Coupling Of Motion Research Articles

Steric Communication between Dynamic Components on DNA Nanodevices.

Biomolecular nanotechnology has helped emulate basic robotic capabilities such as defined motion, sensing, and actuation in synthetic nanoscale systems. DNA origami is an attractive approach for nanorobotics, as it enables creation of devices with complex geometry, programmed motion, rapid actuation, force application, and various kinds of sensing modalities. Advanced robotic functions like feedback control, autonomy, or programmed routines also require the ability to transmit signals among subcomponents. Prior work in DNA nanotechnology has established approaches for signal transmission, for example through diffusing strands or structurally coupled motions. However, soluble communication is often slow and structural coupling of motions can limit the function of individual components, for example to respond to the environment. Here, we introduce an approach inspired by protein allostery to transmit signals between two distal dynamic components through steric interactions. These components undergo separate thermal fluctuations where certain conformations of one arm will sterically occlude conformations of the distal arm. We implement this approach in a DNA origami device consisting of two stiff arms each connected to a base platform via a flexible hinge joint. We demonstrate the ability for one arm to sterically regulate both the range of motion and the conformational state (latched or freely fluctuating) of the distal arm, results that are quantitatively captured by mesoscopic simulations using experimentally informed energy landscapes for hinge-angle fluctuations. We further demonstrate the ability to modulate signal transmission by mechanically tuning the range of thermal fluctuations and controlling the conformational states of the arms. Our results establish a communication mechanism well-suited to transmit signals between thermally fluctuating dynamic components and provide a path to transmitting signals where the input is a dynamic response to parameters like force or solution conditions.

Coupled FPSO roll motion response and tank sloshing in a pair of two row cargo tanks

The advantages offered by Floating Production Storage and Offloading Units (FPSOs) continue to make them high in demand and widely used. Continuous loading and offloading of FPSOs means the presence of slack cargo tanks is inevitable and can impact the seakeeping performance of FPSOs. Published experimental data on this impact is limited. This paper experimentally studies liquid cargo and its effect on roll motion in a pair of two-row cargo tanks of a FPSO model in regular beam waves. The results show that the liquid cargo motion effect on floating vessels cannot be studied using solid cargo. The results also show that varying the liquid cargo loading affects floating vessels’ Response Amplitude Operators (RAOs).

Mixed Seeds of Oat and Vetch Based on DEM-Fluent Coupling Motion Simulation in a Venturi Tube

The gas–solid flow of mixed seeds of oat and vetch in the air-blowing venturi tube was simulated numerically by means of a coupling approach of the discrete element method (DEM) and computational fluid dynamics (CFD). In the gas–solid coupling model, EDEM software was used to depict the discrete particle phase, and ANSYS Fluent software was used to describe the continuous gas phase. The effects of the seed entry angle and inlet air velocity on the uniformity of mixed seed supply were studied and analyzed from the angle of airflow field variation and mixed seeds movement characteristics. The simulation results showed that the seeding angle has a great influence on the seed movement in the tube and affects the pressure and velocity gradient of the airflow field. If the seed insertion angle is too large, the number of collisions between the seed and the tube wall will increase, and the phenomenon of seeds retention and disordered jumping will occur. The inlet air velocity mainly affects the outlet air velocity and seed velocity and has little effect on the change in airfield. With the increase in inlet air velocity, the greater the velocity and force of the seeds, the closer the mixed seeds collide with the wall to the outlet pipe. At high inlet airflow velocity, there is a great disparity in the movement speed between the seeds, resulting in uneven spacing between the seeds. The results showed that under the conditions of 60° seed entry angle and 35~40 m/s inlet air velocity, the airflow field distribution in the tube was uniform and the seed movement was continuous and uniform.

