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Friction

Library

Iconic Diagrams\Mechanical\Translation\Components

Use

Domains: Continuous. Size: 1-D. Kind: Iconic Diagrams (Translation).

C

V

CV

SCVS

LuGre

Use

Domains: Continuous. Size: 1-D. Kind: Iconic Diagrams (Translation).

Introduction

These models represents friction with the fixed world. The amount of friction depends on the normal force that is applied and the friction function that is used. The normal force is given by the input signal Fn. The models have only one initial port p defined. Because any number of connections can be made, successive ports are named p1, p2, p3 etc. 20-sim will automatically create equations such that the resulting force p.F is equal to the sum of the forces of all connected ports p1 .. pn. The velocities of all connected ports are equal to p.v.

p.F = sum(p1.F, p2.F, ....)

p.v = p1.v = p2.v = ....

Due to the use of normal force, the friction models all have a fixed force out causality. The constitutive equations are therefore described as:

p.F = Fn * f(p.v);

with f the friction function.

Description - C

This model represents friction with the fixed world described as coulomb friction:

p.F = Fn*mu_c*tanh(slope*p.v);

Fn: normal force (given by the input signal Fn)

mu_c: the coulomb friction coefficient

slope: the steepness of the coulomb friction curve. Interface - C

 Ports Description p[any] Any number of connections can be made (Translation). Causality Fixed force out Input Fn Normal force [N] Parameters mu_c slope Coulomb friction coefficient [] Steepness of Coulomb friction curve [s/m]

Description - V

This model represents friction with the fixed world described as viscous friction:

p.F = Fn*mu_v*p.v;

Fn: normal force (given by the input signal Fn)

mu_v: the viscous friction coefficient Interface - V

 Ports Description p[any] Any number of connections can be made (Translation). Causality Fixed force out Input Fn Normal force [N] Parameters mu_v Viscous friction coefficient [s/m]

Description - CV

This model represents friction with the fixed world described as coulomb plus viscous friction:

p.F = Fn*(mu_c*tanh(slope*p.v) + mu_v*p.v);

Fn: normal force (given by the input signal Fn)

mu_v: the viscous friction coefficient

mu_c: the coulomb friction coefficient

slope: the steepness of the coulomb friction curve. Interface - CV

 Ports Description p[any] Any number of connections can be made (Translation) Causality Fixed force out Input Fn Normal force [N] Parameters mu_v mu_c slope Viscous friction coefficient [s/m] Coulomb friction coefficient [] Steepness of Coulomb friction curve [s/m]

Description - SCVS

This model represents friction with the fixed world described as static plus coulomb plus viscous plus Stribeck friction:

p.F = Fn *

(( mu_c + (mu_st*abs(tanh( slope*p.v )) - mu_c)

* exp( -((p.v / v_st)^2 )) ) * sign(p.v)

+ mu_v * p.v);

Fn: normal force (given by the input signal Fn)

mu_s: the static friction coefficient

mu_v: the viscous friction coefficient

mu_c: the coulomb friction coefficient

slope: the steepness of the coulomb and static friction curve.

v_st: the characteristic Stribeck velocity. Interface - SCVS

 Ports Description p[any] Any number of connections can be made (Translation). Causality Fixed force out Input Fn Normal force [N] Parameters mu_s mu_v mu_c slope v_st Static friction coefficient [] Viscous friction coefficient [s/m] Coulomb friction coefficient [] Steepness of Coulomb friction curve [s/m] Characteristic Stribeck velocity [m/s]

Description - LuGre

This model represents friction with the fixed world described by the LuGre friction model:

p.F = FN*f_lg(p.v);

Fn: normal force (given by the input signal Fn)

f_lg: the LuGre friction model

Interface - LuGre

Ports

Description

p[any]

Any number of connections can be made (Translation).

Causality

Fixed force out

Input

Fn

Normal force [N]

Parameters

mu_c

mu_s

mu_v

v_st

mu_k

Coulomb friction coefficient []

Static friction coefficient []

Viscous friction coefficient [s/m]

Characteristic Stribeck velocity [m/s]

Stiffness coefficient at zero speed []