New Advances in Mechanisms, Transmissions and Applications

This paper provides a benchmark for motorcycle rear suspension systems. The main goal is to determine whether any of the suspension systems provides clear advantages over the others when seeking for a previously defined progressive wheel rate. A kinetostatic formulation of the mechanism is therefore presented. In this formulation, kinematics is based on groups of elements, while statics is based on the principle of virtual work. This formulation has been proved to be efficient and robust. It allows for building objective functions which are especially suitable for evolutionary algorithm optimization. Results show that there are no significant differences between the four types of analysed suspensions.

The dynamical response of an interconnected suspension system on a standard sport motorcycle is investigated. The paper contains the geometrical analysis of the interconnection system, an explanation of the mathematical model of the motorcycle under study and the results for bump simulations under straight running conditions. The analysis is done by using the state space representation of the motorcycle model which had been obtained by taking advance of VehicleSim software. Optimization processes are performed in order to find the best values of interconnection coefficients. Finally the work concludes that a better performance in terms of suspension precision and comfort can be achieved by an interconnected suspension system on this kind of motorcycle.

This paper shows the development of a motorcycle simulation tool built at the University of Cantabria (UC) whose main aim is to support design tasks for future teams that will take part in the interuniversity competition MotoStudent. The tool has been implemented in a commercial multi-body software (MBS) in order to extend the model in a near future. Besides, the tool makes use of customized menu and user interfaces to have easy and quick use by non-especially trained engineers in MBS. The tool has been evaluated by comparison with a widely proved model and used to improve the UC 2010 prototype planar dynamics.

The suspension system is composed of several deformable elements such as springs and dampers, which connect the car body to wheels and absorb vibrations generated by road irregularities. The main purpose of suspension system is to isolate the vehicle body from disturbances in order to keep wheels in contact with the road surface to contribute to road holding, and in order to maximize passenger ride comfort. This paper describes a semi-active suspension system of 2 degrees of freedom (2DOF), typically referred to as a quarter car model. To design a suspension control system that improve ride comfort, dynamic modelling of semi-active suspension was developed. Control strategies were implemented for these semi-active suspension systems using MATLAB® and Simulink® software. The results show that the semi-active suspension system controlled by a logical strategy minimizes vertical acceleration experienced by passengers, compared to passive suspension system.

This work deals with the topological synthesis of a novel parallel mechanism to be employed in vehicle rear suspensions to improve the overall stability. The approach followed here considers the design of an active rear suspension, with three degrees of freedom, able to adjust the camber, toe and roll angles simultaneously. By applying two distinct methods to perform the topological synthesis, several architecture candidates are generated that satisfy the design specifications. Then, the synthesized candidates are ranked according to some proposed indexes and the most promising topology is selected. In order to evaluate the capability of the parallel mechanism to improve the vehicle dynamic behaviour, numerical simulations are conducted to compare it with a similar vehicle equipped with a conventional suspension system. The obtained results have shown that, in double lane change maneuvers, the novel parallel mechanism is able to reduce not only the yaw rate but also the roll angle.

The aim of the present paper is to set up a first approach of a Vibration Model of a POM Conveyor System, commonly used nowadays in Automobile Industry to transport vehicles and workers together as Final Assembly Lines, composed by extremely long length Polymer Chain. Although these conveyor systems offer a successfully behaviour in terms of reliability, endurance and load capacity, sometimes but rarely appears a swing-effect in the middle and the end of the chain conveyor when a worker walks or gets into the beginning of it. This undesired vibration provokes, as well as an uncomfortable and anti-ergonomic situation for the worker, a loss of quality of the manufactured product, in this case, automobiles. Once the main objective is the study of the swing effect under a dynamic point of view, starting by setting a vibration model based on differential equations, and later, by the use of computer software, to set up a simplified dynamical model to analyse the vibration behaviour to contribute to improve the mechanical design and to reduce this undesired effect.

