Established Dynamic Model Research Articles

Dynamic Properties Analysis of a New Kind of Inter-Connected Hydro-Pneumatic Strut

The dynamic properties of one kind of Inter-Connected Hydro-Pneumatic Struts (IC HPS), which is designed based on the developed double-gas-chamber compacted Hydro-Pneumatic Struts (HPS) integrating double inner gas chambers, will be investigated in this research. Comparing with the traditional IC HPS designs based on single gas chamber compacted HPS, the proposed IC HPS can postpone the force distortion, and then increase the working envelop, provide good stiffness performance and be stable in both In-Phase and Out-of-Phase working condition. The equation of motion of the proposed IC HPS will be derived firstly. And then based on the established dynamic model, the related simulating model will be established utilizing the AMEsim software, and the validity of the established simulating model will be verified on the basis of experimental data and available literatures. The validity and performance of the proposed IC HPS will be verified and investigated through comprehensive comparison with traditional IC HPS designs. Finally, the detailed sensitivity analysis of the essential design parameter of the proposed IC HPS will be presented to illustrate the advantage of the proposed IC HPS design.

The Role of Mistrust in the Modelling of Opinion Adoption

Societies tend to partition into factions based on shared beliefs, leading to sectarian conflict in soci-ety. This paper investigates mistrust as a cause for this partitioning by extending an established opinion dynamics model with Bayesian updating that specifies mistrust as the underlying mechanism for disagreement and, ultimately, polarisation. We demonstrate that mistrust is at the foundation of polarisation. Detailed analysis and the results of rigorous simulation studies provide new insight into the potential role of mistrust in polarisa-tion. We show that consensus results when mistrust levels are low, but introducing extreme agents makes consensus significantly harder to reach and highly fragmented and dispersed. These results also suggest a method to verify the model using real-world experimental or observational data empirically.

Research and Experiment on Path-Tracking Control of Autonomous Tractor Based on Lateral Deviation and Yaw Rate Feedback

HighlightsAutomatic navigation technology in autonomous tractors is one of the key technologies in precision agriculture.A path-tracking control algorithm based on lateral deviation and yaw rate feedback is proposed.The modified steering angle was obtained by comparing the ideal yaw rate with the actual yaw rate.The results demonstrate the efficiency and superior accuracy of the proposed algorithm for tractor path-tracking control.Abstract. The performance of path-tracking control systems for autonomous tractors affects the quality and efficiency of farmland operations. The objective of this study was to develop a path-tracking control algorithm based on lateral deviation and yaw rate feedback. The autonomous tractor path lateral dynamics model was developed based on preview theory and a two-degree-of-freedom tractor model. According to the established dynamic model, a path-tracking control algorithm using yaw angular velocity correction was designed, and the ideal steering angle was obtained by lateral deviation and sliding mode control. The modified steering angle was obtained by a proportional-integral-derivative feedback controller after comparing the ideal yaw rate with the actual yaw rate, which was then combined with the ideal steering angle to obtain the desired steering angle. The simulation and experimental results demonstrate the efficiency and superior accuracy of the proposed tractor path-tracking control algorithm, enabling its application in automatic navigation control systems for autonomous tractors. Keywords: Autonomous tractor, Path-tracking control, Sliding mode control, Yaw rate feedback.

Modeling and Analysis of Gear Shifting Process of Non-Synchronizer AMT Based on Collision Model

