COUSUB/COUXX/COUXX2

Definition

Coupler constraints are used to constrain the relative translational and/or the rotational motion of two or three joints. By using a subroutine-based formulation, for example, you can specify a variable coupler ratio based on system states, relational operators, and logical expressions. A typical example is a nonlinear coupler multiplier ratio defined as a function of an input joint velocity.

Use

User-defined coupler entity example:

<Constraint_UserConstr
     id                  = id     ...
     usrsub_param_string = "USER(r1,… r30)"
     usrsub_dll_name     = "NULL">
  </Constraint_UserConstr>

Format

Fortran Calling Syntax

SUBROUTINE COUSUB (ID, TIME, PAR, NPAR, DISP, NDISP, IFLAG, PHI)
SUBROUTINE COUXX (ID, TIME, PAR, NPAR, DISP, NDISP, IFLAG, DFDA)
SUBROUTINE COUXX2 (ID, TIME, PAR, NPAR, DISP, NDISP, IFLAG, D2FDA2)

C Calling Syntax

void  STDCALL  COUSUB (int *id, double *time, double *par, int *npar, double *disp, int *ndisp, int *iflag, double *phi)
void  STDCALL  COUXX (int *id, double *time, double *par, int *npar, double *disp, int *ndisp, int *iflag, double *DFDA)
void  STDCALL  COUXX2 (int *id, double *time, double *par, int *npar, double *disp, int *ndisp, int *iflag, double *D2FDA2)

Python Calling Syntax

def COUSUB(id, time, par, npar, disp, ndisp, iflag):
    return phi
def COUXX(id, time, par, npar, disp, ndisp, iflag):
    return dfda 
def COUXX2(id, time, par, npar, disp, ndisp, iflag):
    return dfda2

MATLAB Calling Syntax

function phi = COUSUB(id, time, par, npar, disp1, ndisp, iflag)
function dfda = COUSUBXX(id, time, par, npar, disp1, ndisp, iflag)
function d2fda2 = COUSUBXX2(id, time, par, npar, disp1, ndisp, iflag)

Attributes

ID: [integer]; The coupler element identifier.
TIME: [double precision]; The current simulation time.
PAR: [double precision]; An array that contains the constant arguments from the list provided in the user-defined statement.
NPAR: [integer]; The number of entries in the PAR array.
DISP: [double precision]; The array of instantaneous joint displacements.
NDISP: [integer]; The size of the DISP array.
IFLAG: [logical]; The initialization flag.

Output

PHI: [double precision]; The scalar output value of the coupler subroutine.
DFDA: [double precision]; The vector output value of dimension NDISP that contains the partial derivative of PHI with respect to the displacement DISP.
D2FDA2: [double precision]; The vector output value of dimension NDISP that contains the second partial derivative of PHI with respect to the displacement DISP.

Example

def COUSUB(id, time, par, npar, disp, ndisp, iflag):
    phi = disp[0]+par[0]*disp[1]
    return phi
def COUXX(id, time, par, npar, disp, ndisp, iflag):
    dfda =2*[0]
    dfda[0] =1.0dfda[1] = par[0]
    return dfda
def COUXX2(id, time, par, npar, disp, ndisp, iflag):
    d2fda2 = 2*[0]
    return d2fda2