To realize the no-backlash transmission element for wearable human assist robots, a trochoidal gear reducer with a slipping rollers type torque limiter has been developed. This reducer is a kind of a pin gear with planetary motion. That roller-train is fixed only by friction force to slip under an overload. And a preload mechanism has been developed. This mechanism consists of an outer race and a preload generator which have taper contact sections to generate a uniform preload. Also, a calculation method of a trochoidal gear tooth profile by use of polar complex vector geometry is proposed. Then, using the prototype reducer, it is proved that slip occurs in the set torque, and that reducer can rotate without backlash. And it is clear that has the sufficient performances for actuator of wearable human assist robots.

This article shows the uncertainty propagation in the machining of a planetary speed reductor with HCR (High Contact Ratio) gears for high responsibility applications. It is known that in these applications, failure tolerance of a component is very low, so reliability must be close to 100%. In this way, the tolerances associated to the manufacturing process of the individual parts are typically very narrow in order to find higher function reliability. Therefore, the knowledge of which are the error sources in the manufacturing of the gear it is required, if the maximum repeatability (precision) demanded in those narrow tolerances has to be achieved. Also, tolerances are directly related to the acceptance of several unknown factors on system performance. This work will break down the sources of uncertainty, focusing on the manufacturing process by grinding.

An efficiency study of spur gears with profile modifications is presented. One of the objectives of this proposal is to make a comparison between efficiency values obtained by an advanced load contact model and reference values obtained from literature. Moreover, two methodologies for calculating the efficiency are presented: a “Numerical method” and an “Analytical method”. For the same gear pair, different efficiency values are obtained using each method. The differences among efficiency values are discussed and comparisons between both methodologies are made.

Traditional method of geometric design of gearings involves number of simplifications such as taking into consideration only pole-based contact stress instead of using their distribution along line of contact. The purpose of the article is to propose alternative method for interactive geometric design without these disadvantages.

Adaptive mechanical CVT is executed as differential with the closed contour containing toothed wheels. Kinematic chain of differential with two degree of freedom has an additional geometric constraint, which provides mechanical adaptation to variable technological loading. Work is devoted the kinematic and power analysis and synthesis of adaptive mechanical transmission.

The aim of the paper is to present a differential planetary gear box. A basic modeling has been formulated to characterize both its design and operation. At constant power input the planetary gear box is able to provide variable speed of the output link. The main purpose of the differential transmission is on the capability to adapt the operation to variable loading. Designed adaptation provides a motion of output link with a speed that is inversely proportional a loading of the link. This enables to use the differential planetary gear box in the transmissions of vehicles, metal cutting tools and in transmissions where it is necessary smooth control of gear ratio.

The paper deals with spurious residual oscillations and compensation methods in the rest areas of the displacements laws of cam system working links. Currently, cam mechanisms are divided into two basic groups, depending on how excitation motion function is implemented. It is then carried out by a conventional cam mechanism, an electronic cam or in a combination of both systems. Between the excitation motion function and the final working link there is usually a function-generating mechanism with constant or non-constant transfer. The structural arrangement is very varied, but typically it is a compliant system which responds to the excitation motion function with undesirable spurious oscillation.

This paper addresses attention to the conceptual mechanism design of a leg exoskeleton for human rehabilitation purposes. Different mechanism solutions for locomotion rehabilitation are analyzed from a structural and functional viewpoints. By using mobility analysis and considerations on structure design, a new leg exoskeleton is identified with low-cost features and motion ability for rehabilitation purposes.

In the last years, the number of projects studying the human hand from the robotic point of view has increased rapidly, due to the growing interest in academic and industrial applications. Nevertheless, the complexity of the human hand, given its large number of degrees of freedom (DoF) within a significantly reduced space requires an exhaustive analysis, before proposing any applications. The aim of this paper is to provide a complete summary of the kinematic and dynamic characteristics of the human finger as a preliminary step towards the development of hand devices such as prosthetic/robotic hands and exoskeletons imitating the human hand shape and functionality. Kinematics and dynamics are presented for a generic finger; with anthropometric data and the dynamics equations, simulations were performed to understand its behavior.

