Alessandro Cammarata

Individual patient data systematic review and meta-analysis of optic nerve sheath diameter ultrasonography for detecting raised intracranial pressure: protocol of the ONSD research group

BackgroundThe purpose of the optic nerve sheath diameter (ONSD) research group project is to establish an individual patient-level database from high quality studies of ONSD ultrasonography for the detection of raised intracranial pressure (ICP), and to perform a systematic review and an individual patient data meta-analysis (IPDMA), which will provide a cutoff value to help physicians making decisions and encourage further research. Previous meta-analyses were able to assess the diagnostic accuracy of ONSD ultrasonography in detecting raised ICP but failed to determine a precise cutoff value. Thus, the ONSD research group was founded to synthesize data from several recent studies on the subject and to provide evidence on the diagnostic accuracy of ONSD ultrasonography in detecting raised ICP.MethodsThis IPDMA will be conducted in different phases. First, we will systematically search for eligible studies. To be eligible, studies must have compared ONSD ultrasonography to invasive intracranial devices, the current reference standard for diagnosing raised ICP. Subsequently, we will assess the quality of studies included based on the QUADAS-2 tool, and then collect and validate individual patient data. The objectives of the primary analyses will be to assess the diagnostic accuracy of ONSD ultrasonography and to determine a precise cutoff value for detecting raised ICP. Secondly, we will construct a logistic regression model to assess whether patient and study characteristics influence diagnostic accuracy.DiscussionWe believe that this IPD MA will provide the most reliable basis for the assessment of diagnostic accuracy of ONSD ultrasonography for detecting raised ICP and to provide a cutoff value. We also hope that the creation of the ONSD research group will encourage further study.Systematic review registrationPROSPERO registration number: CRD42012003072

An Algorithm to Study the Elastodynamics of Parallel Kinematic Machines With Lower Kinematic Pairs

In this paper, an algorithm to help designers to integrate the elastodynamics analysis along with the inverse positioning and orienting problems of a parallel kinematic machine (PKM) into a single package is conceived. The proposed algorithm applies concepts from the matrix structural analysis (MSA) and finite element analysis (FEA) to determine the generalized stiffness matrix and the linearized elastodynamics equations of a PKM with only lower kinematic pairs. A PKM is modeled as a system of flexible links and rigid bodies connected by means of joints. Three cases are analyzed to consider the combinations between flexible and rigid bodies in order to find the local stiffness matrices. The latter are combined to obtain the limb matrices and, then, the global stiffness matrix of the whole robotic system. The same nodes coming from the links discretization are considered to include joint masses/inertias into the model. Finally, a case study is proposed to show some feasible applications and to compare results to commercial software for validation.

Kinetostatic and Inertial Conditioning of the McGill Schönflies-Motion Generator

This paper focuses on the optimization of the McGill Schönflies Motion Generator. Recent trends on optimum design of parallel robots led us to investigate the advantages and disadvantages derived from an optimization based on performance indices. Particularly, we optimize here two different indices: the kinematic conditioning and the inertial conditioning, pertaining to the condition number of the Jacobian matrix and to that of the generalized inertia matrix of the robot, respectively. The problem of finding the characteristic length for the robot is first investigated by means of a constrained optimization problem; then plots of the kinetostatic and the inertial conditioning indices are provided for a particular trajectory to be tracked by the moving platform of the SMG. Deep connections appear between the two indices, reflecting a correlation between kinematics and dynamics.

The dynamics of parallel Schönflies motion generators: The case of a two-limb system

