Coupling Of Motion Research Articles

Advanced Synchronous Control of Dual Parallel Motion Systems

Dual parallel motion systems are mechanisms that drive load jointly by dual parallel motion axes. For these special mechanisms, diminishing desynchronization between parallel axes is essential to harness the potential performance of the whole system. However, a wide variety of synchronization applications tend to have great differences in control objectives and mechanical structures, which makes it laborious and time-consuming to design customized control schemes. Meanwhile, existing generalized synchronous control schemes are simply based on state compensation, which finitely offset mechanical coupling effect and limit the synchronization performance. To overcome these drawbacks, a generalized model of dual parallel motion systems is presented in this article, which can categorize the synchronous control objective into one uniform expression. By applying motion decoupling strategy to the generalized model, an advanced composite synchronous control scheme is proposed, which provides a generalized synchronization solution with comprehensively considering the motion coupling effect. Finally, simulation and experimental results on a dual-driven gantry platform verify that the proposed control scheme can significantly improve the synchronization performance.

Hierarchical Sliding Mode Control for the Trajectory Tracking of a Tendon-Driven Manipulator

Abstract The tracking control of tendon-driven manipulators has recently become a hot topic. However, the flexible elastic tendon introduces greater residual vibration, making it more difficult to control the trajectory tracking of the manipulator. In this paper, a dynamics model of the elastic tendon-driven manipulator (ETDM) that considers motion coupling is established. A hierarchical sliding mode control (HSMC) method is proposed to realize the trajectory tracking control of the ETDM. On the basis of the Lyapunov design method, the actuator subsliding manifold is defined as the first sliding manifold. The first sliding manifold is then used to construct the joint side subsliding manifold. Furthermore, the total sliding manifold is established based on the joint side sliding manifold and the actuator's sliding manifold. The stability of the proposed HSMC is proved using the Lyapunov stability theory. Finally, simulations and experiments are performed on a two-degree-of-freedom ETDM tracking desired trajectories to demonstrate the effectiveness of the proposed HSMC method. The proposed HSMC exhibits higher tracking accuracy compared with proportional–integral–derivative, and adaptive second-order fast nonsingular terminal sliding mode (SOFNTSM) controls in the simulations. The introduction of different disturbances reveals that HSMC has better robustness than proportional–integral–derivative control. Experimental results show that the maximum error of trajectory tracking is less than 0.025 rad.

Low-lying state investigations of odd-A Mn isotopes around N = 28

Based on the systematic studies for low-lying states of the odd-A 49−57Mn isotopes, the ground-states inversion and the rotational properties of a ground-state-based sequence are revealed and discussed. The energy levels of low-lying states and electromagnetic moments in odd-A 49−57Mn isotopes have been well reproduced in shell-model calculations, and the above phenomena could be understood with obviously different occupation numbers in proton orbitals such as π f 7/2 and π p 3/2, which changes similarly with the obtained quadrupole deformation in covariant density functional theory (CDFT). After considering the coupling of collective rotation and intrinsic single-particle motion, the available experimental magnetic moments in 53Mn and adjacent nuclei can be well explained with CDFT. The present calculations suggest that the 5/2− and 7/2− states in 53Mn are formed by π5/2−[312] and π7/2−[303] respectively. Together with the behavior of levels, this provides proofs for the level sequences of low-lying states in 53Mn distinct from the K π = 5/2− rotational band in 49Cr and other odd-A Mn isotopes.

Study on the Rotation Effect on the Modal Performance of Wind Turbine Blades

With the large-scale development of wind turbines, large flexible blades bear heavier loads. In the actual rotating work of blades, the coupling of structural deformation and motion produces a dynamic stiffening effect and spin softening effect, which affects the dynamic characteristics of blades. In this study, the finite element method is used to model the NREL 5MW blade, and the dynamic stiffening and spin softening effects are investigated using the modal analysis. The influence of rotating effects on the blade’s natural frequency is revealed. It is concluded that the effect of dynamic stiffening is more significant than that of spin softening, and the comprehensive result of the two effects is not simply the superposition of them but presents obvious nonlinearity.

