New Trends in Mechanism and Machine Science

This work shows first the way by which an inversion of the double linked fourbar has been obtained in order to use it as actuation mechanism for an UAV morphing wing after a short structural synthesis step. Then, the kinematical capabilities of this mechanism are outlined and graphically derived: instant center of rotation, lock positions and uncertainty positions.

The problem of kinematic disturbance propagation in the linear statically determinate adjustable structures is studied in the paper. The disturbances have a harmonic form and are called kinematic waves. Existence of different types of kinematic waves in plane and spatial statically determinate structures is demonstrated.

Small perturbations can affect the kinematic properties of manipulators with non-generic architecture. We study in this paper the perturbations of symmetric planar 3-R

$$\underline{\mathrm{P}}$$

R manipulators. We show in particular that one can obtain any of the three possible stable types of behaviour of 3-R

$$\underline{\mathrm{P}}$$

R manipulators for large values of the lengths of the legs.

The aim of this paper is to present the workspace and singularity analysis of a parallel structure that can be used for complex operations such as micro-assembly, electronic circuit testing or for industrial laser cutting or manufacturing. Starting from the inverse geometrical model of the robot, its analytical workspace is determined. A brief look at different types of singularity points is presented. Conclusions and references are presented at the end of the paper.

The paper presents a new parallel reconfigurable robot with six degrees of freedom actuated from the fixed platform by six linear motors disposed in three guiding kinematic chains. With the help of fasteners, the robot can be reconfigured in one with five, four, three or two degrees of freedom. The equations for the determination of the inverse and direct kinematic models are presented. The robot is suitable for assembly and milling operations and can be also used as a module in a minimally invasive surgical system.

A negative answer to the earlier placed question about the existence of a restoring self-stress in the linear space of self-stresses of a fastened framework is obtained. Namely an example of a plane construction reconstructible from its linear space of self-stresses but not reconstructible from any individual self-stress will be described.

In this paper, we propose a new class of mechanisms based on the properties of their graph representation. As opposed to pure parallel or hybrid mechanisms, these mechanisms can not be represented with a series-parallel graph. This characteristic prevents analysis of their mobility by standard methods. We introduce a novel approach based on graph theory to compute their mobility and we apply this method to a non series-parallel mechanism.

This article completes the algebraic analysis of multiple-mode 7-link chains based on the concatenation of two overconstrained 4-link mechanisms with only revolute and prismatic joints, i.e. the Bennett or the overconstrained RPRP mechanisms. Both initial mechanisms are locked in one pose of their one parameter motion. Then they are transformed to a position where one joint coincides and all the links of the basic 4-link mechanisms are deleted. New links that can be arbitrarily inserted between the seven joints. The only possible types of mechanisms in this manner are the 7R, the 5R2P and the 4R3P mechanisms. Those chains have the property, that they can fulfill an arbitrary one parameter motion of the 7-link chain and, additionally, both sub-motions of the basic 4-link chains. In special configurations it is possible to switch between the modes without the need of disconnecting and reassembling. Here an algebraic approach to those mechanisms is presented that gives the opportunity to identify the motion and the transitional configurations exactly. In all of the analyzed types of mechanisms such transition configurations exist.

In the cable-driven robot studies, the mass and the elasticity of cables are often neglected, particularly for small-sized robots.Indeed, this assumption allows one to simplify the robot model and is used in control, design or calibration.We propose in this paper a method using interval analysis to judge the validity of this hypothesis in a given workspace, whatever are the cable characteristics, i.e., the applied tensions and the robot configuration.

The instantaneous motion capability of the end-effector of a manipulator is readily described by the type of screw system spanned. Such systems are classified by finding their principal screws. The analytical determination of such a base has been researched in the past using different techniques. The contribution of this paper is that the procedure presented is a comprehensive method that allows the systematic finding of the principal screws in closed form for screw systems of any order, solves for every special system, and is applicable to Inverse Kinematic singular postures. The method is adequate for computation, making use of a simple generalized eigenproblem.

Protein motion simulation is still a troublesome problem yet to be solved, especially due to its high computational requirements. The procedure presented in this paper makes use of the proteins’ real degrees of freedom without any intermediate energy minization processes that may altere the motion path or result in very high computational cost requirements. In orther to reduce the compuational cost, presented algorithms make use of the balls and rods approach for protein structure modelization. Also, structures are normalized in order to minimize inaccuracies introduced by experimental methods, providing a more efficient but still accurate structure for motion simulation.

The ability of any optimization method to handle inequality constraints is essential for its application to real design problems. This paper presents two alternatives for dealing with this type of constraints within a method developed by the authors. Both alternatives use slack variables technique. In the first one, these variables are considered as dependent ones in the optimization process, whereas in the second are considered as design parameters (independent variables). The second alternative is valid only when the constraint affects a geometrical constant parameter while the former is also valid when the constraint affects a parameter that depends on the mechanism position.

Recently a complete kinematic description of the 3-RPS parallel manipulator was obtained using algebraic constraint equations. It turned out that the workspace splits into two components describing two kinematically different operation modes. Using the algebraic description a complete analysis of all possible self-motions of this manipulator in both operation modes is given.

A wide range of potential applications for parallel cable-driven robots exist. An important factor for detailed concept studies is the dimensioning of the winches. From the economic point of view, the high overload capacity of electrical drives should be taken into account during the selection of the actuator. This paper proposes a method to generate load spectra of the actuators based on dynamic motion sequences. With the gained data a suitable actuator can be selected. Furthermore, it’s shown how the implementation can be used to adjust the internal tension niveau for minimizing the trajectory time under the actuators performance constraints.

