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In this article, an adaptive continuous sliding mode control (SMC) scheme is presented for the trajectory tracking problem of mechanical systems with parameter uncertainties, external disturbances and actuator faults. The hyperbolic tangent function is widely used to replace the signum function in SMC to ensure that the robust term is continuous and to reduce chattering. Since such an approach is difficult for SMC schemes with adaptive gain to induce system stability through Lyapunov functions, we reconstruct the hyperbolic tangent function by taking both the adaptive control gain and sliding variables as inputs. The designed gain dynamics do not require a priori upper bound on lumped uncertainties, including parameter uncertainties, external disturbances and actuator faults, and ensure no overestimated gains. Besides, an adaptive dual-layer super-twisting (ADLST) observer is adopted to accurately estimate unmeasurable velocities, which achieves the synthesis of an adaptive sliding mode observer and the continuous SMC method with adaptive gain. It is proven through the Lyapunov function that all closed-loop signals are ultimately bounded. Comparative simulations are conducted on a two-link rigid manipulator to demonstrate the effectiveness of the adopted observer and the proposed scheme. [ABSTRACT FROM AUTHOR]

Due to assembling, manufacturing errors, and wear, irregular rough surfaces inevitably exist in joints, which will increase the contact stiffness nonlinearity at the joint of the spatial developable mechanism, and the traditional contact force model is difficult to accurately predict the contact force change of irregular rough surface clearance. Aiming at the difficulty of accurately predicting the dynamic behavior of the spatial developable mechanism caused by rough joint clearance, an improved clearance contact force modeling method based on an uncoordinated contact model is proposed in this paper. The influence of rough peak distribution on the contact area is analyzed. The stiffness of the traditional Hertz model is modified based on the probability distribution density function of the rough peak, and an improved contact force model based on dynamic contact stiffness is established. Based on the Lagrange multiplier method, the dynamics model of spatial developable mechanism is constructed. Based on the model, the dynamic analysis of the spatial expansion mechanism is carried out, and the influence of the roughness of the contact surface and the size of the clearance on the dynamic characteristics of the system are explored; as well, the influence of different clearance parameters on the dynamic characteristics of the development mechanism is revealed. Through the analysis, this paper provides a theoretical basis for predicting the effect of a spatial revolute clearance joint on the dynamic characteristics of the mechanism and lays a good foundation for the manufacture and application of the mechanism. [ABSTRACT FROM AUTHOR]

The persistent global issue of manual scavenging in drainage systems, fraught with life-threatening risks, has prompted the development of a tractor powered mechanized drain cleaning system. This innovative solution recycles on-site sewage water, optimizing efficiency through a tractor-trolley setup, recycled water usage, a centrifugal pump replacing vacuum pumps, and the integration of a post-inspection unit for crack and leak detection. The system employs a front water jet with an impact stress of ∼30.10 MPa for penetrating silt, sediments, and debris. Simultaneously, rear jets with ∼20 MPa impact stress each clean pipeline walls and propel the nozzle forward. Inclusion of a power unit (tractor), suction unit, filtration unit, and inspection unit enhances the system's agility, robustness, and affordability compared to alternatives. The system's one of the key advantage is its inspection unit, featuring GoogleNet-powered in-situ crack detection via a camera. Achieving 90% training accuracy in six epochs and 159 iterations, it identifies pipeline features effectively. With its sewage water recycling capability, this mechanized system offers a promising solution to the perilous problem of manual scavenging in drainage systems while promoting sustainability. HIGHLIGHTS Mechanical drain cleaning system.; In-situ recycling of sewage water.; In situ-inspection unit.; Deep learning-based sewage pipeline monitoring system.;