Systematic study of the effect of individual rotational energy levels on the fusion cross-section of 16 O-based reactions of range 480 ≤ Z P Z T ≤ 592

In heavy-ion fusion reactions, the enhancement in the sub-barrier fusion cross-section has been observed as compared to the 1-Dimensional barrier penetration model due to the coupling of many degrees of freedom to the relative motion. This enhancement can be explained theoretically by including nuclear structure effects like deformation and the coupling of relative motion among two colliding nuclei. The present work aims to investigate the effect of individual rotational energy levels on the fusion cross-sections for 16O-based reaction systems, namely, 16O + 182,184,186W, 16O + 176,180Hf, 16O + 174,176Yb, 16O + 166Er, 16O + 148,152,154Sm, 16O + 150Nd at energies below the fusion barrier. Using the CCFULL code, the effect of low-lying rotational energy levels on the fusion cross-section for 16O induced reactions has been investigated at energies below and around the Coulomb barrier. The calculations are performed by assuming the fixed value of diffuseness parameter a 0 = 0.65 fm in the Woods-Saxon nuclear potential and the other two parameters are optimised by fitting the experimental data at the above barrier. Here we have determined the V 0 and r 0 as a function of Z P Z T , where experimental cross-sections are available. From our calculations, it is observed that the hexadecapole deformation (β 4) with different magnitudes has a significant influence on the fusion cross sections. For the case of the +ve value of β 4, beyond 10+, the rotational levels cease to contribute significantly and also there is a significant difference between the contribution of sequential channels. On the other hand, in the case of -ve β 4, up to 6+ levels contribute significantly. Furthermore, we have established an algebraic systematic of fitting, which one can use to determine the parameters V 0, r 0 of Woods-Saxon nuclear potential within the range of Z P Z T lie in between 480 ≤ Z P Z T ≤ 592.

Structural design and active disturbance rejection control of rigid-flexible coupling motion stage for nanopositioning

Mechanical-bearing-guided motion stage is widely used in electronic manufacturing equipment for its excellent high-acceleration performance and low cost, but its positioning precision is limited by the friction of mechanical bearing. To this end, a rigid-flexible coupling motion stage (RFCMS) with compound flexure hinges (CFHs) and a single drive is designed to simultaneously achieve large stroke and nanoscale precision in this work. The friction dead zone is isolated by utilizing the bending deflection of CFHs. To suppress the resonance of CFHs and deal with nonlinear disturbances and uncertainties, a model-based active disturbance rejection control (model-based ADRC) is adopted based on the bending stiffness modeling of CFHs, which can improve the tracking accuracy for the position profile and reduce the estimating error of the extended state observer for the total disturbance. Despite the uncertain control input gain and the nonlinear coupling of the working stage and the rigid frame, the tracking and estimating errors of closed-loop system are theoretically investigated. Experimental results show that RFCMS with model-based ADRC strategy can achieve positioning accuracy within 100 nm in point-to-point motion and has strong robustness to load mass changes.

Computational mathematics model of Passive spiral cochlea

The ear is an important sensory organ of the human body. Cochlea has a pivotal role in the hearing system of human. Nearly 300 million people around the world suffer from sensorineural deafness caused by cochlear lesions. Because the mechanism of cochlear sensing is very complex, it has not been understood completely so far, which has become one of the important problems in medicine today. The basilar membrane in the cochlear canal is the supporting structure of all microstructures, the complex coupling motion between basilar membrane and lymph in cochlear canal is the primary condition for generating the cochlear sound sensing function. Therefore, it is essential to study the dynamic behavior of the basement membranes. By dividing the length of the cochlea into a finite number of elements and giving the radial distribution, a set of governing equations is derived for coupling micromechanics with fluid. Then combining these equations with the matrix combination equation, the complete coupling response of basilar membrane and lymph is obtained. The instantaneous responses of the basilar membrane under different excitations, the time domain responses of the resonance position under different frequency excitations, and the effects of the changes of the mass and stiffness of the basilar membrane on its biomechanical properties and hearing function are analyzed. The results showthat the increase of the mass and stiffness of the basilar membrane leads to the weakening of the maximum response, and the increase of the mass causes the maximum response position to move to the bottom of the basilar membrane; the increase of the basilar membrane stiffness causes the maximum response position to move to the top of the basilar membrane; the changing basilar membrane cross-section can rapidly reduce the characteristic frequencies at the middle and top of the cochlea, thus achieving better filtering and amplification of specific frequency excitation, and enabling the cochlea to have a higher resolution in a specific frequency range of 1000–3000 Hz.This computational mathematics model can provide a numerical analysis platform for implementing the clinical evaluation of lesions in the basilar membrane of the inner ear. Compared with the existing finite element models, this method has faster calculation speed and higher efficiency of parameter analysis.

