Complex Mechanical Systems Research Articles

Numerical identification procedure between a micro-Cauchy model and a macro-second gradient model for planar pantographic structures

In order to design the microstructure of metamaterials showing high toughness in extension (property to be shared with muscles), it has been recently proposed (Dell’Isola et al. in Z Angew Math Phys 66(6):3473–3498, 2015) to consider pantographic structures. It is possible to model such structures at a suitably small length scale (resolving in detail the interconnecting pivots/cylinders) using a standard Cauchy first gradient theory. However, the computational costs for such modelling choice are not allowing for the study of more complex mechanical systems including for instance many pantographic substructures. The microscopic model considered here is a quadratic isotropic Saint-Venant first gradient continuum including geometric nonlinearities and characterized by two Lame parameters. The introduced macroscopic two-dimensional model for pantographic sheets is characterized by a deformation energy quadratic both in the first and second gradient of placement. However, as underlined in Dell’Isola et al. (Proc R Soc Lond A 472(2185):20150790, 2016), it is needed that the second gradient stiffness depends on the first gradient of placement if large deformations and large displacements configurations must be described. The numerical identification procedure presented in this paper consists in fitting the macro-constitutive parameters using several numerical simulations performed with the micro-model. The parameters obtained by the best fit identification in few deformation problems fit very well also in many others, showing that the reduced proposed model is suitable to get an effective model at relevantly lower computational effort. The presented numerical evidences suggest that a rigorous mathematical homogenization result most likely holds.

A novel design for a primary measurement standard for the quantity torque

Primary standards are established using a reference measurement procedure. Through the realization of the definition of a given quantity they provide traceability in the metrology chain. Most torque standards use calibrated weights linked to a lever arm to provide known torques in the rotational axis of the device. These standards do not succeed to provide continuous torque values because of limitation in weights combination and the intrinsic incremental steps of the technique. In automatic machines this can be overcome but it requires a complex mechanical system to operate. In designs that use movable weights along the lever arm the determination of the length of the lever arm is a large source of errors. Zeroing the torque standard also represents a major problem. An innovative and functional design that aims to solve the aforementioned disadvantages is presented.

Analysis of active vibration control of multi-degree-of-freedom flexible systems by Newmark method

A flexible robot arm can be modeled as a lumped-parameter multi-degree-of-freedom mass–spring system. The actuator at one end positions the payload at the other end. The flexibility causes the vibration of the payload at the end point. This paper considers a 4-degree-of-freedom mass–spring system. A closed loop active vibration control system is analyzed to suppress the end-point vibrations. The mathematical model of the system is established by using the Lagrange equations. The average of the displacements of the masses is used for the feedback. A PID control is applied. The numerical solution is obtained by integrating the control action into the Newmark method. The instantaneous average displacement is subtracted from the reference input to find the error signal value at a time step in the Newmark solution. The PID control action is applied to find the actuator signal value in the time step. This input value is used to find the displacements for the subsequent time step. The process is continued until the steady-state value is approximately reached. The analytical solution is given by using the Laplace transform method to check the validity of the Newmark solution. It is observed that the numerical and analytical results are in good agreement. The integration of the control action into Newmark solution as presented in this study can be extended to finite element solutions to simulate the control of complex mechanical systems.

Coordination control of robot manipulators using flat outputs

This paper focuses on the synchronizing control of multiple interconnected flexible robotic manipulators using differential flatness theory. The flatness theory has the advantage of simplifying trajectory tracking tasks of complex mechanical systems. Using this theory, we propose a new synchronization scheme whereby a formation of flatness based systems can be stabilized using their respective flat outputs. Using the flat outputs, we eliminate the need for cross coupling laws and communication protocols associated with such formations. The problem of robot coordination is reduced to synchronizing the flat outputs between the respective robot manipulators. Furthermore, the selection of the flat output used for the synchronizing control is not restricted as any system variable can be used. The problem of unmeasured states used in the control is also solved by reconstructing the missing states using flatness based interpolation. The proposed control law is less computationally intensive when compared to earlier reported work as integration of the differential equations is not required. Simulations using a formation of single link flexible joint robots are used to validate the proposed synchronizing control.

Feature Identification With Compressive Measurements for Machine Fault Diagnosis

Machine fault diagnosis collects massive amounts of vibration data about complex mechanical systems. Performing feature detection from these data sets has already led to a major challenge. Compressive sensing theory is a new sampling framework that provides an alternative to the well-known Shannon sampling theory. This theory enables the recovery of sparse or compressible signals from a small set of nonadaptive linear measurements. However, it is suboptimal to recover the whole signals from the compressive measurements and then solve feature identification problems through traditional DSP techniques. Thus, a novel mechanical feature identification method is proposed in this paper. Its main advantage is that fault features are extracted directly in the compressive measurement domain without sacrificing accuracy, while a significant reduction in the dimensionality of the measurement data is achieved. Moreover, Gaussian white noises are significantly alleviated, which dramatically enhances the reliability of machine fault diagnosis. Parameter analysis is also profoundly investigated through a set of numerical experiments. Numerical simulations and experiments are further performed to prove the reliability and effectiveness of the proposed method.