The effect of lifting load on the kinematic characteristics of lumbar spinous process in vivo

BackgroundThere are limited data on the in vivo natural kinematics of the lumbar spinous process. This paper intends to explore the effect of lifting load on the in vivo movement mode of the lumbar spinous process and its biomechanical changes.MethodsTen asymptomatic subjects between the ages of 25 and 39 underwent CT scans of the lumbar spine in the supine position, and 3D models of L3-L5 were constructed. Using a Dual Fluoroscopy Imaging System (DFIS), instantaneous orthogonal fluoroscopic images of each subject's flexion–extension, left–right bending, and left–right rotational movements were taken under different loads (0 kg, 5 kg, 10 kg). The supine CT model was matched, using computer software, to the bony contours of the images from the two orthogonal views, so that the instantaneous 3D vertebral position at each location could be quantified. A Cartesian coordinate system was ultimately constructed at the tip of the spinous process to obtain the 6DOF kinematic data of the spinous process.ResultsIn different postural movements of the trunk, there was no significant difference in the rotation angle and translation range of the lumbar spinous process under different loads (P > 0.05). In flexion to extension motion, spinous processes mainly rotate < 4° along the medial and lateral axes and translate < 4 mm along the craniocaudal direction. In the left–right bending motion, spinous processes mainly rotate < 5° along the anterior and posterior axes, and the translation is mainly coupling < 2 mm. In the rotational motion, the spinous process is mainly coupled motion, the rotation range is less than 3°, and the translation range is less than 2 mm. The distance between spinous processes measured in the supine position was 6.66 ± 2.29 mm at L3/4 and 5.08 ± 1.57 mm at L4/5.ConclusionThe in vivo kinematics of the lumbar spinous process will not change significantly with increasing low load. In complex motion, the spinous process is dominated by coupling motion.

An InVitro Biomechanical Study of the Ectopic Functional Reconstruction of the Transverse Ligament of Atlas.

To evaluate the stability and function of the C1-C2 joint after ectopic functional reconstruction (EFR) of the C1 transverse ligament. Eight human cadaveric cervical spines (C0-C4) were subjected to invitro biomechanical test with moment control. Spine specimens were tested under the following conditions: 1) left intact; 2) destabilized by severing the transverse ligament of atlas; 3) after EFR of the transverse ligament. Range of motion was measured in flexion, extension, lateral bending, and axial rotation. Destabilization significantly increased range of motion in all directions compared with the intact status (P < 0.001). However, after EFR of the transverse ligament, range of motion in all directions was restored to the intact state. Meanwhile, coupling motions were reproduced in the axial rotation. EFR of the transverse ligament virtually recovers all the physiological functions of the native transverse ligament and might be a promising alternative for the treatment of anterior atlantoaxial dislocation. Further studies are warranted before clinical application of EFR of the transverse ligament.

Vision-Based Underwater Target Following Control of an Agile Robotic Manta With Flexible Pectoral Fins

Manta-inspired robots have been increasingly applied in vision-based underwater tasks. However, owing to the refraction effect and motion coupling problem, their accurate target following control is still poorly understood. This paper proposes a vision-based underwater target following scheme for robotic manta. First, an agile robotic manta equipped with a binocular camera system is constructed. The motion modes are further detailed based on the propulsion analysis to the flexible pectoral fins. Second, a color-based underwater target detection and localization method is conceived. Specifically, the binocular refraction correction is employed to improve the localization accuracy. Third, combing the nonsingular terminal sliding mode controller and fuzzy inference system, a robust target following controller is presented to solve the coupling between distance and azimuth control of the robot. Finally, various aquatic experiments are conducted, verifying the effectiveness and robustness of the proposed underwater target following scheme. The obtained results provide valuable insights into the intelligent control of agile bioinspired robots performing vision-based tasks in dynamic underwater environments.

Human-exoskeleton oscillation model and qualitative analysis of interaction and functional practicality of exoskeletons