In the gear shifting process of a clutchless automated mechanical transmission (AMT), the potential collision between sleeve and dog gear may increase both vehicle jerk and gear changing duration. Therefore, the gear shifting process’s mechanism analysis and dynamic modeling are the essential prerequisites to improve gear shifting quality. This paper analyzes the potential collision between the sleeve and the dog gear which both with concave-convex profiles, the tooth-side chamfer considered. To model the collision process, a fast-determining collision face method based on an intersection map is proposed, and the Monte Carlo method and equivalent depth are employed to calculate the collision stiffness. Then, the stiffness-damping model of the collision process and an 8-degree-of-freedom dynamic model of the gear-shifting system are established. Finally, taking a two-speed clutchless and non-synchronizer automated mechanical transmission (NSAMT) as an example, the established dynamic model of the gear-shifting system is applied, and simulation verification is performed in Matlab/Simulink. The simulation results show that the established model can accurately reflect the changes of forces, speeds, and displacements of sleeve and dog gears during the collision and effectively reflect processes of the disengagement of the sleeve, the speed changes in active synchronization, the engagement of sleeve and gear keeping. Besides, the results also show that the tooth-side chamfer will increase the disengagement time, while it is conducive to gear keeping, and that unloading the drive motor can decrease the disengagement time due to the existence of the tooth-side chamfer.

Dynamic investigation of traction motor bearing in a locomotive under excitation from track random geometry irregularity

ABSTRACT Development of railway locomotive towards high-speed and high-power has a higher requirement on traction motor bearing under the intensified wheel–rail interactions since the dynamic performance of the motor bearing will directly threaten the operation safety of the locomotives. In this paper, a locomotive-track dynamics model with traction motors is established, where a detailed dynamics model of the motor bearing is included by considering comprehensively the dynamic interactions among the major components. Besides, the complicated external and internal excitations, such as the track random geometry irregularity, the time-varying mesh stiffness, the nonlinear contact stiffness between the components of the bearing, and the variable friction coefficient are fully considered. Then, the established dynamics model is validated by comparing it with field test results. The results indicate that intensified wheel–rail interaction will deteriorate the bearing working conditions apparently, which may supply certain guidance for the design of traction motor bearings in a locomotive.

OP535 Cost-Effectiveness Of Internet-Based HIV Screening In Men Who Have Sex With Men in Vancouver, British Columbia, Canada

IntroductionIn Canada, individuals test for HIV commonly through clinic-based screening services (CBSS). However, gay, bisexual and other men who have sex with men (GBMSM) may face barriers accessing such services due to, for example, feeling discomfort disclosing their sexual history or fearing judgment from healthcare providers. To reduce barriers and increase uptake and frequency of screening for sexually-transmitted infections (STIs) including HIV, the British Columbia Centre for Disease Control implemented an internet-based screening service, GetCheckedOnline.com (GCO), in September 2014 in Vancouver, Canada. We assessed the cost-effectiveness of GCO at different uptake scenarios compared to CBSS in Vancouver GBMSM.MethodsCost-utility analyses were conducted from a healthcare payer's perspective using an established dynamic GBMSM HIV compartmental model. The model estimated the probability of becoming infected with HIV, progressing through diagnosis, disease stages, and treatment over a 30-year time horizon. The base case assumed 4.7 percent uptake of GCO, and 74 percent of high-risk and 44 percent of low-risk infrequent testers becoming regular testers in five years. Scenario analyses tested GCO 10 and 15 percent uptakes.ResultsCompared with the conventional CBSS alone, a 4.7 percent GCO uptake increased the costs by CAD90,059 (USD75,680; 95% confidence interval (CI): -CAD420,836, CAD273,987) and gained 3 (95% CI: 0, 6) quality-adjusted life years (QALYs) in a 30-year time horizon. There was a 71 percent probability that GCO was cost-effective at a cost-effectiveness threshold of CAD50,000 (USD42,000) per QALY. The results were consistent in other two uptake scenarios.ConclusionsExpanding HIV screening for GBMSM through increasing uptake of GCO is a cost-effective alternative to expanding the conventional CBSS. We noted that difference in total costs might be smaller if a battery of STI tests is considered, which in turn may affect our cost-effectiveness estimate. For the next phase of cost-utility analysis, we will expand our model to include testing for other STIs.