Abstract The formulation of the mathematical model governing the dynamics of parallel Schönflies motion generators (SMGs) is the subject of this paper. These are robotic systems intended to produce motions that entail displacements of the Schönflies subgroup of rigid-body displacements. Such motions are representative of those produced by the serial robots termed SCARA, which involve three independent translations and one rotation about an axis of fixed direction. The main features of SMGs are illustrated with the aid of the McGill Schönflies motion generator. This robot is composed of two limbs, each being a four-joint RΠΠR - R representing a revolute, Π a Π joint, or a parallelogram linkage - kinematic chain, with only two joints actuated. One important feature of the McGill SMG is its mass distribution, as its moving parts account for about 10 per cent of the mass of its drive units, which are (a) fixed to the robot frame and (b) the only steel parts of the whole robot. Moreover, its joints account for roughly 10 per cent of the total mass of its moving parts, fabricated from aluminium, which justifies neglecting the joint inertia in the mathematical model. This feature calls for a formulation of the model in question in terms of the motor displacements, rather than the joint displacements, as the generalized coordinates of the model. Furthermore, in order to derive the model, the robot is decomposed into two subsystems, the drive and the linkage, the drive being decomposed, in turn, into two subsubsystems, the epicyclic gear train and the right-angled gearbox. The robot kinematics is first derived and then the dynamics model is formulated by means of the natural orthogonal complement. In the framework of this methodology, the inertia and what are called the Coriolis matrices of the mathematical model are additive, in the sense that they can be computed as the sum of the contributions of the different subsystems and subsubsystems of a given mechanical system. The contributions of the subsystems and subsubsystems, in turn, can be computed as the sum of the contributions of the individual moving parts of these. Some general results applicable to all SMGs are derived, which leads to the simplification of the mathematical model of such systems.

On the Elastostatics of Spherical Parallel Machines with Curved Links

The paper presents the elastostatics analysis of a class of lower-mobility Parallel Kinematic Machines: the Spherical Parallel Machines. These robots usually recur to curved links in their structure to satisfy geometric constraints deriving from mobility reason. In fact, to make the mobile platform move with spherical motion all links or a part of these are constrained to have spherical motions too. This condition is generally obtained employing curved links with revolute pairs whose axes intersect at a common center of motion. Recurring to two-node Timoshenko’s beam element with constant strain fields to simulate curved beams in space we adapt a methodology proposed by the same authors to study the elastostatics of Spherical Parallel Machines. The method is finally applied to study the error positioning analysis of the Agile Eye.

KINEMATICS AND DYNAMICS OF A 3-CRU SPHERICAL PARALLEL ROBOT

This paper describes the kinematics and dynamics of a spherical parallel wrist called 3-CRU after the topology of its legs. After a mobility analysis showing the geometrical conditions that yield motions of pure rotation, its kinematics is worked out in closed-form for both position and velocity problems. Then inverse and direct dynamics models are developed and the latter is investigated by the use of the multibody NOC method. Seven bodies are considered by the models: two links for each one of the three legs and the moving platform, while inertial joints parameters have been neglected. Finally, numerical simulations are presented to validate the model. This architecture adopts kinematic pairs that make it suitable for being realized at a mini- or micro- scale. The Authors are presently developing the design of a robot based on such a concept.

Identification of Solar Energy Systems

Abstract The purpose of this paper is to value the parameters on systems using solar energy by a process model. In particular a solar circuit is here examined comprising a flat-plate single glass collector, a boiler and a heat exchanger. First a distributed non-linear 5th order state space model derived from basic physical equations, representing the a priori inrormation, is analyzed in a simulation algorithm. This modelbuilding is assumed as the standard with which reduced and approximate models are obtained. An experimental plant realized in sicily is used for identification. The applied method is the one of generalized least squares for the low noise levels obtained, and the estimated model has lumped time-invariant parameters with prefixed structure in discrete-time form. The results obtained give useful information on the physical considerations and circuit efficiency.