This paper shows a methodology to solve the position problem in Assur’s groups of any class exclusively using revolute pairs. The methodology is based on the elimination of a rigid bar of the Assur’s group which you want to get the position. The resulting 1-DOF linkage can be modeled with one group of primary elements and one or more Assur’s groups of class lower than the original group. Then, an optimization problem consisted in finding the optimal value of the DOF for which the pairs, joined by the eliminated rigid bar, are separated by the original distance, is posed. This methodology also allows unequivocally choose the assembly mode to obtain the original Assur’s group.

The paper presents the workspace and singularity analysis of a parallel robot, which can handle both a laparoscope or an active instrument in minimally invasive surgery (MIS). Using the inverse geometric model of the robot the analytical workspace is achieved. The paper will demonstrate that with this parallel structure, one can obtain the necessary workspace required for a minimally invasive operation. Finally, an in-depth study of different types of singularity is performed and some conclusions are presented.

The main purpose of the paper is to develop a mathematical model that generates the optimal geometrical parameters combination for a 2-DOF parallel mechanism, and to perform a solution to generate the workspace by using neural networks as a performant alternative to the workspace representation based on inverse kinematic model. The paper describes three algorithms that lead to the final solution and an initial testing was made on a functional model of parallel mechanism.

This paper discusses the further development of a binary parallel manipulator named BaPaMan1 (Binary Actuated PArallel MANipulator), which is aimed at the improvement of the structural stiffness and allows task-adaptation. BaPaMan1 is a three DOF spatial parallel robot which comprises flexure hinges and Shape Memory Alloy (SMA) actuators to achieve a low-cost design, well suited for easy operation applications. Measurements have shown that this comes at the cost of poor structural stiffness and end effector accuracy. To counter these issues BaPaMan2 and BaPaMan3 have been developed and are elaborated within this work. During the design phase, an empirical FEA was used to improve the flexure hinge performance, in which relations between several design parameters and the stiffness of the entire system were analyzed. Finally, task-adaptation was achieved using a developed design methodology and parametric CAD model for BaPaMan3, which take advantage of deduced stiffness influencing equations.

Acceleration, braking and turning capabilities are widely influenced by the parameters of the suspension systems. In this paper a geometric configuration of a rear suspension that fits a chosen target curve is obtained. The procedure followed in this study begins by choosing the topology of the rear suspension system. After that, the rear suspension characteristics are selected (highest and lowest force, progressiveness, squat ratio…). Subsequently, user-defined functions are used to obtain the position of each suspension element along the path and, later, to get the forces at each point of the system. Finally, a genetic algorithm is used to obtain an appropriate geometry of the rear suspension elements which fits the given requirements. An example is included to demonstrate the behavior and potential of the method. This strategy takes into account both the progressiveness and desired squat-ratio of the system, which have never been included in a rear suspension design before.

The aim of this study is to analyze the influence that the contact stiffness between the cam and the roller has in the prediction of the dynamic behaviour of the train follower. For this purpose two models based on the Hertzian contact theory are compared. The first model uses the formulation of the general contact assuming a nominal contact point between the cam and the roller. The second model uses the formulation of the cylindrical contact assuming a nominal contact line between them. The objective is to discuss about the convenience of both models when facing the calculations of the deviation from the theoretical motion law, contact forces, contact pressures, life span and surface fatigue in comparison with the surface finishing process for the cam or the roller. The study is set in a conjugate cam mechanism mounted in an automated process for manufacturing wirehoods. Results confirm the goodness of the general contact formulation applied when crowned rollers are used and the results dissuade the cylindrical contact formulation when rollers with cylindrical outer surface are used.

Translational and spherical parallel manipulators with three degrees of freedom and three kinematic chains are considered. Each kinematic chain contains five revolute joints. Structure, kinematics, workspace and singularities of the proposed mechanisms are discussed.

The synthesis of guidance mechanisms is always a compromise between kinematic and design issues. The difficulty of solving such tasks is the strong connection of joint location and kinematic properties. This paper gives an example to resolve this problem by separating this task into the kinematic synthesis and the dimension synthesis by placing several joints of the linkage without change of the kinematic properties. This method will be shown at a geared linkage and a 6-bar Watt linkage. For both linkages, the guidance link is driven by two triads.

This paper introduces a systematic approach to the drive train design and positioning of motors for 3 DOF robotic arms for a new kind of parallel-kinematic manipulator. After a short introduction into the state of the art, the methodology and main considerations are presented and applied to gain a set of principle solutions for possible drive-trains for every link. Combining this principle solutions, nine concepts for the robotic arm are developed.

Current development of opening and closing mechanisms of skylight domes is focused on fire protection as well as climate control. Electromechanical solutions must be energy-saving and must comply with strict regulations. A procedure to optimize the design of the opening mechanism with the aid of 3D-CAD software is presented in this paper.

The paper proposes a numerical method for computation of the base circle radius of cam mechanisms with translating flat-face follower as alternative to the traditional graphic-analytical method. The base circle radius is a very important data in the synthesis of the cam profile. The method uses two conditions: to keep the curvature continuously positive in all points along the cam profile and to avoid inflection or singularity points.

There are two main systems that can be used to coil and uncoil the wires of a wire-driven parallel robots: a rotary motor that turns a drum on which the wire is coiled or a linear motor with a pulley system. The rotary category may be divided into two sub-categories: the system with a spiral guide for the coiling, allowing only layer for the wire and the system without guide, that allows for several wire layers with the drawback that the amount of coiled wire for one motor turn depends upon the number of layer. All three systems are compared in terms of accuracy and compacity.

