Simulink®

Coulomb and Viscous Friction - Model discontinuity at zero, with linear gain elsewhere

Library

Discontinuities

Description

The Coulomb and Viscous Friction block models Coulomb (static) and viscous (dynamic) friction. The block models a discontinuity at zero and a linear gain otherwise. The offset corresponds to the Coulombic friction; the gain corresponds to the viscous friction. The block is implemented as

y = sign(u) * (Gain * abs(u) + Offset)

where y is the output, u is the input, and Gain and Offset are block parameters.

The block accepts one input and generates one output. The input can be a scalar, vector, or matrix. If using a vector or matrix input, the offset and gain must have the same dimensions as the input or be scalars. If using a scalar input, the output will be a scalar, vector, or matrix based on the dimensions of the offset and gain. For example, passing a scalar input to the block when using the default offset produces an output vector with four elements.

Data Type Support

The Coulomb and Viscous Friction block accepts and outputs real signals of type double.

Parameters and Dialog Box

Coulomb friction value

The offset, applied to all input values. The default is [1 3 2 0].

Coefficient of viscous friction

The signal gain at nonzero input points. The default is 1.

Characteristics

Constant

Counter Free-Running