342 research outputs found
Redundant Unilaterally Actuated Kinematic Chains: Modeling and Analysis
Unilaterally Actuated Robots (UAR)s are a class of robots defined by an actuation that is constrained to a single sign. Cable robots, grasping, fixturing and tensegrity systems are certain applications of UARs. In recent years, there has been increasing interest in robotic and other mechanical systems actuated or constrained by cables. In such systems, an individual constraint is applied to a body of the mechanism in the form of a pure force which can change its magnitude but cannot reverse its direction. This uni-directional actuation complicates the design of cable-driven robots and can result in limited performance.
Cable Driven Parallel Robot (CDPR)s are a class of parallel mechanisms where the actuating legs are replaced by cables. CDPRs benefit from the higher payload to weight ratio and increased rigidity. There is growing interest in the cable actuation of multibody systems. There are potential applications for such mechanisms where low moving inertia is required. Cable-driven serial kinematic chain (CDSKC) are mechanisms where the rigid links form a serial kinematic chain and the cables are arranged in a parallel configuration. CDSKC benefits from the dexterity of the serial mechanisms and the actuation advantages of cable-driven manipulators.
Firstly, the kinematic modeling of CDSKC is presented, with a focus on different types of cable routings. A geometric approach based on convex cones is utilized to develop novel cable actuation schemes. The cable routing scheme and architecture have a significant effect on the performance of the robot resulting in a limited workspace and high cable forces required to perform a desired task. A novel cable routing scheme is proposed to reduce the number of actuating cables. The internal routing scheme is where, in addition to being externally routed, the cable can be re-routed internally within the link. This type of routing can be considered as the most generalized form of the multi-segment pass-through routing scheme where a cable segment can be attached within the same link. Secondly, the analysis for CDSKCs require extensions from single link CDPRs to consider different routings. The conditions to satisfy wrench-closure and the workspace analysis of different multi-link unilateral manipulators are investigated. Due to redundant and constrained actuation, it is possible for a motion to be either infeasible or the desired motion can be produced by an infinite number of different actuation profiles. The motion generation of the CDSKCs with a minimal number of actuating cables is studied. The static stiffness evaluation of CDSKCs with different routing topologies and isotropic stiffness conditions were investigated. The dexterity and wrench-based metrics were evaluated throughout the mechanism's workspace.
Through this thesis, the fundamental tools required in studying cable-driven serial kinematic chains have been presented. The results of this work highlight the potential of using CDSKCs in bio-inspired systems and tensegrity robots
Development and Characteristics of a Highly Biomimetic Robotic Shoulder Through Bionics-Inspired Optimization
This paper critically analyzes conventional and biomimetic robotic arms,
underscoring the trade-offs between size, motion range, and load capacity in
current biomimetic models. By delving into the human shoulder's mechanical
intelligence, particularly the glenohumeral joint's intricate features such as
its unique ball-and-socket structure and self-locking mechanism, we pinpoint
innovations that bolster both stability and mobility while maintaining
compactness. To substantiate these insights, we present a groundbreaking
biomimetic robotic glenohumeral joint that authentically mirrors human
musculoskeletal elements, from ligaments to tendons, integrating the biological
joint's mechanical intelligence. Our exhaustive simulations and tests reveal
enhanced flexibility and load capacity for the robotic joint. The advanced
robotic arm demonstrates notable capabilities, including a significant range of
motions and a 4 kg payload capacity, even exerting over 1.5 Nm torque. This
study not only confirms the human shoulder joint's mechanical innovations but
also introduces a pioneering design for a next-generation biomimetic robotic
arm, setting a new benchmark in robotic technology
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Articular human joint modelling
