New Advances in Mechanism and Machine Science

In the paper a new concept of a pseudo-equatorial type 2DOF solar tracking mechanism is described. The mechanism is of parallel linkage type based on two kinematic constraints revolute-sphere (RS) which determine an 1 DOF planar loop RSSR with a passive rotation of the coupler. Two translational actuators directly linked to the frame are used to drive independently the planar loop motion and, respectively, the coupler passive rotation. By their independent motions, the elevation and diurnal angles of the solar active surface fixed on the coupler are independently modified. Tracking performances during the year and on different latitudes are analysed in the paper. In any case the daily tracking efficiency in receiving the direct solar irradiance is higher than 93%.

Design of the gravity balancer prototypes based on the modified Scotch yoke type spring mechanism is presented. Followed by the brief description of the conceptual design and validation of the method, design of a one degree-of-freedom (dof) rotary system is proposed. In the 1st generation prototype model, the spring-gravity system is designed as a whole, while, in the 2nd generation model, the gravity balancer is designed as a modular unit for easy adjustment and simple replacement. The friction force due to the prismatic joints of a Scotch yoke derivative mechanism for the latter model has been greatly reduced by using a bushing bearing along with a guidance pole. As a consequence, by showing the equilibrium of the rotary system being sensitive to the fine-tuned position of the end-effector payload, the 2nd prototype model successfully demonstrates the gravity balancing capability of the entire system at all configurations within its range of motion. The issues related to the design of the one-dof gravity balancer are discussed, and the potential use of such balancers in the multiple-dof system is also proposed.

In this paper, a new method is proposed for structural synthesis of planar closed kinematic chains with all the possible kinds of multiple joints according to given number K-independent loops up to maximum multiple joint factor V_max(K). At first, the new procedure for structural synthesis of non-fractionated and fractionated multiple joint kinematic chains based on the combination of corresponding simple and multiple joints is presented. Then the atlas database with all the possible kinds of multiple joints containing various 24 (case K = 4) multiple joint non-fractionated and fractionated structures is established and illustrated. Next, all the possible multiple joint assortments ([M.J.A.]) for non-fractionated as well as fractionated 10-link 1-DOF multiple joint kinematic chains with up to pentagonal links with K = 4 and up to V_max = 6 are synthesized and separated for the first time. Finally, the complete structural analysis of multiple joint kinematic chains for industrial application in 10-link manipulators designed from the atlas of synthesized multiple joint kinematic chains is conducted.

Having in mind that humans use non-verbal communication extensively is very important to enable social robots with this capacity. There are two basic ways how it can be expressed. First one is by facial expressions by appropriate moving face parts, like eyebrows, eyeballs, eyelids, lips, either as manufactured real parts or by presenting them on screen—combining them is also possible. The second way of non-verbal communication is by gestures. This paper presents the kinematic-dynamic analysis of shrug mechanism for humanoid robots. Based on the set requirements, the cam-worm mechanism that has 1 DOF and enables the simultaneous shrug of both shoulders is proposed. It consists of a worm which is meshed with two worm gears whose directions of rotation are opposite and the two cam mechanisms whose input links—cams, are rigidly attached to the worm gears. Within the kinematic-dynamic analysis, the cam profile and the worm parameters are defined and the torque on the cam/worm gear and the driving torque of the complete cam-worm mechanism are determined. The cam mechanism has a high efficiency in all positions because the values of the pressure angle are within the prescribed ones during the entire movement. Worm mechanism enables a significant reduction of the driving torque and has acceptable efficiency. The rotation range of worm gear/cam is small and the movement of mechanism is very fast wherefore the shrug speed is large, which was one of the main requirement for realization.

