Cardan Joint Research Articles

Design of a parallel robot with additively manufactured flexure hinges for a cryogenic work environment

Automation is ubiquitous in today’s industrial landscape and is finding its way into more and more highly specialised applications - also in the field of cryopreservation. The extreme work conditions in cryobanks place exceptionally high demands on the mechanical and electronic components used. The preservation and storage of biological samples take place at temperatures between -130 °C and -196 °C using liquid nitrogen as a cooling medium. The bearings and joints used in industrial parallel kinematic robots (for example, ball bearings or Cardan joints) jam at these ambient parameters and are unsuitable for an application within a cryobank. We, therefore, develop methods and technologies to enable fully automated handling of biological samples under cryogenic working conditions. The basis for this is a parallel kinematic robot structure that allows the drives to be placed outside the cold environment. In contrast, the rest of the robot structure can be actuated in a cryogenic container.In this context, the passive joints for this parallel robot are designed as additively manufactured monolithic flexure hinges. This paper presents the design, simulation, and construction of the parallel robot and focuses on the flexure hinges fabricated using the selective laser melting process (SLM). We describe the design of the flexure hinges, their intended use in the robot, and the experimental setup used for their validation. We also compare the operating parameters recorded in experiments (such as bending angle, bending moment) with the data obtained in finite element method simulations (FEM). In addition, we describe the geometric constraints and deviations of the manufactured joints due to the manufacturing process.

A dynamic model of a Cardan joint to evaluate the effect of elasticity and manufacturing errors

A dynamic model of a Cardan joint to evaluate the effect of elasticity and manufacturing errors

Morphological and tribological studies of thermal plasma jet deposited coatings used in cardan joints

All wheels drive (AWD) and railway vehicles require a longitudinal transmission. Double cardan joint is one of the most employed transmission, as it allows misalignments between the shafts. This transmission must support the maximum motor torque and high dynamic loads. In such situation, from tribological viewpoint, cardan joints are subjected to abrasive wear. To increase wear resistance of cardan joints, its rolling elements can be coated with ceramic or metal-ceramic coatings. This paper presents an experimental research on microstructure and dry friction characteristics of two steel samples obtained from cardan crosses (40Cr10 and RUL2), coated by two types of metallic powders (METCO32 and METCO72). Microstructural studies of both surface and cross –section of samples were performed using scanning electron microscopy (SEM). Dry tribological tests at constant speed and load were carried out on AMSLER machine. The micro-structural experiments revealed a structure with a relatively homogeneous character, partially melted particles and several microcracks being detected. Following the tribological tests, it was found that the METCO72 coating provides the lowest coefficient of friction, near values being obtained for both substrates of 40Cr10 and RUL2. The best combination is formed by 40Cr10 substrate and METCO72 coating.

Theory of the technological machine state recognition by the criterion of resource uncertainty

The solution to the problems of assessing the technical condition of special equipment is presented at a multidisciplinary level, as a combination of scientific and technical, practice-oriented research. The purpose of study: development of a digital mechanism for assessing the uncertainty of the state of special equipment systems with real-time monitoring of the intensity of parameter changes, recognition and predictive notification of the probability of risk-failure. It has been established that, in accordance with the theory of probability, there can be only one failure in a unit at a time, even if several damages are diagnosed, and then there is always a single cause. The introduction of the concept of “integrated parameter” supplemented the characteristics of functional and structural multiparameter connections of the state of the unit and made it possible to substantiate the mechanism for recognizing the uncertainty of the state of special equipment systems as a whole. A diagnostic model has been built based on the use of the main provisions of information theory, which represents the unit as a system containing the risk of uncertainty in terms of failure, which is distributed over all structural elements of the unit. An algorithm for recognizing the spatial displacement of uncertainty zones is proposed, the translation of which into a digital format with the introduction of a characteristic criterion will provide a search for a defect (risk-failure). The practical implementation of the risk-failure recognition mechanism is carried out on a simulation model of a change in the state of a technical system using the example of a cardan joint of a technological machine, which is under severe operating conditions during reclamation work. The inclusion in the design of technological machines of a digital module for monitoring the technical condition of the unit is substantiated, including: a module for recognizing the elemental structure; a software shell with a calculation algorithm for evaluating parametric changes; module of interface predictive notification of risk-failure; service control module by state.