Signal Accumulation Method for High-Speed Maneuvering Target Detection Using Airborne Coherent MIMO Radar

The airborne coherent multi-input multi-output (MIMO) radar benefiting from coherent integration (including intra-channel integration and inter-channel integration) of multi-channel echoes can obtain superior detection performance for high-speed maneuvering targets. However, due to the coupling motion characteristic between multiple airborne platforms and high-speed targets, the range walk (RW) and Doppler walk (DW) will occur within the intra-channel integration. Besides, the inter-channel signals also exist envelope and phase differences, which will lead to the difficulty in multi-channel integration. We make contributions towards addressing these limitations. On the one hand, we establish a three-dimensional (3-D) geometrical model for high-speed maneuvering target detection with airborne coherent MIMO radar and derive the mathematical expression of radar echoes, while the generalized Radon-Fourier transform (GRFT) is utilized to simultaneously correct the RW and DW for acquiring intra-channel integration. On the other hand, we analyze the properties of GRFT outputs and propose a GRFT-domain integration method to achieve the multi-channel coherent integration. More specifically, the proposed method first constructs a set of coupling equations for the estimation of target motion parameters (i.e., position, velocity and acceleration), then, the target's motion parameters can be estimated by Newton-Raphson method and solving the linear equations. Second, in order to settle the envelope and phase differences between multi-channel echoes, the envelope alignment and phase compensation functions of inter-channel echoes are constituted based on the estimated parameters. Finally, the coherent accumulation of multi-channel echoes can be implemented. Numerical simulations demonstrate the effectiveness of the proposed method.

Optimal Control Design for Decoupling the Direct Drive Stability of Distributed Drive Electric Vehicles

As a new type of drive for electric vehicles, distributed drive has many advantages such as simple structure and easy control, and is one of the important development directions of new energy vehicles in the future. In the past decade, the research on the active safety control of distributed drive electric vehicles has become more and more mature. In this paper, we propose a decoupled optimal control strategy based on the drive torque for the vehicle run-off and motion coupling problems that exist during the straight-line driving of distributed-drive electric vehicles. The upper control logic layer is responsible for cross-swing motion control and drive anti-skid control. The middle control logic layer is responsible for secondary planning of the additional torque from the upper control layer, based on which the decoupled cross-swing motion control with wheel anti-skid is realised. The lower control logic layer is responsible for the optimal distribution of the drive torque for speed following control. The decoupled optimal control of drive torque proposed in this paper can achieve the optimal distribution of drive torque, avoiding vehicle deflection on the premise of ensuring vehicle speed, while preventing excessive wheel slip, realising the decoupled control of vehicle linear motion and enhancing the linear driving stability of the vehicle.

Dynamic Modeling and Analysis of Loader Working Mechanism Considering Cooperative Motion with the Vehicle Body