In this paper we present an algorithm to determine if a six-bar linkage that has been designed as a constrained 3R chain using Burmester Theory is usable. A usable six-bar linkage is one that moves a workpiece smoothly through a given set of task positions with actuation by one joint parameter.

Our algorithm is a two-step process. First the linkage is assembled in each of the task positions and is verified to have the same assembly configuration. Next, a numerical solution of the linkage is tracked between each task position and the assembly is verified to lie on the same branch of one coupler curve. A six-bar linkage that passes this two-part test is usable.

An example using Mathematica demonstrates that this computation can be used to automatically evaluate a large number of design candidates.

Modern turbo-charged internal combustion engines generate fluctuating torques with high amplitudes at the crankshaft. To reduce resultant crankshaft oscillations and their transmission to the drivetrain, flywheels and spring-damper systems like the dual-mass flywheel are commonly provided. Another concept is to couple a flywheel to the crankshaft using a non-uniformly transmitting mechanism in such a manner that the motion of the flywheel compensates the fluctuation torques. The degree of non-uniformity of the mechanism has to be adapted to the actual load and angular speed of the combustion engine. For this purpose a double-crank mechanism with cycloidal-crank input and adjustable crank length is proposed and analyzed. For a desired compensation torque the required transmission function of the mechanism is calculated using a simplified dynamic model. Parameter synthesis of the double-crank mechanism is achieved by means of a numerical optimization procedure based on a multibody model of the overall crankshaft-flywheel system.

In this paper, five positions of a planar RPR serial chain are specified and the synthesis equations for two RR constraints are solved to obtain a six-bar linkage. Analysis of the resulting linkage determines if it moves the end-effector smoothly through the five task positions without a branch defect. The design procedure presented randomly selects variations to the positions of the RPR chain in order to obtain new six-bar linkages. This dimensional synthesis algorithm yields a set of six-bar linkages that move the end-effector near the original task positions. This synthesis procedure is applied to the design of a linkage that generates a square pattern. The procedure yielded 122 defect-free linkages for one million iterations.

Tapered roller bearings are mechanical transmission elements capable of supporting axial and radial loads, both under static, dynamic or variables conditions. All these load combinations on the bearing are capable of inducing high contact pressures on rolling surfaces (raceway inner, raceway outer and rollers) and the relative displacements between the different component parts of the bearing. These high contact pressures on the raceway cause phenomena such as pitting, decreasing the durability of mechanical components significantly. Today, the design of this type of bearings is still based on both analytical techniques and experimental techniques, as well as on the finite element method (FEM). This paper explains the process of setting a finite element model (FEM) of a tapered roller bearing mounted on a vehicle´s axle. To adjust this FE model, Non Linear Submodeling techniques were utilized successively.

In today’s concept, cam mechanisms are mechanisms with

conventional cams

and mechanisms with

electronic cams

. VÚTS, a.s., has the research and application of cam mechanisms of both groups in its research and development program. This paper deals with some aspects of the applications of both groups of cam mechanisms from the point of view of implementations of demanding dynamic working movements. Attention is then focused on intermittent motion functions with rest intervals. Those motion functions are then carried out by electronic cams with rotary servomotors and conventional intermittent mechanisms with radial cams.

The aim of this paper is to develop a methodology for the validation of a Finite Element Model (FE model) which represents commercial brake caliper. The materials’ characteristics are totally unknown so Genetic Algorithms techniques and experimental tests such as test temperature and deformations have been used to determine them. Finally it presented a general vision of these techniques’ potential to reduce the costs of testing and prototyping models which have been replaced by Finite Element Method (FEM).

Planetary gearboxes are usually used in several hard work conditions. In fact, they are well known for their symmetrical structure which allows an equal share of the total external torque applied between the planetary gears, the sun and the ring. However non stationary conditions of work such as overload conditions, torque fluctuation during the start-up process in diesel engines and environmental conditions, may affect seriously and unpredictably the dynamic behavior of a planetary gear transmission. As part of an effort to understand this aspect, the present study assessed the impact of external load fluctuation on a planetary gearbox dynamic behavior. For this, a model of planetary gearbox vibration using the lumped mass approach was developed. The model includes effects such as variable tooth mesh stiffness and non stationary external load. Numerical simulations are carried out using a Newark based algorithm. The dynamic vibration results were analyzed using frequency spectrum analysis and develop analysis. Discussion and results are included based on the overall results and analysis.

In this paper an advanced model of spur gear transmissions developed by the authors is used to study the influence of carrier planet pin hole position errors. The model has been extended with internal meshing features, and thus increasing its capabilities to include planetary transmission modeling. The new features are presented, along with the summary of the model general approach, and the parameters and characteristics of the planetary transmission used in the paper are introduced. The influence of carrier planet pin hole position errors on the planet load sharing is studied, and several static cases are given as examples in order to show the ability of the model. Tangential and radial planet pin hole position errors are considered independently, and the effect of the load level is also taken into account. Two different configurations of the transmission are used, with fixed and floating sun, and the differences in terms of load sharing are shown.

The developed toothed continuously variable transmission (CVT) in the form closed gear differential is reliable mechanical system which provides high load ability and reliability. Laws of mechanics allow creating the mechanical transmission, capable to bring a transfer ratio into accord to loading only due to properties of the mechanism without use of any control. The mechanism acquires property of adaptation to variable external loading. It allows using this transmission for machines which work in the intense force conditions. The account of transmission includes the correct selection of tooth wheels numbers and use of inertial properties of transmission at start up. The mechanical transmission with two degrees of freedom can change output shaft rotation if a stopping of one of wheels for simple creation of a back trailing of the car.