The Influence of Finish Treatment on the Service Life of the Bearing

Roughness in rolling bearings plays a very important role. Improving the reliability of rubbing parts of equipment is an urgent task. Finishing, superfinishing and laping were used as finishing operations. (Research purpose) The research purpose is in investigating the effect of various finishing operations on the durability of the needle bearing of the cardan joint. (Materials and methods) Needle bearings of the GPP 704702K model (with a nominal dynamic load capacity of 160 kilonewtons) were studied. Tests were carried out on a test rig for four cups and spikes of bearings made of 20KhVG high-carbon chromium bearing steel. The article presents the results of measuring the roughness in the axial direction of the spike and the working surface of the bearing, carried out using a T1000 Basic portable semi-automatic device for measuring surface roughness of first accuracy class. (Results and discussion) As the roughness of the raceway increases, the bearing life decreases. It has been noted a difference in the increasing bearing temperature depending on the roughness of the raceway surface and finishing methods. The sample subjected to superfinishing or laping had the smallest temperature increase and there was a tendency to increase the bearing temperature as the surface roughness increased. (Conclusions) The roughness of the raceway has a close relationship with the service life, with a decrease in roughness, the service life increases by about 1.8 times. It was found that superfinishing or lapping with a sand paper after finishing to a certain roughness nmach = 3 micrometers by grinding is more effective than processing a smooth surface by grinding alone. It was found that when the surface roughness of the raceway decreases, the bearing temperature decreases.

Nonlinear numerical and experimental study on the second-order torsional and lateral vibration of driveline system connected by cardan joint

In this article, a nonlinear dynamic model with five degrees-of-freedom for a four-wheel-drive vehicle driveline connected by a cardan joint, including dynamic intersection angle, nonconstant velocity, and additional moment caused by the cardan joint, is established by using the Lagrange method to analyze the driveline coupling vibration in both torsional and lateral directions. High-order Runge–Kutta algorithm is applied to solve the differential equations and to calculate transient responses of the driveline rotors under acceleration condition. The color maps and second-order vibration of the driveline are acquired by frequency spectrum analysis and order tracking analysis, respectively. The second-order vibration and noise of the driveline and vehicle interior caused by the cardan joint is validated by vehicle experimental results and reduced effectively by decreasing intersection angle of the cardan joint under the operational condition. Moreover, application of a flexible coupling instead of the cardan joint significantly reduces the second-order vibration but simultaneously generates low-level third-order vibration.

Magnetometer-free Realtime Inertial Motion Tracking by Exploitation of Kinematic Constraints in 2-DoF Joints.

Inertial Measurement Units (IMUs) are used to track the motion of kinematic chains in a wide variety of robotic and biomedical applications. However, inertial motion tracking is severely limited by the fact that magnetic fields are inhomogeneous in indoor environments and near electronic devices. Methods that use only accelerations and angular rates for orientation estimation yield no absolute heading information and suffer from heading drift. To overcome this limitation, we propose a novel method that exploits an orientation-based kinematic constraint in joints with two degrees of freedom (DoF), such as cardan joints, saddle joints, the human wrists, elbow or ankles. The method determines the relative heading of the joint segments in real time by minimization of a nonlinear cost function. A filter for singularity treatment ensures accurate tracking during motion phases for which the cost function minimum is ambiguous. We experimentally validate the method in metacarpophalangeal (MCP) joints between the palm and the fingers. Accurate relative orientation tracking is achieved continuously despite several singular motion phases and even though the heading components of the 6D orientations drift by more than 360 degrees within ten minutes. The proposed method overcomes a major limitation of inertial motion tracking and thereby facilitates the use of this technology in robotic and biomechanical applications.

Contribution of dynamic modeling to prognostics of rotating machinery

Abstract Prognostics of rotating machines parts is an important subject in the maintenance field. The paper focuses on the contribution of the dynamic models for the development of reliable prognostics and diagnostics algorithms. The dynamic models enable prediction of changes in dynamic behavior reflecting the fault type and severity. New condition indicators and signal processing techniques can be developed based on these insights. The models can be used to build databases of simulated signals that can be used to perform sensitivity analysis with respect to geometrical tolerances, environmental and operating conditions, severity, type, and location of faults. A research methodology towards physics-based prognostics of rotating machinery is proposed. The methodology combines experiments with comprehensive dynamic models, and it is demonstrated with examples of rolling-element bearings, gear transmissions, and cardan joints. It is important to well validate the models and to assure their completeness. Therefore, experiments and models are complementary: the experimental results should be used to validate the model assumptions, and the models enable comprehensive interpretation of the test results. The combination of the two allow the generalization of the conclusions and algorithms with a high level of confidence.