Copyright @ Cambridge University Press 2009.The work reported in this paper encapsulates the theories and algorithms developed to drive the core analysis modules of the software which has been developed to model a musculoskeletal structure of anatomic joints. Due to local bone surface and contact geometry based joint kinematics, newly developed algorithms make the proposed modeller different from currently available modellers. There are many modellers that are capable of modelling gross human body motion. Nevertheless, none of the available modellers offer complete elements of joint modelling. It appears that joint modelling is an extension of their core analysis capability, which, in every case, appears to be musculoskeletal motion dynamics. It is felt that an analysis framework that is focused on human joints would have significant benefit and potential to be used in many orthopaedic applications. The local mobility of joints has a significant influence in human motion analysis, in understanding of joint loading, tissue behaviour and contact forces. However, in order to develop a bone surface based joint modeller, there are a number of major problems, from tissue idealizations to surface geometry discretization and non-linear motion analysis. This paper presents the following: (a) The physical deformation of biological tissues as linear or non-linear viscoelastic deformation, based on spring-dashpot elements. (b) The linear dynamic multibody modelling, where the linear formulation is established for small motions and is particularly useful for calculating the equilibrium position of the joint. This model can also be used for finding small motion behaviour or loading under static conditions. It also has the potential of quantifying the joint laxity. (c) The non-linear dynamic multibody modelling, where a non-matrix and algorithmic formulation is presented. The approach allows handling complex material and geometrical nonlinearity easily. (d) Shortest path algorithms for calculating soft tissue line of action geometries. The developed algorithms are based on calculating minimum âsurface massâ and âsurface covarianceâ. An improved version of the âsurface covarianceâ algorithm is described as âresidual covarianceâ. The resulting path is used to establish the direction of forces and moments acting on joints. This information is needed for linear or non-linear treatment of the joint motion. (e) The final contribution of the paper is the treatment of the collision. In the virtual world, the difficulty in analysing bodies in motion arises due to body interpenetrations. The collision algorithm proposed in the paper involves finding the shortest projected ray from one body to the other. The projection of the body is determined by the resultant forces acting on it due to soft tissue connections under tension. This enables the calculation of collision condition of non-convex objects accurately. After the initial collision detection, the analysis involves attaching special springs (stiffness only normal to the surfaces) at the âpotentially colliding pointsâ and motion of bodies is recalculated. The collision algorithm incorporates the rotation as well as translation. The algorithm continues until the joint equilibrium is achieved. Finally, the results obtained based on the software are compared with experimental results obtained using cadaveric joints
A continuum robotic platform for endoscopic non-contact laser surgery: design, control, and preclinical evaluation
The application of laser technologies in surgical interventions has been accepted in the clinical
domain due to their atraumatic properties. In addition to manual application of fibre-guided
lasers with tissue contact, non-contact transoral laser microsurgery (TLM) of laryngeal tumours
has been prevailed in ENT surgery. However, TLM requires many years of surgical training
for tumour resection in order to preserve the function of adjacent organs and thus preserve the
patientâs quality of life. The positioning of the microscopic laser applicator outside the patient
can also impede a direct line-of-sight to the target area due to anatomical variability and limit
the working space. Further clinical challenges include positioning the laser focus on the tissue
surface, imaging, planning and performing laser ablation, and motion of the target area during
surgery. This dissertation aims to address the limitations of TLM through robotic approaches and
intraoperative assistance. Although a trend towards minimally invasive surgery is apparent, no
highly integrated platform for endoscopic delivery of focused laser radiation is available to date.
Likewise, there are no known devices that incorporate scene information from endoscopic imaging
into ablation planning and execution. For focusing of the laser beam close to the target tissue, this
work first presents miniaturised focusing optics that can be integrated into endoscopic systems.
