33 research outputs found

    High performance linear actuation systems

    Get PDF
    Author name used in this publication: Norbert C. CheungRefereed conference paper2006-2007 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

    Improving the Angular Velocity Measured with a Low-Cost Magnetic Rotary Encoder Attached to a Brushed DC Motor by Compensating Magnet and Hall-Effect Sensor Misalignments

    Get PDF
    This paper proposes a method to improve the angular velocity measured by a low-cost magnetic rotary encoder attached to a brushed direct current (DC) motor. The low-cost magnetic rotary encoder used in brushed DC motors use to have a small magnetic ring attached to the rotational axis and one or more fixed Hall-effect sensors next to the magnet. Then, the Hall-effect sensors provide digital pulses with a duration and frequency proportional to the angular rotational velocity of the shaft of the encoder. The drawback of this mass produced rotary encoder is that any structural misalignment between the rotating magnetic field and the Hall-effect sensors produces asymmetric pulses that reduces the precision of the estimation of the angular velocity. The hypothesis of this paper is that the information provided by this low-cost magnetic rotary encoder can be processed and improved in order to obtain an accurate and precise estimation of the angular rotational velocity. The methodology proposed has been validated in four compact motorizations obtaining a reduction in the ripple of the estimation of the angular rotational velocity of: 4.93%, 59.43%, 76.49%, and 86.75%. This improvement has the advantage that it does not add time delays and does not increases the overall cost of the rotary encoder. These results showed the real dimension of this structural misalignment problem and the great improvement in precision that can be achieved.This research was funded by the Spanish Ministry of Science and Innovation, grant number PID2020-118874RB-I00

    Laboratorní stanoviště servopohonu malého výkonu se stejnosměrným motorem

    Get PDF
    The main goal of this thesis focuses on two main parts, which is to present theoretical analysis for each type of DC motor, their power source, control method and establish a servomotor laboratory to determine the speed, position and torque control and increase or decrease the speed of the unit with an analogue button based on the selected DC motor, to program the DC motor it is necessary to use the Motion Manager 6.0 software manufactured by Faulhaber. Lab tasks are created and based on demonstration results for the purpose of supporting students to continue their practice.Hlavní cíl této práce je zaměřen na dvě části, kterými jsou představení teoretické analýzy pro každý typ krokového motoru, jeho napájení, metody řízení a vytvoření laboratorního stanoviště krokového servopohonu k určení přesné cílové polohy každého písmene v abecedě určené integrovaným pravítkem na laboratorním stojanu vybraného krokovém motoru spolu s měničem a programem EziMotion. Na základě získaných výsledků demonstračních měření jsou vytvořeny laboratorní úlohy, které mají studentům pomoci při získávání znalostí430 - Katedra elektronikydobř

    Design of a Flexible Control Platform and Miniature in vivo Robots for Laparo-Endoscopic Single-Site Surgeries

    Get PDF
    Minimally-invasive laparoscopic procedures have proven efficacy for a wide range of surgical procedures as well as benefits such as reducing scarring, infection, recovery time, and post-operative pain. While the procedures have many advantages, there are significant shortcomings such as limited instrument motion and reduced dexterity. In recent years, robotic surgical technology has overcome some of these limitations and has become an effective tool for many types of surgeries. These robotic platforms typically have an increased workspace, greater dexterity, improved ergonomics, and finer control than traditional laparoscopic methods. This thesis presents the designs of both a four degree-of-freedom (DOF) and 5-DOF miniature in vivo surgical robot as well as a software architecture for development and control of such robots. The proposed surgical platform consists of a two-armed robotic prototype, distributed motor control modules, custom robot control software, and remote surgeon console. A plug-in architecture in the control software provides the user a wide range of user input devices and control algorithms, including a numerical inverse kinematics solver, to allow intuitive control and rapid development of future robot prototypes. A variety of experiments performed by a surgeon at the University of Nebraska Medical Center were used to evaluate the performance of the robotic platform. Adviser: Shane Farrito

    Robotics for Natural Orifice Transluminal Endoscopic Surgery: A Review

    Get PDF
    Natural Orifice Transluminal Endoscopic Surgery (NOTES) involves accessing the abdominal cavity via one of the bodies’ natural orifices, for example, mouth, anus, or vagina. This new surgical procedure is very appealing from patients’ perspectives because it eliminates completely abdominal wall aggression and promises to reduce postoperative pain, in addition to all other advantages brought by laparoscopic surgery. However, the constraints imposed by both the mode of access and the limited technology currently available make NOTES very challenging for the surgeons. Redesign of the instruments is imperative in order to make this emerging operative access safe and reproducible. In this paper, we survey on the state-of-the-art devices used in NOTES and introduce both the flexible instruments based on improvement of current endoscopic platforms and the revolutionary concept of robotic platforms based on the convergence of communication and micromechatronics technologies. The advantages and limitations of each category are addressed. Potential solutions are proposed to improve the existing designs and develop robust and stable robotic platforms for NOTES

