exists two regimes for impulsive actuation. There is a regime for impact-like actuation and a regime for longer duration impulsive actuation
Design, Implementation and Control of a Magnetic Levitation Device
Magnetic levitation technology has shown a great deal of promise for micromanipulation
tasks. Due to the lack of mechanical contact, magnetic levitation systems are free of problems caused by friction, wear, sealing and lubrication. These advantages have made magnetic levitation systems a great candidate for clean room applications. In this thesis, a new large gap magnetic levitation system is designed, developed and successfully tested. The system is capable of levitating a 6.5(gr) permanent magnet in 3D space with an air gap of approximately 50(cm) with the traveling range of 20x20x30 cubic millimeters. The overall positioning accuracy of the system is 60 micro meters. With the aid of finite elements method, an optimal geometry for the magnetic stator is proposed. Also, an energy optimization approach is utilized in the design of the electromagnets.
In order to facilitate the design of various controllers for the system, a mathematical model of the magnetic force experienced by the levitated object is obtained. The dynamic magnetic force model is determined experimentally using frequency response system identification. The response of the system components including the power amplifiers, and position measurement system are also considered in the development of the force model.
The force model is then employed in the controller design for the magnetic levitation device. Through a modular approach, the controller design for the 3D positioning system is started with the controller design for the vertical direction, i.e. z, and then followed by the controller design in the horizontal directions, i.e. x and y.
For the vertical direction, several controllers such as PID, feed forward and feedback linearization are designed and their performances are compared. Also a control command conditioning method is introduced as a solution to increase the control performance and the results of the proposed controller are compared with the other designs.
Experimental results showed that for the magnetic levitation system, the feedback linearization controller has the shortest settling time and is capable of reducing the positioning error to RMS value of 11.56μm. The force model was also utilized in the design of a model reference adaptive feedback linearization (MRAFL) controller for the z direction. For this case, the levitated object is a small microrobot equipped with a remote controlled gripper weighting approximately 28(gr). Experimental results showed that the MRAFL controller enables the micro-robot to pick up and transport a payload as heavy as 30% of its own weight without a considerable effect on its positioning accuracy. In the presence of the payload, the MRAFL controller resulted in a RMS positioning error of 8μm compared with 27.9μm of the regular feedback linearization controller.
For the horizontal position control of the system, a mathematical formula for distributing the electric currents to the multiple electromagnets of the system was proposed and a PID control approach was implemented to control the position of the levitated object in the xy-plane. The control system was experimentally tested in tracking circular and spiral trajectories with overall positioning accuracy of 60μm.
Also, a new mathematical approach is presented for the prediction of magnetic field distribution in the horizontal direction. The proposed approach is named the pivot point method and is capable of predicting the two dimensional position of the levitated object in a given vertical plane for an arbitrary current distribution in the electromagnets of the levitation system. Experimental results showed that the proposed method is capable of predicting the location of the levitated object with less than 10% error
Magnetically Driven Micro and Nanorobots
Manipulation and navigation of micro and nanoswimmers in different fluid environments can be achieved by chemicals, external fields, or even motile cells. Many researchers have selected magnetic fields as the active external actuation source based on the advantageous features of this actuation strategy such as remote and spatiotemporal control, fuel-free, high degree of reconfigurability, programmability, recyclability, and versatility. This review introduces fundamental concepts and advantages of magnetic micro/nanorobots (termed here as "MagRobots") as well as basic knowledge of magnetic fields and magnetic materials, setups for magnetic manipulation, magnetic field configurations, and symmetry-breaking strategies for effective movement. These concepts are discussed to describe the interactions between micro/nanorobots and magnetic fields. Actuation mechanisms of flagella-inspired MagRobots (i.e., corkscrew-like motion and traveling-wave locomotion/ciliary stroke motion) and surface walkers (i.e., surface-assisted motion), applications of magnetic fields in other propulsion approaches, and magnetic stimulation of micro/nanorobots beyond motion are provided followed by fabrication techniques for (quasi)spherical, helical, flexible, wire-like, and biohybrid MagRobots. Applications of MagRobots in targeted drug/gene delivery, cell manipulation, minimally invasive surgery, biopsy, biofilm disruption/eradication, imaging-guided delivery/therapy/surgery, pollution removal for environmental remediation, and (bio)sensing are also reviewed. Finally, current challenges and future perspectives for the development of magnetically powered miniaturized motors are discussed
Modular robots for sorting
Current industrial sorting systems allow for low error, high throughput sorts with tightly
constrained properties. These sorters, however, are often hardware limited to certain
items and criteria. There is a need for more adaptive sorting systems for processes that
involve a high throughput of heterogeneous items such as import testing by port authorities, warehouse sorting for online retailers, and sorting recycling. The variety of goods
that need to be sorted in these applications mean that existing sorting systems are unsuitable, and the objects often need to be sorted by hand. In this work I detail my design
and control of a modular, robotic sorting system using linear actuating robots to create
both low-frequency vibrations and peristaltic waves for sorting. The adaptability of
the system allows for multimodal sorting and can improve heterogeneous sorting systems.
I have designed a novel modular robot called the Linbot. These Linbots are based on
an actuator design utilising a voice coil for linear motion. I designed this actuator to be
part of a modular robot by adding on-board computation, sensing and communication. I
demonstrate the individual characteristics of these robots through a series of experiments
in order to give a comprehensive overview of their abilities. By combining multiple
Linbots in a collective I demonstrate their ability to move and sort objects using
cooperative peristaltic motion.
In order to allow for rapid optimisation of control schemes for Linbot collectives I
required a peristaltic table simulator. I designed and implemented a peristaltic table
simulator, called PeriSim, due to a lack of existing solutions. Controllers optimised in
simulation often suffer from a reduction in performance when moved to a real-world
system due to the inaccuracies in the simulation, this effect is called the reality gap. I
used a method for reducing the reality gap called the radical envelope of noise hypothesis,
whereby I only modelled the key aspects of peristalsis in PeriSim and then varied the
underlying physics of the simulation between runs. I used PeriSim to optimise controllers
in simulation that worked on a real-world system.
I demonstrate the how the Linbots and PeriSim can be used to build and control an
adaptive sorter. I built an adaptive sorter made of a 5x5 grid of Linbots with a soft
sheet covering them. I demonstrate that the sorter can grade produce and move objects
of varying shapes and sizes. My work can guide the future design of industrial adaptive
sorting systems
- …