Experimental trials characterise the optical properties and the ablation performance. A robotic
platform is realised for manipulation of the focusing optics. This is based on a variable-length
continuum manipulator. The latter enables movements of the endoscopic end effector in five
degrees of freedom with a mechatronic actuation unit. The kinematic modelling and control of the
robot are integrated into a modular framework that is evaluated experimentally. The manipulation
of focused laser radiation also requires precise adjustment of the focal position on the tissue. For
this purpose, visual, haptic and visual-haptic assistance functions are presented. These support
the operator during teleoperation to set an optimal working distance. Advantages of visual-haptic
assistance are demonstrated in a user study. The system performance and usability of the overall
robotic system are assessed in an additional user study. Analogous to a clinical scenario, the
subjects follow predefined target patterns with a laser spot. The mean positioning accuracy of the
spot is 0.5 mm. Finally, methods of image-guided robot control are introduced to automate laser
ablation. Experiments confirm a positive effect of proposed automation concepts on non-contact
laser surgery.Die Anwendung von Lasertechnologien in chirurgischen Interventionen hat sich aufgrund der atraumatischen Eigenschaften in der Klinik etabliert. Neben manueller Applikation von fasergefĂŒhrten
Lasern mit Gewebekontakt hat sich die kontaktfreie transorale Lasermikrochirurgie (TLM) von
Tumoren des Larynx in der HNO-Chirurgie durchgesetzt. Die TLM erfordert zur Tumorresektion
jedoch ein langjÀhriges chirurgisches Training, um die Funktion der angrenzenden Organe zu
sichern und damit die LebensqualitĂ€t der Patienten zu erhalten. Die Positionierung des mikroskopis chen Laserapplikators auĂerhalb des Patienten kann zudem die direkte Sicht auf das Zielgebiet
durch anatomische VariabilitÀt erschweren und den Arbeitsraum einschrÀnken. Weitere klinische
Herausforderungen betreffen die Positionierung des Laserfokus auf der GewebeoberflÀche, die
Bildgebung, die Planung und AusfĂŒhrung der Laserablation sowie intraoperative Bewegungen
des Zielgebietes. Die vorliegende Dissertation zielt darauf ab, die Limitierungen der TLM durch
robotische AnsÀtze und intraoperative Assistenz zu adressieren. Obwohl ein Trend zur minimal
invasiven Chirurgie besteht, sind bislang keine hochintegrierten Plattformen fĂŒr die endoskopische
Applikation fokussierter Laserstrahlung verfĂŒgbar. Ebenfalls sind keine Systeme bekannt, die
Szeneninformationen aus der endoskopischen Bildgebung in die Ablationsplanung und -ausfĂŒhrung
einbeziehen. FĂŒr eine situsnahe Fokussierung des Laserstrahls wird in dieser Arbeit zunĂ€chst
eine miniaturisierte Fokussieroptik zur Integration in endoskopische Systeme vorgestellt. Experimentelle Versuche charakterisieren die optischen Eigenschaften und das Ablationsverhalten. Zur
Manipulation der Fokussieroptik wird eine robotische Plattform realisiert. Diese basiert auf einem
lÀngenverÀnderlichen Kontinuumsmanipulator. Letzterer ermöglicht in Kombination mit einer
mechatronischen Aktuierungseinheit Bewegungen des Endoskopkopfes in fĂŒnf Freiheitsgraden.
Die kinematische Modellierung und Regelung des Systems werden in ein modulares Framework
eingebunden und evaluiert. Die Manipulation fokussierter Laserstrahlung erfordert zudem eine
prĂ€zise Anpassung der Fokuslage auf das Gewebe. DafĂŒr werden visuelle, haptische und visuell haptische Assistenzfunktionen eingefĂŒhrt. Diese unterstĂŒtzen den Anwender bei Teleoperation
zur Einstellung eines optimalen Arbeitsabstandes. In einer Anwenderstudie werden Vorteile der
visuell-haptischen Assistenz nachgewiesen. Die Systemperformanz und Gebrauchstauglichkeit
des robotischen Gesamtsystems werden in einer weiteren Anwenderstudie untersucht. Analog zu
einem klinischen Einsatz verfolgen die Probanden mit einem Laserspot vorgegebene Sollpfade. Die
mittlere Positioniergenauigkeit des Spots betrÀgt dabei 0,5 mm. Zur Automatisierung der Ablation
werden abschlieĂend Methoden der bildgestĂŒtzten Regelung vorgestellt. Experimente bestĂ€tigen
einen positiven Effekt der Automationskonzepte fĂŒr die kontaktfreie Laserchirurgie
Development of an In-Vitro Passive and Active Motion Simulator for the Investigation of Shoulder Function and Kinematics
Injuries and degenerative diseases of the shoulder are common and may relate to the jointâs complex biomechanics, which rely primarily on soft tissues to achieve stability. Despite the prevalence of these disorders, there is little information about their effects on the biomechanics of the shoulder, and a lack of evidence with which to guide clinical practice. Insight into these disorders and their treatments can be gained through in-vitro biomechanical experiments where the achieved physiologic accuracy and repeatability directly influence their efficacy and impact.
