constraint modify higher_pair_contact point_curve
Allows you to modify a point_curve.
Format:
constraint modify higher_pair_contact point_curve |
|---|
point_curve_name = | existing pcurve |
new_point_curve_name = | new name for pcurve |
adams_id = | geom._id |
comments = | string |
curve_name = | existing acurve |
i_marker_name = | An existing marker |
j_floating_marker_name = | An existing fmarker |
ref_marker_name = | existing marker |
displacement_ic = | length |
no_displacement_ic = | true |
velocity_ic = | velocity |
no_velocity_ic = | true |
ic_ref_marker_name = | existing marker |
Description:
Parameter | Value Type | Description |
|---|
point_curve_name | Existing Pcurve | Specifies the name of an existing point_curve. |
New_point_curve_name | New pcurve name | Specifies the name of the new point_curve. You may use this name later to refer to this point_curve. |
adams_id | Integer | Specifies an integer used to identify this element in the Adams data file. |
Comments | String | Specifies comments for the object being created or modified. |
curve_name | Existing Acurve name | Specifies the name of a CURVE that defines the contour or shape on which the fixed marker can move. |
i_marker_name | Existing marker name | Specifies the name of a fixed MARKER that Adams constrains to lie on the curve defined by CURVE and REF_MARKER. |
j_floating_marker_name | Existing floating marker name | Specify an existing floating marker name. |
ref_marker_name | Existing marker | Specifies the name of a MARKER fixed on the part containing the curve on which the I_MARKER must move. |
displacement_ic | Length | Specifies the initial point of contact on the curve. |
no_displacement_ic | true | Specifies that if a DISPLACEMENT_IC has been set via any means, to "UNSET" the displacement initial condition. |
velocity_ic | Velocity | Specifies the initial tangential velocity of the I_MARKER along the curve. |
no_velocity_ic | True | Specifies that if a VELOCITY_IC has been set via any means, to "UNSET" the velocity initial condition. |
ic_ref_marker_name | Existing marker | Specifies the name of a the fixed MARKER defining the coordinate system in which the values for DISPLACEMENT_IC values are specified. |
Extended Definition:
1. Adams View will not allow you to have two point_curves with the same full name, so you must provide a unique name.
Normally, entity names are composed of alphabetic, numeric, or '_' (underscore) characters, and start with an alphabetic or '_' character. They may be any length. For more information, see
Using Extended Names.
By enclosing the name in double quotes, you may use other printable characters, or start the name with a numeral. If a name contains characters, or starts with a numeral, you must always quote the name when entering it.
Note that you can specify the parentage of an entity (for example, what part "owns" a marker or a geometry element) when you CREATE it by changing the name. If you enter just the entity name, then the default parent will be assigned by Adams View. If you type in the full name, then you may over ride the default parent. In most cases, when creating an entity, Adams View will provide a default name. The default name that Adams View provides will specify the parentage that it has assumed.
You may, or course, delete this name and use your own. The form of a full name is:
"...._NAME.GRAND_PARENT_NAME.PARENT_NAME.ENTITY_NAME"
The number of levels used varies from case to case and the parentage must exist before an entity can be assigned to it.
2. When you use the FILE ADAMS_DATA_SET WRITE command, Adams View writes an Adams data file for your model. AdamsAdams requires that each modeling element be identified by a unique integer identifier. If you use this parameter to specify a non-zero identifier, Adams View will use it in the corresponding statement in the Adams data file.
You may also enter zero as an identifier, either explicitly or by default. The next time you write an Adams file, Adams View will replace the zero with a unique, internally-generated identifier.
Adams View will permanently store this identifier with the element just as if you had entered it yourself.
Normally, you would let all identifiers default to zero, and Adams View would generate the identifiers for you. You are never required to enter a non-zero identifier. You only need to specify it if, for some reason, you wish to control the Adams file output.
3. The REF_MARKER is used to associate the shape defined by the CURVE to the part on which the REF_MARKER lies. The curve coordinates are therefore specified in the coordinate system of the REF_MARKER. The floating J marker and REF_MARKER must belong to the same PART.
You may identify a marker by typing its name or by picking it from the screen.
If the marker is not visible on the screen, you must type the name. You may also find it convenient to type the name even if the marker is displayed.