Significant aspect of the socially interactive robots are eyes which present the most expressive part of the face, especially when it is rigid as is the case with majority of the robots. For this reason to the design and realization of the eyes a particular attention should be dedicated. This paper presents the drive system of the robot eyeballs and eyelids with 8 DOFs. Eyeballs drive system has 4 DOFs and consists of two symmetrical planar mechanisms that enable independent motion of the eyeballs about the yaw axis—abduction/adduction movements and two identical spatial mechanisms that enable independent motion of the eyeballs about the pitch axis—elevation/depression movements. Eyelids drive system has 4 DOFs and consists of four structurally equal spatial mechanisms that enable independent motion of each eyelid—mechanisms for driving the upper and lower eyelids, respectively, are symmetrical. Based on the kinematic analysis, motion simulation of eyeball and upper/lower eyelid is performed. Velocities of the eyeball/eyelids movements are within the parameters of the human eye. The structure of the eyeballs drive system is such that enables inserting the camera directly into the eyeballs. In this way it is possible to achieve some of the functions of robots artificial vision such as recognizing objects, distance estimation etc.

The purpose of the research is to develop a numerical method for the kinetostatic analysis of linkages that guide the rear beam axle of some road vehicles (mainly, commercial and off-road vehicles). The study is performed in two distinctive stages, which are then integrated in an unitary numerical algorithm, with the aim to evaluate the way in which the suspension system behaves under various loading states. For beginning, the static equilibrium of the suspension mechanism is expressed by considering the external loads and the reactions that occur in the force generating elements of the suspension system, depending on the linear and angular deformations of these flexible (compliant) elements. In the second stage, the kinematics of the suspension mechanism is performed by an original analytical algorithm, with the aim to establish the variations of the global coordinates of the design points that are used to express the linear and angular deformations of the compliant elements. Then, the two algorithms are coupled in an optimization problem that intend to determine the value(s) of the independent kinematic parameter(s) for which the minimum value of the static equation is reached.

The paper uses as forces transmission quality index the coefficient’s determinant of the system serving to static analysis without friction. Then it does the connection between this determinants value and the configuration parameter, expressing the length between exterior joints centres. Aided this length, the conditions for a favourable transmission regime, it formulates. It formulates also the driving link rotatability condition for the simplest mechanism, containing the 0/4/2 structural group.

The paper analyzes the structural and geometric-kinematic aspects of the articulated bar mechanisms used to actuate the doors of urban buses. A mechanism of this kind consists of two main parts: the control mechanism mounted under or above the door, and the crank-slider final mechanism which actuates the folding doors. The analyzed mechanisms have in their structure simple dyad chains or complex chains of triad type. For these types of planar linkages that are equipping the urban buses, the topological and geometric structure is analyzed in order to find solutions to minimize the swept volume of them.

The paper presents the method of geometrical synthesis of two new kinematic schemes of articulated planar mechanisms used to actuate the urban bus doors. The stages of solving geometrical synthesis for the two and three relative-associated positions of the bars articulated to the body are performed. In order to optimize the geometric synthesis and to avoid the mechanism stalling, the limiting of the pressure angle is required. One of the two proposed mechanisms has kinematic chains of dyad type in its structure, and the other mechanism also includes a triad-type kinematic chain. The new solutions have a smaller swept volume regarding the control mechanism.

The paper presents three kinematic schemes of planar mechanisms with bars used to open/close a cabinet (buffet). The mechanisms are mounted on the left and right walls of the cabinet, working in parallel, in a vertical plane. Both mechanisms are hinged to a single door that swings 90° in a vertical plane from a vertical position (closed) to a horizontal position (open). The three kinematic schemes proposed for door actuation have in their structure either only revolute joints (RRRR) or revolute and prismatic joints in the variants RRTR and RRRT. To each of the three kinematic schemes of mechanisms, an analytical method of geometric synthesis for two and three associated positions has been presented.

