Cosmos work motion essential

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COSMOSMotion Essentials Training
COSMOSMotion 2007

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© 2007 SolidWorks Corp. Confidential.
About this course
Prerequisites
Course Design Philosophy
Using this book
A note about files
Conventions used in this book
Class Introductions

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COSMOSWorks
Adv. Professional
Professional
Design Validation Products
Designer
Static
Vibration
& Buckling
Thermal
Drop Test
Fatigue
Nonlinear
Post-dynamics
COSMOSEMS Electromagnetic
COSMOSMotion
COSMOSFloWorks
Flow Simulation
Optimization

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What is Motion Simulation ?
Study of moving systems or mechanisms
Motion of a system is determined by
–Mechanical joints connecting the parts
–The mass and inertia properties of the components
–Applied forces to the system (Dynamics)
–Driving motions (Motors or Actuators)
–Time

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Mechanism types
Kinematic System
–Movement of part(s) under enforced or constrained motion
–Fully controlled and only one possible motion result irrespective of force and mass
–Zero degree of freedom
Dynamic System
–Movement of part(s) under free motion subject to forces
–Partially controlled and infinite number of results depending on forces
–Greater than zero degrees of freedom

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Understanding Basics
Mass and Inertia
–Newton’s First Law
–Conservation of momentum
Degrees of freedom
–Rigid body
–Grounded parts
–Moving parts
Constraints
–Restrictions placed on a part’s movement in specific degrees of freedom
–Mechanical joints are connections that restrict the movement of one part to another
Joint motion
Gravity
x
y
Pendulum restrained
to pivot about mounting
point

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Mapping of SolidWorks assembly mates (constraints) to COSMOSMotion joints.
100+ ways of defining SolidWorks mates.
Basic constraint types are merged to simplified mechanical joints.
–One Orthogonal Concentric mate in SolidWorks becomes a Concentric joint.
–One Coincident and One Orthogonal Concentric mates in SolidWorks becomes a Revolute joint.
–One Point to Point coincident mate in SolidWorks becomes a spherical joint
Constraint Mapping

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User Interface
Pull down menu
Intellimotion builder
Motion toolbar
Intellimotion browser

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User Interface
Pull down menu
Intellimotion builder
Motion toolbar
Intellimotion browser

Lesson 1
Governor Mechanism

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Lesson 1: Topics
Introduction to the COSMOSMotion Feature Manager
Understand basic capabilities of COSMOSMotion
Run a Simulation
Create a result plot

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Lesson 1: Defining and Simulating a Mechanism
Parts
–Moving Parts
–Ground Parts
Constraints
–Joints
–Joint Primitives
–Cam Constraints
Forces
–Applied Forces
–Flexible Connectors
–Gravity
Results
Translational DistanceCollar and Slider. Initial Distance :345mmSlider Distance:323mmMinumium Distance :22mm

Lesson 2
Crankslider Mechanism

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Lesson 2: Topics
Create moving and ground parts
Review basic joint types in COSMOSMotion
Understand Automatic Constraint mapping
Apply motion to a joint
Create a result plot

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Lesson 2: Constraint Mapping Concept
1 Coincident and 1 concentric mates becomes a revolute joint
1 Concentric mate becomes a cylindrical joint
A point on a point coincident mate becomes a spherical joint
A point on an axis coincident mate becomes an Inline Joint

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Lesson 2: Results
Collar-1 not only translates along collar_shaft-1 but also rotates.
The rotation needs to be prevented

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Lesson 2: Motion on Joints
Joint Types
Type of motion allowed
Available options under Motion On list
Cylindrical
Rotation and translation in one direction
Rotate Z
Translate Z
Revolute
Only Rotation in one direction
Rotate Z
Translational
Only Translation in one direction
Translate Z
Spherical
Rotations in all directions, No translation
Rotate X
Rotate Y
Rotate Z

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Lesson 2: Results
Power Consumption in Mechanism
Why is Power Consumption negative in some places? Conversion: Pound_force foot/sec to WattPound_force foot/sec to HP1Pound_force foot/sec =1.3558W1Pound_force foot/sec =0.00134HP1ft =12in4pound_force foot/sec =0.451933W4pound_force foot/sec =0.000447HP