This workâs rationale was that developing a simulator with greater physiologic accuracy and testing capabilities would improve the quantification of biomechanical parameters. This dissertation describes the development and validation of a simulator capable of performing passive assessments, which use experimenter manipulation, and active assessments â produced through muscle loading. Respectively, these allow the assessment of functional parameters such as stability, and kinematic/kinetic parameters including joint loading.
The passive functionality enables specimen motion to be precisely controlled through independent manipulation of each rotational degree of freedom (DOF). Compared to unassisted manipulation, the system improved accuracy and repeatability of positioning the specimen (by 205% & 163%, respectively), decreased variation in DOF that are to remain constant (by 6.8°), and improved achievement of predefined endpoints (by 21%). Additionally, implementing a scapular rotation mechanism improved the physiologic accuracy of simulation. This enabled the clarification of the effect of secondary musculature on shoulder function, and the comparison of two competing clinical reconstructive procedures for shoulder instability.
This was the first shoulder system to use real time kinematic feedback and PID control to produce active motion, which achieved unmatched accuracy (
These developments can be a powerful tool for increasing our understanding of the shoulder and also to provide information which can assist surgeons and improve patient outcomes
Medical robots for MRI guided diagnosis and therapy
Magnetic Resonance Imaging (MRI) provides the capability of imaging tissue with fine resolution and
superior soft tissue contrast, when compared with conventional ultrasound and CT imaging, which
makes it an important tool for clinicians to perform more accurate diagnosis and image guided therapy.
Medical robotic devices combining the high resolution anatomical images with real-time navigation, are
ideal for precise and repeatable interventions. Despite these advantages, the MR environment imposes
constraints on mechatronic devices operating within it. This thesis presents a study on the design and
development of robotic systems for particular MR interventions, in which the issue of testing the MR
compatibility of mechatronic components, actuation control, kinematics and workspace analysis, and
mechanical and electrical design of the robot have been investigated. Two types of robotic systems
have therefore been developed and evaluated along the above aspects.
(i) A device for MR guided transrectal prostate biopsy: The system was designed from components
which are proven to be MR compatible, actuated by pneumatic motors and ultrasonic motors, and
tracked by optical position sensors and ducial markers. Clinical trials have been performed with the
device on three patients, and the results reported have demonstrated its capability to perform needle
positioning under MR guidance, with a procedure time of around 40mins and with no compromised
image quality, which achieved our system speci cations.
(ii) Limb positioning devices to facilitate the magic angle effect for diagnosis of tendinous injuries:
Two systems were designed particularly for lower and upper limb positioning, which are actuated and
tracked by the similar methods as the first device. A group of volunteers were recruited to conduct
tests to verify the functionality of the systems. The results demonstrate the clear enhancement of the
image quality with an increase in signal intensity up to 24 times in the tendon tissue caused by the
magic angle effect, showing the feasibility of the proposed devices to be applied in clinical diagnosis
Design and development of robust hands for humanoid robots
Design and development of robust hands for humanoid robot
Kinematics and Robot Design IV, KaRD2021
This volume collects the papers published on the special issue âKinematics and Robot Design IV, KaRD2021â (https://www.mdpi.com/journal/robotics/special_issues/KaRD2021), which is the forth edition of the KaRD special-issue series, hosted by the open-access journal âMDPI Roboticsâ. KaRD series is an open environment where researchers can present their works and discuss all the topics focused on the many aspects that involve kinematics in the design of robotic/automatic systems. Kinematics is so intimately related to the design of robotic/automatic systems that the admitted topics of the KaRD series practically cover all the subjects normally present in well-established international conferences on âmechanisms and roboticsâ. KaRD2021, after the peer-review process, accepted 12 papers. The accepted papers cover some theoretical and many design/applicative aspects
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A novel musculoskeletal joint modelling for orthopaedic applications
This thesis was submitted for the degree of Docter of Philosophy and awarded by Brunel University.The objective of the work carried out in this thesis was to develop analytical and
computational tools to model and investigate musculoskeletal human joints. It was