Comparing with three-translation Delta Parallel Mechanisms (PM), 4-DOF three-translation and one-rotation (3T1R) PMs have complex topological structures, which result in complex forward kinematics and inverse dynamics solutions. Therefore, the investigation of novel 3T1R PMs with simple forward kinematics and dynamics solutions is still not completed yet. Coupling degree reduction of a PM can directly reduce its complexity of forward kinematics and dynamics. By using coupling-reducing methods proposed by authors, five original 3T1R PMs with coupling degree 2 are analyzed, which lead to ten novel 3T1R PMs with coupling degree 1 while their basic function, such as DOF and output motion type of the moving platform, stay same. Thus, the forward kinematics and inverse dynamics solutions of the ten 3T1R PMs can be easily obtained by using one dimensional search method or by solving a one-variable polynomial equation.

This study aims to present a new virtual model of an elbow prosthesis with as few components as possible, having a simpler technological approach which can be an important base for the study of the complex behavior of the elbow joint. The prosthetic system is of spherical type consisting of three parts: a part implanted in the humerus, a part implanted in the ulna bone and a third part transforms the assembly from an unconstrained prosthesis in a semi-constrained prosthesis. The kinematic simulation of the flexion-extension and pronation-supination movements of the spherical prosthesis—joint assembly was performed. The virtual model is designed in Solid Works software. By using the finite element method, the healthy elbow joint and the prosthetic elbow joint assembly were analysed and the comparative diagrams of the maximum stress in healthy elbow joint and in prosthetic elbow joint concerning the flexion-extension and pronation-supination movements were drawn and analysed.

Spinal deformities appear very frequently in child or adult population. Researches in this field are widely spread and continuously developing now-days, as the current schemes of treatment are long-lasting, costly and not very effective. The authors propose an investigation method based on a set of sensors, which are accelerometers and provide data in order to generate a mathematical model of the spine, namely a high degree polynomial. Basic parameters, such as the Cobb angle are computed within the mathematical algorithm. The angles acquired by the sensors are recorded as functions of time, so that the change in shape of the spine during the exercises prescribed by the kinetotherapist is subject of study and a criterion for optimizing the nature and intensity of the exercises.

This paper presents the kinematics of modular a parallel robot for post-stroke rehabilitation of elbow and wrist. The targeted motions for rehabilitation are: elbow flexion, pronation/supination, flexion/extension and adduction/abduction (radial/ulnar deviation) of the wrist. The kinematic structure of the robotic system is presented starting from general considerations concerning the rehabilitation protocol of the upper limb. Its kinematics is developed and simulation results are presented for a proposed training exercise.

Stroke is one of the major causes of disabilities among elderly people which have a negative effect on the life quality and independent living. Robotic assisted rehabilitation enable physical therapists to create patient oriented, individual therapies aiming to achieve high level of recovery for the motoric lost functions. However there exists no standardization in the design of such devices. This paper presents a set of critical design characteristics and constraints for rehabilitation robotics. Based on this data an innovative spherical robot for shoulder rehabilitation is presented. Its workspace modelling and trajectory simulation illustrate the robot capabilities of performing from simple to complex trajectories having a high degree of universality for the given task.

The paper presents research on one DOF (Degree of Freedom) hip joint of an exoskeleton regarding the possibilities and effects of rotation axis misalignment in the hip joint. By rotation axis misalignment, we understand the difference of alignment between the hip joint axis of rotation in human and exoskeleton; we also consider only parallel, not angular axis misalignments in our model. The proposed approach for the development of exoskeletons is to take into consideration inherent axis misalignments and analyze the possibilities to reduce their effects on the ergonomics of the device. The first step in this approach is the quantification of effects of rotation axis misalignments in exoskeletons and to achieve this, we developed the kinematic model which is presented in this paper. Most approaches focus on perfectly aligned axis of rotation, while this is not the case in our study, we focus on an acceptable misalignment for the user.

In this paper a locomotion system kinematic analysis is presented in order to obtain the hips, knees and ankles motions equations for a child walking. With these equations an experimental test bed was especially designed and simulated for locomotion rehabilitation by using MSC Adams. The whole human locomotion system was analyzed from kinematic viewpoints. Based on the obtained results a locomotion rehabilitation test bed prototype for a 7 years old child with locomotion disabilities was fabricated.

