scholarly journals Asymmetric drop coalescence launches fungal ballistospores with directionality

2017 ◽  
Vol 14 (132) ◽  
pp. 20170083 ◽  
Author(s):  
Fangjie Liu ◽  
Roger L. Chavez ◽  
S. N. Patek ◽  
Anne Pringle ◽  
James J. Feng ◽  
...  
Keyword(s):  
Surface Energy ◽  
Numerical Simulations ◽  
Relative Position ◽  
Colloidal Particles ◽  
Mechanistic Model ◽  
Fungal Species ◽  
Adaxial Side ◽  
Drop Coalescence ◽  
Model Based ◽  
Directional Control

Thousands of fungal species use surface energy to power the launch of their ballistospores. The surface energy is released when a spherical Buller's drop at the spore's hilar appendix merges with a flattened drop on the adaxial side of the spore. The launching mechanism is primarily understood in terms of energetic models, and crucial features such as launching directionality are unexplained. Integrating experiments and simulations, we advance a mechanistic model based on the capillary–inertial coalescence between the Buller's drop and the adaxial drop, a pair that is asymmetric in size, shape and relative position. The asymmetric coalescence is surprisingly effective and robust, producing a launching momentum governed by the Buller's drop and a launching direction along the adaxial plane of the spore. These key functions of momentum generation and directional control are elucidated by numerical simulations, demonstrated on spore-mimicking particles, and corroborated by published ballistospore kinematics. Our work places the morphological and kinematic diversity of ballistospores into a general mechanical framework, and points to a generic catapulting mechanism of colloidal particles with implications for both biology and engineering.

Impedance Control of Dual-Arm Systems Based on the Object with Senseless Force

2013 ◽  
Vol 765-767 ◽  
pp. 1920-1923
Author(s):  
Li Jiang ◽  
Yang Zhou ◽  
Bin Wang ◽  
Chao Yu
Keyword(s):  
Numerical Simulations ◽  
Relative Position ◽  
Position Control ◽  
Impedance Control ◽  
Force Sensors ◽  
Operational Space ◽  
Novel Approach ◽  
Control Scheme ◽  
Statics And Dynamics ◽  
Dual Arm

A novel approach to impedance control based on the object is proposed to control dual-arm systems with senseless force. Considering the motion of the object, the statics and dynamics of the dual-arm systems are modeled. Extending the dynamics of dual-arm system and the impedance of object to the operational space, impedance control with senseless force is presented. Simulations on a dual-arm system are carried out to demonstrate the performance of the proposed control scheme. Comparing with position control, results of numerical simulations show that the proposed scheme realizes suitable compliant behaviors in terms of the object, and minimizes the error of the relative position between the manipulators even without force sensors.

scholarly journals Model-Based Analysis of Yo-yo Throwing Motion on Single-Link Manipulator

2020 ◽  
Vol 32 (4) ◽  
pp. 822-831
Author(s):  
Hokuto Miyakawa ◽  
◽  
Takuma Nemoto ◽  
Masami Iwase
Keyword(s):  
Angular Velocity ◽  
Numerical Simulations ◽  
Integrated Model ◽  
Analysis Method ◽  
Model Based ◽  
Single Link ◽  
Throwing Motion ◽  
Model Based Analysis

This paper presents a method for analyzing the throwing motion of a yo-yo based on an integrated model of a yo-yo and a manipulator. Our previous integrated model was developed by constraining a model of a white painted commercial yo-yo and a model of a plain single-link manipulator with certain constraining conditions placed between two models. However, for the yo-yo model, the collisions between the string and the axle of the yo-yo were not taken into account. To avoid this problem, we estimate some of the yo-yo parameters from the experiments, thereby preserving the functionality of the model. By applying the new integrated model with the identified parameters, we analyze the throwing motion of the yo-yo through numerical simulations. The results of which show the ranges of the release angle and the angular velocity of the joint of the manipulator during a successful throw. In conclusion, the proposed analysis method is effective in analyzing the throwing motion of a manipulator.

scholarly journals Modified Mechanistic Model Based on Gaussian Process Adjusting Technique for Cutting Force Prediction in Micro-End Milling

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Xiaoping Liao ◽  
Zhenkun Zhang ◽  
Kai Chen ◽  
Kang Li ◽  
Junyan Ma ◽  
...  
Keyword(s):  
Gaussian Process ◽  
Cutting Force ◽  
Cutting Forces ◽  
End Milling ◽  
Mechanistic Model ◽  
Machining Process ◽  
Mechanistic Models ◽  
Machining Processes ◽  
Model Based ◽  
Micro End Milling

Micro-end milling is in common use of machining micro- and mesoscale products and is superior to other micro-machining processes in the manufacture of complex structures. Cutting force is the most direct factor reflecting the processing state, the change of which is related to the workpiece surface quality, tool wear and machine vibration, and so on, which indicates that it is important to analyze and predict cutting forces during machining process. In such problems, mechanistic models are frequently used for predicting machining forces and studying the effects of various process variables. However, these mechanistic models are derived based on various engineering assumptions and approximations (such as the slip-line field theory). As a result, the mechanistic models are generally less accurate. To accurately predict cutting forces, the paper proposes two modified mechanistic models, modified mechanistic models I and II. The modified mechanistic models are the integration of mathematical model based on Gaussian process (GP) adjustment model and mechanical model. Two different models have been validated on micro-end-milling experimental measurement. The mean absolute percentage errors of models I and II are 7.76% and 6.73%, respectively, while the original mechanistic model’s is 15.14%. It is obvious that the modified models are in better agreement with experiment. And model II performs better between the two modified mechanistic models.