In the previous exoskeleton research, the development method of the exoskeleton-function-expectation prediction in the initial design stage is lacking, which is not conducive to reviewing the system-parameter influences on exoskeleton performances, nor to exploring the exoskeleton optimization direction. In this paper, a human-exoskeleton oscillation model is designed by integrating the main functions of one load-supporting exoskeleton in the gravity direction into the double-mass coupled oscillator model. The model simplifies the human-exoskeleton coupling motion into the human-exoskeleton oscillation motion in the gravity direction, and in the oscillation process qualitatively calculates the multiple functional expectations of the exoskeleton, such as the load-supporting capability, the human-exoskeleton interaction force, the oscillation response of the backpack and the power-assistance ability. By comparing the test results of the model with previous research, the model performance was analyzed. And further, the reasons for the unsatisfying load-supporting efficiency of previous exoskeletons were explained and the influences of system parameters for the system expectations were evaluated, which helps to provide a theoretical basis for improving the exoskeleton load-supporting efficiency and human-body comfort. In addition, the combination of the exoskeleton supporting static load and the suspension system buffering dynamic load is a new direction, and the model of the paper is also beneficial to evaluate the interference degree of the exoskeleton to the suspension system.

Design and Analysis of a Multi-Knuckle Coupled Grasper With Equal Angles at Each Knuckle During Motion

Abstract In this study, a coupled multi-knuckle mechanical finger was designed. The finger is composed of same-structured knuckles in a connecting link structure, and the knuckles can be combined arbitrarily. The coupling motion is completed under the drive of a single actuator. First, the influences of the angular relationship between the knuckles and working stroke of the knuckles on the actual grasping range of the finger were evaluated, and the kinematic analysis of the knuckle was performed using the closed-loop vector method. Next, an optimization design method based on a genetic algorithm was proposed, which considered the angular relationship as the objective function to optimize the knuckle, which is illustrated with an example. The angle between each pair of knuckles is approximately constant and equal, which indicates that the finger has an approximately circular envelope curve. Subsequently, the finger motion simulation was carried out to verify the optimization design results and evaluate the error in the finger grasping process. The grasper is capable of completing accurate envelopes on cylinders with diameters ranging from 38.97 mm to 127.60 mm. Finally, the prototype of the manipulator was constructed according to the parameters obtained in the optimization design example. The feasibility of the design was verified through a grasping experiment using beakers and other objects. It provides a reference for angle optimization and envelope curve design of the grasper.

Effective-mode analysis of the dynamics of weakly bound molecular systems by an example of hydrogen-bonded water clusters

A method for the analysis of internal dynamics of nonlinear weakly bound polymolecular systems based on the effective-mode approach is proposed. The method enables one to estimate the number of the governing collective degrees of freedom of the system of interest at a preset accuracy under particular conditions and analyze the character of the modes depending on the activation energy of the system and the duration of its dynamic propagation, which provides qualitative and quantitative information about the coupling of diverse motions and the respective energy redistribution. The method is applied to the analysis of the dynamics of small water clusters stabilized by hydrogen bonds, which are unique spectacular examples of the systems with a pronounced coupling between the intramolecular and substantially delocalized intermolecular oscillations. The dynamic trajectories were generated in the adiabatic approximation at the Born-Oppenheimer level with the use of the quantum chemical description of selected clusters at the $\mathrm{MP}2/6\ensuremath{-}311++G(d,p)$ level. The initial conditions corresponded to different variants of the excitation of low-frequency normal modes, and the dynamic runs were carried out at a time step of 0.5 fs and the whole duration of 50 to 100 ps. Different prevailing characters of the cluster dynamics were identified depending on the molecular size, the total activation energy, and the mean potential-energy-increment to kinetic-energy-increment ratio, from an efficient accumulation of the excess kinetic energy on the effective modes of the cluster to the dissociation of the cluster into constituting fragments. The signs of the corresponding processes in the overlap matrices of the effective-mode vectors, kinetic-energy distribution over the modes, and the correlation between the number of the modes and the mean kinetic energy of the cluster are distinguished.