In this paper, a novel disturbance observer and a Lyapunov-based control approach are developed for the crane control. For existing works, the assumption on the disturbances is strong and the motivation of these methods is to reject disturbances by feedback control. To tackle these problems, this paper proposes a novel composite control strategy consisting of a nonlinear control method and a finite time disturbance observer. Specifically, first, based on the system dynamic equations, a disturbance estimator is put forward, which can exactly identify the unknown disturbances in finite time. Next, an elaborate Lyapunov function is constructed and a disturbance-compensation-based control approach is presented for the overhead crane system with double-pendulum dynamics. Then, rigorous theoretical analysis is given to prove that all of the states of the closed-loop system asymptotically converge to the origin. At last, simulation tests are included to verify the effectiveness and robustness of the proposed method. [ABSTRACT FROM AUTHOR]

Uncertainties caused by measuring errors or incomplete knowledge affect the dynamic response and functional reliability of the mechanical system, particularly for the mechanisms with clearance joints. Considering that dependency between the interval parameters in the uncertain quantification of mechanical systems with clearance joints is prone to be ignored, in this article, a dynamic analysis procedure considering the correlation between interval parameters is presented. Firstly, the continuous contact force model and modified friction force model are embedded into the deterministic dynamic governing equations of the mechanical system with clearance joints derived by the Lagrangian method. To characterize the correlation between interval uncertainties, the convex ellipsoid model is employed, and a Chebyshev-based convex scanning method is developed to obtain the bounds of dynamic response. Finally, a robot manipulator with clearance joint considering dependent uncertainties is illustrated as an example to investigate the clearance effect and correlations between uncertainties on the dynamic behavior. In the numerical simulation, the geometrical parameters of the manipulator arm are regarded as dependent interval parameters. The results show that the dependence between interval uncertainties induces relatively conservative bounds and should be considered carefully in the case of a large clearance size existing in the mechanical system. [ABSTRACT FROM AUTHOR]

Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Switched positive Persidskii systems with distributed and unbounded delays are studied. Right-hand sides of these systems are linear combinations of nonlinearities of a sector type. Special constructions of diagonal Lyapunov--Krasovskii functionals are proposed and conditions are derived under which the absolute stability of the considered systems can be proved with the aid of such functionals. The developed approaches are applied to the stability analysis of a mechanical system with switched nonlinear positional forces and to a problem of mobile agent deployment. Results of numerical simulations are presented confirming the theoretical conclusions. [ABSTRACT FROM AUTHOR]

Rice straw stands out as the primary agricultural residue posing significant challenges for both farmers and the Egyptian government. Its volume accounts for approximately 18% of the total annual waste generated. Livestock farmers typically harvest the straw and feed it to their animals. However, the process of manually mixing molasses, urea, and salts with the straw often leads to inconsistent blending and uneven distribution of the mixture. This inconsistency poses a considerable risk to the health of the animals, potentially resulting in fatalities. Thus, a mechanical system for producing animal feed (rice straw cutting mixed with additives of urea, minerals and molasses) was developed. This system consists of a chopping unit, mixing unit, and pumping & distribution unit. Measurements included the uniformity of the cut rice straw pieces within the preferred size, the uniformity of the dissolved additives mixture and the uniformity of the additives distribution on cut rice straw. Crude protein and urea percentages were measured in the final product. The results showed a maximum production rate of 0.6 ton h-1 the suitability of the developed system for mixing the additives with the cut rice straw. The suitability of the developed system was determined through the uniformity of the distribution of the additives on the cut rice straw. The results showed that the optimum content of crude protein of 6.2% was found at urea content of 5% and a mixing unit shaft speed of 300 rpm and 5 min mixing time. Also, the developed system achieved a rate of return of 19% and a payback period of about two years. [ABSTRACT FROM AUTHOR]

