Experimental Investigation of Friction Dynamics Associated With Normal Load

1995 ◽  
Author(s):  
Pierre E. Dupont ◽  
Prakash S. Kasturi
Keyword(s):  
Normal Force ◽  
Normal Load ◽  
System Stability ◽  
Complete Understanding ◽  
Order Model ◽  
Friction Behavior ◽  
Ongoing Research ◽  
Stability And Control ◽  
And Control ◽  
Friction Dynamics

Abstract In the last five years, it has become clear that for a broad range of systems which exhibit significant friction, the dynamics of the friction itself must be included to reach a complete understanding of system stability and control issues. Dynamics associated with variations in velocity have received most of the attention while those associated with variations in normal load have been largely ignored. This paper presents results of ongoing research in the experimental identification of friction dynamics due to variations in both normal load and velocity for a line contact in boundary lubrication. Tests were conducted with inputs consisting of step changes in velocity and normal force. Our analyses indicate that a first or second order model is necessary to represent dynamic friction behavior associated with these inputs.

scholarly journals Advanced Modelling of KF Implemented Flying Wing

2019 ◽  
Vol 11 (4) ◽  
Author(s):  
Widanalage Dakshina ◽  
Thiwanka Fernando
Keyword(s):  
Extreme Condition ◽  
Flow Conditions ◽  
Ongoing Research ◽  
Stability And Control ◽  
Advanced Phase ◽  
Landing Gears ◽  
Two Phases ◽  
The Stability ◽  
And Control ◽  
Base Design

This research carries out the advanced phase in correlation with the previous published design of KF Implemented Flying Wing. At the primary stage the basic design was considered under omission of non-static components and turbulent conditions. At this stage the simulations have taken a step ahead with improved flow conditions and advanced modeling of the design. As per the design aspects the engines, pylons, landing gears and shape improvements were done with solid modeling. Due to the computational limitations this was divided in to two phases as cruising conditions with non-static components and further studies to be carried out in Takeoff and Landing conditions with extended landing gears. Under the stability and control conditions a separate research is being carried out in achieving the optimum capability. Propfan engine selected for extreme condition evaluations. The implementations were made without disrupting the base design which was presented in phase one basic simulation carried out prior to this. The simulation results deemed to be promising for the first stage as well as the effect of new components. The secondary target areas are to be carried out in further ongoing research as well

scholarly journals Stability and control of planar compass gait walking with series-elastic ankle actuation

2016 ◽  
Vol 39 (3) ◽  
pp. 312-323 ◽  
Author(s):  
Deniz Kerimoğlu ◽  
Ömer Morgül ◽  
Uluç Saranli
Keyword(s):  
Equations Of Motion ◽  
Period Doubling ◽  
Basic Structure ◽  
System Stability ◽  
Gravitational Potential Energy ◽  
Extended Model ◽  
Stability And Control ◽  
Inclined Surfaces ◽  
And Control ◽  
Series Elastic

Passive dynamic walking models are capable of capturing basic properties of walking behaviours and can generate stable human-like walking without any actuation on inclined surfaces. The passive compass gait model is among the simplest of such models, consisting of a planar point mass and two stick legs. A number of different actuation methods have been proposed both for this model and its more complex extensions to eliminate the need for a sloped ground, balancing collision losses using gravitational potential energy. In this study, we introduce and investigate an extended model with series-elastic actuation at the ankle towards a similar goal, realizing stable walking on level ground. Our model seeks to capture the basic structure of how humans utilize toe push-off prior to leg liftoff, and is intended to eventually be used for controlling the ankle joint in a lower-body robotic orthosis. We derive hybrid equations of motion for this model, and show numerically through Poincaré analysis that it can achieve asymptotically stable walking on level ground for certain choices of system parameters. We then study the bifurcation regimes of period doubling with this model, leading up to chaotic walking patterns. Finally, we show that feedback control on the initial extension of the series ankle spring can be used to improve and extend system stability.