The paper discusses design requirements and presents a leg exoskeleton for human rehabilitation purposes. The exoskeleton is based on an underactuated mechanism to achieve a leg walking motion with desired human-like behavior. A design solution with appropriate parameters is presented with its peculiarities and the operation performances are characterized via a dynamic simulation.

This study presents the authors research to develop a powered wheelchair for disabled people. The wheelchair is intended mainly for use in buildings area. The proposed solution for the wheelchair propulsion uses a chain transmission for each wheel and two motors. The benefits of the chain transmission, from ergonomic aspect is that they ensure the wheelchair folding for easy transportation with a vehicle and allows the motors placing in the front, thus providing better stability to access ramps and for climbs. From dynamic perspective, implementation of a chain transmission in the wheelchair propulsion, improves dynamic performances by multiplying the torque. Simulations performed in ADAMS reveal optimal performance of the wheelchair. Based on the proposed design of the wheelchair a prototype is manufactured and are presented experimental obtained results for motion analysis.

Assessing the posture of the human body in real time is a great challenge, given the alarming increase of diseases in the bone system, in general and of the spine, in particular, generated by the adoption of inadequate positions in the current activities. Knowing the posture of the spine can help the doctor in preventing or diagnosing a disease and designing a customized treatment. The data presented in this paper is part of the research carried out in the SPINE project [13]. The aim of this paper is to present a methodology for the reconstruction and visualization of a human spine, i.e. calculating the positions and representation of vertebrae in 3D format, using mechanical software applications.

In this paper, a neurorobotic robot ‘eye’ for investigating the neural control of eye movements is developed and the performance of a computational model of image stabilization based on the adaptive filter model of the cerebellum is evaluated. For in-depth analysis, the cerebellum microcircuit is investigated and bioinspired control algorithm is developed. Inverse oculomotor plant model is simulated on Matlab/Simulink; first using simple Vestibulo-Ocular Reflex model; then using a second order model with Model Reference Adaptive Control. In addition, the robot ‘eye’ is built as a camera mount gimbal system and its architecture is calibrated.

The ankle structure holds one of the most important role in the human biomechanics. Due to complexity of everyday activities this joint is the most prone to be injured part of the lower limb. For a complete recovery of the locomotor function, recovery exercises are mandatory. The existent ankle rehabilitation equipments allow only simple rehabilitation exercises, which cannot be used safely without the aid of a therapist. The introduction of robotic physical recovery systems represents a modern alternative to traditional recovery. Actuated devices are advantageous because they allow many types of exercises on same device, and also they accurate measure forces and angular motions. The purpose of this two part paper is to propose two rehabilitation devices, based on different actuating mechanisms. In this first part, structural synthesis, some kinematic and designing aspects of two new ankle rehabilitation devices are presented. The systems are based on the spatial four-bar and Scotch Yoke mechanism, respectively. As requirements for the proposed devices the following aspects have been considered: the systems must be easy to program, financially affordable and they need to offer the two movements (dorsiflexion/plantar flexion and inversion-eversion) required for a complete recovery of the injured ankle.

Ankle exercises are long-term and repetitive and cannot offer information about patient’s evolution. Due to these aspects a need for easy-to-use mechatronic devices emerges. The purpose of this two parts paper is to propose two rehabilitation devices, based on different actuating mechanisms (spatial four-bar and Scotch Yoke mechanism respectively). In the first part the structural synthesis and some kinematic aspects of the proposed devices have been presented. For the second part, 3D models and preliminary numerical simulations of the systems are performed. The simulation results are encouraging, both mechanisms covering all the required movements for a complete recovery of the ankle joint.

This paper outlines the potential of service robots as applied in frames of Cultural Heritage. Several applications are discussed such as inspection, searching/surveillance operations, identification, analysis, preservation and restoration of Cultural Heritage goods. Key design requirements are outlined for robots to be applied for servicing Cultural Heritage goods or sites. Related experiences at LARM in Cassino are outlined in order to clarify aspects of engineering feasibility and implementation.