On the Stiffness Analysis and Elastodynamics of Parallel Kinematic Machines

Accurate models to describe the elasticity of robots are becoming essential for those applications involving high accelerations or high precision to improve quality in positioning and tracking of trajectories. Stiffness analysis not only involves the mechanical structure of a robot but even the control system necessary to drive actuators. Strategies aimed to reduce noise and dangerous bouncing effects could be implemented to make control systems more robust to flexibility disturbances, foreseing mechanical interaction with the control system because of regenerative and modal chattering (1). The most used approaches to study elasticity in the literature encompass: the Finite Element Analysis (FEA), the Matrix Structural Analysis (MSA), the Virtual Joint Method (VJM), the Floating Frame of Reference Formulation (FFRF) and the Absolute Nodal Coordinates Formulation (ANCF). FEA is largely used to analyze the structural behavior of a mechanical system. The reliability and precision of the method allow to describe each part of a mechanical system with great detail (2). Applying FEA to a robotic system implies a time-consuming process of re-meshing in the pre-processing phase every time that the robot posture has changed. Optimization all over the workspace of a robot would require very long computational time, thus FEA models are often employed to verify components or subparts of a complex robotic system. The MSA includes some simplifications to FEA using complex elements like beams, arcs, cables or superelements (3–5). This choice reduces the computational time and makes this method more efficient for optimization tasks. Some authors recurred to the superposition principle along with the virtual work principle to achieve the global stiffness model (6–8). Others considered the minimization of the potential energy of a PKM to find the global stiffness matrix (9), while some approaches used the total potential energy augmented adding the kinematic constraints by means of the Lagrange multipliers (10; 11). The first papers on VJM are based on pseudo-rigid body models with “virtual joints” (12–14). More recent papers include link flexibility and linear/torsional springs to take into account bending contributes (15–19). These approaches recur to the Jacobian matrix to map the stiffness of the actuators of a PKM inside its workspace; especially for PKMs with reduced mobility, it implies that the stiffness is limited to a subspace defined by the dofs of its end-effector. Pashkevich et al. tried to overcome this issue by introducing a multidimensional lumped-parameter model with localized 6-dof virtual springs (20). Finally, the FFRF and ANCF are powerful and accurate formulations, based on FEM and continuum mechanics, to study any flexible mechanical system (21). The FFRF is suitable 5

Dynamics of a high-performance motorcycle by an advanced multibody/control co-simulation

The present work aims at the development of an advanced control system implemented through Adams/View-Matlab/Simulink co-simulation for a high-performance motorcycle dynamics study. In particular, the purpose of this study is to create a model able to consider several aspects of the rider–motorbike dynamic simulation and its control system, generally treated separately in the literature, making also use of an original and accurate modelling of the rider. From a previous multi-body model of motorcycle/virtual rider, developed by the authors, a flexible tool is created to simulate system dynamics to follow any trajectory at a prescribed velocity profile. Considering high-performance motorcycle dynamics are greatly influenced by the rider’s weight, his movements have been accurately replicated to obtain the most realistic results. To simulate the passive impedance of rider’s arms, a torque was applied to the steering as per the literature. The aerodynamic force was modelled as a function of kinematics variables and rider’s posture. The control system is very flexible and adaptable to different manoeuvres realistically reproducing engine and braking performance, steering torque and rider movements. Numerical results show that the control system can accurately direct the motorcycle/rider system along an entire lap of the Monza circuit, following a desired path at a given velocity profile. The model developed allows a complete view of the motorbike-rider dynamic behaviour thus being useful during both design phase and set-up, with a considerable saving in terms of both cost and time; it can also evaluate the influence on the system dynamics of riders with different anatomical characteristics and driving styles.

Design of an Underwater Towfish Using Design by Rule and Design by Analysis

The European unfired pressure vessel code EN13445-3 [1] has been used to design a preliminary prototype of a towfish. The towfish is essentially an underwater vessel equipped with various sensors, cameras, hydroplanes and control systems that are used to capture data on the levels of pollutants in the sea and at the same time monitor plankton and jellyfish levels. The towfish is towed behind a surface ship and is designed to dive to a depth of 50m below sea level. The depth of dive can be controlled by means of hydroplanes. Data, signals and electrical power are transferred from the towfish to the surface ship and vice versa via the towing line. From a structural point of view the towfish is a vessel acted upon by external pressure and local loads. Design by rule (DBR) was first used to calculate some of the various dimensions and thicknesses of the towfish components. The various components were designed mainly to prevent failure due to buckling. Design by analysis (DBA) based on Annex B of the pressure vessel code EN13445-3 [1] was then used to carry out further buckling checks that were not possible to do using design by rule. At the end of the paper the results from the two design approaches are compared and any major differences are highlighted.Copyright