Conformal Weyl-Euler-Lagrangian equations on 4-Walker manifolds

The main purpose of the present paper is to study almost complex structures conformal Weyl-Euler-Lagrangian equations on 4-dimensional Walker manifolds for (conservative) dynamical systems. In this study, routes of objects moving in space will be modeled mathematically on 4-dimensional Walker manifolds that these are time-dependent partial differential equations. A Walker n-manifold is a semi-Riemannian n-manifold, which admits a field of parallel null r-planes, with r ≤ 2 . It is well-known that semi-Riemannian geometry has an important tool to describe spacetime events. Therefore, solutions of some structures about 4-Walker manifold can be used to explain spacetime singularities. Then, here we present complex analogues of Lagrangian mechanical systems on 4-Walker manifold. Also, the geometrical-physical results related to complex mechanical systems are also discussed for conformal Weyl-EulerLagrangian equations for (conservative) dynamical systems and solution of the motion equations using Maple Algebra software will be made.

Simulation and Energy Analysis of Thermal Environment of Unassisted Passive Solar House

The greenhouse effect it the most basic work principle of the passive solar house The passive solar house provide indoor heating relying on natural circulation, without any other mechanical power, with the excess heat stored in the walls, ceilings and ground hot body to radiate heat into the room at night, to maintain a certain temperature. It takes in, keeps, stores and distributes solar thermal energy by reasonable arrangement of building orientation and surrounding environment, smart manipulation of the inner and outer space and the proper selection of the building materials, structure and construction, so as to solve the problem of building heating. The heat collection and storage of the passive solar house mainly uses the building envelop walls or windows or the simple tablet device as a heat collector, which can be freely controlled by people, without the complex mechanical equipment and complex pipe ventilation system. The test takes a residential building as example for energy consumption simulation and from the results; we can obtain the temperature distribution in each room and the distribution of the annual heating and coldness load. Study the effect on the room temperature and reducing heating energy consumption by the different ways of thermal insulation.

METHODOLOGICAL FUNDAMENTALS OF DETERMINATION OF UNPOWERED ROLLING STOCK MAINTENANCE CHARACTERISTICS

Purpose. The paper involves: 1) confirmation of the technical characteristics of cars and their modifications, as well as indicators of unfailing work probability during the time between overhauls or service hours; 2) improving the methodological approaches to assess the maintenance characteristics of new and modernized equipment of rail transport on the example of not self-propelled rolling stock, namely, railway freight cars; 3) solution of scientific and applied problems in assessment the maintenance characteristics of the new and modernized railway equipment. Methodology. The basic methodological approaches to the assessment of the maintenance characteristics on the example of not self-propelled rolling stock, namely, railway freight cars were considered. The analysis of the reliability of the car, which is considered as a complex mechanical system, where all system elements are connected in series, wherein each element includes m is serially connected parts. The failure of each part of the calculation will result in refusal of the car. Thus, the car is a system without redundancy. Findings. The evaluation technic of the maintenance characteristics of freight cars in controlled operation with taking into account the features of the new generation of cars was improved. Specified: the duration of the tests, the frequency of inspection of the control group of cars controlled by the parameters of the car, the reasons for the early termination of controlled operation. Identified failures in the process of controlled operation are divided according to their nature. Originality. The authors proposed a method of assessing the maintenance characteristics of railway equipment in trial operation as an example of a new generation of freight cars. Practical value. The results allow assessing the maintenance characteristics of new and modernized rail transport equipment during the maintenance test.

Dynamics design for multiple launch rocket system using transfer matrix method for multibody system

Dynamics design for complex mechanical systems has become an important research field and development direction at present, capturing attentions of an increasing number of engineers and scientists worldwide. Based on many advantages of the transfer matrix method for multibody system in studying multibody system dynamics, a design problem of a multiple launch rocket system is solved in this paper. Particular attention is addressed to model actions of the exhaust flow on the multiple rocket launcher, which are associated with firing order and firing intervals of rockets. Combined with a genetic algorithm, firing order and firing intervals are optimized to achieve optimum impact point dispersion reduction. The results of numerical simulation and verification tests show good agreement, while the dispersion characteristics of rockets have been improved in a low-cost way.