Study on the mechanism of drilling speed increase considering the axial vibration of drill string

Based on the existing research and combining with downhole conditions, this paper proposes a new type of downhole vibration tool to increase the rate of penetration (ROP), shorten the drilling and completion cycle and achieve more productive operations. As a whole, the axial vibration of the drill string is analyzed uniformly and the ROP is increased. A dynamic analysis model of the axial vibration of the drill string in the horizontal well is established. Based on the research on the working mechanism of the tool, this paper analyzes the flow area, pressure drop and axial force of the core valve system and determines the change law of the axial force. The field experiments verified the correctness of the established dynamic model method and the rationality of the tool and showed that the tool has a significant effect of increasing the ROP. The theoretical model established in this paper can improve the understanding of drill string dynamics. The proposed design method can provide ideas for the development of new drag reduction and speedup tools, and the calculation results can provide a reference for the determination and optimization of key parameters for drilling speedup.

Wave Motion Dynamic Analysis of Planar Frame Structures With Clearance Joints

Abstract Due to kinematic function requirements, deployable structures inevitably have many clearance joints. The existence of clearance joints not only reduces the structural stiffness but also leads to complex nonlinear dynamic characteristics. This paper proposed a general numerical method based on the wave motion theory, which is able to analyze these complex nonlinear dynamic characteristics of frame structures with clearance joints. The dynamic model of frame structures with clearance joints is derived on the basis of continuous wave equations. The clearance joint is modeling by combining Lankarani and Nikravesh contact model with the Ambrósio friction model. The established dynamic model of frame structures is solved by the finite difference time domain (FDTD) method. A triangular frame structure with two clearance joints is taken as the numerical example for the verification of the proposed numerical method. Numerical results show that the longitudinal wave affects the distribution direction of contact positions and the transverse wave mainly affects the distribution range of contact positions. It has been also found that the introduction of torsional springs with reasonable pretension torque is able to significantly improve the distribution of contact positions and reduce state uncertainties of clearance joints in structural vibrations.

Control Method Based on Sensor Data for Stable Walking of a Biped Robot under Port Environment

Jing, C.L., You, X.F., and Xia, T., 2020. Control method based on sensor data for stable walking of a biped robot under port environment. In: Guido Aldana, P.A. and Kantamaneni, K. (eds.), Advances in Water Resources, Coastal Management, and Marine Science Technology. Journal of Coastal Research, Special Issue No. 104, pp. 271–275. Coconut Creek (Florida), ISSN 0749-0208.In spite of great improvement of walking ability after the merging of various walking techniques, there still exists a large gap between a biped robot and a person. In particular, under some complex environments such as port, the development and perfection of the control theory based on the detected sensor data are of great significance to achieving ideal walking ability for the robot. In this study, the detected sensor data are merged into the established dynamic model, and then, both the force and the moment of the connecting rod are accurately calculated for programming actual ZMP trajectory. Further, the data are sent to the slave computer for robot control, thereby enhancing the walking stability. The present simulation results prove that the biped robot can successfully realize stable walking.

Dynamic Pore-Scale Network Modeling of Spontaneous Water Imbibition in Shale and Tight Reservoirs

Spontaneous water imbibition plays an imperative role in the development of shale or tight oil reservoirs. Spontaneous water imbibition is helpful in the extraction of crude oil from the matrix, although it decreases the relative permeability of the hydrocarbon phase dramatically. The dynamic pore-scale network modeling of water imbibition in shale and tight reservoirs is presented in this work; pore network generation, local capillary pressure function, conductance calculation and boundary conditions for imbibition are all presented in detail in this paper. The pore network is generated based on the characteristics of Barnett shale formations, and the corresponding laboratory imbibition experiments are matched using this established dynamic pore network model. The effects of the wettability, throat aspect ratio, viscosity, shape factor, micro-fractures, etc. are all investigated in this work. Attempts are made to investigate the water imbibition mechanisms from a micro-scale perspective. According to the simulated results, wettability dominates the imbibition characteristics. Besides this, the viscous effects including viscosity, initial capillary pressure and micro-fractures increase the imbibition rate, while the final recovery factor is more controlled by the capillarity effect including the cross-area shape factor, contact angle and the average pore-throat aspect ratio.