The dynamic behavior of a single stage bevel gear is investigated in this paper. One of the major parameters influencing this behavior is the mesh stiffness variation, geometrical and local damages errors. Mesh stiffness is modeled for the cases of straight or spiral bevel gears. Deterioration of one tooth which affects the gear mesh stiffness is considered in this work. Tooth crack is modeled and introduced in the system motion equations, by a reduction in the stiffness. It was observed that the vibration signatures are dominated by mesh frequency and harmonics. Moreover, amplitude modulation appears when a crack is included in the simulation, and simultaneously higher vibration levels are observed.

The presence of undercut at the tooth root, non-equal addendum on pinion and wheel, non-standard tooth height or non-standard center distance may have decisive influence on the load sharing between pairs of teeth in simultaneous contact of spur gears. The curve of variation of the meshing stiffness along the path of contact, quite symmetric respect the midpoint of the interval of contact, loses its symmetry for non-standard geometries and operating conditions. As a consequence, the critical contact points for bending and wear calculations may be shifted from their locations for standard gears. In this paper, a non-uniform model of load sharing of standard spur gears, obtained from the minimum elastic potential criterion, has been enhanced to fit with the meshing conditions of the above mentioned non-standard spur gear pairs.

The objective of this development is to design, build and test a magnetic-superconductor cryogenic non-contact harmonic drive (MAGDRIVE). This harmonic drive is a mechanism provided with an input axle and an output hub with a great reduction ratio and it will be able to function at cryogenic temperatures. It is based on “non-contact magnetic teeth” instead of fitting teeth on a flexural wave as conventional harmonic drives are based on. Non-contact magnetic teeth are activated by a magnetic wave (similar to an electrical engine) and stabilized by the use of superconductor materials. This can solve the problems of contact wearing and mechanical fatigue. Superconductors are also used for non-contact bearings and for shielding the magnetic fields to avoid electromagnetic interferences or emission. The first preliminary analyses show very promising mechanical performances of the reduction gear. They have demonstrated that the transmitted torque density capability is independent of the size of the gear. Also, the choice of the material for the soft-magnetic teeth is not a critical decision provided that they have a minimum required magnetic permeability. Moreover, some dynamical simulations have shown that the reduction ratio is achieved.

After some considerations regarding the compatibility of robots with minimally invasive intervention, this paper presents a methodology to design mechanical polyarticulated modular system, with emphasis on functional requirements and technical specifications. The methodology is based primarily on determining the number of degrees of freedom, operating space volume (motion) and kinematic analysis of multi body models of the robotic arm. Considered robotic arm with ball joint includes a lot of similar elements adjacent to rigid vertebrae interconnected by cables (wires), arranged in series. Each vertebra is made of inverse (opposite) segments single or double curved (spherical surfaces). By combining the unique configuration of the vertebrae provide robotic arm the ability to tackle any route defined in 3D space. Determination of operating space is made numerically by formulating a binary representation. Kinematic analyzes are used to define the model’s ability to perform in a satisfactory and acceptable precision movements for exploration and interventions in a limited space, making it possible to define the technical design specification. Simplicity and small size are advantageous for reliability, security, quick installation and ease of use.

A comparative study of the dynamics of the 3-PRS parallel mechanism between the full case, considering the parasitic motions, and a simplified one, ignoring the parasitic motions, is presented in this work. A simplified dynamic model would be of great interest to determine the dimensions of the actuators and to solve the dynamic problem much easier and faster. The dynamic problem of the manipulator is studied using the Newton-Euler approach and a simulation in Matlab verifies that the parasitic motions can be ignored in the dynamic problem, for some given conditions.

The study aims to devise means of obtaining polyhedral linkages for homothetic deployment of polyhedral shapes by embedding planar link groups in faces of the polyhedral shape of interest. The questions of which polyhedral shapes may be suitable for such a purpose and what are the compatibility conditions for spatially assembling planar link groups are addressed. Homohedral and tangential polyhedral shapes are found to be suitable for the task and some examples of linkages are worked out.

Some of the most important devices in machine tools are collet chucks, which are often used in turning, milling, grinding and inspection. Researchers have focused on tool clamping devices based on spring collets, tool collet chucks that must achieve high rotational speeds while maintaining good rotational accuracy but none of them have presented an analytical model to determinate the initial static clamping force in automatic collet chuck holders, widely used in turning machines, taking into account the effect of the main cutting force. This paper first describes analytically the clamping-unclamping principle of the automatic collet chuck holders in its initial static state. Second, it presents the finite element method, static analysis, that were conducted to check this principle. The results will confirm the linear behavior of the two models with excellent levels of correlation.

The design of shaking-moment-balanced linkages still is challenging. Considering moment balance in the very beginning of the design process of mechanisms is important for finding applicable solutions. For this purpose, the method of principal vectors is investigated, showing a compact notation of the angular momentum with respect to the center of mass. The moment-balance conditions are derived for three links in series from which balance solutions are synthesized and illustrated. The application for moment balancing of a 4R four-bar linkage is shown.

In this paper, a device based upon a specific cable-driven parallel mechanism to interact with hemispherical surfaces is proposed and investigated. This device could be of use in, for example, the automated cleaning of glass domes. Because the cables move on the hemispherical surface, they are curved. A method is developed to calculate the inverse kinematics and the workspace of this mechanism. This method and device are applied to and evaluated for an example of a large glass dome, showing its potential for this purpose.