This paper aims to demonstrate a systematic procedure for the structural selection and dimensional synthesis of the arm to be integrated into a mobile manipulator. The manipulator will be utilized for Bots2ReC H2020 project which aims at developing an autonomous robotic solution for removing asbestos contamination from real world-rehabilitation sites. The synthesis procedure is initiated by identifying requirements and constraints on the mobile manipulator. The Interactive Geometric Software (IGS) is used to carry out the preliminary synthesis. The synthesis procedure highlights the utility of IGS in developing the conceptual and dimensional design of the arm and assesses its performance to satisfy given requirements and constraints. Redundancy is used to meet the desired requirements while satisfying the constraints.

This paper present a novel design and a kinematic analysis of a variable neutral-line manipulator. Variable stiffness, as well as a high flexibility are the most wanted characteristics for snake like robots. In the last few years in modern medicine, Minimally Invasive Surgery played an important role. In endoscopic surgery or single-port surgery the main goals are: reducing the operative and post-operative stresses for the patients, fast healing process, reducing the number of days of hospitalization. The paper presents the design and some considerations of a snake like robot unit, followed by preliminary simulation of the proposed model.

For developing better walking machines researchers are studying different types of leg configuration. Among the variety of leg configurations designed and tested around the world there are few simple and single DOF leg mechanisms that offer a good and economical solution for artificial locomotion. These configurations were already successfully implemented in the structure of various walking prototypes. Choosing the best leg configuration for building a walking robot to ensure stability and certain step characteristics during motion, it can be done by analysing the kinematic characteristics and the path curve shape described by the end point. For this reason, three single DOF leg mechanisms configurations are chosen for being analysed and compared in terms of kinematic properties. Specialized mechanism simulation software was used.

This paper introduces a novel hybrid structure design that is composed of rigid links and cables for a robotic leg with static walking. The proposed mechanism is characterized by actuated hip joints, passive knee joints and an actuated prismatic foot joint. The foot is the moving platform of the proposed mechanism which possesses pure translational motion due to the passive parallelograms with cables. Kinematic analysis has been worked out for evaluating a typical human-like gait trajectory. A 3-D model has been developed and simulation are made in SolidWorks® environment. Simulation results show that the proposed mechanism is able to perform an ovoid walking cycle of a foot point and the computed actuator torques and forces are in a feasible range for a low-cost and easy-operation design. The simulation results will be used for a prototype construction in a future work.

In this paper, the authors present hexagonal and parallelepipedic modules used for reconfigurable mobile robots. These modules are equipped with types of wheels like the classic and omnidirectional type. By combining these modules the authors achieve multiple types of constructive solutions of wheeled mobile robots. By equipping the hexagonal modules with legs the authors propose new development direction in this domain.

In this paper is presented an analysis on velocity variation for an autonomous vehicle that is navigating in narrow environment and following a predefined path. The autonomous vehicle is based on an Ackermann steering model that can be simplified to a bicycle dynamic model. For safety navigation along the path the vehicle must taking into account the cinematic and dynamic considerations to avoid lateral slipping and rolling off. In a virtual environment, created with the use of the Virtual Robot Experimentation Platform, was simulated the way in which the Ackermann steering vehicle followed two predefined paths for which the turns have been smoothed by using clothoids as additional curves. The first path consisted in a linear segment, a turn and another linear segment, while the second path consisted in a turn and linear segment. The variation of the velocity was analysed for both scenarios taking into account that in the first one the vehicle accelerates on a straight line, while in the second one it accelerates while steering.

The aim of the present paper consists in presentation of new method of kinematical analysis of biplanetary gear. In particular, the method lies in preparation of chats of relative and absolute tangent velocities of particular gear parts. The algorithm is based on less complicated approach of determination of distribution of relative tangent velocities of wheels and arms of the considered gear. The obtained value of kinematical ratio was additionally achieved via other known analytical method, for comparison.