Achieving precise load detection for Intelligent Loaders is an important task, which directly affects the operation energy efficiency and the fatigue life analysis for the loader’s working mechanism. The operation of the mechanism is regarded as a 3-DOF (degree of freedom) planar motion process coordinated with the vehicle body. Affected by complex dynamic coupling in motion, the existing dynamic models of the mechanism have the problem of insufficient accuracy, which is not conducive to the precise calculation of load. Taking the reverse six-linkage loader as the research object, an accurate dynamic model of the mechanism is established considering its cooperative motion with the vehicle body. Firstly, the kinematic description of the mechanism is given by the Rodriguez method. Then, to overcome the coupling effect caused by the cooperative motion, the sufficient inertia forces of the mechanism are established in joint space using the Lagrange method. Furthermore, to overcome the coupling effect caused by the complex structure, the Newton–Euler method is used to establish the force mapping relations between the joint space and the drive space by multi-body modeling. Finally, the dynamic model of the mechanism in drive space is obtained, and the specific mapping relations between the bucket force, the vehicle driving force, and the drive parameters are given. Compared with existing dynamic models in simulation, the analysis shows that the average and maximum absolute errors of the vehicle driving force calculated by the established model do not exceed 20% of the existing model errors, and the corresponding errors of the bucket force do not exceed 10% of the existing model errors, which proves that the motions of vehicle body and front-end mechanism, as well as the force of the tilt hydraulic cylinder, play important roles in improving the model accuracy. The established model is superior to existing models and is more suitable for cooperative motion with the vehicle body.

Modeling and Characteristic Analysis of Combined Beam Tri-Stable Piezoelectric Energy Harvesting System Considering Gravity

The emergence of the vibration energy harvesting system makes it possible for wireless monitoring nodes in coal mines to realize self-power supply. In order to reveal the influence of gravity effect on the response characteristics of the combined beam tri-stable piezoelectric energy harvesting system (CTEHS), the system’s nonlinear magnetism is calculated according to the principle of point magnetic charge dipole, and the system’s nonlinear resilience is obtained through experimental measurements and nonlinear fitting methods. Based on the Lagrange equation, the system’s electromechanical coupling motion model considering gravity is established. The system’s motion equation is solved numerically based on the Runge–Kutta algorithm, and the effects of the end magnet mass and the initial vibration point on the bifurcation behavior, potential energy, and system output performance are investigated by emulation and experiment. The research shows that the magnet’s gravity effect causes a change in the stable equilibrium position and the system’s motion state and also causes the system to generate additional gravitational potential energy, which leads to a potential asymmetric well of the system. Under the consideration of magnet gravity, the appropriate end magnet mass and initial vibration point can not only reduce the system’s requirements for external excitation strength but also effectively improve the system’s response and output. This research provides a new theoretical basis for the optimal design of the tri-stable piezoelectric energy harvesting system.

Ultrastrong coupling between electron tunneling and mechanical motion

The ultrastrong coupling of single-electron tunneling and nanomechanical motion opens exciting opportunities to explore fundamental questions and develop new platforms for quantum technologies. We have measured and modeled this electromechanical coupling in a fully suspended carbon nanotube device and report a ratio of ${g}_{\text{m}}/{\ensuremath{\omega}}_{\mathrm{m}}=2.72\ifmmode\pm\else\textpm\fi{}0.14$, where ${g}_{\text{m}}/2\ensuremath{\pi}=0.80\ifmmode\pm\else\textpm\fi{}0.04\phantom{\rule{0.16em}{0ex}}\mathrm{GHz}$ is the coupling strength and ${\ensuremath{\omega}}_{\mathrm{m}}/2\ensuremath{\pi}=294.5\phantom{\rule{0.16em}{0ex}}\mathrm{MHz}$ is the mechanical resonance frequency. This is well within the ultrastrong coupling regime and the highest among all other electromechanical platforms. We show that, although this regime was present in similar fully suspended carbon nanotube devices, it went unnoticed. Even higher ratios could be achieved with improvement on device design.

A characterization method for low-frequency seismic noise in LIGO

We present a method to characterize the noise in ground-based gravitational-wave observatories such as the Laser Gravitational-Wave Observatory (LIGO). This method uses linear regression algorithms such as the least absolute shrinkage and selection operator to identify noise sources and analyzes the detector output vs noise witness sensors to quantify the coupling of such noise. Our method can be implemented with currently available resources at LIGO, which avoids extra coding or direct experimentation at the LIGO sites. We present two examples to validate and estimate the coupling of elevated ground motion at frequencies below 10 Hz with noise in the detector output.