Modeling and Dynamic Analysis of Body-Fixed and Space-Fixed Flexible Rotors

Two types of spinning beam models, body-fixed rotor and space-fixed rotor, are available in the literatures. However, the appropriate selection of the models is not clear. This paper provides the comparison of both models and shows the proper applications of the models. The two formulations are derived using the extended Hamilton principle with three sequential Euler-angle rotations. Numerical method is used to obtain the frequencies and stabilities of the two models. It is found that the body-fixed rotor can be employed to describe the motion of a rotor driven by cardan joints, and the space-fixed rotor can be applied to describe the spinning motion about a fixed axle in space. The space-fixed rotor may lose stability due to self-excited vibration, while the body-fixed rotor will remain stable all along. The instability threshold of space-fixed rotor is obtained for different slenderness ratios. The clear distinguishment of the two models paves a better way to choose proper rotor models in different engineering applications.

Influence of Vibrational Loads on Needle Skew in Cardan-Joint Bearings

The influence of vibration on the operation of cardan joints is studied. An equation is derived to describe the oscillation of the needle’s skew angle in bearings under the action of the variable torque from vibrational forces. In both dynamics and statics, this angle is found to depend on the dimensions of the joint and on the load applied to a single needle in the operational zone of the bearing.

The study of the positioning of a flexible manipulator

The purpose of this paper is a theoretical study of the positioning accuracy of the end part of the developed flexible manipulator. The research was carried out on the basis of its computer and physical models. In the process of computer modelling with the use of Matlab Robotics Toolbox software environment and on the basis of the developed physical model, the principles of determining the position of the end part of a flexible manipulator at known tilt angles of links were set up, taking into account that the geometric dimensions of the models were identical. The results of modelling are presented in the graphs of the coordinate comparison. Based on the results of experiments, we can conclude that, in order to achieve high accuracy of positioning of the end part of a flexible manipulator, it is recommended to avoid the use of cardan joints between the links, or to choose cardan mechanisms with reduced free travel.

Transmission with Cardan Joint Parametre Influence to Centrifugal Pump Characteristics

Transmission with cardan joints and non­linear gearbox elements generates vibrations caused by spinning motion of transmission. This affects the pressure and productivity of centrifugal pump. The momentum of centrifugal pump in turn affects dynamic characteristics of transmission. In order to find the effect of transmission elements on centrifugal pump we investigate transmission composed of asynchronous electrical engine, gear box, cardan joint and Ziegler Ultra centrifugal pump. We create mathematical models of transmission and centrifugal pumps and investigate how the dynamic effects of transmission influence productivity centrifugal pump. This model can be applied to study the transmission parameters, effect of intake and outflow parameters on productivity of centrifugal pump and presence of cavitation. The paper includes results and conclusions of mathematical model.

A Study on Design Method of Intelligent platform trolley

In this paper, a design method of detachable intelligent platform trolley is presented. The detachable intelligent platform trolley has three driving modes, and the rubber blanket and the cardan joint in the structure filter effectively the road surface turbulence and improve the safety of the driver. The design idea of the active wheel fixed structure and the driven steering wheel structure is emphatically introduced. At last, The results show that the right panel of intelligent platform trolley as the research object and analyses the load, static stress of the right panel of platform trolley mainly concentrated in the panel at the front and back ends and other connectors on the contact surface. In addition, the safety factor can meet the design requirements by analysis.

The influence of the technological deviations over the vibration inherent frequencies at bending from the three-shafts transmission

The technological deviations of manufacturing and assembly , lead to the change of the kinematic parameters and at further efforts in the kinematic pairs of the cardan joint mechanism from the component of the poly-cardan transmissions.The variation of these forces is constant in the local systems of reference of the kinematic pairs and harmonic varies in the general system of reference in which one of the axes coincides with the rotation axis.The component of the forces that acts perpendiculary on the direction this axis is a permanent source of excitation, leading to the change of their own frequencies and vibration modes at bending. In this paper are deducted the connections between technological deviations ,the excitation forces and own frequencies and vibration modes at bending and based on the results of numerical application conclusions will be drawn.