The wind/hydro energy conversion systems that integrate speed increasers are known on the market for more than half a century, the classical solutions with one rotor being currently widely implemented worldwide. The issue of increasing their energy performance is still of great interest, many innovative solutions being presented in the literature. A relatively new variant with high performances uses counter-rotating rotors and a speed increaser, being able to supply additional energy due to the use of a secondary rotor and a planetary transmission summing the input motions or torques and, consequently, obtaining higher power compared to a classical system with one input and one output. The solution of speed increaser with two independent inputs requires a complex control to correlate the power generated at the inputs to the generator requirements. A possible solution to avoid this impediment may be the use of a 1DOF planetary speed increaser with two inputs and one output, which sums the input torques and, thus, allows an additional supply of power compared to the classical turbines by using a secondary rotor that is kinematically dependent of the main one. Therefore, the paper is focused on determining the operating point (the parameters of the steady-state regime) for the counter-rotating turbine containing a 1DOF planetary speed increaser with two inputs and one output, considering the mechanical characteristics of the rotors and generator, and the transmission functions of the speed increaser established by taking into account the friction losses. Finally, the obtained analytical model is numerically simulated on a case study.

This paper presents a new pose parametrization technique based on n-th order Cayley transforms. Our study is built on the properties of maps that link the dual vectors with the special Euclidean displacement Lie group SE(3) and the Lie group of the orthogonal dual tensors. The resulted parametrization framework is complete and embeds multiple of the reported attitude parameterization Cayley maps, while extending them towards pose parameterization.

The paper presents the effect of dry friction upon the follower from a mechanism with rotating cam and translating knife edge follower. The contact between the ground and follower is regarded by equivalence as two non-conforming contacts positioned symmetrically about the symmetry plane of the prismatic pair, normal to the direction of velocity of the follower. There are discussed all possible contact solutions. An algorithm is proposed and verified concerning the identification of the actual contact case and the time when this position is reached. For an actual mechanism with imposed uniform rotational motion of the cam, there are found all reactions working upon the follower, for both assumptions: with and without dry friction.

The paper presents a solution for coupling two shafts with non-coplanar axes using an intermediary element. The intermediary part is connected with the ground via a spherical pair while, to the shafts, two point-surface contacts are used. For the proposed model, the positional analysis, a CAD model and numerical validation of the solution are presented. The advantage of the tetrapod coupling consists in constructive simplicity and controlled reliability by the possibility of replacing the higher pairs of the intermediary element with linkages with lower pairs.

Despite of some drawbacks (interference, small contact ratio) internal gears with small difference in numbers of teeth have some advantages, especially when they are used in hypocycloid mechanisms (high transmission ratio and high torque at small size). This paper is focusing on using these kinds of gears in mechanisms that are using the benefits of them. Some mechanisms converting rotary motion into translation and hypocycloid mechanisms will be discussed.

The aim of this paper is to determine the components of shot force at football. With this aim in view, there is proposed a simply device which can be used to determine the components of shot force. This device, having a simple construction, can be used personalized, determining both the force of the shot and the angle of the force vector. Using the relationships presented in the paper, the angular velocity of the leg can be also calculated during the shot of the ball.

In this paper, a novel robotic arm for LARMbot humanoid is designed as based on parallel-serial structure is described. The upper arm is a tripod parallel structure with 3-Degrees-of-Freedom that are actuated by linear motors, while the forearm is a serial link controlled by a single servomotor. The structure is characterized with its kinematics and a CAD design is proposed in order to test its functioning.

We propose a novel design of a parallel manipulator of Stewart Gough type for virtual reality application of single individuals; i.e. an omni-directional treadmill is mounted on the motion platform in order to improve VR immersion by giving feedback to the human body. For this purpose we modify the well-known octahedral manipulator in a way that it has one degree of kinematical redundancy; namely an equiform reconfigurability of the base. The instantaneous kinematics and singularities of this mechanism are studied, where especially “unavoidable singularities” are characterized. These are poses of the motion platform, which can only be realized by singular configurations of the mechanism despite its kinematic redundancy.