Purpose: For most existing control approaches, the overhead crane systems are usually modeled as the single-pendulum model. However, when the hook mass is too large to be ignored and the distance between the payload and the hook cannot be neglected, the crane exhibits double-pendulum dynamics. Therefore, the double-pendulum dynamics of the overhead crane systems are taken into consideration in this study. Methods: A new enhanced anti-swing control strategy is developed for the positioning and swing elimination control of overhead crane systems. First, based on the system dynamic equations, an auxiliary control input is introduced. Then, an elaborate Lyapunov function is constructed and a nonlinear anti-swing control approach is presented for the overhead crane system with double-pendulum dynamics. Finally, rigorous theoretical analysis is given to prove the convergence of the system states, that is, positioning and swing elimination control objective is achieved. Results and Conclusion: Simulation tests are included to verify the effectiveness and robustness of the devised approach. In addition, a comparison study between the proposed method and existing control methods is provided. The obtained simulation results show that the proposed control method possesses superior control performance. [ABSTRACT FROM AUTHOR]

Due to assembling, manufacturing errors, and wear, irregular rough surfaces inevitably exist in joints, which will increase the contact stiffness nonlinearity at the joint of the spatial developable mechanism, and the traditional contact force model is difficult to accurately predict the contact force change of irregular rough surface clearance. Aiming at the difficulty of accurately predicting the dynamic behavior of the spatial developable mechanism caused by rough joint clearance, an improved clearance contact force modeling method based on an uncoordinated contact model is proposed in this paper. The influence of rough peak distribution on the contact area is analyzed. The stiffness of the traditional Hertz model is modified based on the probability distribution density function of the rough peak, and an improved contact force model based on dynamic contact stiffness is established. Based on the Lagrange multiplier method, the dynamics model of spatial developable mechanism is constructed. Based on the model, the dynamic analysis of the spatial expansion mechanism is carried out, and the influence of the roughness of the contact surface and the size of the clearance on the dynamic characteristics of the system are explored; as well, the influence of different clearance parameters on the dynamic characteristics of the development mechanism is revealed. Through the analysis, this paper provides a theoretical basis for predicting the effect of a spatial revolute clearance joint on the dynamic characteristics of the mechanism and lays a good foundation for the manufacture and application of the mechanism.

This article considers the problem of nonlinear oscillations of the motion of liquids completely filling an axisymmetric cylindrical vessel moving around the horizontal axis. The motion of each fluid is assumed to be potential and formulated in a cylindrical coordinate system. The influence of nonlinear coefficients on the characteristics of dynamic processes during the finite rotational motions of the vessel is estimated and the case of the forced angular oscillations of a vessel with liquids relative to a fixed axis is considered. The main nonlinear effects associated with the rotation of the diameter of the interface of liquids are also revealed. An approximate solution of the obtained nonlinear equations, found by the Bubnov–Galerkin method, is used in the article. As a result of the transformation, the amplitude-frequency characteristics (AFC) and stability regions of a two-layer liquid are constructed under the forced angular oscillations of a round cylindrical vessel. [ABSTRACT FROM AUTHOR]

Clearances in joints are unavoidable due to assemblage, manufacturing errors and wear, which will lead to poor dynamic performances and undesirable vibrations due to impact forces in clearance joints. In dynamics analysis of planar mechanical system, it is usually assumed that the revolute joint is planar joint with radial clearance. However, the axial clearance in the revolute joint and the clearance in the translational joint are ignored. In fact, even planar mechanical systems may exhibit out-of-plane motion due to misalignments. In this work, a planar slider-crank mechanism is used as the example to investigate the effects of mixed clearances on the dynamic responses of planar mechanical system considering radial and axial clearances in spatial revolute joint due to axis misalignment as well as clearance in planar translational joint. The dynamic responses of the planar slider-crank mechanism system with two spatial revolute clearance joints and a planar translation clearance joint are investigated using computational and experimental methodology. The mathematic model of the spatial revolute clearance joint and the planar translational clearance joint are presented. The clearance joints are considered as force constraints and the joint components of an imperfect joint with clearance are modeled as contact bodies. The normal contact force model of clearance joint is established using continuous contact force model. The friction effect is considered using modified Coulomb friction model. Different case studies are presented and discussed to investigate the effects of the mixed clearances on the dynamic responses of the planar slider-crank mechanism. [ABSTRACT FROM AUTHOR]