Passive Fault Tolerance for a Magnetic Bearing Under PID Control

2001 ◽  
Author(s):  
Benjamin Choi ◽  
Andrew Provenza
Keyword(s):  
Fault Tolerance ◽  
Fault Tolerant ◽  
Magnetic Bearing ◽  
System Stability ◽  
Integral Term ◽  
Stability And Control ◽  
Stiffness And Damping ◽  
And Control ◽  
Component Failures ◽  
Detection Mechanisms

NASA Glenn Research Center (GRC) has developed a Fault-Tolerant Magnetic Bearing Suspension rig to enhance the safety of the bearing system for multiple component failures. A simple proportional-integral-derivative (PID) controller with no fault detection mechanisms was tested in a passive way where the initial bias current and control gains for all the eight heteropolar poles were not changed for the remaining active poles in the fault situations. The action of the integral term in the controller generated autonomous corrective actions for the pole failures to return the rotor to the set point (middle position) after the failure transient. The system stability and control of the rotor position were maintained over the entire speed range, where the rotor passes through the rigid body critical speeds and other rotor disturbances, provided that there was sufficient position stiffness and damping at low speeds. As far as the summation of force vectors of two attracting forces and rotor weight is zero, the passive fault tolerance was successfully demonstrated by using as few as two active poles out of the eight independent poles from each radial bearing (that is simply, 12 out of 16 poles dead). The rotor was spun without losing stability or desired position up to the rig’s maximum allowable speed of 20,000 rpm.

Surface Topography and Friction Dynamics in Brake Systems Described by a Cellular Automaton

2005 ◽  
Author(s):  
M. Mueller ◽  
G. P. Ostermeyer
Keyword(s):  
Friction Coefficient ◽  
Kinetic Energy ◽  
Cellular Automata ◽  
Relative Velocity ◽  
Friction And Wear ◽  
Normal Load ◽  
Friction Behavior ◽  
Plastic Deformations ◽  
Parameter Dependent ◽  
Friction Dynamics

For the description of a friction event it is necessary to understand the friction coefficient μ as a process-parameter dependent not only on the surface-structure but also for instance on the relative velocity, normal load, temperature and the event itself. In brake systems, for example, growing and destroying processes of hard thin patches determine the friction power and the transfer of kinetic energy into heat and plastic deformations, such as wear. So the interaction of friction and wear is given by an equilibrium of flow of different processes resulting in growing effects or lowering effects on the friction coefficient itself [2]–[4]. The aim of this paper is to show the detailed interaction of this topographical dynamics and the friction behavior with the Method of Cellular Automata.

scholarly journals Experimental Investigation into the Tractive Prerolling Behavior of Balls in V-Grooved Tracks

2008 ◽  
Vol 2008 ◽  
pp. 1-10 ◽  
Author(s):  
Kris De Moerlooze ◽  
Farid Al-Bender
Keyword(s):  
Experimental Investigation ◽  
Theoretical Model ◽  
Normal Load ◽  
Displacement Curve ◽  
Friction Behavior ◽  
Rolling Element ◽  
Element System ◽  
Motion Characterization ◽  
And Control ◽  
Hysteresis Friction

In a rolling element system, the period of transition between motion commencement and the attainment of steady state, gross rolling, and termed prerolling is of common concern to many engineering applications. This region is marked by hysteresis friction behavior, with a characteristic friction-displacement curve, which is in particular relevant to motion characterization and control issues. In a previous paper, the authors carried out a theoretical analysis of tractive prerolling, leading to a model for simulating this phenomenon. The present paper is dedicated to the experimental investigation of tractive prerolling friction behavior, including validation of the theoretical model. Firstly, a kinematic analysis of the rolling motion in V-grooved tracks is carried out. Secondly, the influence of the normal load on the frictional behavior, in prerolling up to the attainment of gross rolling, is investigated on a dedicated test setup. Finally, the newly developed theoretical model is validated by comparison with the experimental results. Satisfactory agreement is obtained between theory and experiment.

Stability and Control of a Parametrically Excited Rotating Beam

1998 ◽  
Vol 120 (4) ◽  
pp. 462-470 ◽  
Author(s):  
S. C. Sinha ◽  
Dan B. Marghitu ◽  
Dan Boghiu
Keyword(s):  
Equations Of Motion ◽  
System Stability ◽  
Flexible Beam ◽  
Parametrically Excited ◽  
Stability And Control ◽  
Rotation Parameters ◽  
The Stability ◽  
And Control ◽  
Time Invariant ◽  
Time Periodic

In this paper the stability and control of a parametrically excited, rotating flexible beam is considered. The equations of motion for such a system contain time periodic coefficients. Floquet theory and a numerical integration are used to evaluate the stability of the linearized system. Stability charts for various sets of damping, parametric excitation, and rotation parameters are obtained. Several resonance conditions are found and it is shown that the system stability can be significantly changed due to the rotation. Such systems can be used as preliminary models for studying the flap dynamics and control of helicopter rotor blades and flexible mechanisms among other systems. To control the motion of the system, an observer based controller is designed via Lyapunov-Floquet transformation. In this approach the time periodic equations are transformed into a time invariant form, which are suitable for the application of standard time invariant controller design techniques. Simulations for several combinations of excitation and rotation parameters are shown.

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