Standing up deals with the transition from two stable postures, namely the seated and standing ones, with a movement concerning all body segments except the feet. The transfer from sitting to standing and back requires both voluntary movement of different body segments that contribute to the change of posture and equilibrium control during an important displacement of the Centre Of Gravity (COG) of the body. This operation can be considered of great importance for impaired and elderly people to achieve minimal mobility and independence in daily life activities. In this paper we propose the design of a simplified mechanism to be used in assisting device for aiding the sit-to-stand. In particular, experimental tests are carried out to track and record point trajectories and the orientation of the trunk during the sit-to-stand. Twenty healthy adult volunteers were recruited for a trial in order to derive a suitable theoretical trajectory of the point of interest. Finally, according to the experimental results, a proposal and simulation are presented for a novel mechanical system. In particular, in this paper a suitable theoretical trajectory of the point of interest is used to derive a 1-DOF mechanism, which is able to reproduce the requested motion.

This research project presents the construction of a Dental Virtual Articulator that permits the design of collision-free geometry on dental prostheses. Thanks to this articulator kinematic analysis can be taken into account in the design of dental prostheses. This is an improvement of the utmost importance in this field. Several steps have been followed in the development of this virtual articulator. First, in order to obtain a digitalized data of each individual patient, plaster models of his/her upper and lower parts of the jaw were scanned. Afterwards, depending on the required accuracy or on the patient’s setting data available in each case, the type of articulator was selected. Then, using a CAD system, the missing teeth were statically modelled. Also, the opening/closing movements and the lateral occlusion were simulated with the CAD system in order to analyze possible occlusal collisions and modify the design accordingly. Finally, this paper discusses the still existing shortcomings of virtual articulator simulation and provides a detailed research prospect as well. The main practical implications of this paper are, on the one hand, the improvement in dental CAD/CAM systems by adding the kinematic analysis, and on the other, since each of them has an individual pattern of movement, the analysis of the simulations of different articulators.

A simulation model of a parallel medical robot is presented in this paper. The robot consists of two modules: the PARAMIS robot and an additional parallel module. The parallel module is used to obtain a mechanically fixed remote center of motion (RCM), enabling the structure to manipulate active instruments. The new structure provides the necessary motion control with respect to the particularities and restrictions of minimally invasive applications. A simulation based on the developed kinematic models is performed using the Simulink software from MATLAB. Another simulation of the imposed motion is performed using the CAD model of the structure. The numerical results obtained during the simulations are compared and show that the robotic structure is correctly modelled and reliable.

The main purpose of this paper is to develop a novel experimental design of knee prosthesis for trans-femoral amputees, which uses a geared linkage in order to generate a rotational movement of the knee joint. The geared linkage with linear actuator can reproduce an approximately linear transmission function for a very large rotation angle. This property of the geared linkage allows an easier control of the walking gait. Such prosthesis becomes active by empowering it with an electro-pneumatic circuit and an electro-pneumatic control unit, which allows the control of the swing phase.

In this paper we present concept, prototype and first experimental results of a force/ torque-sensor based motion control and fall prevention system for an active walker mobility aid to support walking and the sit to stand transfer. For detection of the user intention and for characterization of possible fall situations a 6Dforce/ torque sensor is used in combination together with a real-time SIMULINK® signal pre- and postprocessing. To improve situation awareness of the signal processing, a mathematical model of the human body is used in the background. Finally we present first experimental results acquired with a passive type rollator using our lab test course.

The development of robotic devices to apply in rehabilitation process of human lower limbs is justified by the large number of people with lower limb problems due to stroke and/or accidents. In this paper is presented a cable-based parallel manipulator for lower limb rehabilitation which is composed by a fixed base and a moving platform that can be connected from two to six cables performing the movement of human gait and the individual movements of hip, knee and ankle. In this paper an optimization analysis of the motors position is made using Genetic Algorithms, considering its workspace, in such way that the cables have a minimum tension on it. For this, the static force analysis is made using the Jacobian matrix.