Three 2-DOF 1T1R and One 3-DOF 2T1R Full-Hinged Novel Parallel Mechanisms With Zero Coupling Degree and Motion Decoupling: Design and Analysis

AbstractThis paper presents the design and analysis of a family of full-hinged partially-decoupled novel parallel mechanisms (PMs) featuring one/two translation(s) and one rotation (1T1R/2T1R). First, three 2DOF 1T1R and one 3DOF 2T1R novel spatial PMs are proposed, according to topology design theory of PM based on position and orientation characteristic (POC) equations. The 3DOF 2T1R PM is illustrated to show its topological characteristics, such as POC set, degrees-of-freedom (DOF), and coupling degree (k), which show that the PM does not produce parasitic motion, with the coupling degree k being equal to zero. Second, the kinematic and dynamic performances of the 3DOF 2T1R PM are analyzed, including symbolic forward position solutions based on its topological characteristics, the workspace based on both the forward and inverse position solutions, respectively, the singular configurations based on the inverse position solutions, and the dynamic analysis built by means of the virtual work principle based on the single-open-chain units. Finally, the potential application of the proposed 3DOF 2T1R PM, namely, lifting and transferring lightweight workpieces between two perpendicular conveyor belts on the floor, is introduced.

Numerical simulation on the deposition characteristics of MSWI fly ash particles in a cyclone furnace

In melting municipal solid waste incineration (MSWI) fly ash by cyclone furnace, the deposition characteristics of particles affect the slag flow and the secondary MSWI fly ash formation. In this study, the composition mechanism based on critical viscosity is selected as the particle deposition model to predict the deposition and rebound of particles on the furnace wall. The Riboud model with an accurate viscosity prediction performance is selected, then the particle deposition model is integrated into a commercial computational fluid dynamics (CFD) solver through the user-defined function (UDF) to realize the coupling of particle motion and deposition process. The results show that under the same case, the deposition rate decreases obviously with the increase of MSWI fly ash particle size. And the escape rate reaches a maximum at particle size 120 μm. Controlling the particle size of fly ash particles within 60 μm can effectively reduce the generation of secondary MSWI fly ash. During the forward movement of the fly ash inlet position, the escape of MSWI fly ash particles with large particle sizes has been significantly weakened. This measure not only lowers the post-treatment cost but also dramatically reduces the pretreatment step of MSWI fly ash before the melting and solidification process. In addition, the deposition rate and quality will reach the maximum values, respectively, along with gradually increasing MSWI fly ash input flow. Overall, this study has the guiding significance for reducing the pretreatment steps and post-treatment costs of MSWI fly ash by melting in the cyclone furnace.

Combined Thermal and Wear Analysis of Linear Rolling Guide Subjected to Rigid–Flexible Coupling Motion Stage

The local heat and wear generated due to friction in a precision motion stage in electronic packaging equipment have a significant impact on its positioning precision. In this paper, we studied the temperature changes over time and the wear of a linear rolling guide (LRG) in a rigid–flexible coupling motion stage (RFCMS), both analytically and experimentally, and we proposed an evaluation method for LRG wear in an RFCMS. According to Fourier’s law and the law of conservation of energy, the differential equation of heat conduction for the LRG and the thermal boundary conditions were established. Steady-state and transient thermal simulations were carried out using ANSYS Workbench to predict the temperature increase in the LRG due to friction. Finally, a test apparatus was built to demonstrate that an RFCMS reduced the operating temperature of the LRG, which also reduced the wear on the contact surface. Through response surface methodology, the levels of the influence of different flexure hinge thicknesses, strokes, velocities, and accelerations on the temperature change rate (TCR) of the LRG were obtained, as well as the approximate regression equation of four variables of the TCR. This provided a new research method for precision maintenance, life design, and operational parameter selection for high-precision motion stages.

Kinematics Analysis of 6-Degrees-of-Freedom Parallel + Serial Type Hybrid Mechanisms Containing Parallel Mechanism With High Coupling Motions

AbstractThe existing displacement of parallel + serial type hybrid mechanisms is mainly solved by the equivalent serial mechanism (SM) method. However, a large number of lower mobility parallel mechanisms (PMs) that have high coupled motions at the end-effector cannot be equivalent to SMs. Thus, the displacement problem especially for the inverse displacement of this type of hybrid mechanisms has not been well solved. On the basis of this situation, this article takes a 6-degrees-of-freedom (DOFs) 3-UPU + 3R hybrid mechanism as an example to give a general method to solve the displacement problem. First, based on the inverse displacement and pose coupling relationship of the 3-UPU PM, its forward displacement is solved by Sylvester’s dialytic elimination method, and then the forward displacement of the 3-UPU + 3R hybrid mechanism is obtained by the superposition method. Second, by skillfully dealing with the relationship between coupling motions of the 3-UPU PM and the motion of hybrid mechanism, three nonlinear equations containing three unknown motion parameters are obtained, and the inverse displacement problem is solved using Sylvester’s dialytic elimination. The research in this article is valuable in the kinematics modeling of hybrid mechanisms.