The paper propose an iterative method for computing the direct kinematic of a 3-RRPS manipulator by considering for each leg a rotary and a linear actuator. It was calculated the error due to difference between the computed mobile triangle vertices and its sides length. To identify the possible angles solutions, it was developed a special function that determine a threshold value applied to the calculated sides of mobile triangle, depending on iteration phases and manipulator dimensional values. The iterations steps lead to refine the range values of ψ angles and its inappropriate values removal. The method can be successfully used for the kinematic analysis of several structure types of legs, by preserving the distance between the connection joints with the fixed and mobile frames.

In this paper we propose a dynamic sliding mode control strategy for a cable-driven parallel robot. The proposed control algorithm provides stability of the end-effector for improving the robot performance in terms of tracking a desired path. A non-linear control technique is proposed for a robust management of uncertainty and error conditions. Numerical simulations have been carried out by developing a specific code which includes a graphical user interface for a user-friendly real time visualization of end-effector position as well as modification of the system parameters. Results of simulation for a dynamic model with sliding mode control are discussed for different trajectories applied for this robot, in order to confirm the validity of accurate tracking of a desired path. The effectiveness of the proposed robust control scheme is demonstrated through different simulation results.

The aim of the paper is to develop an optimization method of a spatial 2 degrees of freedom (DOF) parallel mechanism(PM) used for orientation of a solar panel. The purpose of the optimization is to define the right set of geometrical parameters of the PM that assure a correlation between the angular workspace of the PM with the relative angles of the sun (azimuth, elevation) between the winter and summer solstices. The spatial PM is actuated using three FESTO fluidic muscles and the corresponding kinematics of the PM have been included in the fitness function of the optimization. The numerical model of the angles of the sun between the winter and summer solstices has been developed as a scattered grid of angles considered for the city Cluj-Napoca.

In this paper are presented aspects concerning winding process of complex shapes products. The focus is related to the carbon fiber tensioning systems. The goal of the study is to obtain composite complex structures made of impregnated carbon fiber. In order to obtain a product with a good behaviour it is necessary to establish nominal values of the parameters and more important to keep them constant to different steps of the processes. A new system structure for the tensioning device regarding the hardware components and the software system will be presented.

In this paper are presented aspects concerning winding process of complex shapes products. The focus is related to the carbon fiber tensioning methods. The goal of the study is to obtain composite complex structures made of impregnated carbon fiber. In order to obtain an material with similar or better characteristics comparing with steel or aluminium alloy, the material properties must be constant. The carbon fiber density must be same in all points. Density is characterized by parameters like winding trajectory, resin quantity, fiber layers and especially carbon fiber tension during the winding process.

This paper intends to present an integrated program in order to put in connection ones of fundamental problems regarding 6R(RRR) parallel mechanisms: inverse kinematics (IKP), direct kinematics (DKP), mechanism workspace and singularities avoidance. Of course, this type of mechanism represents a subject of large interest in scientific literature, all of specific enumerated problems being exhaustively treated. In this context, ours paper character is only practical one. Being a versatile instrument, this approach allows the students (e.g.), without great amount of time consumption, to determine the mechanism workspace, to solve IKP for different imposed trajectories, to verify driving movements using DKP and to verify also the presence/absence of singularities inside mechanism workspace.

The paper proposes a device for finding the coefficient of rolling friction using a sphere in contact with the inner surface of a ring that rotates about a horizontal axis. The motion of the ball is characterized by the fact that for a stipulated rotation speed of the ring the centre of the ball executes a damped oscillatory motion and at equilibrium the centre of the ball is situated on different vertical than the one the centre of the ring is positioned. It is assumed that this feature is produced by the rolling friction torque that is proportional with the normal pressing force and the nonlinear differential equation of motion is obtained for the intended dynamic model. By the integration of the equation of motion there are confirmed the oscillatory motion of the ball and the eccentric equilibrium position and it is found a dependency of equilibrium position on the coefficient of rolling friction.

