FRICTION
The FRICTION function returns force and other friction data from the FRICTION statement. You can use this function in only REQUEST and SENSOR function expressions.
Format
FRICTION (id, index)
Arguments
id | An integer variable specifying the identification of a FRICTION statement from which output data is requested. |
INDEX | An integer variable specifying the output component index to be returned. See the table below for a list of component indices depending on friction formulation. |
Friction Index
Original Formulation
Index | Name | Description |
|---|---|---|
1 | FFX | Friction force along the x-axis of the JOINT’s J marker |
2 | FFY | Friction force along the y-axis of the JOINT’s J marker |
3 | FFZ | Friction force along the z-axis of the JOINT’s J marker |
4 | FTX | Friction torque about the x-axis of the JOINT’s J marker |
5 | FTY | Friction torque about the y-axis of the JOINT’s J marker |
6 | FTZ | Friction torque about the z-axis of the JOINT’s J marker |
7 |  | Friction coefficient along the x-axis of the JOINT’s J marker |
8 |  | Friction coefficient along the y-axis of the JOINT’s J marker |
9 |  | Friction coefficient along the z-axis of the JOINT’s J marker |
10 |  | Friction coefficient about the x-axis of the JOINT’s J marker |
11 |  | Friction coefficient about the y-axis of the JOINT’s J marker |
12 |  | Friction coefficient about the z-axis of the JOINT’s J marker |
13 |  | Effective friction coefficient at static friction (returns zero if sliding) |
14 | Vx | Joint velocity at sliding surfaces along the x-axis of the JOINT’s J marker |
15 | Vy | Joint velocity at sliding surfaces along the y-axis of the JOINT’s J marker |
16 | Vz | Joint velocity at sliding surfaces along z-axis of the JOINT’s J marker |
17 | Wx | Joint angular velocity about the x-axis of the JOINT’s J marker |
18 | Wy | Joint angular velocity about the y-axis of the JOINT’s J marker |
19 | Wz | Joint angular velocity about the z-axis of the JOINT’s J marker |
20 | CREEP_X | Static friction creep along the x-axis of the JOINT’s J marker |
21 | CREEP_Y | Static friction creep along the y-axis of the JOINT’s J marker |
22 | CREEP_Z | Static friction creep along the z-axis of the JOINT’s J marker |
23 | CREEP_RX | Static friction creep about the x-axis of the JOINT’s J marker |
24 | CREEP_RY | Static friction creep about the y-axis of the JOINT’s J marker |
25 | CREEP_RZ | Static friction creep about the z-axis of the JOINT’s J marker |
26 | BETA | Stiction transition factor |
LuGre Formulation
Index | Name | Description |
|---|---|---|
1 | FFX | Friction force along the x-axis of the JOINT’s J marker |
2 | FFY | Friction force along the y-axis of the JOINT’s J marker |
3 | FFZ | Friction force along the z-axis of the JOINT’s J marker |
4 | FTX | Friction torque about the x-axis of the JOINT’s J marker |
5 | FTY | Friction torque about the y-axis of the JOINT’s J marker |
6 | FTZ | Friction torque about the z-axis of the JOINT’s J marker |
7 | Vx | Joint velocity at sliding surfaces along the x-axis of the JOINT’s J marker |
8 | Vy | Joint velocity at sliding surfaces along the y-axis of the JOINT’s J marker |
9 | Vz | Joint velocity at sliding surfaces along z-axis of the JOINT’s J marker |
10 | Wx | Joint angular velocity about the x-axis of the JOINT’s J marker |
11 | Wy | Joint angular velocity about the y-axis of the JOINT’s J marker |
12 | Wz | Joint angular velocity about the z-axis of the JOINT’s J marker |
13 | ZX | Microscopic average bristle deflection of the contact surface along the x-axis of the JOINT’s J marker |
14 | ZY | Microscopic average bristle deflection of the contact surface along the y-axis of the JOINT’s J marker |
15 | ZZ | Microscopic average bristle deflection of the contact surface along the z-axis of the JOINT’s J marker |
16 | RZX | Microscopic average bristle rotational deflection of the contact surface about the x-axis of the JOINT’s J marker |
17 | RZY | Microscopic average bristle rotational deflection of the contact surface about the y-axis of the JOINT’s J marker |
18 | RZZ | Microscopic average bristle rotational deflection of the contact surface about the z-axis of the JOINT’s J marker |
19 | D_ZX | Microscopic average bristle velocity of the contact surface along the x-axis of the JOINT’s J marker |
20 | D_ZY | Microscopic average bristle velocity of the contact surface along the y-axis of the JOINT’s J marker |
21 | D_ZZ | Microscopic average bristle velocity of the contact surface along the z-axis of the JOINT’s J marker |
22 | D_RZX | Microscopic average bristle rotational velocity of the contact surface about the x-axis of the JOINT’s J marker |
23 | D_RZY | Microscopic average bristle rotational velocity of the contact surface about the y-axis of the JOINT’s J marker |
24 | D_RZZ | Microscopic average bristle rotational velocity of the contact surface about the z-axis of the JOINT’s J marker |
25 | FSS | Frictional Force due to microscopic bristle displacement |
26 | MSS | Frictional Moment due to microscopic bristle rotation |
Examples
Request/101
,F2=FRICTION (2,1)/, F3=FRICTION (2,2)/, F4=FRICTION (2,3)/
,F6=FRICTION (2,4)/, F7=FRICTION (2,5)/, F8=FRICTION (2,6)/
,F2=FRICTION (2,1)/, F3=FRICTION (2,2)/, F4=FRICTION (2,3)/
,F6=FRICTION (2,4)/, F7=FRICTION (2,5)/, F8=FRICTION (2,6)/
This REQUEST statement defines a user REQUEST that returns the friction forces associated with the statement FRICTION/2. The second component of the user request contains the X component of the friction-force vector resolved in the associated J marker coordinate system of the JOINT.
Caution: | The FRICTION function is accessible only through the REQUEST and SENSOR function expressions. The FRICTION function evaluates to zero if the index corresponds to a force or velocity which is not used by the corresponding friction model. For example, if FRICTION/2 from above is applied on a translational joint, then FRICTION (2,1) would be zero because the friction force is applied along the z axes of the joint. |
See other Element-specific applied force measures available.