Appraisement and Analysis of Dynamical Stability of Under-Constrained Cable-Driven Lower-Limb Rehabilitation Training Robot

SUMMARYThe dynamical stability of the cable-driven lower-limb rehabilitation training robot (CLLRTR) is a crucial question. Based on the established dynamics model of CLLRTR, the solution to the wrench closure of the under-constrained system is presented. Secondly, the stability index of CLLRTR is proposed by the Krasovski method. Finally, in order to analyze the stability distribution of CLLRTR in the workspace, the stability evaluation index in the workspace is calculated using the eigenvalue decomposition method. The stability distribution laws of CLLRTR are further verified by the experimental study. The results provide references for studying trajectory planning and anti-pendulum control of CLLRTR.

Tribo-dynamic analysis and motion control of a rotating manipulator based on the load and temperature dependent friction model

Joint friction has a significant influence on the dynamics and motion control of manipulators. However, the friction effect is often omitted or simplified in previous studies. In this paper, we establish the dynamics model of a single joint in a rotating industrial manipulator taking detailed friction effects into consideration and propose a new control algorithm for the friction compensation purpose. Firstly, the manipulator dynamics modeling is carried out employing a recently-proposed extended static friction model, which depicts load and temperature influence on Coulomb, Stribeck and viscous terms. Moreover, based on the established dynamics model, the paper presents a new adaptive fast nonsingular terminal sliding mode (AFNTSM) controller. The proposed approach has the advantages of continuous control inputs, fast convergence rate, no singularity and great robustness against disturbances. Furthermore, its adaptive property does not require any prior knowledge of the upper bound of the uncertainties. Finally, the proposed controller is applied to the manipulator joint trajectory tracking problem with varying friction subject to load and temperature changes. The numerical simulation verifies the effectiveness of our proposed method and its advantages over other controllers.

Three-dimensional Numerical Simulation of the Flow Field in the Potato Storage in Summer

In recent years, with the rapid growth of potato demand, potato storage has become extremely important. It is vital that controls the ambient temperature and wind speed during potato storage. Therefore, this work simulated the temperature field and air flow organization in a potato storage using the underfloor air supply. The established computational fluid dynamics (CFD) model was used to study the temperature field and airflow organization in the warehouse under different air supply parameters, and compared the results to get their change rule. On this basis, the influence of the underfloor air supply on the flow field was studied to verify its feasibility. The results show that under reasonable conditions, the underfloor air supply can effectively guarantee the required temperature and airflow organization.

Investigation on evolvement of dynamic behaviors of ship stern shaft-bearing system under the different rub-impact states based on attractor

The ship stern shaft-bearing system is a typical nonlinear system, and its dynamic behavior is complex. In order to investigate the evolvement of dynamic behavior from the system, the attractor theory is introduced. Based on the calculated dynamic responses of the established dynamic model, the system's attractors were reconstructed, and the evolvement of dynamic behaviors under different rub-impact states was discussed. The results show that under the full annular rub-impact state, the attractor of the system is limit cycle attractor, and the volume of it increases gradually; under the partial rub-impact state, the attractor of the system goes through the process of breaking the tours attractor into a chaotic attractor and then converging into a tour attractor, and the volume of the attractor increases at first and then decreases; under the no rub-impact state, the attractor of the system is limit cycle attractor, and its volume decreases gradually. These characters of attractors demonstrate that under different rub-impact states, the system has experienced periodic motion, quasi-periodic, and chaotic motion. The attractors also reveal the evolutions of convergence and divergence.