In this paper, a test bench for study the efficiency of spur gear is presented. Based on the proposed design scheme a virtual model of the test bench is developed in SolidWorks, both for manufacture and for simulation purpose. The main principle of the test bench it is that the load is performed internally on a closed circuit composed from two sets of spur gears, for that reason it is not necessary to use a brake system. Using a HBM acquisition system and strain gauge transducers it is established the experimental variation of the torque on the shafts of the gears. In this way is established the experimental efficiency of the spur gear set. The bench is designed into a modular design, for test can be used a set of different gear pairs with same axle distance.

In this study, a drill dynamometer for measure dynamic forces and torques, using strain gauge transducers has been designed, manufactured and tested. The dynamometer is connected to a HMB data acquisition system. Drill forces signal are captured processed and transformed into numerical data with the help of hardware and software of the MGC. Plus acquisition system. The principle of the dynamometer measurement is based on strain gauge transducers which measures elastic deformations produced by the loads. The elastic element used in the construction consists in a spoked wheel which measures simultaneously the force and torque. The elastic deformations produced by the force and torque, bends the double embedded spokes. It is presented the dynamometer design and principle of measuring. In order to verify the elastic element deformations, it is performed a FEA analysis in ANSYS. The experimental model is calibrated and in the final stage is made experimental measurements of drill force and torque.

This paper has as subject, in a first stage, the experimental study of dynamic friction coefficients between the links of a toothed chain (steel) and two chain guides, made from PAx and PA66, in lubricated conditions. Then there are highlighted the characteristics of the contact area between the toothed links and the guide fragments by using the finite element method. At the end of the paper there are presented the conclusions regarding the tests and the finite element modelling of the frictional contact between the chain link and the PAx.

The aim of this paper is to define and to analyse the theoretical contact forces that appear in a sprocket—silent chain joint. The contact force between the links and the teeth flanks of the sprocket can be considered as a reaction to the axial force (tensioning force) transmitted throughout the pins. The centrifugal force is considered to be constant and the friction between the elements is not considered. This paper is presenting an analysis of forces in the joints of links and between links and sprocket in order to establish a distribution along links and the influence of number of teeth of sprockets and centrifugal force on number of links transmitting the load.

One of the chain types used in machine construction is the bush chain. These types of chains can be with long or short links. In this paper it is proposed a case study, in which there is considered a standardized bush chain with short links, with known geometry of chain and sprocket. This is the starting point in the establishment of the contact between the sprocket and the chain during functioning. This will enable the precise determination of the static contact forces (value and direction). According to the literature, the pitch of a new chain should be bigger than its nominal value with up to 0.1%. In functioning, the pitch of the chain increases due to the wear of pin-bush joints and due to elastic deformation. This work proposes a comparative study of the most representative parameter, the contact angle (α) between the sprocket and the chain bush, for different sprocket sizes and different deviations of the chain pitch to the standard, which influence the contact forces and transmission behaviour. The evolution of the contact angle during gearing, in function of the sprocket’s number of teeth and the pitch difference (x), is highlighted with the help of the numerical simulations which permit drawing of some recommendations regarding the functionality of the transmission, minimization of vibrations or taking out the chain from functioning.

The paper analyses the way to increase the resistance of HCR external involute gearing from a scuffing point of view. The scuffing is the most important damage of teeth flanks of HCR involute gears. In the case of warm scuffing; it is the combined action of high pressure between surfaces, high sliding speeds, and excessive contact temperature, resulting from pressure and sliding speed values, which cause oil film rupture between the teeth flanks. Adopting suitable geometry of the tooth curve profile, it will be defined certain values addendum heights for meshing wheel according to criteria of specific slips and corrected head shape of the teeth of both wheels. The paper deals with assessment and theoretical analysis of the impact of the HCR tooth profile resistance to scuffing on the basis of integral temperature criterion according to Winter-Michaelis criterion, researching especially two factors: factor of load distribution (X _ε ) and factor of gear geometry (X _G ).