recognised that the FEA was used by many researchers in modelling human
musculoskeletal motion, loading and stresses. However the continuum mechanics
played only a minor role in determining the articular joint motion, and its value was
questionable. This is firstly due to the computational cost and secondly due to its
impracticality for this application. On the other hand, there isnât any suitable software
for precise articular joint motion analysis to deal with the local joint stresses or non
standard joints. The main requirement in orthopaedics field is to develop a modeller
software (and its associated theories) to model anatomic joint as it is, without any
simplification with respect to joint surface morphology and material properties of
surrounding tissues. So that the proposed modeller can be used for evaluating and
diagnosing different joint abnormalities but furthermore form the basis for performing
implant insertion and analysis of the artificial joints. The work which is presented in this thesis is a new frame work and has been developed for human anatomic joint analysis which describes the joint in terms of its surface geometry and surrounding
musculoskeletal tissues. In achieving such a framework several contributions were
made to the 6DOF linear and nonlinear joint modelling, the mathematical definition of
joint stiffness, tissue path finding and wrapping and the contact with collision analysis. In 6DOF linear joint modelling, the contribution is the development of joint stiffness and damping matrices. This modelling approach is suitable for the linear range of tissue stiffness and damping properties. This is the first of its kind and it gives a firm analytical basis for investigating joints with surrounding tissue and the cartilage. The 6DOF nonlinear joint modelling is a new scheme which is described for modelling the motion of multi bodies joined by non-linear stiffness and contact elements. The proposed method requires no matrix assembly for the stiffness and damping elements or mass elements. The novelty in the nonlinear modelling, relates to the overall algorithmic approach and handling local non-linearity by procedural means. The mathematical definition of joint stiffness is also a new proposal which is based on the mathematical definition of stiffness between two bodies. Based on the joint stiffness matrix properties, number of joint stiffness invariants was obtained analytically such as the centre of stiffness, the principal translational stiffnesses, and the principal rotational stiffnesses. In corresponding to these principal stiffnesses, their principal axes have been also obtained. Altogether, a joint is assessed by six principal axes and six principal stiffnesses and its centre of stiffness. These formulations are new and show that a joint can be described in terms of inherent stiffness properties. It is expected that these will be better in characterising a joint in comparison to laxity based characterisation. The
development of tissue path finding and wrapping algorithms are also introduced as new approaches. The musculoskeletal tissue wrapping involves calculating the shortest
distance between two points on a meshed surface. A new heuristic algorithm was
proposed. The heuristic is based on minimising the accumulative divergence from the straight line between two points on the surface and the direction of travel on the surface (i.e. bone). In contact and collision based development, the novel algorithm has been proposed that detects possible colliding points on the motion trajectory by redefining the distance as a two dimensional measure along the velocity approach vector and perpendicular to this vector. The perpendicular distance determines if there are potentially colliding points, and the distance along the velocity determines how close they are. The closest pair among the potentially colliding points gives the âtime to collisionâ. The algorithm can eliminate the âfly passâ situation where very close points may not collide because of the direction of their relative velocity. All these developed
algorithms and modelling theories, have been encompassed in the developed prototype
software in order to simulate the anatomic joint articulations through modelling
formulations developed. The software platform provides a capability for analysing joints as 6DOF joints based on anatomic joint surfaces. The software is highly interactive and driven by well structured database, designed to be highly flexible for the future developments. Particularly, two case studies are carried out in this thesis in order to generate results relating to all the proposed elements of the study. The results obtained from the case studies show good agreement with previously published results or model based results obtained from Lifemod software, whenever comparison was possible. In some cases the comparison was not possible because there were no equivalent results; the results were supported by other indicators. The modelling based results were also supported by experiments performed in the Brunel Orthopaedic Research and Learning
Centre
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