CPG-Inspired Locomotion Control for a Snake Robot Basing on Nonlinear Oscillators

The article focuses on locomotion control of a snake-like robot with cardan joints using a central pattern generator (CPG) approach. A double chain structure of a CPG model is developed based on no...

Robot Engineering Implementation for Monitoring Small-Diameter Pipelines

Background/Objectives: The developed NDT method requires measuring sensor motion along the pipe and around its circumference. This article focuses on determining the design a robotic device for sensor delivery and motion in pipelines. Methods/Statistical Analysis: The review of the existing control systems, examined design concepts, advantages and disadvantages enabled to develop a robotic device considering the following: •It shall consist of several modules interconnected by hinge joints •Secure traction of the robotic device requires expanding modules in the pipe and determines the use of three tracking mechanisms for motion unit. •The braking track shall be applied to ensure crossing of the inclined and vertical sections. Findings: As a result of the research, design documentation of the robot motion unit was developed and its unit design was determined, we have obtained an engineering study of the robotic device motion unit, which consists of two motion modules and the motor control circuit stacked together via cardan joints. The motion module consists of a track and a folding mechanism. The authors have also justified the selected technical solutions verified by appropriate calculations the required parameters: motion drive calculation, thrust drive calculation, electric motor and advancing mechanism selection. Applications/Improvements: This device provides solution for timely inspection of corrosion damage in subsurface pipelines of small-diameter heating networks (DN200, DN400) of housing and public utilities in places inaccessible for external inspection.

The Numerical Study of Efforts from the 4r Symmetrical Spherical Quadrilateral Mechanism with Technical Deviations

The technological (geometrical) deviations determine in the intermediate couples of the cardan joint supplementary efforts due to restrained movement. The 4R spherical quadrilateral mechanism, where by R is notated the rotation kinematic pair, from which is obtained the cardan mechanism, is of third family, as consequence, multiple statically indeterminate and for calculating the reactions from the kinematic pairs it is applied the elastic linear calculation, using the relative displacements method noted in plukerian coordinates. The results of the numerical solving of this problem will be presented under the form of a diagrams and will be commented.

Model for the Motion of Misaligned Shafts with Elastic Plate Coupling

Using the MathCAD software, this publication aims to develop a novel model to interpret the analytical results for an elastic structure as a substitute to flexible coupling between two misaligned axes. This model is used for the analysis of the motion of two deformed components comprising of the cardan joint, as well as the coupling with elastic plates.

The influence of breast support on torso, pelvis and arm kinematics during a five kilometer treadmill run

Many women wear sports bras due to positive benefits associated with these garments (i.e. reduction in breast movement and breast pain), however the effects these garments have on upper body running kinematics has not been investigated. Ten female participants (32DD or 34D) completed two five kilometer treadmill runs (9kmh−1), once in a low and once in a high breast support. The range of motion (ROM) and peak torso, pelvis, and upper arm Cardan joint angles were calculated over five gait cycles during a five kilometer run. Peak torso yaw, peak rotation of the pelvis, peak pelvis obliquity, ROM in rotation of the pelvis, and ROM in upper arm extension were significant, but marginally reduced when participants ran in the high breast support. The running kinematics reported in the high breast support condition more closely align with economical running kinematics previously defined in the literature, therefore, running in a high breast support may be more beneficial to female runners, with a high breast support advocated for middle distance runners.

Steel compliant Cardan universal joint

In this paper, a compliant Cardan universal joint made of steel is introduced. This is the first steel compliant universal joint that is reported in the literature. The mechanism is produced from two different sheet metals; thus, it has the advantage of easiness in manufacturing. Many mechanisms with different dimensions are designed. Resultant stresses at flexural hinges are determined via analytical and finite element analysis method. Torque transmission capacities of these mechanisms are determined. Guidelines, trends, and parameter trade-offs for the design of such mechanisms are presented. Fatigue life of these mechanisms is estimated theoretically. Further, one of these mechanisms is manufactured and tested for fatigue strength. It is verified that results of experiments are consistent with theoretical predictions. It is strongly believed that the steel version of compliant Cardan joint has a great potential to be used in industry.