The aim of this work is to explain the advances made in the development of biped robot PASIBOT. The wish of add mimetic skills to the basic robot lead us include a pair of linear actuators in the hip of the robot. In order to determine the best trajectories that will define these mimetic skills, a mathematical model is developed and implemented in Matlab, creating a user interface with the aim of facilitate the researcher’s work. This software not only solves the equations, but also offers several options to visualize the results obtained. The correct definition of these trajectories will be the input data for further analysis, including dynamics in Msc.Adams and on the physical prototype. Unfortunately, the lack of space for this paper prevent us from developing the control strategies in a suitable way.

The study aimed to develop a walking mobile robot and model its four-legged gait. At first, a review of existing structures was conducted and then the robot’s purpose and design parameters were specified. On this basis, the kinematic structure and the geometry of the robot’s legs were determined. After that, a numerical model of the quadruped robot was built in MD Adams. Mechanical structure of construction was designed and relevant drawings of individual parts were made using Inventor. General algorithm of four-legged gait used for this robot was specified. Simulations of the model’s actions in MD Adams were performed to determine the kinematic and dynamic properties of the movement. Among others, walking on wheels and on feet, using the lateral surfaces of wheels, were examined and results have been presented.

This paper presents the general structure of wheel-legged robot module and sensory systems. The scheme, interfaces and system components will be presented. Basing on initial experiments the sensor properties and suitability for a particular task – detection, identification and overcoming encountered obstacles on the robot’s path were assessed.

This paper proposes a general formulation of the dynamic model of constrained, articulated limb of wheel-legged mobile robot. Dynamic model of the system has been formulated in terms of actuated joints using Euler-Lagrange formulation. Implicit kinematic model is used to provide dependences between articulated and unarticulated joint rates, velocities and accelerations used in the model. Based on dynamic model of the system a nonlinear controller has been proposed. Numerical model of the limb has been built in order to verify the validity of the control laws. Exemplary simulations have been presented to show asymptotic stability of control system.

This paper addresses the path planning problem for an hybrid wheeled–legged hexapod. In particular, the proposed procedure is aiming to identify optimal trajectories for a leg when it has to step over an obstacle. The proposed procedure is a combination of a quick random search algorithm together with an optimisation method. This combination is used to achieve a good compromise between computational costs and path planning performance. The optimization method is efficiently solved by using a genetic algorithm to achieve properly smooth leg movements. A case of study is numerically solved by referring to a built prototype of Cassino Hexapod at LARM in Cassino.

Compliant mechanisms have several advantages, especially smaller number of elements and therefore less movable joints. The flexural members furthermore allow an integration of special functions like balancing or locking. To take advantage of compliant elements in applications a robust synthesis tool is needed.Most of the common synthesis methods focus on energy storage or shape optimization. The purely geometrical approach presented in this paper concentrates on solving guidance tasks with maximum design freedom within the installation space. An easy to use step-by-step synthesis procedure is provided through which the user is able to design mechanisms with a compliant beam element. The necessary analysis of the compliant beam element can be done by numerical analysis as well as through experiments. The synthesis method is presented using an application for a cup holder mechanism made of fibre reinforced material.

The Bennett overconstrained 6R linkages are the double-planar, the double-spherical and the plano-spherical 6R linkages. These mechanisms are obtained by combining simple planar and/or spherical mechanisms and then removing one of the common links. This paper presents the derivation of the input/output relationships for these mechanisms using the decomposition method. This method is based on writing the input/output equations for the two imaginary loops comprising the 6R mechanism and then eliminating the imaginary joint variable. It is found that the resulting input/output equations contain up to 4

th

power of trigonometric terms, such as cos

4

θ

.

Mechanisms including friction and multiple clearance contacts usually could be modelled by continuous or discontinuous force laws. In this contribution the non-smooth behaviour of a planar 6-bar linkage mechanism with revolute clearance joints is simulated by the methods of unilateral contacts. Within a noncommercial simulation framework flow separation as well as high frequency tangential pendulum motion in the clearance joints can be detected and a spring as a device of reaction force balancing is analysed.