Lesson 3
Piston Crankshaft Mechanism

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Lesson 3 Topics
Review basic joint types in COSMOSMotion
Create Mechanical Joints
Apply motion to a joint
Create and review results

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Lesson 3: Basic Joint Types
Joints used to constrain the relative motion of a pair of rigid bodies by physically connecting them.
Joint Primitives used to enforce standard geometric constraints

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Lesson 3: Joint definition
Location
Direction

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Lesson 3 Results
Torque required to drive the mechanism

Lesson 4
Coupler

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Lesson 4 Topics
Simulate motion of gears using joint couplers
Joint coupler to associate the movement of one joint with another
Modeling gear-mate from SolidWorks model
ConversionConvert RPM to deg/s1RPM =360degree1min =60s100RPM =600deg/s

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Lesson 4: Couplers
Any one of the following joint combinations will create a coupler:
–Revolute-Revolute
–Revolute-Translational
–Revolute-Cylindrical
–Translational-Cylindrical
–Translational-Translational
–Cylindrical-Cylindrical
Only motion transfer. No load transfer

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Lesson 4: Coupler Definition

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Simulate Couplers using Gear Mate in SolidWorks
Lesson 4: Gear Mate in SolidWorks

Lesson 5
Door Mechanism

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Lesson 5 Topics
Create springs and damper entities in COSMOSMotion
Attach different parts together to move them as a single entity
Constrain the motion of a cylindrical joint to achieve correct mechanism behavior
Modify springs and dampers to achieve desired design goals

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Lesson 5 Attaching Parts
Physically attach one part to another
Two parts will be welded or rigidly connected to one another.
No relative motion between the two parts
Initial orientation between the two parts will be locked and will be maintained throughout the simulation

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Lesson 5: Springs
Translational Spring Force = -k (X - X0)n + F0
Where:
k = Spring stiffness coefficient (always > 0)
X = Current distance between the spring connection points
X0 = Reference length of the spring (Free length)
n = Exponent defining spring characteristic
F0 = Reference force of the spring (preload)
Positive force repels the two parts.
Negative force attracts the two parts.
Similar force expression applies to Torsional Springs

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Lesson 5: Dampers
Translational Damper Force = c*vn
Where:
c - Translational damping coefficient
v - Current relative velocity between parts at the attachment points
n - Exponent.
Similar force expression applies to Torsional Dampers

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Lesson 5: Results
gas_piston-1 not only translates along gas_cylinder-1 but also rotates.
The rotation needs to be prevented

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Lesson 5: Results
Velocity goal is satisfied
Door does not stop in 30 seconds
Should we increase or decrease spring stiffness?
Spring stiffness: 1 N/mm
Damper Co-efficient: 5 N (sec/mm)

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Lesson 5: Results
Velocity goal is satisfied
Door stops in 30 seconds
Spring stiffness: 2 N/mm
Damper Co-efficient: 10 N (sec/mm)

Lesson 6
Hatchback Mechanism

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Lesson 6 Topics
Create an Action Only force to simulate an
Change the mass properties of a part
Use Impact forces to control two parts from interfering each other

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Affect the dynamic behavior of a mechanism
Do not prohibit or prescribe motion and so do not add or remove degrees-of-freedom from your model.
Force Entities
–Translational and Torsional Springs
–Translational and Torsional Dampers
–Action-Only Forces/Moments
–Action-Reaction Forces/Moments
–Impact Forces
–Flexible Connectors
–Gravity
Lesson 6: Forces

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Lesson 6: Force Definition
Force Type
–Whether the loading is a force or a moment.
Location
Direction
–Along an axis defined by an edge, plane or cylindrical surface.
–Along the line-of-sight between two points
Magnitude
–Enter a pre-defined function expression (step, harmonic, spline).
–Enter an equation directly into the Function Expression field using the library of built-in COSMOSMotion functions. Cylinder ComponentBore Diameter:0.49inBore Radius :0.245inArea:0.19sq. inPressure :500PsiForce:94.30Lbs

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Lesson 6: Action Only Force

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Lesson 6: Material Properties
Adding Materials
Modifying Material Properties

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Lesson 6: Results

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Lesson 6: Impact Forces
Intermittent force that is dependent on relative distance between two components).
Impact forces are used to simulate the collision between two parts.
As two parts approach within a specified distance, the impact force becomes active, and a force specified by the impact parameters is applied to both of the colliding parts.
The collision is dependent on the materials and geometry of the bodies colliding.