The article considers the dynamics of a nonlinear mechanical system under the action of a kinematic perturbation on it. The object's vibration isolation system is described by a rigid cubic power characteristic and is based on compensation of external perturbations — the introduction of an additional elastic element with negative stiffness into the suspension. Numerical modeling of the system is performed, the results of which are analyzed by the method of spectral analysis, based on the representation of the correlation function on a small time interval by a square polynomial. As a result of the analysis, it is found that in the pre-resonant and resonant regions, the general solution should consist of three components: a subharmonic of the order of 1/3, the fundamental harmonic, and the third harmonic. It is noted that only the subharmonic of the order of 1/3 and the fundamental harmonic are important in the resonant zone. It is also noted that even simple nonlinear mechanical systems in the study of dynamics should use approximate analytical and numerical methods in combination with spectral analysis, since traditional methods of nonlinear mechanics are not adapted to solving problems taking into account a relatively large number of harmonic components that appear due to nonlinearity.

Objective: In order to effectively solve the problems of low efficiency, quality fluctuation and increasing labor cost of artificial sorting. Methods: A mechanical system based on differential separation principle was designed to complete the classification and separation device of Pleurotus eryngii, and the differential separation principle was introduced and modeled. Results: The test prototype was built and the principle verification test was completed. The success rate of separation of special mushroom was 99.5%, and that of other varieties was 100%. Conclusion: The test device can achieve good differential separation effect.

In this paper, an extension of an algorithm for the implicit discretization of a super‐twisting sliding mode observer is presented. Implicit and explicit discretization algorithms for homogeneous differentiators, where no physical model information is considered, are investigated in literature. This article studies the behavior when considering models of a rather general class of nonlinear systems. The discrete equations of the super‐twisting observer are reformulated as generalized equation and an algorithm for the step‐by‐step solution is given. The uniqueness of the derived algorithm is investigated with an equivalent variational inequality formulation which is derived for a class of nonlinear systems. Furthermore, a semi‐implicit predictor‐corrector discretization is presented which is an approximation method for the presented algorithms and allows an explicit implementation in practical applications. Accuracy properties under noise and sampling are given. The algorithm is applied on two mechanical example systems taken from practice. [ABSTRACT FROM AUTHOR]

Optimal control theory allows finding the optimal input of a mechanical system modelled as an initial value problem. The resulting minimisation problem may be solved with known direct and indirect methods. We propose time discretisations for both methods, direct midpoint (DMP) and indirect midpoint (IMP) algorithms, which despite their similarities, result in different convergence orders for the adjoint (or co-state) variables. We additionally propose a third time-integration scheme, Indirect Hamiltonian-preserving (IHP) algorithm, which preserves the control Hamiltonian, an integral of the analytical Euler–Lagrange equations of the optimal control problem. We test the resulting algorithms to linear and nonlinear problems with and without dissipative forces: a propelled falling mass subjected to gravity and a drag force, an elastic inverted pendulum, and the locomotion of a worm-like organism on a frictional substrate. To improve the convergence of the solution process of the discretised equations in nonlinear problems, we also propose a computational simple suboptimal initial guess and apply a forward–backward sweep method, which computes each set of variables (state, adjoint and control) in a staggered manner. We demonstrate in our examples their practical advantage for computing optimal solutions. [ABSTRACT FROM AUTHOR]