Evaluation models and criteria of motion performance for underwater gliders

The motion performance of underwater gliders (UGs) is an important basis for their preliminary design. Because of their unique buoyancy-driven mode, the UGs differ greatly in dynamic model and working principle from the propeller-driven underwater vehicles, such as submarines, torpedoes and autonomous underwater vehicles (AUVs). Therefore, it's inadvisable to use the evaluation models and criteria of motion performance for the latters, which are established on the basis of their dynamic models, to evaluate the performance of UGs. There is a lack of applicable evaluation models and criteria to motion performance of UGs. In addition, as the effects of seawater depth on UGs are generally neglected in the dynamic model, its effects on the motion performance of UGs still need to be investigated further. In this paper, based on an established applicable dynamic model and evaluation models (the free perturbation and maneuverability equations) in the vertical plane, the applicable evaluation criteria are derived and the characteristics of motion performance of UGs under the effects of seawater depth variation are investigated. The results show that, the evaluation models and criteria of motion performance for the buoyancy-driven UGs show significant difference from those for the propeller-driven underwater vehicles. As velocity of the UG is affected by seawater depth variation, its dynamic stability is also affected obviously. With the increasing seawater depth, its dynamic stability becomes stronger, and its change rate of surfacing speed (maneuverability) increases obviously with seawater depth. The present work enriches motion performance theory of UGs, and provides valuable guidance for their applications in the deep-sea region.

Health and Economic Impacts of the National Menu Calorie Labeling Law in the United States: A Microsimulation Study.

Excess caloric intake is linked to weight gain, obesity, and related diseases, including type 2 diabetes mellitus and cardiovascular disease (CVD). Obesity incidence is rising, with nearly 3 in 4 US adults being overweight or obese. In 2018, the US federal government finalized the implementation of mandatory labeling of calorie content on all menu items across major chain restaurants nationally as a strategy to support informed consumer choice, reduce caloric intake, and potentially encourage restaurant reformulations. Yet, the potential health and economic impacts of this policy remain unclear. We used a validated microsimulation model (CVD-PREDICT) to estimate reductions in CVD events, diabetes mellitus cases, gains in quality-adjusted life years, costs, and cost-effectiveness of the menu calorie labeling intervention, based on consumer responses alone, and further accounting for potential industry reformulation. The model incorporated nationally representative demographic and dietary data from National Health and Nutrition Examination Surveys 2009 to 2016; policy effects on consumer diets and body mass index-disease effects from published meta-analyses; and policy effects on industry reformulation, policy costs (policy administration, industry compliance, and reformulation), and health-related costs (formal and informal healthcare costs, productivity costs) from established sources or reasonable assumptions. We modeled change in calories to change in weight using an established dynamic weight-change model, assuming 50% of expected calorie reductions would translate to long-term reductions. Findings were evaluated over 5 years and a lifetime from healthcare and societal perspectives, with uncertainty incorporated in both 1-way and probabilistic sensitivity analyses. Between 2018 and 2023, implementation of the restaurant menu calorie labeling law was estimated, based on consumer response alone, to prevent 14 698 new CVD cases (including 1575 CVD deaths) and 21 522 new type 2 diabetes mellitus cases, gaining 8749 quality-adjusted life years. Over a lifetime, corresponding values were 135 781 new CVD cases (including 27 646 CVD deaths), 99 736 type 2 diabetes mellitus cases, and 367 450 quality-adjusted life years. Assuming modest restaurant item reformulation, both health and economic benefits were estimated to be about 2-fold larger than based on consumer response alone. The consumer response alone was estimated to be cost-saving by 2023, with net lifetime savings of $10.42B from a healthcare perspective and $12.71B from a societal perspective. Findings were robust in a range of sensitivity analyses. Our national model suggests that the full implementation of the US calorie menu labeling law will generate significant health gains and healthcare and societal cost-savings. Industry responses to modestly reformulate menu items would provide even larger additional benefits.