Dynamic simulation and advanced control are two areas that are becoming important in the field of design and industrial production. Dynamic simulation is a design tool now consolidated and commonly used in industries such as automobile and the related ones because it replaces the expensive tests with prototypes. Well, the results can provide simulation tools such as advanced control techniques critically depend on the quality of the data from which the mechanical model systems are generated. Direct measurement of these data or physical parameters (mass, location of centers of gravity, inertia tensors, friction parameters, etc) is problematic in systems that are being designed. We also have to consider that these parameters may change significantly over the life of the mechanical system. The alternative measurement is the identification of these parameters from experimental data acquired during the operation of mechanical systems. The actual proposal of this work is to design a wheel rim for light vehicle able to determinate the forces and moments that are transmitted to the axis of the vehicle wheel during use. The necessary instrumentation is designed using extensometry techniques, and the design process focuses on the study of the wheel rim deformations associated with the different forces acting on it. The study of strain performed on models analyzed by finite element techniques considering the different types of forces acting on the rim. Modeling the deformations behavior of the wheel rim, and doing a proper instrumentation based on the FEM analysis the results will be develop the procedure for the instrumentation of the rim to obtain the desired measurements.

The paper presents the adaptation of the technique for motion and path synthesis to the problem in which the motion equations of two links are coupled. The method is employed to design a feeder for carrying products between two points. The feeder is assumed to be an one degree of freedom system of six links connected by means of revolute joints. The jaws of the gripper catch the product and transports to other work stand where the gripper releases the product and moves back to its initial position. No extra drive of the gripper is needed as the movement of the jaws is driven by the active link of the feeder. The mathematical basis of the method is presented. The problem is formulated as an optimization task. An exemplary solution is presented and discussed.

In this paper a driving linkage is designed with a fairly simple procedure for a fairly simple structure for implementation in a rural water pump in Andes regions. The aim is to provide a mechanism solution that can be easily implemented for comfort and efficiency issues with proper adjustments and available materials in rural environments with very limited resources.

The paper deals with a low-cost robot link concept. By simplifying common means for the development of parallel kinematic machines, a means to optimize the dimensioning, regarding link stiffness, is found. To underline the utility of the design concept, called rigid hexapod, a way for geometric adjustment of the lightweight structure is presented.

This work is focused in the integration of a scan-head in a machine tool for laser processing of large areas. The scan-head is a device typically used for marking operations and provides very high linear speeds. Despite scanners present high accuracy for marking speeds below 5,000 mm/s, over this limit, accuracy problems were found. In this kind of device the motion is controlled using high precision actuators but there is no positioning closed-loop and workspace area is typically limited to small working areas. On the other hand, the positioning error varies also with working area plane positioning. This becomes a problem for processing complex shape surfaces. The work presented deals with characterization of the scan head, to identify the parameters affecting the error, the influence of the error with working plane positioning and with the integration of fast rotary axes of the scan head with conventional linear axes of a machine-tool. The proposed solution is based on a NC parent program controlling the linear axis of the machine-tool with integrated subprograms that control rotary axes of the scan-head.

The handling system developed at the IGM enables a quick adaption of the kinematic structure to a new motion task through a modular and versatile concept. Several parallel kinematic robotic arms integrate an object in the kinematic structure by adapting to the object with the end-effectors. Current developments provide the manipulation only of ferromagnetic objects. This paper introduces the development process of an end-effector for a 3-DOF robotic structure using a design methodology increasing the range of objects to be manipulated. Through definition of a solution set with subsequent systematic analysis different concepts for a vacuum gripper are developed. Compressed-air is used as power supply. The robotic local structure is a spherical linkage where the pneumatic hose must be integrated.

The category of Haptic Feedback-Systems (HFS) is presented. These systems allow the operator to interact intuitively with a chosen simulation scenario. The systems reaction is unlike usual output tactile and kinaesthetic perceptible. The fundamentals of haptic will be illustrated as well as the basic structure of HFS. Subsequently a general survey of the state of the scientific and technical knowledge is given and fields of application are discussed. The process of mechanism design and development is emphasized. HFS are practically not used in this process up to now. The conventional procedures for dimensioning technical devices do not permit statements according ergonomic questions or perception of actuating forces. To allow proper evaluation usually a time-consuming and cost intensive prototype has to be built. The application of a universal HFS to interactively support certain phases of the mechanism design process is envisioned.