Objectives: After bonding brackets to the first deciduous molar in a 2 × 4 technique, a three-dimensional finite element analysis (3D FEA) is used to demonstrate the biomechanical changes in an orthodontic system. This study aims to opt for the appropriate type of orthodontic technology by analyzing and comparing the mechanical systems produced by two types of 2 × 4 techniques employing rocking-chair archwires. Materials and methods: Herein, the maxilla and maxillary dentition are modeled by cone beam computed tomography (CBCT) and 3D FEA. Common clinically used 0.016-inch round archwires (material: titanium-molybdenum alloy and stainless-steel) and 0.018-inch round archwires (material: titanium-molybdenum alloy and stainless-steel) are bent into the shape of a rocking chair with a depth of 3 mm. The forces and moments applied to the brackets are transferred to the dentition to evaluate the biomechanical effects of the 2 × 4 technique after the bracket is bonded to the first deciduous molar. Results: For the central incisor, the teeth-moving distance in all three directions increases with bracket bonding to the first deciduous molar applying the 0.016-inch rocking-chair archwire. For the lateral incisor, the tooth root moves toward the gingival side when using 0.016-inch and 0.018-inch archwires. Moreover, for the same archwire size, the lateral incisors move toward the gingival side by bonding the bracket to the first deciduous molar. After bonding a bracket to the first deciduous molar, using rocking-chair archwires of 0.016 inch or 0.018 inch, the buccal movement distance of the first molar crown increases in the X-axis direction. In the Y-axis and Z-axis directions, the modified 2 × 4 technique significantly increases the effect of backward-tipping compared with the traditional 2 × 4 technique. Conclusions: In clinical practice, the modified 2 × 4 technique can be used to increase the movement distance of anterior teeth to a certain extent and accelerate the orthodontic teeth movement. Moreover, the modified 2 × 4 technique is better in anchorage conservation of the first molar than the traditional technique. Clinical relevance: Although the traditional 2 × 4 technique is widely used in early orthodontic treatment, we found mucosal damage and abnormal archwire deformation might affect orthodontic treatment time and effect. The modified 2 × 4 technique is a novel approach that avoids these drawbacks and improves orthodontic treatment efficiency. [ABSTRACT FROM AUTHOR]

A generalized method for finding an optimal control of the amplitude of one-dimensional oscillations in the vicinity of the equilibrium position for a scleronomous multidimensional mechanical system with friction is proposed. The oscillatory degree of freedom of the system does not lend itself to direct control. Its motion is influenced by other, directly controlled degrees of freedom. They are chosen as control functions. The directly controlled coordinates can include both positional and cyclic ones. The method does not use adjoint variables in the sense of Pontryagin's maximum principle and does not increase the dimension of the original system of differential equations of motion. The effectiveness of the method is demonstrated as applied to a specific oscillatory mechanical model with dry and viscous friction. [ABSTRACT FROM AUTHOR]

Copyright of Packaging & Food Machinery is the property of Packaging & Food Machinery Magazine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Purpose: The stability problem for non-conservative multi-parameter dynamical system is usually associated with labor-intensive calculations, and numerical methods do not always allow one to obtain the desired information. The presence of circulatory forces often leads to the so-called "destabilization effect" of the system under the influence of small dissipative forces. In this regard, it seems important to develop analytical approaches that make it possible to use a simplified scheme for checking the stability conditions. Methods: When obtaining and analyzing stability conditions, the algebra of polynomials and elements of mathematical analysis are applied. To obtain a simplified scheme for checking the stability conditions, an asymptotic method is used. Results and Conclusion: A mechanical system with four degrees of freedom which is under the action of dissipative, potential and non-conservative potential (circulatory) forces is considered. The stability problem of friction-induced vibrations is studying. In the case of weak damping an analytical approach is proposed that makes it possible to simplify the analysis of stability conditions, which, due to the presence of many uncertain parameters, are very cumbersome. With the help of numerical testing, the adequacy of the results obtained for the reduced conditions and full stability conditions was established. The results of the analysis make it possible to single out the "advantageous" regions in the space of dimensionless parameters, which makes it possible to improve the design of the system to increase its reliability. [ABSTRACT FROM AUTHOR]

Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The existing hydraulic support modeling method has the problems of single modeling mode and lack expression of internal actions of the model. It is difficult to realize deep knowledge mining of the digital twin model. The modeling of hydraulic support only studies the mechanical or hydraulic parts separately. It is difficult to master its overall dynamic characteristics. In order to solve the above problems, taking the shield hydraulic support ZY6800/08/18D as the research object, a hydraulic support digital twin joint modeling method is proposed. The three-dimensional solid models of the mechanical system and the hydraulic system of the hydraulic support are established by using the SolidWorks software. The three-dimensional solid model is imported into the MapleSim software by .sldasm file format. The kinematic pair is used for connecting the mechanical part, and the hydraulic element is used for connecting the hydraulic part. The twin models of the mechanical system and the hydraulic system of the hydraulic support are established. The twin models are combined to carry out data interaction and model optimization with the physical entity through a database. In order to make the model one to one mapping physical entity, the hydraulic support digital twin is established, including system layer, information layer and physical layer. The consistency experiment of virtual and real is carried out on the digital twin of the hydraulic support. Under the condition of inputting the same signal into the physical entity and the twin, the consistency of the angle change of the connecting rod between the physical entity and the twin is analyzed. The rationality and accuracy of the model are verified. The results show that the fitting degree of the angle of the connecting rod between the physical entity and the twin is 0.986, which is close to 1. The fitting degree is good, which indicates that the position and attitude information of the twin model driven by real data is basically consistent with the running result of the physical entity. The overall angle error of the connecting rod is from −0.198° to +0.185°, which meets the precision requirements within the precision range of the tilt sensor. The motion law of the digital twin model conforms to the actual motion state of the hydraulic support. The mutual mapping and mutual fusion between the physical entity and the digital twin are realized.

The method of calculation of natural frequencies and forms of oscillations of a two-link mechanical system of a robot manipulator is proposed. Links of the system are considered as straight rods with a step change of cross-sectional parameters. The equations of motion of a mechanical system are based on the technical bending theory. The analysis of oscillation processes is carried out using the matrix method of initial parameters.

Copyright of Food & Machinery is the property of Food & Machinery Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Computer Measurement & Control is the property of Magazine Agency of Computer Measurement & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A moving target tracking control problem for marching tank based on adaptive robust feedback control scheme is addressed. A series of preparations is needed for tank gun before shooting a target, the purpose of this paper is to design a control system to fulfill two requirements in this process: the turret-barrel system of tank needs to be adjusted from off-target position to command position and point to the moving target stably when there are strong uncertainties (modeling error, uncertain disturbance with unknown boundaries and road excitation) in the system. Considering the characteristic of coupled interaction, the first thing we do in this paper is to build a coupled analysis model of turret - barrel system with uncertainty term in state-space form. Second, an adaptive robust feedback control scheme is proposed by adding adaptive law to overcome the uncertainty. Third, multi-body dynamics software is used to establish the mechanical mechanism of the tank, and DC-motor module is established in SIMULINK environment, thus the target information and tracking error of the control system is collected and transferred, the gear-ball screw is derived directly by the output torque of the DC-motor module. Finally, the control system and the 3D model are combined together by means of RecurDyn/SIMULINK co-simulation, the turret-barrel system of tank can approximately track the moving target in a certain range. With the adaptive robust feedback control, the target action is completely followed when the target location is constantly changing.

For the control of dynamic systems such as an Electro-Hydraulic Actuator (EHA), there is a need to optimize the control based on simulations, since a prototype or a physical system is usually not available during system design. In consequence, no system identification can be performed. Therefore, it is unclear how well a simulation model of an EHA can be used for multicriteria optimization of the position control due to the uncertain model quality. To evaluate the suitability for control optimization, the EHA is modeled and parameterized as a grey-box model using existing parameters independent of test bench experiments. A method for multi-objective optimization of a controller is used to optimize the position control of the EHA. Finally, the step responses are compared with the test bench. The evaluation of the step responses for different loads and control parameters shows similar behavior between the simulation model and the physical system on the test bench, although the essential phenomena could not be reproduced. This means that the model quality achieved by modeling is suitable as an indication for the optimization of the control by simulation without a physical system. [ABSTRACT FROM AUTHOR]