Active learning surrogate models for the conception of systems with multiple failure modes

Due to the performance and certification criteria, complex mechanical systems have to taken into account several constraints, which can be associated with a series of performance functions. Different software are generally used to evaluate such functions, whose computational cost can vary a lot. In conception or reliability analysis, we thus are interested in the identification of the boundaries of the domain where all these constraints are satisfied, at the minimal total computational cost. To this end, the present work proposes an iterative method to maximize the knowledge about these limits while trying to minimize the required number of evaluations of each performance function. This method is based first on Gaussian process surrogate models that are defined on nested sub-spaces, and second, on an original selection criterion that takes into account the computational cost associated with each performance function. After presenting the theoretical basis of this approach, this paper compares its efficiency to alternative methods on an example.

Tunnel Operations, Maintenance, Inspection, and Evaluation Manual, 2015: Practical Implications for Fire Protection and Life Safety Systems

Practical implications of the new Tunnel Operations, Maintenance, Inspection, and Evaluation (TOMIE) Manual with regard to fire protection and life safety systems (FPLSS) are discussed, and resources are suggested for assistance in TOMIE manual implementation in this subject area. The new TOMIE manual takes a major and long-needed step toward the formalization of road tunnel inspection and maintenance requirements and protocols. The new program will not only benefit the condition and life of the structural elements of the tunnel but also enhance the public’s safety. According to the manual, “many tunnels have complicated functional systems such as lighting, ventilation, drainage, fire detection and alarms, fire suppression, communication and traffic control; these systems must be kept in good working order to minimize death and injury during an emergency such as a vehicle collision, fire, flood, earthquake, or criminal act.” All the operating mechanical and electrical systems mentioned above can be considered FPLSS. In an emergency each of these systems, and several others, has a role to play in ensuring that occupants have the best chance to survive and that responders can reach the scene as quickly as possible. This paper briefly examines FPLSS inspection and testing as related to the TOMIE manual. Although the TOMIE manual is an important step forward in protecting infrastructure and ensuring public safety, it cannot cover all the detailed requirements for operating, maintaining, inspecting, and evaluating the complex mechanical and electrical systems of FPLSS.

Comparative Study of Gearbox Fault Diagnosis by Vibration Measurements

Vibration analysis has been demonstrated to be one of the best tools to detect faults in a gearbox by providing abundant information about the operating condition of a gearbox. However, a gearbox generates complex vibration signals, which makes it difficult to diagnose when a fault occurs. There are several fault diagnosis methods that can be utilized to analyze the underlying signals. The time-frequency method has been used and showed some promising results. On the other hand, it also has its drawback when it is applied to a complex mechanical system such as gearboxes. This paper thus attempts to examine the effectiveness of several diagnosis methods to detect faults in a gearbox from vibration measurements. The results show that the cepstrum method can provide a more accurate indication of a faulty gearbox compared to other diagnosis methods.

Research on Assembly Data Mining Technology of Complex Mechanical System

The discipline between the assembly process and the final performance of complex mechanical system is unclear and the performance target is usually reached by experienced technicians. To find out the discipline and obtain the knowledge which may be hiding in the experience of technician, data mining technology is put forward to analyze the assembly data. By establishing the structure and procedure of the data mining process and encapsulating the data mining template of the assembly data, the knowledge of the discipline and assembly experience can be extracted through a case study. These knowledge can be used for assembly quality prediction, parameter optimization, process improvement and success rate increase.

High-Precision and Fast Response Control for Complex Mechanical Systems - Servo performance of dedicated servo recording systems

The dedicated servo recording system for hard disk drives (HDDs) has servo bursts continuously stored in between data recording layer and the soft underlayer of conventional perpendicular magnetic recording media. It provides high sampling rate for the servo control of the mechanical actuation system, which is thus enabled to quickly respond to high-frequency vibrations and achieve high positioning accuracy. The servo performance of the dedicated servo HDDs is investigated by applying low-frequency external vibrations, and its advantages over conventional servo are evaluated and verified. Dual-stage actuation mechanism is further applied to enhance the servo performance for effective utilizing the high sampling rate for the servo control. The high servo bandwidth, such as 5 and 10 kHz, is then achieved with sufficient position error signal (PES) samples provided by the dedicated servo. Not only to the low-frequency vibrations, the servo control loop with the high servo bandwidth is also able to significantly reduce the audio vibration impact on the PES. Simulation and testing results are provided, in this paper, to study and verify the servo performance of the dedicated servo recording systems.

Dynamics of Complex Mechanical Systems Based on Lie Groups and Lie algebra

Adjoint transformations and adjoint operators of Lie groups and Lie algebra are discussed in this paper to study the recursive dynamics of complex systems. The dynamics based on Lie groups and Lie algebra of tree topology systems is then developed. Efficient dynamics algorithms for closed-loop systems and flexible systems can be developed. Simulation results show that the dynamic problems can be solved quickly and efficiently using the method. This study provides a foundation for real-time control based on dynamics.