This paper presents considerations on the valuable contributions of Giuseppe Antonio Borgnis in the 19-th century developments on Mechanism Design in terms of representation of machine mechanical designs and terminology for the rising discipline on Theory of mechanisms.

Double-spherical six-bar linkage is one of the Bennett over-constrained 6R linkages. Kinematic synthesis of such linkages can be tedious and impossible to solve for analytically. In order to cope with higher number of unknowns in these types of linkages, decomposition method is a valuable tool. This paper focuses on the function generation synthesis of double-spherical six-bar linkage. Two procedures for applying decomposition method are explained. Two numerical studies are conducted for both procedures to evaluate the performance of each procedure.

This paper presents a novel 4 dofs (3T-1R) parallel actuatedly redundant mechanism and its workspace analysis, based on a performance index involving velocity and force capabilities. The robot is capable of performing a half-turn about the z axis. Moreover, having all of its prismatic actuators along one direction; the x motion is independent- only limited by the stroke of the prismatic actuators. The mechanism is characterized by elevated dynamical capabilities having its actuators at base.

Mechanisms and manipulators having parallel structure are rapidly spreading. Designs of mechanisms are constantly evolving, new ones appearing. According to that, the study of designs with some special features is rather relevant. In this paper, the parallel translational mechanism, in which all linear actuators located on the base, was considered. The Plucker coordinates matrix and the solution of the inverse kinematics problem were obtained. Also an improvement of the manipulator was proposed, and the Plucker coordinates matrix and the solution of the inverse kinematics problem were obtained for this advanced mechanism.

This article considers the five-link spatial mechanism of manipulating robot with revolute and prismatic kinematic pairs. It is shown that making geometric analysis using classical methods is not rational. This article presents a numerical method of geometric analysis, kinematic and dynamic calculations of a mechanism.

Model Based Predictive Control (MPC) is an interesting approach due to its ability to consider the constraints of the controlled system and easily adapt to the future reference changes. In this paper, a novel robust MPC controller is presented, which considers the effect of the Tool Center Point (TCP) estimation errors and the model uncertainties of the mechanical structure. In order to show its effectiveness, its application to the 5R parallel manipulator is detailed. Simulation validation is provided to demonstrate that the proposed approach can exploit all the theoretical capabilities of the mechatronic system.

This paper examines parameter identification for six-degree-of-freedom (6-DOF) parallel manipulators, from the point of view of measurement redundancy. A redundant passive chain with a displacement sensor is installed between the moving stage and the machine frame, and is passively expanded and contracted by actuation of the 6-DOF manipulator. Linear encoders built in seven prismatic joints in the passive chain and six actuated chains measure change in length of the chains during traveling of the end-effector. Moreover, length error in one of the seven chains can be calculated from the forward kinematics of a 6-DOF parallel manipulator consisting of the remaining 6 chains. Consequently, comparison between the measured seven lengths and calculated seven lengths reveals seven length errors at each pose of the end-effector because seven combinations are possible. The least-squares method using a Jacobian matrix corrects 37 kinematic parameters so that the length errors of the seven chains are minimized. The above calculations were repeated until convergence in both numerical simulations and experiments employing a coordinate measuring machine based on the parallel manipulator. Moreover, coordinate measurement using a 3-D ball plate was performed to verify the identified parameters. The measurement result demonstrated that the average coordinate error of 0.161 mm was reduced to 0.066 mm.

In this paper, an optimal design methodology for three-degree-of-freedom planar or spatial parallel manipulators is presented. In particular, cuspidal manipulators, which own the ability of performing non-singular transitions, are addressed. The design procedure incorporates the transitioning ability into the design criteria. An initial stage of the procedure comprises the analysis of different designs by means of characterizing configuration space entities. This gives an overall insight into the capacities of the robot. Then, the dimensional synthesis focuses on cuspidal designs in order to find the set of optimum design parameters such that the operational workspace is as larger as possible having also a regular shape. So as to illustrate the methodology, the 3-S

P

S-S spatial orientation manipulator is used.