scholarly journals Numerical simulations of one laser-plasma model based on Poisson structure

2020 ◽  
Vol 405 ◽  
pp. 109172
Author(s):  
Yingzhe Li ◽  
Yajuan Sun ◽  
Nicolas Crouseilles
Keyword(s):  
Numerical Simulations ◽  
Poisson Structure ◽  
Laser Plasma ◽  
Plasma Model ◽  
Model Based

A mechanistic model-based force-feedback scheme for voice-coil actuated radial contour turning

2001 ◽  
Vol 41 (8) ◽  
pp. 1131-1147 ◽  
Author(s):  
Rohit G Reddy ◽  
Richard E DeVor ◽  
Shiv G Kapoor ◽  
Zongxuan Sun
Keyword(s):  
Force Feedback ◽  
Mechanistic Model ◽  
Model Based ◽  
Feedback Scheme

Model-Based Predictive Control of Workpiece Accuracy in Bar Turning

1998 ◽  
Vol 120 (1) ◽  
pp. 57-67 ◽  
Author(s):  
A. M. Shawky ◽  
M. A. Elbestawi
Keyword(s):  
Real Time ◽  
Mechanistic Model ◽  
Cutting Fluid ◽  
Open Architecture ◽  
Time Model ◽  
Integral Control ◽  
Model Based ◽  
Full State Feedback ◽  
On Line ◽  
Bar Turning

In this paper a real-time model-based geometric control system is proposed for workpiece accuracy in bar turning. An on-line ultrasonic measurement system that operates in the presence of cutting fluid is employed for workpiece diameter measurement. A state space mechanistic model is used to overcome the delay in the feedback loop. A Kalman Filter is used in a predictor-corrector fashion to update model predictions using on-line measurements. A full state feedback controller with an integral control action is designed and used to manipulate the tool position in real-time for machining error compensation. The performance of the proposed control strategy is evaluated through cutting experiments performed on a CNC turret lathe retrofitted with an open architecture controller.

scholarly journals Model-based design of transverse wall oscillations for turbulent drag reduction

2012 ◽  
Vol 707 ◽  
pp. 205-240 ◽  
Author(s):  
Rashad Moarref ◽  
Mihailo R. Jovanović
Keyword(s):  
Turbulent Flow ◽  
Numerical Simulations ◽  
Eddy Viscosity ◽  
Traditional Approach ◽  
Turbulent Viscosity ◽  
Transverse Wall ◽  
Mean Velocity ◽  
Model Based ◽  
Turbulent Drag ◽  
Linearized Model

AbstractOver the last two decades, both experiments and simulations have demonstrated that transverse wall oscillations with properly selected amplitude and frequency can reduce turbulent drag by as much as $40\hspace{0.167em} \% $. In this paper, we develop a model-based approach for designing oscillations that suppress turbulence in a channel flow. We utilize eddy-viscosity-enhanced linearization of the turbulent flow with control in conjunction with turbulence modelling to determine skin-friction drag in a simulation-free manner. The Boussinesq eddy viscosity hypothesis is used to quantify the effect of fluctuations on the mean velocity in flow subject to control. In contrast to the traditional approach that relies on numerical simulations, we determine the turbulent viscosity from the second-order statistics of the linearized model driven by white-in-time stochastic forcing. The spatial power spectrum of the forcing is selected to ensure that the linearized model for uncontrolled flow reproduces the turbulent energy spectrum. The resulting correction to the turbulent mean velocity induced by small-amplitude wall movements is then used to identify the optimal frequency of drag-reducing oscillations. In addition, the control net efficiency and the turbulent flow structures that we obtain agree well with the results of numerical simulations and experiments. This demonstrates the predictive power of our model-based approach to controlling turbulent flows and is expected to pave the way for successful flow control at higher Reynolds numbers than currently possible.

Numerical simulations of self-propelled jumping upon drop coalescence on non-wetting surfaces

2014 ◽  
Vol 752 ◽  
pp. 39-65 ◽  
Author(s):  
Fangjie Liu ◽  
Giovanni Ghigliotti ◽  
James J. Feng ◽  
Chuan-Hua Chen
Keyword(s):  
Numerical Simulations ◽  
Liquid Bridge ◽  
Flat Surface ◽  
Three Dimensional ◽  
Superhydrophobic Surfaces ◽  
Ohnesorge Number ◽  
Drop Coalescence ◽  
Out Of Plane ◽  
Potential Applications ◽  
Cutoff Radius

AbstractCoalescing drops spontaneously jump out of plane on a variety of biological and synthetic superhydrophobic surfaces, with potential applications ranging from self-cleaning materials to self-sustained condensers. To investigate the mechanism of self-propelled jumping, we report three-dimensional phase-field simulations of two identical spherical drops coalescing on a flat surface with a contact angle of 180°. The numerical simulations capture the spontaneous jumping process, which follows the capillary–inertial scaling. The out-of-plane directionality is shown to result from the counter-action of the substrate to the impingement of the liquid bridge between the coalescing drops. A viscous cutoff to the capillary–inertial velocity scaling is identified when the Ohnesorge number of the initial drops is around 0.1, but the corresponding viscous cutoff radius is too small to be tested experimentally. Compared to experiments on both superhydrophobic and Leidenfrost surfaces, our simulations accurately predict the nearly constant jumping velocity of around 0.2 when scaled by the capillary–inertial velocity. By comparing the simulated drop coalescence processes with and without the substrate, we attribute this low non-dimensional velocity to the substrate intercepting only a small fraction of the expanding liquid bridge.

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