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Impact Force = Spring Force + Damping Force
Stiffness: Depends on material properties and curvature of interacting surfaces
Exponent: Determines impact force characteristic
Max Damping: Simulates energy loss in collision
Penetration: Depth at which maximum damping occurs.
Length: distance at which the impact force is activated (parts contact)
Lesson 6: Impact Parameters

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Lesson 6: Impact Parameters
Good numbers for impact parameters:
Stiffness: 10000 lb/in 10000 N/mm
Exponent: 1.1-1.3 1.1-1.3
Damping: 0.1-100 lb-s/in 1-100
Penetration: 0.0001 in 0.01 mm
d cannot be specified as 0
Height of Piston:0.95inImpact Distance Clearance Distance 1in0.05in0.95in0in0.9in-0.05inComponents interfere0.85in-0.15in1.3in0.35inThis values are linearly proportionaly due to the exponent input.

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Lesson 6: Results
Translational displacement of the concentric joint between the piston and cylinder parts
Notice that the displacement is held at 8 inches which means that the impact force does not allow further translation between the parts

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Lesson 6: Results
Magnitude of the impact force applied

Lesson 7
Contacts

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Lesson 7 Topics
Apply Point to curve contact
Apply Curve to curve contact
Apply 3D Contact

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Point-curve - Restricts a point on one rigid body to lie on a curve on a second rigid body.
Curve-curve - Constrains one curve to remain in contact with a second curve.
Intermittent curve-curve - Applies a force to prevent curves from penetrating each other. Only active if the parts are touching
3D Contact – Applies a force to prevent bodies from penetrating each other. Only active if the parts are touching
Lesson 7: Understanding Contacts

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Contact is similar to an impact force in that the material properties of the parts are used to define the contact parameters.
Contact differs from an impact force since any point along a curve or geometry is used in the contact
Contact simulates friction forces between parts.
Lesson 7: Impact Forces Vs Contacts

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Lesson 7: 3D Contact
Surface Representation of parts:
–Tessellated Geometry
Faster but less accurate in certain contact situations like point to surface or multiple contacts
–Precise Geometry
Longer simulation time but produces accurate results
Contact Containers

Lesson 8
Railcar Mechanism

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Lesson 8: Topics
Apply Gravity force to the mechanism
Create an Action-Reaction force to accelerate the railcar
Learn some advanced plotting techniques in COSMOSMotion

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Lesson 8: Action Reaction Force

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Lesson 8: Results
Probing translational velocity plot of body-1

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Lesson 8: Results
Plotting multiple plots in the same XY graph

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Lesson 8: Results
Replacing X axis time scale with a desired results quantity

Lesson 9
Floor Jack Mechanism

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Lesson 9 Topics
 Apply motion to a part
Use different types of motion functions
Make a design change and study mechanical advantage

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Lesson 9: Part Motion

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Lesson 9: Function Types
 Constant
Step Function
d0 = Initial value of displacement
d1 = Final value of displacement
t0 = Start step time
t1 = Final step time
Harmonic
Amplitude; Frequency; Time Offset; Phase Shift; Average

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Lesson 9: Function Types
 Spline
–You can use your own motion data to control your mechanism by importing data points.
–To import data points, they must be in a .TXT or .CSV file format.
–You may import an unlimited number of data points.
-20
0
20
40
60
80
100
0
1
2
3
4
Overshoot
0
20
40
60
80
100
0
1
2
3
4
Data Points

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Lesson 9: Results
Translational Displacement of the cylinder joint connecting the piston and cylinder
Force on handle
Force to move the piston. A very small force is required to push the handle. This gets amplified internally at the piston cylinder area

Cosmos work motion essential

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