Integrating Dynamics into Design and Motion Optimization of a 3-PRR Planar Parallel Manipulator with Discrete Time Transfer Matrix Method

This paper presents a novel method of dynamic modeling and design optimization integrated with dynamics for parallel robot manipulators. Firstly, a computationally efficient modeling method, the discrete time transfer matrix method (DT-TMM), is proposed to establish the dynamic model of a 3-PRR planar parallel manipulator (PPM) for the first time. The numerical simulations are performed with both the proposed DT-TMM dynamic modeling and the ADAMS modeling. The applicability and effectiveness of DT-TMM in parallel manipulators are verified by comparing the numerical results. Secondly, the design parameters of the 3-PRR parallel manipulator are optimized using the kinematic performance indices, such as global workspace conditioning index (GWCI), global condition index (GCI), and global gradient index (GGI). Finally, a dynamic performance index, namely, driving force index (DFI), is proposed based on the established dynamic model. The described motion trajectory of the moving platform is placed into the optimized workspace and the initial position is determined to finalize the end-effector trajectory of the parallel manipulator by the further optimization with the integrated kinematic and dynamic performance indices. The novelty of this work includes (1) developing a new dynamic model method with high computation efficiency for parallel robot manipulators using DT-TMM and (2) proposing a new dynamic performance index and integrating the dynamic index into the motion and design optimization of parallel robot manipulators.

Dynamic analysis of tapping mode atomic force microscope (AFM) for critical dimension measurement

Transient dynamics of tapping mode atomic force microscope (AFM) for critical dimension measurement are analyzed. A simplified nonlinear model of AFM is presented to describe the forced vibration of the micro cantilever-tip system with consideration of both contact and non-contact transient behavior for critical dimension measurement. The governing motion equations of the AFM cantilever system are derived from the developed model. Based on the established dynamic model, motion state of the AFM cantilever system is calculated utilizing the method of averaging with the form of slow flow equations. Further analytical solutions are obtained to reveal the effects of critical parameters on the system dynamic performance. In addition, features of dynamic response of tapping mode AFM in critical dimension measurement are studied, where the effects of equivalent contact stiffness, quality factor and resonance frequency of cantilever on the system dynamic behavior are investigated. Contact behavior between the tip and sample is also analyzed and the frequency drift in contact phase is further explored. Influence of the interaction between the tip and sample on the subsequent non-contact phase is studied with regard to different parameters. The dependence of the minimum amplitude of tip displacement and maximum phase difference on the equivalent contact stiffness, quality factor and resonance frequency are investigated. This study brings further insights into the dynamic characteristics of tapping mode AFM for critical dimension measurement, and thus provides guidelines for the high fidelity tapping mode AFM scanning.

Data-driven fault diagnosis for dynamic traction systems in high-speed trains

Traction systems are an important aspect of high-speed trains, and their reliable operation is crucial. With data available from trains, this paper proposes an optimal fault detection and diagnosis (FDD) strategy for dynamic traction systems. Based on the established dynamic model, using sensor measurements, a correlation-aided subspace identification technique is proposed to formulate residual signals and corresponding test statistics for fault detection. Then, a modified support vector machine (SVM) is designed for optimally solving the diagnosis bias caused by the difference in the apparent probabilities of multiple fault scenarios. The feasibility and effectiveness of the proposed optical FDD performance are illustrated in the CRRC experimental platforms.

Model updating of gun recoil mechanism based on time domain response

For gun launching dynamics modeling, the accuracy of the recoil and counterrecoil model is important. In order to improve the accuracy of gun recoil mechanism modeling, the rigid-flexible coupling firing dynamics model of a small-caliber gun was established, and the recoil displacement of the gun was tested by live firing test. Aiming at the error between the simulation curve and the test curve of the recoil displacement changing with time, taking the correlation coefficient of the two curves as the objective function, the dynamics model of the recoil mechanism was modified based on the time-domain response using the optimization algorithm. The modified results show that the difference of the maximum recoil displacement decreases from 9% to 0.1%, and the similarity between the simulation curve and the test curve reaches 0.99. The modified results based on the time-domain response effectively improve the accuracy of the recoil model, so that the established dynamics model can more truly reflect the dynamic characteristics of the recoil mechanisms, and provide the basic conditions for ensuring the simulation accuracy of the launch dynamics model.