Accelerating the pace of engineering and science

• Trials

# Coulomb and Viscous Friction

Model discontinuity at zero, with linear gain elsewhere

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 block output matches the MATLAB® result for:

`y = sign(x) .* (Gain .* abs(x) + Offset)`

where y is the output, x is the input, Gain is the signal gain for nonzero input values, and Offset is the Coulomb friction.

The block accepts one input and generates one output. The input can be a scalar, vector, or matrix with real and complex elements.

• For a scalar input, Gain and Offset can have dimensions that differ from the input. The output is a scalar, vector, or matrix depending on the dimensions of Gain and Offset.

• For a vector or matrix input, Gain and Offset must be scalar or have the same dimensions as the input. The output is a vector or matrix of the same dimensions as the input.

## Data Type Support

The Coulomb and Viscous Friction block supports real inputs of the following data types:

• Floating point

• Built-in integer

• Fixed point

The block supports complex inputs only for floating-point data types, double and single. The output uses the same data type as the input.

## Parameters and Dialog Box

Coulomb friction value

Specify the offset that applies to all input values.

Coefficient of viscous friction

Specify the signal gain for nonzero input values.

## Examples

### Scalar Input

Suppose that you have the following modelmodel:

In this model, block input x and Gain are scalar values, but Offset is a vector. Therefore, the block uses element-wise scalar expansion to compute the output.

### Vector Input

Suppose that you have the following modelmodel:

In this model, vector dimensions for block input x and Offset are the same.

### Matrix Input

Suppose that you have the following modelmodel:

In this model, matrix dimensions for block input x and Offset are the same.

## Characteristics

 Direct Feedthrough Yes Sample Time Inherited from the driving block Scalar Expansion Yes Dimensionalized Yes Multidimensionalized No Zero-Crossing Detection Yes