    Wireless capsule endoscope for targeted drug delivery

    Get PDF
    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

    Reimplantable Microdrive for Long-Term Chronic Extracellular Recordings in Freely Moving Rats

    Get PDF
    Extracellular recordings of electrical activity in freely moving rats are fundamental to understand brain function in health and disease. Such recordings require a small-size, lightweight device that includes movable electrodes (microdrive) to record either a new set of neurons every day or the same set of neurons over time. Ideally, microdrives should be easy to implant, allowing precise and smooth displacement of electrodes. The main caveat of most commercially available microdrives is their relatively short half-life span, in average ranging from weeks to a month. For most experiments, recording days–weeks is sufficient, but when the experiment depends on training animals for several months, it is crucial to develop new approaches. Here, we present a low-cost, reusable, and reimplantable device design as a solution to extend chronic recordings to long-term. This device is composed of a baseplate that is permanently fixed to the rodent’s skull, as well as a reusable and replaceable microdrive that can be attached and detached from the baseplate, allowing its implantation and reimplantation. Reimplanting this microdrive is particularly convenient when no clear neuronal signal is present, or when the signal gradually decays across days. Our microdrive incorporates a mechanism for moving a 16 tungsten-wire bundle within a small (∼15 mm3) lightweight device (∼4 g). We present details of the design, manufacturing, and assembly processes. As a proof of concept, we show that recordings of the nucleus accumbens core (NAcc) in a freely behaving rat are stable over a month. Additionally, during a lever-press task, we found, as expected, that NAc single-unit activity was associated with rewarded lever presses. Furthermore, we also show that NAc shell (NAcSh) responses evoked by freely licking for sucrose, consistent with our previously published results, were conserved from a first implant to a second microdrive reimplant in the same rat, notably showing reimplantation is possible without overtly affecting the functional responses of the area of interest. In sum, here we present a novel microdrive design (low-cost, small size, and light weight) that can be used for long-term chronic recordings and reimplanted in freely behaving rats

    NASA Tech Briefs Index, 1977, volume 2, numbers 1-4

    Get PDF
    Announcements of new technology derived from the research and development activities of NASA are presented. Abstracts, and indexes for subject, personal author, originating center, and Tech Brief number are presented for 1977

    The design and characterisation of miniature robotics for astronomical instruments

    Get PDF
    Micro robotics has the potential to improve the efficiency and reduce cost of future multi-object instruments for astronomy. This thesis reports on the development and evolution of a micro autonomous pick-off mirror called the Micro Autonomous Positioning System (MAPS) that can be used in a multi-object spectrograph. The design of these micro-autonomous pick-off mirrors is novel as they are capable of high precision positioning using electromagnetic propulsion through utilising non-conventional components and techniques. These devices are self-driven robotic units, which with the help of an external control system are capable of positioning themselves on an instruments focal plane to within 24 μm. This is different from other high precision micro robotics as they normally use piezoelectric actuators for propulsion. Micro robots have been developed that use electromagnetic motors, however they are not used for high precision applications. Although there is a plethora of literature covering design, functionality and capability of precision micro autonomous systems, there is limited research on characterisation methods for their use in astronomical applications. This work contributes not only to the science supporting the design of a micro-autonomous pick-off mirror but also presents a framework for characterising such miniature mechanisms. The majority of instruments are presented with a curved focal plane. Therefore, to ensure that the pick-off mirrors are aligned properly with the receiving optics, either the pick-off mirror needs to be tipped or the receiving optics repositioned. Currently this function is implemented in the beam steering mirror (i.e. the receiving optics). The travel range required by the beam steering mirror is relatively large, and as such, it is more difficult to achieve the positional accuracy and stability. By incorporating this functionality in the pick-off mirror, the instrument can be optimised in terms of size, accuracy and stability. A unique self-adjusting mirror (SAM) is thus proposed as a solution and detailed. As a proof-of-concepts both MAPS and SAM usability in multi-object spectrographs was evaluated and validated. The results indicate their potential to meet the requirements of astronomical instruments and reduce both the size and cost
    corecore