Due to its anatomic structure, the wrist is often considered the most complex joint in the human body. Despite extensive research, it remains controversial how the carpal bones interact to provide our hand with mobility, precision and strength. We applied a method for the design of cam-and-follower mechanisms to in-vivo measured data of carpal bones. The measured input data comprised the surfaces of three carpal bones (scaphoid, lunate and capitate) as well as eight poses of these bones throughout the range of motion of the hand. The resulting points on the envelope surfaces of the first two bones well approximated the surface of the latter one. This method is novel in the investigation of bone interaction since it correlates measured bone motion to bone geometry. It can be applied to adjacent bones in any joint without modification. The results are furthermore promising for the estimation of the contact area between adjoining bones.

In this paper a locomotion system kinematic analysis is presented in order to obtain the knee motion equations for a child walking. With these equations a modular knee orthosis with flexible elements was designed and simulated through finite elements analysis with ADAMS. The whole human locomotion system is analyzed. Based on these results a modular knee orthosis prototype for a 7 years old child with locomotion disabilities was fabricated. The prototype was evaluated through experimental tests with CONTEMPLAS motion analysis equipment.

In this paper we present the kinematics model of a biomechanism which represent the legs of a four legged mammal. The anterior and posterior legs are realized as plane mechanisms, with articulated bars. Each anterior leg has a complex structure with three closed contours, mean while each posterior leg has only two closed contours. Each mechanism is actuated by an electric motor. The geometric and kinematics modelling of the anterior leg mechanism is achieved by means of some vectorial and scalar equations. Also, the kinematics simulation is achieved by means of Msc.Adams software, considering as basis, the upper platform of each mechanism.

In this paper a cable-based system is presented for rehabilitation of the wrist movements. The proposed structure consists of one or two cables that allow the movement of abduction-adduction and flexion-extension with different limits of movement and speed. The development of this robotic device is justified by the large number of people with upper limb problems. It starts with a study of the basic movements of wrist joint and the structures actually in use. The graphical simulations of the cable-based parallel structure for rehabilitation of the wrist movements are presented showing the viability of the proposed structure. Finally preliminary experimental tests are presented.

The objective of this study is to simulate the Stand-to-Prone-to-Aim task of a soldier using a full-body, three dimensional digital human model. The digital human is modeled as a 55 degree of freedom branched robot. Six degrees of freedom represent the orientation and position of the pelvis coordinate frame of the digital human and 49 degrees of freedom represent the revolute joints which model the human joints. Motion is generated by a multi-objective optimization approach minimizing the mechanical energy and joint discomfort simultaneously. The optimization problem is subject to constraints which represent the limitations of the environment, the digital human model and the motion task. Design variables are the joint angle profiles. Using the given method, we can predict a realistic motion for the “Stand-to-Prone-to-Aim” task. We are also able to very well predict the “Natural Point of Aim” for this task which is validated (along with other determinants of motion) and matches very closely with the experimental data which is motion captured in the VSR Lab at the University of Iowa. Inevitable transfers of weapon as an external object between the two hands have to occur in performing this task. Collision avoidance of the rifle with the hands and body during these rifle transfers is a very challenging constraint that has been implemented. These collision avoidance modules use compound primitives such as finite cylinders and finite planes whose edges are smoothed out in order to have continuous gradients for the collision avoidance constraint.

This paper presents an experimental characterization of human locomotion by a cable-based measuring system, namely CATRASYS, which has been designed and built at LARM (Laboratory of Robotics and Mechatronics). With CATRASYS, trajectories of the human limb extremity and its orientation have been characterized by lab tests during walking. Forces that are exerted by a limb of the experimental subject against cable sensors have been measured as well. Based on experimental results, modelling and characterization of the walking gait has been proposed in this paper.

Two main difficulties are presented when a study of muscle forces is carried out. First, the complexity of modeling muscle behavior. Second, the impossibility of measuring all the needed parameters in order to tune the model for a specific subject. Since the first problem has been widely studied the aim of this work is to propose a new approach to estimate muscle parameters in a non-invasive way and with no additional measure. Thus, a general methodology to estimate parameters valid for any task is proposed. A particular task is performed in order to compare different set of parameters and to validate the new approach. Results show a good agreement between the forces got with the new set of parameters and the EMG records.

Sit-to-Stand can be considered the most common operation that can be performed in daily life. Standing up is a complex task characterized by the transfer from one stabilized posture to another with movement of 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 trunk. The trajectory of the COG is characterized by a movement forward and then backward with simultaneous vertical displacement. Consequently, the entire movement requires a strong coordination between posture and movement. In this paper an experimental procedure is described to track and record point trajectories and the orientation of the trunk during the sit-to-stand. This analysis will be used to get information for further design of novel assisting devices. Then, design requirements are given according to the numerical and experimental results.

The use of robots that share their workspace with humans in cooperative tasks, involves new risks for human safety. To ensure safety of the user, flexible robots and variable stiffness actuators are growing in interest. In this paper, a dynamic model of the collision between a 1 d.o.f. robot arm and a human head is presented. This model incorporates the many times neglected link and gear transmission flexibility. The contribution of the link flexibility and the variable stiffness actuator to human safety and to robot joint protection is evaluated. The head injury criterion and fracture force of cranial bones have been used as safety criteria for the human head.

The paper analyses the conditions imposed on the relative positions of two parts which must be assembled by using robotic insertion. The relations that have to be satisfied by the axes of the parts to be assembled and the requirements imposed on the robot are established. Based on the conditions imposed on the relative positions of the axes of the parts to be assembled by insertion, the requirements that the assembly robots must meet have been determined. The influences both of the positioning errors and of the orientation errors of the robot on the execution of the assembly operation have been analysed.