Monocular Vision-Based Calibration Method for the Axial and Transverse Sensitivities of Low-Frequency Triaxial Vibration Sensors With the Elliptical Orbit Excitation

The low-frequency triaxial vibration sensors have been gradually applied in many engineering fields of vibration monitoring because they can measure the multidirection vibrations simultaneously. The accurate axial and transverse sensitivities, determined by the calibration method, are the prerequisite for ensuring their measurement accuracy. Currently, the laser interferometry (LI) which is based on a single component or a tricomponent linear shaker is usually applied to calibrate these sensitivities. However, the former has to require the multiple reinstallations of the sensor and the latter cannot avoid the motion coupling caused by the shaker, these inevitably increase the calibration uncertainty. In this article, we investigate a monocular vision (MV)-based two-component shaker calibration method, which determines the axial sensitivity based on the time-spatial synchronization and transverse sensitivity at the elliptical orbit excitation. The MV method is used to measure this excitation, and a plane sensitivity model is presented to describe these sensitivities. This investigated method can simultaneously reduce the uncertainties caused by the reinstallations and motion coupling to improve the calibration accuracy. Experimental results compared with the LI and Earth's gravitation method demonstrate that the investigated method obtains the satisfactory accuracies both in axial sensitivity magnitude and phase as well as transverse sensitivity magnitude and direction calibration.

Design of a compact long-stroke high-precision rigid-flexible coupling motion stage driven by linear motor

Design of a compact long-stroke high-precision rigid-flexible coupling motion stage driven by linear motor

Design and Prototyping of an Underactuated Index Finger Exoskeleton

At present, the rehabilitation treatment methods for hand dysfunction caused by stroke are mainly to reconstruct or improve the hand motor function of stroke patients through motor learning. To realize smooth motion without the interference of the underactuated hand exoskeleton system, this paper designs and manufactures an exoskeleton system in which a single motor drives the index finger MCP and PIP to rotate. The simulation results show that the system can realize 0-90° motion of MCP and 0-110° motion of PIP, and the motion is smooth and without interference. The system is prototyping by 3D printing. By testing the prototype, the actual movement range of the prototype is slightly smaller than the design index, and it can achieve the 0-90° movement of the MCP, but the PIP can only achieve the 0-90° movement. Through further research and analysis, it is determined that this phenomenon is caused by unreasonable motion coupling between MCP and PIP, inaccurate axial positioning, and offset of the rotation center of each joint. The system will be used as the basis for follow-up research and will continue to be optimized in combination with the problems shown in the actual wearing, and finally design and manufacture a complete set of underactuated hand exoskeleton systems that can move smoothly without interference.

A Two-Segment Continuum Robot With Piecewise Stiffness for Maxillary Sinus Surgery and Its Decoupling Method

With the use of tendon-driven continuum manipulators, it is possible to reach deep-seated small lesions in a constrained anatomical space. This circumvents the difficulties encountered by existing straight endoscopes and surgical instruments, which require direct line of sight access during inspection and operation. However, maintaining adequate stiffness while ensuring smoothness and flexibility during operation for a continuum robot with a small diameter is difficult. In this article, we present the design, modeling, and validation of a new two-segment continuum robot for maxillary sinus surgery. It addresses the coupling effects that can affect the safety and precise operation within the maxillary sinus. To overcome potential distal-to-proximal deviations, a piecewise stiffness structure for the continuum manipulator is proposed. Modified kinematics, based on variable curvature continuum kinematics, is used to resolve motion coupling, and a model of the continuum manipulator with varying stiffness is proposed, with due consideration of tension coupling. Experiments are carried out to validate the proposed design, modeling, and compensation schemes. Results show that the proposed manipulator can flexibly and accurately reach the target positions in the maxillary sinus model. Comparisons of continuum robots with and without the proposed compensation schemes demonstrate the practical value and potential clinical use of the proposed method.

