Notes on new friction models and nonholonomic mechanics

Both the dynamic characteristics and structural nonlinearities of an actuator will affect the flutter boundary of a fin–actuator system. The actuator models used in past research are not universal, the accuracy is difficult to guarantee, and the consideration of nonlinearity is not adequate. Based on modularization, a high-fidelity modeling method for an actuator is proposed in this paper. This model considers both freeplay and friction, which is easy to expand. It can be directly used to analyze actuator characteristics and perform aeroelastic analysis of fin–actuator systems. Friction can improve the aeroelastic stability, but the mechanism of its influence on the aeroelastic characteristics of the system has not been reported. In this paper, the LuGre model, which can better reflect the friction characteristics, was integrated into the actuator. The influence of the initial condition, freeplay, and friction on the aeroelastic characteristics of the system was analyzed. The comparison of the results with the previous research shows that oversimplified friction models are not accurate enough to reflect the mechanism of friction’s influence. By changing the loads, material, and geometry of contact surfaces, flutter can be effectively suppressed, and the power loss caused by friction can be minimized.

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Friction models for grease lubricated ball-race contacts

IOP Conference Series Materials Science and Engineering ◽

10.1088/1757-899x/997/1/012012 ◽

2020 ◽

Vol 997 ◽

pp. 012012

Author(s):

G Ianuş ◽

D Cojocaru ◽

M C Oprişan ◽

V Cârlescu ◽

D N Olaru

Keyword(s):

Friction Models

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Assessment of Steady and Unsteady Friction Models in the Draining Processes of Hydraulic Installations

Water ◽

10.3390/w13141888 ◽

2021 ◽

Vol 13 (14) ◽

pp. 1888

Author(s):

Óscar E. Coronado-Hernández ◽

Ivan Derpich ◽

Vicente S. Fuertes-Miquel ◽

Jairo R. Coronado-Hernández ◽

Gustavo Gatica

Keyword(s):

Mathematical Model ◽

Turbulent Flow ◽

Water Velocity ◽

Experimental Facility ◽

Governing Equations ◽

Pressure Oscillations ◽

Air Pocket ◽

Friction Models ◽

The Mathematical Model

The study of draining processes without admitting air has been conducted using only steady friction formulations in the implementation of governing equations. However, this hydraulic event involves transitions from laminar to turbulent flow, and vice versa, because of the changes in water velocity. In this sense, this research improves the current mathematical model considering unsteady friction models. An experimental facility composed by a 4.36 m long methacrylate pipe was configured, and measurements of air pocket pressure oscillations were recorded. The mathematical model was performed using steady and unsteady friction models. Comparisons between measured and computed air pocket pressure patterns indicated that unsteady friction models slightly improve the results compared to steady friction models.

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Developments in Modelling Bone Screwing

Current Directions in Biomedical Engineering ◽

10.1515/cdbme-2020-3029 ◽

2020 ◽

Vol 6 (3) ◽

pp. 111-114

Author(s):

Jack Wilkie ◽

Paul D. Docherty ◽

Knut Möller

Keyword(s):

Material Properties ◽

Frictional Coefficient ◽

Viscous Friction ◽

Model Parameters ◽

General Shape ◽

Bone Material ◽

Bone Material Properties ◽

Modelling Methodology ◽

Recorded Data ◽

Friction Models

AbstractINTRODUCTION: A torque-rotation model of the bone-screwing process has been proposed. Identification of model parameters using recorded data could potentially be used to determine the material properties of bone. These properties can then be used to recommend tightening torques to avoid over or under-tightening of bone screws. This paper improves an existing model to formulate it in terms of material properties and remove some assumptions. METHOD: The modelling methodology considers a critical torque, which is required to overcome friction and advance the screw into the bone. Below this torque the screw may rotate with elastic deformation of the bone tissue, and above this the screw moves relative to the bone, and the speed is governed by a speed-torque model of the operator’s hand. The model is formulated in terms of elastic modulus, ultimite tensile strength, and frictional coefficient of the bone and the geometry of the screw and hole. RESULTS: The model output shows the speed decreasing and torque increasing as the screw advances into the bone, due to increasing resistance. The general shape of the torque and speed follow the input effort. Compared with the existing model, this model removes the assumption of viscous friction, models the increase in friction as the screw advances into the bone, and is directly in terms of the bone material properties. CONCLUSION: The model presented makes significant improvements on the existing model. However it is intended for use in parameter identification, which was not evaluated here. Further simulation and experimental validation is required to establish the accuracy and fitness of this model for identifying bone material properties.

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Modeling of Piezo-Actuated Stick-Slip Micro-Drives: An Overview

Advances in Science and Technology ◽

10.4028/www.scientific.net/ast.81.39 ◽

2012 ◽

Vol 81 ◽

pp. 39-48 ◽

Cited By ~ 12

Author(s):

Ha Xuan Nguyen ◽

Christoph Edeler ◽

Sergej Fatikow

Keyword(s):

Mechanical Model ◽

Integrated Model ◽

Friction Model ◽

Fundamental Importance ◽

Future Research ◽

Stick Slip ◽

Research Activities ◽

Model Combining ◽

Friction Models

This paper gives an overview about problems of modeling of piezo-actuated stick-slip micro-drives. It has been found that existing prototypes of such devices have been investigated empirically. There is only few research dealing with the theory behind this kind of drives. By analyzing the current research activities in this field, it is believed that the model of the drive depends strongly on the friction models, but in most cases neglecting any influences of the guilding system.These analyses are of fundamental importance for an integrated model combining friction model and mechanical model offering promising possibilities for future research.

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