The paper focuses on the accuracy improvement of geometric and elasto-static calibration of industrial robots. It proposes industry-oriented performance measures for the calibration experiment design. They are based on the concept of manipulator test-pose and referred to the end-effector location accuracy after application of the error compensation algorithm, which implements the identified parameters. This approach allows the users to define optimal measurement configurations for robot calibration for given work piece location and machining forces/torques. These performance measures are suitable for comparing the calibration plans for both simple and complex trajectories to be performed. The advantages of the developed techniques are illustrated by an example that deals with machining using robotic manipulator.

In this paper a novel strategy to construct a dynamically equivalent model of a biped robot is proposed. The model is composed by four point masses, one at the hip, one at each leg and one at the group composed by the head, arms and trunk. The masses are located at the center of percussion of each group. The method to obtain the equivalent model is described, and such a model is obtained out of a biped with parameters close to a human being. Once the equivalent model is obtained, it is validated by performing a decoupling of the dynamics of the biped and testing it using step inputs. The decoupling is done using the information provided by the equivalent model. Finally with the decoupled dynamics, the undamped natural frequency of each group (they are the both legs and the head, arms and trunk group) is calculated to confirm that each controller behaves linearly.

The collision is an obvious phenomenon in many mechanical systems such as mechanisms with intermittent motion, kinematic discontinuities and clearance joints. As a result of an impact, the values of the system state variables change, eventually looking like discontinuities in the system velocities and accelerations. The impact is characterized by large forces that are applied and are removed in a short time period. The numerical description of the collision phenomenon is strongly dependent on the contact-impact force model used to represent interaction between the system components. The model for the contact-impact force must consider the material and geometric properties of the colliding surfaces, information on the impact velocity contributes to an efficient integration, and account for some level of energy dissipation. These characteristics are ensured with a continuous contact force model, in which the deformation and contact forces are considered as continuous functions. Thus, the main purpose of this work is to present a study of the contact force model on the dynamic response of mechanical systems. Impacts within a revolute clearance joint in a four-bar mechanism are used as an example to compare different contact force models.

It has been recognized by many theoretical and experimental investigations that the constitutive contact force law considered to model and analyze contact-impact phenomena is of paramount importance in the prediction of the dynamic behavior of mechanical systems. The main goal of this work is to present a numerical and experimental comparative study on different compliant contact force models. The contact force models utilized in this study are based on the classical Hertzian contact theory, which is augmented with damping terms to accommodate the energy loss during the impact process. The classical impact between a steel ball and a massive surface is used as the demonstrative example of application. The influence of the initial impact velocity and coefficient of restitution is also studied throughout this work.

Suspension condition has a direct influence on the behavior of brakes, direction, stability, etc., on a motor vehicle and right operation of the car depends directly on the fatigue suffered gradually during the service life. Nowadays, there is no evidence of any regulation testing the suspension system in the homologation process of a vehicle. Inspection and verification of vehicle suspension conditions is carried out by Periodic Motor Vehicle Inspections (PMVI’s). The aim is to determine the suspension system performance. It is not possible to remove parts of the vehicle and the inspection must be rapid and reliable. Currently, there are suspension benches whose results and rejection criteria are not suitable. This has been already demonstrated by several authors as Dr. Velasco (Criterio de inspección en bancos de ensayo del sistema de suspensión de un vehículo automóvil. Tesis doctoral, Universidad Carlos III de Madrid, 1997) and Dr. Calvo (Determinación de un criterio de inspección para verificar el comportamiento dinámico del sistema de suspensión de un vehículo automóvil. Tesis doctoral, Universidad Carlos III de Madrid, 2003). With the current methods of inspection, test results may be significantly altered by some factors such as tyre pressure inflation, the value of the suspended mass and non suspended mass. This paper proposes a method to determine the fundamental characteristics of the suspension system of a vehicle, i.e. stiffness and damping of the suspension. It also can be applied without removing any part during PMVI’s and in a reasonable time. Thus, the values of the masses, conditions, type of tyre or the tyre pressure inflation would not affect the test result. From this point of view, it is possible to define a suitable and objective rejection criterion in PMVI’s.

Input Shaping is a feedforward technology that do not induces unwanted dynamics for systems described by ordinary differential equations. This work examines the issue of Input Shaping for multibody oscillatory systems described by differential algebraic equations (DAEs). A Double Pendulum has been choosed as show case, because this multibody system without flexible bodies exhibits two oscillatory modes that Input shaping might cancel. Firstly, the constraint equations corresponding to the prismatic and the two revolute joints have been formulated. Thus the Jacobian corresponding to those equations has been carried out. Customary techniques for the numerical integration of the Differential Algebraic Equations formulated with basis in the Jacobian plus Lagrange multipliers to model the contact forces were developed. The response to a white noise feed into the trolley driver variable was obtained by undergoing such numerical integration. The time response to the white noise corresponding to the orientation of the local axis of each link was collected. Thus the FFT of both time signals allows the experimental estimation of the natural frequencies associated to both modes of vibration. Finally a two mode Input Shaper has been designed for the multimode system. Several comparisons were presented for the shaped and unshaped responses. Input Shaping a type of Finite Impulse Response (FIR) Filtering performs well for mitigating the oscillations. The difficulties to prove this statement, facing with DAEs, have been overcome by this novel work.

This paper presents the derivation of the torsional receptances for a universal joint. The joint is modeled as two inertias connected by a massless cross-piece. The equations of motion and resulting receptances reveal that the universal joint may be represented as a variable inertia. The inertia is a function of misalignment angle and angular position. It is shown that the inertia variation may be approximated by a second order cosine for typical misalignment angles. Systems with variable inertia are known to exhibit non-linear vibration behaviour.

