Alessandro Cammarata

University of Catania | UNICT · Department of Industrial Engineering (DIIM)

A generalization of the spherical linear interpolation (or slerp) for the finite rotations to the case of more than two control variables on SO(3) is introduced to design an objective FE-formulation for the non-linear space Cosserat rod model. The interpolation uses the De Casteljau’s algorithm. In this way, the same interpolation degree can be us...

In this paper, a method is presented for stiffness analysis of a module-based shape morphing snake-like robot. Snake-like robots have the characteristic of adapting to unstructured environments by exploiting their ability to reconfigure their body’s shape. However, the excellent mobility contrasts with the ability to transmit high loads, precluding...

In this paper an algorithm for obstacle avoidance of a serial collaborative robot based on impedance control is presented. Collaborative robots are robots that share their workspace with humans. Therefore, particular attention must be paid to control techniques to avoid being struck by the robot during its operations. This article presents an imped...

The problem of imposing the reference conditions in a floating frame of reference formulation is coupled with the necessity to reduce the interfaces to virtual nodes required to define the multibody joints. Two methods are implemented for rigid and interpolation multipoint constraints, and the reference condition matrix is derived employing all the...

The field of micromanipulation is rapidly growing and evolving thanks to advancements in microfabrication technologies and the increased demand for precise and accurate manipulation of microscale objects [...]

Micro-electro-mechanical-systems (MEMS) extensively employed planar mechanisms with elastic curved beams. However, using a curved circular beam as a flexure hinge, in most cases, needs a more sophisticated kinetostatic model than the conventional planar flexures. An elastic curved beam generally allows its outer sections to experience full plane mo...

Large Deployable Reflector (LDR) systems are commonly used as mesh reflectors for large aperture space antennas in aerospace applications since they provide affordability while guaranteeing at the same time a high gain and a high directivity. To improve the surface accuracy several methods have been studied, most of which measure the distance betwe...

A dynamic model of a Conjugate-Surface Flexure Hinge (CSFH) has been proposed as a component for MEMS/NEMS Technology-based devices with lumped compliance. However, impacts between the conjugate surfaces have not been studied yet and, therefore, this paper attempts to fill this gap by proposing a detailed multibody system (MBS) model that includes...

The influence of interface reduction on the dynamics of flexible multibody systems has not been well investigated and the conventional multipoint constraints still suffer when applied to multibody systems. Here, we propose a novel approach to derive rigid and interpolation multipoint constraints exploiting the role of the reference conditions, used...

Background and Goal of Study: In order to monitor progress and to detect patients at risk of a clinical deterioration, it is standard to use a form of an Early Warning Score (EWS). This is done manually by nurses in many centres, and is limited by human factors such as errors, subjectivity, fatigue, costs etc. Furthermore, the score needs proper in...

Modeling a flexible multibody system employing the floating frame of reference formulation (FFRF) requires significant computational resources when the flexible components are represented through finite elements. Reducing the complexity of the governing equations of motion through component-level reduced-order models (ROM) can be an effective strat...

This paper applies the Rudnick and Milton method through the dynamic evaluation of the probability of airborne contagion, redefining all parameters and variables in discretized form. To adapt the calculation of the risk of contagion to real needs, scenarios are used to define the presence of people, infected subjects, the hourly production of the q...

The most popular strategy to reduce the complexity of flexible multibody systems modeled using the Floating Frame of Reference Formulation (FFRF) is based on reduced-order models (ROM) derived through component modes. In this paper, we propose the use of global modes to build a feasible modal basis of reduction. The global modes are derived from th...

The elastodynamic analysis of parallel robots still has limitations related to the difficulty of including parts with several input/output nodes. This results in the impossibility of considering fully flexible parallel mechanisms and, therefore, most of the models proposed in the literature only consider flexible legs connected to a rigid moving pl...

In this paper, a novel reduction method for planar flexible mechanisms based on global flexible modes is proposed. Using the framework provided by the finite-element floating frame of reference formulation (FE-FFRF), the global flexible modes of a planar mechanism are derived from the linearized modal equations of motion at a given linearization po...

This paper is focused on the application of the fundamental model reduction techniques used in structural dynamics to flexible multibody systems. In particular, an effective computational approach is developed and tested in this work for adapting the conventional structural model condensation strategies to the dynamics of flexible multibody systems...

Large Deployable Reflectors (LDR) are receiving considerable attention from aerospace government companies and researchers. In this paper, the design of the opening system of a LDR is presented. Starting from an elementary cell, a first ideal kinematic model is discussed. Then, a more complex “design model” including feasible design solutions for j...

