The DIF1 function returns the value of the time derivative of the state variable associated with DIFF/id. In instances where DIFF/id is used to define an implicit algebraic equation, DIF1 returns an approximation of the time derivative obtained by numerical differencing.
Format
DIF1(id)
Arguments
id | An integer variable that specifies the identifier of a DIFF statement. |
Examples
SFORCE/1, I=21, J=11, ROTATION
, FUNCTION= -20*(AZ(21,11)-10)**1.5
, -5*WZ(21,11,11)
DIFF/1, IC=0, FUNCTION=SFORCE(1,0,8,11)*WZ(21,11)
This SFORCE statement specifies a nonlinear rotational spring acting between Markers 21 and 11. The spring torque acts about the z axis of Marker 11. DIFF/1 specifies the instantaneous power used by SPRING/1.
The expression DIF(1) returns the integral of the instantaneous power (that is, the total work done by SPRING/1). DIF1(1) returns the instantaneous power in SPRING/1.