The deployment of a virtual implementation of a Hexaglide type parallel robot in the LinuxCNC machine controller running on RTAI RT Linux is presented and assessed. This HiL simulation is used to safely test different experiments and control algorithms before deploying them on the real system. State of the art algorithms to efficiently perform Real-Time system’s state integration are presented. The symbolic library LIB3D_MEC-GiNaC has been used to generate and adapted to automatically export the matrices required by the different algorithms. Three different parametrization strategies are implemented and compared. Performance improvement due to optimization by atomization are also reported. Excellent (under 10

− 5

s) Real-Time performance is achieved on standard off the shelf hardware.

This paper presents an analysis and simulation of the dynamic behavior of an electric vehicle.Governing dynamic equations are formulated and a three-dimensional prototype is built, which allows the collection of data on mass and inertia of its components.All these variables are implemented in a Multibody System (MBS) model.This model is analyzed by using SimMechanics, a tool for MBS analysis.Some of the results of this analysis are used as an input to simulate the suspension system in detail.The main contribution of this paper is the proposal, once validated the model, of a modification in the distribution of mass of the vehicle which improves its dynamic performance.Moreover, due to the integration of this model in MATLAB/Simulink environment, it is possible to add control systems properly, such as electronic stability control and autonomous control.

High-lift devices of transport aircraft reshape the wing in order to increase the lift during certain portions of flight. They are moved by complex mechanisms. To simulate the behaviour of high-lift devices under aerodynamic loads an elastic multibody model is developed that comprises the flap and slat mechanisms and an elastic wing structure. Elastic bodies are described by finite element models that are integrated into the multibody formulation by modal approaches. Simulation examples show applications of the model for the analysis of critical load cases.

In this paper a centralized non-linear model predictive control (NMPC) for redundantly actuated Parallel Kinematic Machines (PKM) is proposed. The controller has the structure of an augmented PD controller with variable gains. These gains are intended to minimize the future tracking error. With this approach the computation error is kept low. To emphasize the robustness of the method, experiments with a planar 2DOF redundantly actuated PKM with industrial torque motors are presented.

Wire-based Stewart-Gough platforms are known to allow fast movements of the end-effector. But as for every robotic system, their performance and energy efficiency can be optimized by the generation of end-effector trajectories suited for that particular robot type. In this contribution the optimal control strategy is applied on an innovative wire-based storage-retrieval machine in order to design time, power and energy optimal trajectories.

This paper presents the special low-level control model for, (inc.), mechanical systems that allows avoiding of building sophisticated mathematical models of the whole controlled system. The proposed model also allows to improve adaptation using additional weight values (probability and predicate). Recommendation for application and effect estimation of the model are given on high level of abstraction, without influence of realization-specific problems.

The public urban bike services demand more robust mechanical devices to resist misuse and vandalism. An innovative wheel hub integrated bike brake was designed making use of CAD-3D and numerical analysis tools and considering both technological and economical criteria. Unlike the other existing hub integrated bike brakes, the new design ensures an homogeneous pressure distribution on the braking pads, which maximizes its lifespan, reduces the maintenance costs and guarantees an uniform performance along the brake lifespan. As the other existing hub integrated brakes, the new design is very compact, robust and low sensitive to adverse environmental conditions and dirt.

This article starts from the structural analysis of a specific spatial gripping mechanism used in wood harvesting heads. This mechanism adapts the pressure direction to the trunk diameter. Considering particularities such as the symmetry plane of the mechanism and the actuator location, a structural synthesis is performed to find all the joint combinations allowing such an adaptive gripping behavior. Finally, nine innovative equivalent mechanisms are generated and represented in 3D. A critical review of the found solutions is established to identify their respective advantages.

A non-contact linear mechanism based on stable superconducting magnetic levitation with a long permanent magnet as a slider and two fixed superconducting disks which define the slide way has been designed, built and tested. The slider can be moved stably along a stroke of 11.5mm by supplying a low current in the coils located at the end of the stroke. The levitation remains stable thanks to the superconductor disks providing a reliable mechanism for linear displacement in a cryogenic environment. The response is linear with a sensitivity of 522m/mA for displacements lower than 6mm. Pitch, yaw and roll have been measured demonstrating an overall good performance. Roll and yaw were always below 300rad, that is one order of magnitude lower than the pitch (4,500rad). A decrease of the pitch has been obtained by modifying some geometrical parameters of the mechanism.

Traditional techniques of endoscopy based on flexible endoscopes are fairly reliable but poorly tolerated by patients and do not give access to the small bowel. It has been demonstrated that magnetic fields are usable for manipulating an untethered magnet, either using fixed coils or mobile permanent magnets. We introduce a novel approach for magnetic manipulation and present the preliminary results obtained by simulating a planar manipulation system including multiple mobile coils.

The problem of increase robots autonomy is discussed in relation to general design issues. The properties of biological locomotion are shortly discussed and compared to their technical analogies. The examples of biologically inspired solutions used in robotics are given. The factors limiting the autonomous robots development are characterised. The motion properties of animals with simple and more complex body build are summarised and the features of legged robots are related to it. The biological rolling – and technical wheeled locomotion are discussed. The paper is concluded by discussion of future developmental needs in robotics.

Besides conventional lectures and exercises, application focused training provides an excellent opportunity to enhance understanding of mechanism theory. At RWTH Aachen University such training in the form of practical courses is part of the curriculum for students of mechanical engineering. This paper presents a concept for this kind of courses. At the application of cup-holders students perform hands-on analyses of the mechanisms in order to comprehend their kinematical structure and behavior. Based on this, diverse modeling approaches are used to illustrate different aspects of kinematics and design.