If you created the marker by reading an Adams data set or graphics file, the marker name is the letters MAR followed by the Adams data set marker ID number. The name of Adams MARKER/101 is MAR101, for example. If you created the marker during preprocessing, you gave it a name at that time.
If a marker is available by default, you may identify it by entering its name only. If it is not, you must enter its full name. To identify a marker under a different part, for instance, you may need to enter the model and part names as well. For example, you may specify marker 'pivot' from model 'links', part 'lower_arm' by entering ".links.lower_arm.pivot". If you type a "?", Adams View will list the markers available by default.
You must separate multiple marker names by commas.
If the marker is visible in one of your views, you may identify it by picking on it.
You need not separate multiple marker picks by commas.
4. If the point specified is not exactly on the curve, Adams uses a point on the curve nearest to that specified. By default, DISPLACEMENT_IC is specified in the REF_MARKER marker coordinate system. If another coordinate system is more convenient, you may supply the IC_REF_MARKER argument and enter DISPLACEMENT_IC in IC_REF_MARKER marker coordinates. If you supply DISPLACEMENT_IC values, Adams assembles the system with the I_MARKER at the specified point on the curve, even if it must override part initial conditions in order to do so. If you do not supply DISPLACEMENT_IC, Adams assumes the initial contact is at the point on the curve closest to the initial I_MARKER position. However, it may adjust that contact point to maintain other part or constraint initial conditions.
5. The velocity_ic parameter specified the speed at which the I_MARKER is initially moving relative to the curve. The VELOCITY_IC is negative if the I_MARKER is moving towards the start of the curve, positive if the I_MARKER is moving toward the end of the curve, and zero if the I_MARKER is stationary on the curve.
If you supply the VELOCITY_IC, Adams gives the I_MARKER the specified initial tangential velocity along the curve, even if it must override part initial conditions in order to do so. If you do not supply VELOCITY_IC, Adams assumes the initial tangential velocity is zero, but may adjust that velocity to maintain other part or constraint initial conditions.
6. The POINT_CURVE command defines a point-to-curve constraint, which restricts a fixed point defined on one part to lie on a curve defined on a second part. This is an instance of a higher pair constraint.
The part containing the I_MARKER is free to roll and slide on the curve that is fixed to a second part. Lift-off is not allowed, i.e., the I_MARKER must always lie on the curve.
The curve itself may be planar or spatial, open or closed. The "floating J" marker origin defines the contact point on the curve; its orientation defines the tangent, normal, and binormal at the contact point. A POINT_CURVE constraint removes two translational degrees-of-freedom from the system. Adams restricts the origin of the I_MARKER to always lie on the curve. The I_MARKER may translate only in one direction relative to the curve, along the instantaneous tangent. The I marker is free to rotate in all three directions.
More than one POINT_CURVE or CURVE_CURVE element may reference the same CURVE statement. If the mechanism contains several similar contacts, you may enter just one CURVE statement, then use it with several POINT_CURVE or CURVE_CURVE constraints, each with a different REF_MARKER.
The VELOCITY_IC is specified in the reference frame of the part containing the REF_MARKER. In other words, the VELOCITY_IC is the speed of the I_MARKER specified from the standpoint of an observer on the part containing the curve. This means that if the I_MARKER is not moving globally but the curve is, then VELOCITY_IC is still non-zero.
The initial conditions arguments, DISPLACEMENT_IC and VELOCITY_IC, impose constraints that are active only during an initial conditions analysis. Adams does not impose these initial conditions during subsequent analyses.
For a kinematic analysis, the initial conditions are redundant. Do not use the DISPLACEMENT_IC or VELOCITY_IC arguments on the POINT_CURVE command for systems with zero degrees of freedom.
Cautions:
1. For the no_displacement_ic and no_velocity parameters, setting these parameters to true is not the same as setting the value to zero. A zero displacement/velocity is not the same as "no" displacement/velocity. Therefore, by setting this parameter to true there is no longer a displacement initial condition for this element.
2. The I_MARKER and REF_MARKER must belong to different parts.
3. Adams aborts the simulation if the contact point moves off the end of an open curve. The user should make sure the CURVE statement defines the curve over the expected range of motion.
4. The IC_REF_MARKER must be on the same part as the REF_MARKER.
Tip: | The x, y, z values associated with the CURVE are the coordinates of points lying on the CURVE and are calculated in the coordinate system of the REF_MARKER. |