In the present work the iterative Improved Reduced System technique (IRS) is extended to flexible mechanisms to include the joint constraints. Starting from the two-step method described in [1] by the same authors, we create an iterative method similar to the iterative IRS used in structural mechanics. Finally, the method is applied to a RSCR spati...

In this paper, a novel static condensation method is extended to mechanisms and structures with internal joints. The formulation is framed inside the static reduction techniques in a similar way to the classic Guyan–Iron reduction. A new class of joint nodes is added to the existing classes of inner and boundary nodes to consider joint constraints...

In this paper, an extended Craig-Bampton method is proposed. Despite the common procedure widely used in structural dynamics to create superelements to be combined by means of joints; here, the joints are included in the reduction procedure. This novelty makes it possible to obtain larger superelements that might be subparts of a mechanism or even...

The interactive design for industrial applications is today carried out through methods and tools, with different level of accuracy and simulation times. Consequently, the time necessary for virtual prototyping and analysis phases are often long and may be definitely reduced by means of optimization of tools and methodologies. Compliant mechanisms...

The trade-off between the design phase and the experimental setup is crucial in satisfying the accuracy requirements of large deployable reflectors. Manufacturing errors and tolerances change the root mean square (RMS) of the reflecting surface and require careful calibration of the tie-rod system to be able to fit into the initial design specifica...

The tradeoff between the design phase and the experimental setup is crucial to satisfy the accuracy requirement of Large Deployable Reflectors. Manufacturing errors and tolerances change the RMS of the reflecting surface and require careful calibration of the tie rod system to be able to fit into the initial design specifications. To give a possibl...

A two-step algorithm for the dynamic reduction of flexible mechanisms inspired to the IRS method for structures is proposed. The classic Guyan-Iron condensation is first extended to multibody systems by introducing the joint compatibility equations in the equations of motion written in terms of slave and the new class joint-nodes. It is demonstrate...

Deployable mesh reflector antennas are widely used for space applications and the form-finding analysis plays an important role to reach the high surface accuracy. In this paper, an optimized algorithm extends the traditional force density method for the form-finding analysis of an asymmetric offset antenna. The optimization problem is solved by mi...

Monitoring of marine pollution is currently being given a lot of importance as an aid to legislators for when it comes to protecting the environment. A clean marine environment is very important in order to sustain healthy life for all creatures and plants that live in the sea and beyond. The work presented in this paper includes work done within t...

In the present work a novel rear suspension for motorcycles, able to achieve the required progressiveness in terms of rigidity by using a constant-stiffness spring and an innovative compact mechanism, is studied. The key component is an eccentric system inserted in the shock absorber head. As reference, the rear suspension of the Ducati Multistrada...

Reaction forces and torques in overconstrained mechanisms are tied to the elasticity of the system. External wrenches applied to a mechanism generate joint reactions that can be determined only employing the stiffness analysis. This paper describes a novel method to find nodal displacements and rotations of overconstrained mechanisms due to clearan...

In the present work, by means of an integrated approach, a new rear suspension for motorcycles, able to achieve the required progressiveness in terms of rigidity by using a constant-stiffness spring and a compact mechanism, has been studied. The key component is an eccentric system inserted in the shock absorber head. As reference, we analyzed the...

The present paper is focused on the theoretical and experimental analysis of a three-axes MEMS gyroscope, developed by ST Microelectronics, implementing an innovative feedforward PI quadrature compensation architecture. The gyroscopes structure is explained and equations of motion are written; modal shapes and frequencies are obtained by finite ele...

This paper presents a complete stiffness analysis of spatial mechanisms. Links flexibility is modeled through structural elements while joints are inherently considered by means of kinematic relations including their degree of freedoms (dofs) and degree of constraints (docs). Actuation stiffness can be included as well as flexibility of some docs c...

A novel approach to study the elastodynamics of Spherical Parallel Robots is described through an exact dynamic model. Timoshenko arches are used to simulate flexible curved links while the base and mobile platforms are modelled as rigid bodies. Spatial joints are inherently included into the model without Lagrangian multipliers. At first, the equi...

Interactive simulations in Virtual Reality, such as haptic interaction, are more and more used to test or optimize nonlinear mechanical systems subjected to large deformations. FE algorithms are often not suitable for such purposes due to the high computational burden and the long simulation times. This paper provides a modified version of the clas...