This work presents the quantification of the improvement in the high-cycle fatigue strength of machine parts manufactured with medium-carbon steels by means of low-plasticity burnishing. A complete experimental study has been performed on specimens: surface integrity, in-depth residual stresses, residual stresses relaxation, alternating bending fatigue tests and fractographic analysis. The tests show that the fatigue strength of ball-burnished components is significantly improved in the range 10

4

to 10

6

cycles, and the fatigue limit is increased by 20%. The residual stresses in the surface layer are non-isotropic biaxial compressive stresses varying in time because of stress relaxation. The quantitative data here provided are the modifying coefficient for the Marin equation and a uniaxial effective mean stress for each stress level. For fatigue calculations, this effective constant mean stress is equivalent to the effects produced by ball burnishing, and is an alternative to the calculations based on modifying coefficients.

The most versatile general purpose clamping device is collet chuck. Most of collet chucks use solid thin slotted clamping sleeves made of a hardened steel and ground to a high degree of accuracy on both internal and external surfaces. This paper first presents a straightforward analytical model to determinate the static stiffness of collet sleeves. Second, it presents the Finite Element Method (FEM) analyses that were conducted to check the proposed analytical model. Third, it describes an automatic (wedge-actuated) prototype, which was designed and built for determining the static stiffness of collet sleeves. The proposed analytical model was verified by means of Finite Element Analyses (FEA) and experimental investigations. The results will confirm the linear behavior of the models with excellent levels of correlation. The work results provide reliable theoretical and technical supports for the optimization of the design and application of collet sleeves.

An index is introduced, the minimum degree of constraint satisfaction, which quantifies the robustness of the equilibrium of an object with a single scalar. This index is defined under the assumptions that the object is supported by forces of known lines of action and bounded amplitudes, and that the external perturbation forces and moments vary within a known set of possibilities. A method is proposed to compute the minimum degree of constraint satisfaction by resorting to the quick hull algorithm. The method is then applied to two examples chosen for their simplicity and diversity, as evidence of the broad spectrum of applications that can benefit from the index. The first example tackles the issue of fastening a workpiece, and the second, the workspace of a cable-driven parallel robot. From these numerical experiments, the minimum degree of constraint satisfaction proves useful in grasping, cable-driven parallel robots, Gough-Stewart platforms and other applications.

Plastic strains states generated after assembly process in shrinks fits are not desirable since could limit the good conditions performance of joined parts. So design methods leading to reduce those states are strongly welcomed. In this paper, the effects of one of those methods, a grooved hub, on the plastic strain distribution at the interface are analyzed from the results of diverse numerical simulations of the thermal assembly process by means of FEM. According to results, the proposed geometry is revealed as an effective method for notably reducing the plastic strain state with loss of the maximum transmitted torque lower than 6%. This way, the working conditions are closer to the ones established in the theoretical design of the shrink fit.

The components of machines very often present defects that can grow to fatigue cracks when they are submitted to the working solicitations. In the case of shaft,this is particularly important because the catastrophic failures can lead to personal injuries or economic problems. When a cracked shaft rotates, the breathing mechanism appears. The crack opens and closes passing from the open state to the close state with a transition that produces a partial opening. The shafts present additionally misalignments or/and unbalances that alter their normal function. In this paper, we present a Finite Element Method (FEM) study of the influence of the eccentricity in the breathing mechanism of a rotating cracked shaft. The classical Jeffcott rotor model has been chosen for this study. To simulate the rotation of the shaft, different angular positions have been considered. The Stress Intensity Factor (SIF) along the crack front during the rotation has been studied considering different angles of eccentricity. The work allows to know the influence of the unbalance of rotating shafts in the crack breathing mechanism, in the values of the Stress Intensity Factor and in the propagation of cracks.

The aim of the present work is to present a fast identification method to estimate the inertial and friction parameters of a rigid body dynamic model of an electromechanical actuator. These are the dominant effects that determine the dynamics of machines and although the inertia is easily predictable, the friction can only be accurately known performing experimental measurements. The work provides the mathematical aspects of the identification method as well as several practical aspects for its implementation. The procedure is applied to an actuator based on a motor and a gearbox, and a comparison of the torque estimated and the real one are provided.