07_section7_constraints
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• Appropriate parts are connected by each constraint. • Correct directions are specified for each constraint. • Correct type of DOF (translational versus rotational) are removed by each constraint. • There are any redundant constraints in the system.
• Question: What would happen if the joint initial conditions in a system were different from the part initial conditions?
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software
S7 - 7
Degrees of Freedom (DOF) (Cont.)
• Determining the number of system DOF
– Adams/View provides an estimated number of system DOF by using the Gruebler’s Count:
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software
S7 - 13
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software
S7 - 14
S7 - 10
Merging Geometry (Cont.)
• Adding new geometry to an existing part.
– Note: Adams/Solver handles simulations better if you merge geometry on a rigid part as opposed to constraining multiple parts. – Question: When you merge geometry, is the overlapping volume accounted for?
– Between two vectors – Defined by three markers – Defined throughout a simulation
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software
S7 - 12
Angle Measures (Cont.)
• Degrees of Freedom (DOF) • Joint Initial Conditions (ICs) • Angle Measures
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software
S7 - 2
Constraints
• Constraint equations in Adams
– Constraints are represented as algebraic equations in Adams/Solver. – These equations describe the relationship between two markers. – Joint parameters, referred to as I and J markers, define the location, orientation, and the connecting parts:
• Constraints and DOF – Each DOF in mechanical system simulation (MSS) corresponds to at least one equation of motion. – A freely floating rigid body in three-dimensional space is said to have six DOF. – A constraint removes one or more DOF from a system, depending on its type.
– See also: DOF removed by a revolute joint in Appendix A.
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software
S7 - 8
Joint Initial Conditions (ICs)
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software
S7 - 3
Constraints Example
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software
S7 - 4
Use of Markers in Constraints
S7 - 5
Use of Markers in Constraints (Cont.)
• Anatomy of a constraint in Adams
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software
S7 - 6
DegreeI, is fixed to the first part. • Second marker, J, is fixed to the second part.
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software S7 - 11
Angle Measures
• Definition of angle measures: They are used to measure the included angle, θ:
• Characteristics of joint initial conditions
– You can specify displacement and velocity initial conditions for revolute, translational, and cylindrical joints. – Adams/View uses the specified initial conditions of the joint while performing a simulation, regardless of any other forces acting on the joint. – If you do not specify joint initial conditions, Adams/Solver calculates the conditions of the connecting parts while performing a simulation depending on the other forces acting on the joint.
• Notes:
– The units used for angle measures are in current Adams/View angle units (degrees or radians). – The sign convention (+/-) is defined such that the first nonzero value is positive.
SystemDOF (number of movable parts DOF/part)
i type
[# Constraints # DOF(Constraint)]
– Adams/View also provides the actual number of system DOF, as it checks to see if:
• Definition of a constraint
– Restricts relative movement between parts. – Represents idealized connections. – Removes rotational and/or translational DOF from a system.
SECTION 7
CONSTRAINTS
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software
S7 - 1
What is in this Section
• Constraints
• Use of Markers in Constraints
S7 - 9
Merging Geometry
• Methods of attaching multiple geometry to a part
– Use fixed joint to constrain geometric objects.
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software
• Question: What would happen if the joint initial conditions in a system were different from the part initial conditions?
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software
S7 - 7
Degrees of Freedom (DOF) (Cont.)
• Determining the number of system DOF
– Adams/View provides an estimated number of system DOF by using the Gruebler’s Count:
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software
S7 - 13
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software
S7 - 14
S7 - 10
Merging Geometry (Cont.)
• Adding new geometry to an existing part.
– Note: Adams/Solver handles simulations better if you merge geometry on a rigid part as opposed to constraining multiple parts. – Question: When you merge geometry, is the overlapping volume accounted for?
– Between two vectors – Defined by three markers – Defined throughout a simulation
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software
S7 - 12
Angle Measures (Cont.)
• Degrees of Freedom (DOF) • Joint Initial Conditions (ICs) • Angle Measures
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software
S7 - 2
Constraints
• Constraint equations in Adams
– Constraints are represented as algebraic equations in Adams/Solver. – These equations describe the relationship between two markers. – Joint parameters, referred to as I and J markers, define the location, orientation, and the connecting parts:
• Constraints and DOF – Each DOF in mechanical system simulation (MSS) corresponds to at least one equation of motion. – A freely floating rigid body in three-dimensional space is said to have six DOF. – A constraint removes one or more DOF from a system, depending on its type.
– See also: DOF removed by a revolute joint in Appendix A.
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software
S7 - 8
Joint Initial Conditions (ICs)
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software
S7 - 3
Constraints Example
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software
S7 - 4
Use of Markers in Constraints
S7 - 5
Use of Markers in Constraints (Cont.)
• Anatomy of a constraint in Adams
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software
S7 - 6
DegreeI, is fixed to the first part. • Second marker, J, is fixed to the second part.
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software S7 - 11
Angle Measures
• Definition of angle measures: They are used to measure the included angle, θ:
• Characteristics of joint initial conditions
– You can specify displacement and velocity initial conditions for revolute, translational, and cylindrical joints. – Adams/View uses the specified initial conditions of the joint while performing a simulation, regardless of any other forces acting on the joint. – If you do not specify joint initial conditions, Adams/Solver calculates the conditions of the connecting parts while performing a simulation depending on the other forces acting on the joint.
• Notes:
– The units used for angle measures are in current Adams/View angle units (degrees or radians). – The sign convention (+/-) is defined such that the first nonzero value is positive.
SystemDOF (number of movable parts DOF/part)
i type
[# Constraints # DOF(Constraint)]
– Adams/View also provides the actual number of system DOF, as it checks to see if:
• Definition of a constraint
– Restricts relative movement between parts. – Represents idealized connections. – Removes rotational and/or translational DOF from a system.
SECTION 7
CONSTRAINTS
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software
S7 - 1
What is in this Section
• Constraints
• Use of Markers in Constraints
S7 - 9
Merging Geometry
• Methods of attaching multiple geometry to a part
– Use fixed joint to constrain geometric objects.
ADM701, Section 7, March 2013 Copyright© 2013 MSC.Software