*MotionPair()

Applies a motion pair to a joint pair or constrains the motion between two marker pairs.

Syntax

*MotionPair(motion_name,"motion_label",JOINT, joint_name, TRANS|ROT) OR *MotionPair(motion_name,"motion_label",MARKERS, i_marker_name, j_marker_name, direction)

Arguments

motion_name: The variable name of the motion pair.; Data type: varname
motion_label: The descriptive label of the motion pair.; Data type: label
JOINT|MARKERS: Type of motion applied to a joint or two markers.; Data type: keyword
joint_name: The joint pair to which the motion pair is applied.; Data type: CylJointPair, RevJointPair, or TransJointPair
TRANS|ROT: This argument indicates whether the motion is applied to the translational or rotational degree of freedom when using a cylindrical joint pair.
i_marker_name: The first of two marker pairs for which displacement is being controlled.; Data type: MarkerPair
j_marker_name: The second of two marker pairs for which displacement is being controlled.; Data type: MarkerPair
direction: The direction of the constraint.; Data type: X, Y, Z, B1, B2, or B3

Example

*RevJointPair(j_crank_piv, "Crank pivot", 
                           b_crank, 
                           B_Ground, 
                           p_crank_pivot,   
                           p_crank_pivot_axis)
*MotionPair(crnk_rot, "Crank rotation", 
                       JOINT, j_crank_piv)
*SetMotion(crank_rot, LEFT, DISP, 0.0)
*Motion(motion_0, "Motion 0", MARKERS, marker_5, marker_6, B2)

Context

*BeginMdl()

*DefineAnalysis()

*DefineSystem()

Properties

Table 1.
Property	Returns Data Type	Description
l	Motion	Left motion.
label	string	The descriptive label of the motion pair.
r	Motion	Right motion.
state	boolean	Control state (TRUE or FALSE).
varname	string	The variable name of the motion pair.
id	long integer	The solver ID of the motion.
jt	CylJointPair, RevJointPair, or TransJointPair	The joint pair to which the motion pair is applied.
im	MarkerPair	The first of two marker pairs for which displacements are being controlled.
jm	MarkerPair	The second of two marker pairs for which displacement is being controlled.
direction	string	The direction of the constraint.
type		The type of motion specified: DISP, VEL, or ACCL
value	string	The value or solver expression for the motion.

Comments

A *MotionPair() statement can be specified for any revolute, translational, or cylindrical joint pair. However, a motion pair cannot be specified for a joint pair in compliant mode.

The TRANS|ROT flag is required only when a motion pair is applied to a cylindrical joint pair.

If no *SetMotion() statement is present, the displacement of the joint pair is set to zero.

The individual markers of a *MotionPair() can be referred to as motion.l (left marker) and motion.r (right marker).