The paper aims to identify the situations in which a complex elastic system, which is subject to mechanical vibrations, can act as a dynamic absorber of vibrations for certain frequencies. The conditions that the system must fulfill in order to achieve this goal are determined and then a calculation example is presented. The method is interesting because it allows to avoid attaching an absorber specially built for this, a situation that complicates the project and increases manufacturing costs. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Mine Automation is the property of Industry & Mine Automation Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Due to assembly, wear and manufacturing errors and clearance in the joints are inevitable. When the clearance is introduced into a mechanical system, the impact force in the clearance joint will cause undesirable vibration of the system. In this paper, the dynamic responses of the mechanical system with two revolute clearance joints are studied using computational and experimental methodology. The clearance joint is considered as force constraint. The normal contact force and tangential friction force between the journal and bearing in a clearance joint are modeled using a nonlinear contact force model considering energy loss and a modified Coulomb friction model considering a dynamic friction coefficient, respectively. A planar slider‐crank mechanism with two revolute clearance joints is used to implement the study. The dynamic responses obtained from numerical simulation are compared with the experimental test. Numerical simulations and experimental tests for different clearance sizes and crank speeds are presented and discussed, respectively. The simulation results agree quite well with those of the experiment for different cases, which proves the accuracy and efficiency of the computational method for dynamics analysis of the mechanical system with two revolute clearance joints in this study. The investigation indicates that the clearances in revolute joints significantly affect the dynamic characteristics of mechanical systems, which must be considered in the precision analysis, design, and control of multibody systems, especially for high‐speed machinery.

Intelligent fault diagnosis has been a promising way for condition-based maintenance. However, the small sample problem has limited the application of intelligent fault diagnosis into real industrial manufacturing. Recently, the generative adversarial network (GAN) is considered as a promising way to solve the problem of small sample. For this purpose, this paper reviews the related research results on small-sample-focused fault diagnosis methods using the GAN. First, a systematic description of the GAN, and its variants, including structure-focused and loss-focused improvements, are introduced in the paper. Second, the paper reviews the related GAN-based intelligent fault diagnosis methods and classifies these studies into three main categories, deep generative adversarial networks for data augmentation, adversarial training for transfer learning, and other application scenarios (including GAN for anomaly detection and semi-supervised adversarial learning). Finally, the paper discusses several limitations of existing studies and points out future perspectives of GAN-based applications. • Generative adversarial network for intelligent fault diagnosis under small sample is discussed. • A systematic description of the generative adversarial network, and its variants, is provided. • Existing studies based on generative adversarial network for mechanical fault diagnosis are systematically reviewed and classified in this paper. • Limitations of existing studies, as well as future perspectives, are provided in this paper. [ABSTRACT FROM AUTHOR]

In this paper, a novel gain-scheduled sliding-mode-type (SM-type) iterative learning (IL) control approach is proposed for the high-precision trajectory tracking of mechanical systems subject to model uncertainties and disturbances. Based on the SM variable, the proposed controller is synthesized involving a feedback regulation item, a feedforward learning item, and a robust switching item. The feedback regulation item is adopted to regulate the position and velocity tracking errors, the feedforward learning item is applied to handle the model uncertainties and repetitive disturbance, and the robust switching item is introduced to compensate the nonrepetitive disturbance and linearization residual error. Moreover, the gain-scheduled mechanism is employed for both the feedback regulation item and feedforward learning item to enhance the convergence speed. Convergence analysis illustrates that the position and velocity tracking errors can eventually regulate to zero under the proposed controller. By combining the advantages of both SM control and IL control, the proposed controller has strong robustness against model uncertainties and disturbances. Lastly, simulations and comparisons are provided to evaluate the efficiency and excellent performance of the proposed control approach. [ABSTRACT FROM AUTHOR]

Considered in this paper are mathematical models of mechanics together with the theory of electrical circuits, and their similar dynamical structure is revealed. Using basic analogies, a chain of mechanical springs and an equivalent electrical analogue are constructed. Examples of "successful" borrowings are given, when methods of the theory of electrical circuits may be used to solve stabilization problems for a mechanical system formed by a set of interconnected mechanical subsystems. [ABSTRACT FROM AUTHOR]