In an attempt to improve the way students prepare for industry a 3rd year mechanisms and multibody systems class was given an assignment with a non-traditional scope and marking guide. Although the team based assignment, like those of prior years, involved mobility analysis of real historical systems in the form of a formal report, it was proposed that the assignment be marked to industry expectations. This meant 100% if the conclusions were satisfactory and 0% if they were not. This experience produced many interesting outcomes and these are discussed. The paper describes the process that led to the implementation of this new assignment structure. The methodology used in its development and reflections of both the authors and the students are discussed.

Engineering education is a fruitful research issue due to the evolution produced in the Universities. The design and analysis of real mechanisms enhance the skills and knowledge acquired during the Mechanical Engineering degree. This paper show a teaching methodology based on the development of individual project and how it improves the students’ competences. We propose the design of an impact machine, because it is a multidisciplinary problem. To model the mechanism, a 3D Computer Aided Design software was used. This software helps to understand the mechanical system and the components involved in its assembly. The simulation of the movement and the working conditions are compared with a theoretical model. The understanding of this software is very important for professional engineers.

Max Kohl Company, in Chemnitz (Germany), was a manufacturer of educational mechanisms that were distributed all around the world. In the early twentieth century, the University of Salamanca (USAL) bought some of them for the Engineering School of Béjar. Now, this collection of mechanisms is being restored by a group of professors of the Engineering School. The mechanism characterization was carried out with the help of Max Kohl Chemnitz catalogues. This initiative and other are being discovered by researchers working in the European Project thinkMOTION. The thinkMOTION Project aims to create the world’s largest open-access digital library of content in the field of machines and mechanisms. This paper shows brief descriptions of some the mechanisms and the way they look like once they are uploaded to the digital library.

In 2005, in the library of the Applied Mechanics room there were found 14 worksheets titled

Work Process of Steam Engine

by Professor V. Grinevetsky, Rector of Imperial Moscow Technical School (former name of the Bauman Moscow State Technical University). In the early years of Imperial Moscow Technical School (IMTS), the course of

Thermodynamics and Steam Engines

was lectured by the academic staff of its Applied Mechanics Department. Their research task was to trace Grinevetsky’s career as a scientist and his relations with the Department of Applied Mechanics. This article describes the results of such research efforts.

CaPaMan (Cassino Parallel Manipulator) has been developed as novel parallel architecture with mechanically robust design and user-friendly operation. It was conceived in the early 1996 at LARM in Cassino and since then it has been continuously improved in operation and design as well as it has been applied in different applications up to the today solutions. The paper illustrates historical evolution of CaPaMan designs with their characteristics also for future developments.

Nowadays, the Kinematics science may become less important in some fields, nevertheless it is more preponderant in others. The paper focuses on the incipient stages of the Kinematics science, tries to investigate the factors that led to its formation, and emphasizes the influence of organizing thinking in this process, but it does not fully interpret the historical moment. Ampère is considered to be the man who founded Kinematics as science. Therefore, our analysis is mostly oriented towards one of Ampère’s work –

Essai sur la philosophie des sciences

–, where he lays the foundation of

Kinematics of Mechanisms

. We also debate the meanings of some expressions used over time to denote the speed ratio of different points of a mechanism, ratio which is also reminded in Ampère’s work.

Some ancient mechanical clocks were able to indicate moon phases in addition to telling time (its usual labour). This article, which is a contribution to industrial archaeology [1] and machines history, exposes a mechanical solution that Fernando de Tapia y Castilla (1749–1841), famous clockmaker from Alcalá la Real (Jaén, España), developed in 1810 to get an higher precision in moon phases indicator than in other mechanical clocks before. This new method was published in his “

Nuevo método sobre el modo de poner la luna en toda clase de reloges de ruedas con exâctitud y sin el herror que hasta ahora se ha observado. Por un ingenio Español aficionado a esta profesión. Año de 1810

”.

The mathematical model of spindle optimization design is established by analyzing the spindle’s structure and the situation of deformation under load in the course of working. Aiming at the problems of traditional optimization design method, this article applies genetic algorithm, uses real number code rule and evolving genetic algorithm to optimization design the spindle. In the platform of VC++, the Machine tool spindle optimization design system based on genetic algorithm can be built by using C++. Through the example design and result analysis, the Machine tool spindle structural parameters using the optimization design method of the Machine tool spindle based on genetic algorithm is realized with the advantages of excellence and reliability, which shows the benefit and applied value of genetic algorithm used in the spindle optimization design.

In this paper, changes in the stress and strain states generated in elements fitted during the assembly process of a press fit by axial shaft insertion have been analyzed. The influence of material yielding resistance, using the von Mises criterion, on such changes has been studied. Besides, the minimum force needed for full assembling has been determined, finding that the value of such force can be lower than the one obtained theoretically, what could modify the working conditions foreseen in design. Simulations are based on the finite element method (FEM).

This paper proposes the design of a simple mechanical clutch with multiple functions. This type of clutch combines the safety and elastic function of the clutch. The constructive design must be correlated with the technological one. Thus, it is possible to obtain mechanical components with reduced building limit and weight, with high durability and low cost. The use of the clutches is determined by the machine’s characteristics and kinematic chain where the clutch is placed, respectively the operating mode of the motor engine. The clutch will take constructive and functional deviations, shocks, and tensional vibration. This paper presents the design and the generation of the clutch; the geometrical model and the moment of torsion of the clutch are determined. The static characteristic of the clutch, obtained experimental, emphasizes the role and importance of the clutch in mechanical transmissions.