modelPartialFriction
Information
Basic model for Coulomb friction that models the stuck phase in a reliable way.
This procedure is implemented in a "clean" way by state events and leads to a mixed continuous/discrete system of equations if friction elements are dynamically coupled which has to be solved by appropriate numerical methods. The method is described in [Otter1999] (see also a short sketch in UsersGuide.ModelingOfFriction).
The parameter w_small is introduced for particular
cases where a reinit is triggered at zero velocity.
For such – rather rare – cases the friction handling
logic is no longer correct. On the other hand, introducing
w_small in general leads to problems when more
friction elements are connected together. To omit such problems
in the most common situations, the parameter has a large
value per default, thus eliminating its effect.
The user has to set w_small to
a small value only when the special case with
reinit occurs.
References
| [Otter1999] | Otter M., Elmqvist H., and Mattsson S.E., "Hybrid Modeling in Modelica based on the Synchronous Data Flow Principle", CACSD'99, Aug. 22.-26, Hawaii 1999. |
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Integer | Unknown | 3 | Value of mode is not known |
| Integer | Free | 2 | Element is not active |
| Integer | Forward | 1 | w_relfric > 0 (forward sliding) |
| Integer | Stuck | 0 | w_relfric = 0 (forward sliding, locked or backward sliding) |
| Integer | Backward | -1 | w_relfric < 0 (backward sliding) |
| Advanced | |||
| SI.AngularVelocity | w_small | 1.0e10 | Relative angular velocity near to zero if jumps due to a reinit(..) of the velocity can occur (set to low value only if such impulses can occur) |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| SI.AngularVelocity | w_relfric | Relative angular velocity between frictional surfaces | |
| SI.AngularAcceleration | a_relfric | Relative angular acceleration between frictional surfaces | |
| SI.Torque | tau0 | Friction torque for w_relfric=0 and forward sliding | |
| SI.Torque | tau0_max | Maximum friction torque for w_relfric=0 and locked | |
| Boolean | free | = true, if frictional element is not active | |
| Real | sa | Path parameter of friction characteristic tau = f(a_relfric) | |
| Boolean | startForward | = true, if w_relfric=0 and start of forward sliding | |
| Boolean | startBackward | = true, if w_relfric=0 and start of backward sliding | |
| Boolean | locked | = true, if w_rel=0 and not sliding | |
| Integer | mode | Mode of friction (-1: backward sliding, 0: stuck, 1: forward sliding, 2: inactive, 3: unknown) |