This change has been incorporated into the documentation in Release 2009a (R2009a). For previous releases, read below for any additional information:
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 Offset corresponds to the Coulombic friction and by default we give it four values. The default Offset vector lets you test the same input against 4 different offsets. You may wish to have only one.
The Gain corresponds to signal gain at nonzero input points and is set to 1 by default..
You can also right click on the block and choose 'Look under mask' to see the implementation.