AN INTERPOLATION METHOD FOR DETERMINING THE FREQUENCIES OF PARAMETERIZED LARGE-SCALE STRUCTURES

<p>Parametric Model Order Reduction (pMOR) is an emerging category of models developed with the aim of describing reduced first and second-order dynamical systems. The use of a pROM turns out useful in a variety of applications spanning from the analysis of Micro-Electro-Mechanical Systems (MEMS) to the optimization of complex mechanical systems because they allow predicting the dynamical behavior at any values of the quantities of interest within the design space, e.g. material properties, geometric features or loading conditions. The process underlying the construction of a pROM using an SVD-based method [18] accounts for three basic phases: a) construction of several local ROMs (Reduced Order Models); b) projection of the state-space vector onto a common subspace spanned by several transformation matrices derived in the first step; c) use of an interpolation method capable of capturing for one or more parameters the values of the quantity of interest. One of the major difficulties encountered in this process has been identified at the level of the interpolation method and can be encapsulated in the following contradiction: if the number of detailed finite element analyses is high then an interpolation method can better describe the system for a given choice of a parameter but the time of computation is higher. In this paper is proposed a method for removing the above contradiction by introducing a new interpolation method (RSDM). This method allows to restore and make available to the interpolation tool certain <em>natural</em> components belonging to the matrices of the full FE model that are related on one side, to the process of reduction and on the other side, to the characteristics of a solid in the FE theory. This approach shows higher accuracy than methods used for the assessment of the system’s eigenbehavior. To confirm the usefulness of the RSDM a Hexapod will be analyzed.</p>

ESA as a Significant Tool for Intensification of Structural Elements of Pipe Systems

Complex mechanical systems intended for gas transport are formed by complicated technological piping units. Their main components are gas pipelines, compressor stations, connection and distribution nodes, etc. As a part of their operation, monitoring but especially within long-term intensification of their technical competence, it is necessary to solve a variety of complex technical problems. These are mainly related to monitoring and prediction of lifespan of critical system elements, then also to monitoring corrosion damaged pipeline and related repairs and eventually to rectification of older bridges and other temporary or unsatisfactory technical solutions. Important interacting negative factors in the process are gradual degradation of used material, presence of residual stresses, etc. Solving these problems is unthinkable without active application of experimental modeling, relevant experimental methods and corresponding hardware and software. This mainly includes means of modal analysis and analysis of deformation and mechanical stresses. The article also presents relevant conclusions from solving environment of specific technical problems in the conditions of gas piping transport system in the Slovak Republic.

A condensed transfer function method as a tool for solving vibroacoustic problems

Substructuring approaches are nowadays widely used to predict numerically the vibroacoustic behavior of complex mechanical systems. Some of these methods are based on admittance or mobility frequency transfer functions at the coupling interfaces. They have already been used intensively to couple subsystems linked by point contacts and enable to solve problems at higher frequency while saving computation costs. In the case of subsystems coupled along lines, a Condensed Transfer Function method is developed in the present paper. The admittances on the coupling line are condensed in order to reduce the number of coupling forces evaluated. Three variants are presented, where the transfer functions are condensed using three different functions. After describing the principle of the CTF method, simple structures will be given as test cases for validation.

Cavity-mediated coupling of mechanical oscillators limited by quantum back-action

A complex quantum system can be constructed by coupling simple quantum elements to one another. For example, trapped-ion or superconducting quantum bits may be coupled by Coulomb interactions, mediated by the exchange of virtual photons. Alternatively quantum objects can be coupled by the exchange of real photons, particularly when driven within resonators that amplify interactions with a single electro-magnetic mode. However, in such an open system, the capacity of a coupling channel to convey quantum information or generate entanglement may be compromised. Here, we realize phase-coherent interactions between two spatially separated, near-ground-state mechanical oscillators within a driven optical cavity. We observe also the noise imparted by the optical coupling, which results in correlated mechanical fluctuations of the two oscillators. Achieving the quantum backaction dominated regime opens the door to numerous applications of cavity optomechanics with a complex mechanical system. Our results thereby illustrate the potential, and also the challenge, of coupling quantum objects with light.

An influence of the stepping motor control and friction models on precise positioning of the complex mechanical system

This paper aims to investigate, both experimentally and theoretically, the electromechanical dynamic interaction between a driving stepping motor and a driven laboratory belt-transporter system. A test-rig imitates the operation of a robotic device in the form of a working tool-carrier under translational motion. The object under consideration is equipped with measurement systems, which enable the registration of electrical and mechanical quantities. Analytical considerations are performed by means of a circuit model of the electric motor and a discrete, non-linear model of the mechanical system. Various scenarios of the working tool-carrier motion and positioning by the belt-transporter are measured and simulated; in all cases the electric current control of the driving motor has been applied. The main goal of this study is to investigate the influence of the stepping motor control parameters along with various mechanical friction models on the precise positioning of a laboratory robotic device.