Temporal and spatial resolution of distal protein motions that activate hydrogen tunneling in soybean lipoxygenase

The enzyme soybean lipoxygenase (SLO) provides a prototype for deep tunneling mechanisms in hydrogen transfer catalysis. This work combines room temperature X-ray studies with extended hydrogen-deuterium exchange experiments to define a catalytically-linked, radiating cone of aliphatic side chains that connects an active site iron center of SLO to the protein-solvent interface. Employing eight variants of SLO that have been appended with a fluorescent probe at the identified surface loop, nanosecond fluorescence Stokes shifts have been measured. We report a remarkable identity of the energies of activation (Ea) for the Stokes shifts decay rates and the millisecond C-H bond cleavage step that is restricted to side chain mutants within an identified thermal network. These findings implicate a direct coupling of distal protein motions surrounding the exposed fluorescent probe to active site motions controlling catalysis. While the role of dynamics in enzyme function has been predominantly attributed to a distributed protein conformational landscape, the presented data implicate a thermally initiated, cooperative protein reorganization that occurs on a timescale faster than nanosecond and represents the enthalpic barrier to the reaction of SLO.

Robust tracking control of unknown models for space in-cabin robots with a pneumatic continuum arm

The service robots of space station in-cabin have attracted more and more attention. The space in-cabin robot with a pneumatic continuum arm is studied in this paper. It could be safer, more efficient and more flexible than the space rigid robot. However, the coupling motion of the moving base and the pneumatic continuum continuous arm brings a new challenge for controlling the end-effector to track the desired path. In this paper, a new control method based on the zeroing neural network (ZNN) is developed to solve the high-precision kinematics trajectory tracking control problem of unknown models. The real-time Jacobian matrix of the in-cabin robots with a pneumatic continuum arm is estimated by the input–output information when the parameter and the structure of the kinematic model are unknown. Moreover, this paper also employs a modified activation function power-sigmoid activation function (PSAF) to improve the robustness. In addition, it is proved through the Lyapunov stability theory that the proposed control approach is convergent and stable. Finally, the simulation results are given to show the effectiveness and robustness of the proposed control method for space in-cabin robots with a pneumatic continuum arm.

Design and testing of a large-workspace XY compliant manipulator based on triple-stage parallelogram flexure

This paper proposes a new XY compliant parallel manipulator with large workspace and low coupling motion by resorting to planar arrangement of multistage parallelogram mechanisms. The triple-stage parallelogram flexure is chosen as the basic mechanism for motion transmission and decoupling. Its fixed and moving ends adopt planar and spatial connections, respectively. By this connecting scheme, more types of general multistage parallelogram flexures can be constructed. The driving stiffness and resonant frequency of the manipulator are derived based on statics analysis of theoretical mechanics and dynamics analysis via Lagrangian equation. The accuracy of the analytical model is confirmed by performing finite element analysis simulation, and the performance variances of three manipulators are compared. Moreover, a prototype of the XY compliant manipulator has been fabricated and tested. Results show that the workspace of the parallel manipulator is 1.51 cm × 1.48 cm, and the coupling ratios of the two axes are 1.11% and 1.06%, respectively. The volume ratio is introduced as a compactness indicator for comparison study versus existing designs. The centimeter-level stroke can promote the application of XY parallel manipulators in more industrial scenarios.