A smooth-drive scheme for piezoelectric stage by coupling of stick-slip motion and inertial impact

The piezoelectric stick-slip stage is very important in industrial manufacturing and precision machining. However, due to the stick-slip principle, it is inevitable to produce backward motion, which leads to a decrease in precision and efficiency. A novel smooth-drive scheme for piezoelectric stage is proposed by coupling stick-slip motion and inertial impact in this paper. In the coupling counteract phase, the sliding friction force of stick-slip driving mechanism (SDM) is counteract by the impact force of inertial impact driving mechanism (IDM), thus eliminating the backward motion and realizing the smooth driving of the stage. The feasibility of the stage is analyzed by theoretical calculation and transient dynamics simulation. In addition, the designed stage is fabricated and conducted a complete set of experimental tests. The external dimensions of the stage is 45 mm (L) × 24 mm (W) × 22 mm (H), and the mass is 84 g. Experimental results show that the piezoelectric stage can not only achieve smooth driving, but also actively adjust the output smoothness by adjusting the excitation voltage of PZT I and PZT II. The linear fitting correlation coefficient R2 of the displacement curve can reach above 0.999, and it still keeps good smoothness at 200 Hz. The maximum vertical mass load of the stage is 4 kg, which is about 47 times the mass of the stage, and the resolution of stick-slip state is about 85 nm. The scheme has positive reference value in the field of stable and accurate positioning.

Variable Time Headway Policy Based Platoon Control for Heterogeneous Connected Vehicles With External Disturbances

This article develops a new platoon control strategy for heterogeneous connected vehicles (CVs) subject to time delays and external disturbances. Specifically, based on the third-order vehicle model, a novel platoon controller is developed by embedding the variable time headway (VTH) spacing policy and the nonlinear motion coupling interactions between CVs. Simultaneously, an integral sliding mode (ISM) controller is developed to resist the disturbances. Then, the condition of asymptotic stability for the CV platoon and the upper bound of communication delay are deduced by using the Lyapunov theorem. Also, the string stability is proved by using the infinity-norm method. Finally, extensive simulations and co-simulations are provided to show the validity of the developed controller. Moreover, experiments with intelligent micro vehicles are conducted further to validate the practical feasibility of the developed controller.

Analysis of Kinematic Characteristics of Saanen Goat Spine under Multi-Slope.

In order to improve the slope movement stability and flexibility of quadruped robot, a theoretical design method of a flexible spine of a robot that was based on bionics was proposed. The kinematic characteristics of the spine were analyzed under different slopes with a Saanen goat as the research object. A Qualisys track manager (QTM) gait analysis system was used to obtain the trunk movement of goats under multiple slopes, and linear time normalization (LTN) was used to calibrate and match typical gait cycles to characterize the goat locomotion gait under slopes. Firstly, the spatial angle changes of cervical thoracic vertebrae, thoracolumbar vertebrae, and lumbar vertebrae were compared and analyzed under 0°, 5°, 10°, and 15° slopes, and it was found that the rigid and flexible coupling structure between the thoraco-lumbar vertebrae played an obvious role when moving on the slope. Moreover, with the increase in slope, the movement of the spine changed to the coupling movement of thoraco-lumbar coordination movement and a flexible swing of lumbar vertebrae. Then, the Gaussian mixture model (GMM) clustering algorithm was used to analyze the changes of the thoraco-lumbar vertebrae and lumbar vertebrae in different directions. Combined with anatomical knowledge, it was found that the motion of the thoraco-lumbar vertebrae and lumbar vertebrae in the goat was mainly manifested as a left-right swing in the coronal plane. Finally, on the basis of the analysis of the maximin and variation range of the thoraco-lumbar vertebrae and lumbar vertebrae in the coronal plane, it was found that the coupling motion of the thoraco-lumbar cooperative motion and flexible swing of the lumbar vertebrae at the slope of 10° had the most significant effect on the motion stability. SSE, R2, adjusted-R2, and RMSE were used as evaluation indexes, and the general equations of the spatial fitting curve of the goat spine were obtained by curve fitting of Matlab software. Finally, Origin software was used to obtain the optimal fitting spatial equations under eight movements of the goat spine with SSE and adjusted-R2 as indexes. The research will provide an idea for the bionic spine design with variable stiffness and multi-direction flexible bending, as well as a theoretical reference for the torso design of a bionic quadruped robot.