In this paper, the elastostatic model of a novel hybrid robot for minimally invasive surgery is presented. The parallel robot has two identical limbs of SPU type and a RRR limb which allows the end-effector to accomplish spherical motion. The robot has three actuated joints for the parallel architecture and one for the translation along the longitu...

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, general...

The dynamic equilibrium in steady-state conditions is of great importance for the attitude control of an underwater towed vehicle. The paper aims to investigate which parameters allow to maintain a given horizontal attitude at a desired depth. Some simplifications as constant speed of the boat, negligible inertial effects of the towline are introdu...

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...

Solar tracking systems and heliostats often rely on serial mechanisms with one or two motorized axes. In this paper we propose a parallel kinematic machine of type U-2PUS optimized to have a large workspace able to follow the sun's apparent motion during the year. Some issues such as singularity avoidance and link/joint collisions are included insi...

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 condi...

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 j...

In this paper the elastodynamic optimization of a 3T1R parallel manipulator is performed. The robot is first divided into subsystems including its four legs and the moving platform; then, each leg is split into three modules. A module is made of flexible and rigid links coupled by means of ideal joints. Once the global stiffness and inertia matrice...

This study is aimed to numerically investigate the elastodynamics of a mono-axial MEMS accelerometer. The vibrating part of the device is dipped into a fluid micro-channel and made of a proof mass connected to the frame by two flexible legs. The adopted mathematical model lies on a linearized motion equations system, where the mass matrix is obtain...

This paper discusses the dynamic simulations of a Towfish equipped with three wings, two of which can be moved for a possible stability depth control. The models describing the 3D geometry of both vehicle and towing cable are implemented, their main parameters and the acting forces are evaluated and then simulated using a multibody dynamic software...

In this paper we analyze the elastodynamics model of Icaro, a lower-mobility Parallel Kinematic Machine (PKM) for pure translational motions. The aim of this work is to individuate sources of undesired parasitic rotation motions arising during task performing in order to modify the geometry of some critical components. The analysis is based on a fo...

In this paper, a new method is presented for stiffening a tripod made of fixed-length legs. The idea is to add a pair of clamping plates to each leg. In doing so, the out-of-plane motion of the leg is fully constrained, thereby significantly increasing its bending stiffness. Compared to the existing designs, the advantage of this new design is that...

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 th...

In this paper a proposal for a control system that provides liquid cargo movement from one side to another is made. The system acts to minimise the effects of lateral load transfer and fluid oscillation. This consists of a main tank, two lateral tanks, regulators and a set of electropumps effecting the movement of the fluid. According to literature...

The article describes the design of a robotic wrist able to perform spherical motions: its mechanical architecture is based on parallel kinematics and is suitable to be realized at the mini-or micro-scale by means of flexible joints. In view of the preliminary design, a rigid body model has been studied first and the direct and inverse kinematic an...

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...

: The drawing up of the present work has demanded at first a mobility analysis, and then the study of the inverse and direct kinematic analyses of the 3-CRU manipulator. The peculiar architecture of every leg has allowed to obtain relatively simple relations for both the kinematic analyses. Finally, the study of dynamics and numerical simulations h...

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...

This paper proposes the kinematics and dynamics of a five-bar linkage, using a novel and s implified approach. First, a method based on the natural orth ogonal complement is used to derive the dynamic equations of the mechanism. Subsequently, an optimization method for the dynamic balancing of the linkage is proposed. The c onditions of dynamic bal...

This paper presents kinematic and dynamic analyses of a two-degree-of-freedom pointing parallel mechanism. The mechanism consists of a moving platform, connected to a fixed platform by two legs of type PUS (prismatic-universal-spherical). At first a simplified kinematic model of the pointing mechanism is introduced. Based on this proposed model, th...

The comparison of mechanisms with different topology or with different geometry, but with the same topology, is a necessary operation during the design of a machine sized for a given task. Therefore, tools that evaluate the dynamic performances of a mechanism are welcomed. This paper deals with the dynamic isotropy of 2-dof mechanisms starting from...

. In this paper a procedure for the virtual prototype of an experimental test to evaluate fatigue life for mechanical components of a scooter frame is implemented. The proposed work is finalized to demonstrate the accuracy and reliability of the numerical simulation to drastically reduce the time of real experiments and tests. The roller test bench...

. In this paper a deployable hold-down and release mechanism (DHRM) for satellite antennas manufactured by Thales Alenia Space Italia is presented. The aim is to describe and analyse the mechanical behavior of the DHRM in terms of stiffness, stress analysis, joint response and resonance frequencies. These mechanisms are used to firmly hold down the...