Analysis modeling and experiment of bionic winding soft actuator inspired by plant tendrils

As a special group of plants, vine plants can be spontaneously fixed with supports by winding or adsorbing. If the vine winding behavior is combined with a soft actuator, it is expected to improve the performance of the soft actuator in unstructured environments. Based on the pneumatic network structure, this study proposes a soft actuator with a symmetrical chamber and capable of winding or bending motion by imitating the winding motion of vine plants. Through the coupling motion of the symmetrical chamber under different or the same pressures, the winding flexibility of imitating vine plants can be better realized. Based on the minimum potential energy method and the constant curvature assumption, combined with the Yeoh model for large deformation of super elastic body, the deformation trajectory model of soft actuator in two states of unilateral winding and bending is constructed. The influence of structural design parameters of soft actuator on winding deformation is analyzed by finite element analysis. Finally, the reliability of the theoretical mathematical model is verified by experiments, the working performance of the software driver is tested, and the possible future applications are demonstrated.

Synchronization of a vibration system excited by two eccentric rotors on different rigid frames

This paper is focused on synchronization of a dynamic model with three rigid frames (RFs) driven by two reverse rotating eccentric rotors (ERs) distributed on different RFs. The differential equations of motion are established based on Lagrange equation. Applying the average method of small parameters, the condition is derived for the vibration system to meet synchronous motion. The stability condition of the vibration system is obtained by using Lyapunov indirect method. To investigate the selected motion characteristic on synchronous state in various frequency regions, theoretical results are discussed with frequency ratio numerically. Coupled motion of the vibration system, phase difference between two ERs, motion phase between RFs, and amplitude–frequency characteristics of RFs are discussed qualitatively to reveal the selected motion characteristic. A series of experiments are done to further illustrate the selected motion characteristic in sub-resonant state and super-resonant state of the vibration system with vertical direction. Finally, the experimental results validate the predication of the theoretical method.

Spectral signatures of excess-proton waiting and transfer-path dynamics.

Signatures of solvated excess protons in infrared difference absorption spectra, such as the continuum band between the water bend and stretch bands, have been experimentally known for a long time and have recently been used to analyze protonation dynamics in photoactive proteins. However, the theoretical basis for linking spectral signatures with the microscopic proton-transfer mechanism so far relied on normal-mode analysis. We analyze the excess-proton dynamics in ab initio molecular-dynamics simulations of aqueous hydrochloric acid solutions by trajectory-decomposition techniques. The continuum band in the 2000 cm−1 to 3000 cm−1 range is shown to be due to normal-mode oscillations of temporary H3O+ complexes. An additional prominent peak at 400 cm−1 reports on the coupling of excess-proton motion to the relative vibrations of the two flanking water molecules. The actual proton transfer between two water molecules, which for large water separations involves crossing of a barrier and thus is not a normal mode, is characterized by two time scales: Firstly, the waiting time for transfer to occur in the range of 200 fs to 300 fs, which leads to a broad weak shoulder around 100 cm−1, consistent with our experimental THz spectra. Secondly, the mean duration of a transfer event of about 14 fs, which produces a rather well-defined spectral contribution around 1200 cm−1 and agrees in location and width with previous experimental mid-infrared spectra.

A Novel Evaluation Index and Optimization Method for Ankle Rehabilitation Robots Based on Ankle-Foot Motion.

The ability of ankle rehabilitation robots to accurately mimicking the actual human ankle motion is an important judgment basis for robot-assisted rehabilitation training. This paper proposes an evaluation index and mechanism parameter optimization method based on ankle-foot motion trajectory by exploring the human ankle-foot motion principle. First, the ankle UR equivalent model and a 3-degree-of-freedom (DOF) parallel ankle rehabilitation robot are described. Second, the ankle-foot motion data are measured by the body surface marker method, which proved the coupling of ankle-foot motion. Then, a new evaluation index, the ankle-foot motion comfort zone, is proposed, which is essentially the superimposed ankle-foot motion trajectory measured about 3-5 mm wide. Third, a mechanism parameter optimization method, is proposed in terms of the ankle-foot motion comfort zone as the evaluation index, which is applied to the 3-DOF parallel ankle rehabilitation robot, and the optimization results proved the feasibility of the method. Finally, the optimized rehabilitation robot is fitted with different ankle motions, and a prototype model is designed for kinematics simulation, which verifies the adaptability of the optimization method. This study provides a theoretical basis for the configuration design of ankle rehabilitation robots and provides a new direction for the optimization of the mechanism parameters.