Coulomb and Viscous Friction

Model discontinuity at zero, with linear gain elsewhere

• Library:

• Simulink / Discontinuities

  HDL Coder / 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.

Ports

Input

Port_1 — Input signal

scalar | vector | matrix

The input signal to the model of Coulomb and viscous friction.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | fixed point

Output

Port_1 — Output signal

scalar | vector | matrix

The output signal calculated by applying the friction models to the input.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | fixed point

Parameters

To edit the parameters for the Coulomb and Viscous Friction block, double-click the block icon.

Coulomb friction value — Static friction offset

[1320] (default) | real values

Specify the offset that applies to all input values.

Programmatic Use

Block Parameter: offset

Type: character vector

Value: real values

Default: '[1 3 2 0]'

Coefficient of viscous friction — Dynamic friction coefficient

1 (default) | real values

Specify the signal gain for nonzero input values.

Programmatic Use

Block Parameter: gain

Type: character vector

Value: real values

Default: '1'

Model Examples

Scalar Expansion with the Coulomb and Viscous Friction Block

A model with a scalar input to a Coulomb & Viscous Friction block that uses scalar expansion to output a vector.

Open Model

Block Characteristics

Data Types	double | fixed point | integer | single
Direct Feedthrough	no
Multidimensional Signals	no
Variable-Size Signals	no
Zero-Crossing Detection	no

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

HDL Code Generation

Generate Verilog and VHDL code for FPGA and ASIC designs using HDL Coder™.

HDL Coder™ provides additional configuration options that affect HDL implementation and synthesized logic.

HDL Architecture

This block has a single, default HDL architecture.

HDL Block Properties

ConstrainedOutputPipeline	Number of registers to place at the outputs by moving existing delays within your design. Distributed pipelining does not redistribute these registers. The default is 0. For more details, see ConstrainedOutputPipeline (HDL Coder).
InputPipeline	Number of input pipeline stages to insert in the generated code. Distributed pipelining and constrained output pipelining can move these registers. The default is 0. For more details, see InputPipeline (HDL Coder).
OutputPipeline	Number of output pipeline stages to insert in the generated code. Distributed pipelining and constrained output pipelining can move these registers. The default is 0. For more details, see OutputPipeline (HDL Coder).

Restrictions

HDL code generation does not support complex input.

PLC Code Generation
Generate Structured Text code using Simulink® PLC Coder™.

Fixed-Point Conversion
Design and simulate fixed-point systems using Fixed-Point Designer™.