constraint modify higher_pair_contact curve_curve

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:

The number of levels used varies from case to case and the parentage must exist before an entity can be assigned to it.

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.

If you supply I_DISPLACEMENT_IC, Adams assembles the system with the contact 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 I_DISPLACEMENT_IC, Adams assumes the initial contact is at the point on the first curve closest to J_CURVE in the input configuration. In this case, Adams may adjust that contact point to maintain other part or constraint initial conditions.

If you supply J_DISPLACEMENT_IC, Adams assembles the system with the contact 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 J_DISPLACEMENT_IC, Adams assumes the initial contact is at a point on the second curve closest to ICURVE in the input configuration. In this case, Adams may adjust that contact point to maintain other part or constraint initial conditions.

If you supply I_VELOCITY_IC, Adams gives the contact point the specified initial velocity along the first curve, even if it must override part initial conditions in order to do so. If you do not supply I_VELOCITY_IC, Adams assumes the initial velocity is zero, but may adjust that velocity to maintain other part or constraint initial conditions.

If you supply J_VELOCITY_IC, Adams gives the contact point the specified initial velocity along the second curve, even if it must override part initial conditions in order to do so. If you do not supply J_VELOCITY_IC, Adams assumes the initial velocity is zero, but may adjust that velocity to maintain other part or constraint initial conditions.

Adams constructs the first curve from the I_CURVE curve and the I_REF_MARKER, the second curve from the J_CURVE value and the J_REF_MARKER. In both cases, the CURVE command (I_CURVE or J_CURVE) defines x and y coordinates along the curve as a function of the independent parameter (u). The z coordinates of the curves must be zero. The reference marker (I_REF_MARKER or J_REF_MARKER) defines the part the constraining curve is attached to and the coordinate system in which Adams applies the coordinates from the CURVE statement. Both I_CURVE and J_CURVE may be open or closed, defined analytically or as a set of discrete data points.

The CURVE_CURVE constraint removes three degrees-of-freedom from the system. Adams restricts the motion of the parts such that the curves are always in contact and the curves are tangent at the contact point. Although Adams requires that the curves lie in parallel planes, the CURVE_CURVE command does not enforce this. You must build the model in such a way that the curves are held in parallel planes, which will remove another three degrees of freedom. Assuming the curves are held in parallel planes, a CURVE_CURVE leaves two relative degrees of freedom between the curves. The first curve may slide or roll on the second, but may not move perpendicular to the curve tangents at the contact.

Internally, Adams actually generates five constraint equations, but also adds two new system variables and equations for a net decrease of one degree-of-freedom. The added system variables are the two curve parameters at the contact points on the curves. Two of the constraints restrict the x and y coordinates at the contact point on the first curve to match the x and y coordinates at the contact point on the second curve. The third constraint restricts the tangent at the contact point on the first curve to be parallel to the tangent at the contact point on the second curve.

More than one POINT_CURVE or CURVE_CURVE statement 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 I_VELOCITY_IC and J_VELOCITY_IC are specified in the reference frame of the part containing the I_REF_MARKER or J_REF_MARKER marker, respectively. In other words, the I_VELOCITY_IC is the speed of the contact point specified from the standpoint of an observer on the part containing the first curve. This means if the contact point is not moving globally, but the first curve is, then I_VELOCITY_IC is still non-zero.

Adams detects a fatal user error if the contact point moves off the end of an open curve. You should make sure the CURVE statement defines the curve over the expected range of motion. The initial conditions arguments, I_DISPLACEMENT_IC, J_DISPLACEMENT_IC, I_VELOCITY_IC and J_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 I_DISPLACEMENT_IC, J_DISPLACEMENT_IC, I_VELOCITY_IC or J_VELOCITY_IC arguments on the CURVE_CURVE statements for systems with zero degrees of freedom.

Adams requires that there be a unique contact point in the vicinity of the I floating and J floating markers during simulation. If this condition is violated, Adams may be unable to find the correct contact point or may even jump from one contact point to the next.

One way to ensure that contact points are unique is to specify curve shapes that are convex. Note that for a convex curve, any line segment connecting two points on the curve lie in the domain of the curve. The same is not true for non-convex curves.