Contact forces are generated only when the contacts are enabled.

The active parameter selects how the contacts are enabled. It has the following settings:

Always Active, the default, means the contacts are always enabled.

Boolean Signal means the contacts are enabled when the enable contact boolean input is true.

Start/Stop Time means the contacts are enabled at specified start time, $T_{\mathrm{on}}$, and disabled at a specified stop time, $T_{\mathrm{off}}$.

The on/off parameter is used with the Start/Stop Time selection and has the following settings:

Start Time means the contacts are enabled at $T_{\mathrm{on}}$.

Stop Time means the contacts are disabled at $T_{\mathrm{off}}$.

Start/Stop Time means the contacts are enabled at $T_{\mathrm{on}}$ and disabled at $T_{\mathrm{off}}$.

The use record boolean parameter, if enabled, specifies the name of an external record parameter that defines the parameters of the contact.

The mode parameter selects one of three modes: Linear spring and damper, Linear spring and limited damper, and Hunt and Crossley. The first two use the $c$ and $d$ parameters to set the spring and damping constants. The Hunt and Crossley model uses the parameters $c_n$, $d_n$, $n$, $p$, and $q$. See the Multibody Contact Modes help page for the resulting force equations.

The $\mathrm{\mu }$ parameter is the coefficient of friction between contacting bodies.

The $k_{\mathrm{\mu }}$ parameter is a smoothness coefficient for sliding friction, it scales $\mathrm{\mu }$ by $\tanh \left(k_{\mathrm{\mu }}\left|v_t\right|\right)$, where $v_t$ is the tangential velocity.

The $\mathrm{\epsilon }$ parameter specifies a minimum length used when normalizing vectors.